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 Roller v Flat aka Major Intensity
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DanM
Sitting Bull

139 Posts

Posted - 11 Jan 2019 :  12:17:57 PM  Show Profile  Reply with Quote
Ok Guys, ready to have your heads explode like mine did.

My understanding of the value of a roller cam has everything to do with the ability to use a more aggressive lobe profile. If I want to minimize overlap while maximizing the duration at .050 and especially at 0.200" I want a lobe that is steep and flat on top. That's how it has been explained in every article written on the subject.

YET! If you compare the actual numbers for the cams the truth is the opposite. For example... (and the Lunata and the Comp Cams have the same effect)(and I am assuming hydraulic only for now)

Flat tappet cam.
"advertised aka 0.006" 256
duration at 0.050" 213
duration at 0.200" 125

Roller cam
"advertised aka 0.006" 258
duration at 0.050" 207
duration at 0.200" 120

So we see that for basically the same overlap (assuming same LSA) the flat tappet cam has MORE duration where it matters. WTF?

The term to describe the difference between advertised duration and duration at 0.050" is "major intensity". The major intensity for the flat tappet cam is 43. The major intensity of for the roller cam is 51. This is the exact opposite of what I want.

I would like to have someone find me a cam that reads more like this
"advertised duration" 256
duration at .050" 222

Corncob2061
Cochise

USA
346 Posts

Posted - 11 Jan 2019 :  1:37:36 PM  Show Profile  Reply with Quote
Roller cams are slower off the seat than a flat tappet. They do not get their area under the curve early in the profile. So on a small cam like the only place the roller will have more area under the curve is going to be over the nose of the cam. Other than gains from friction a small roller cam like that offers very little performance gains over a flat tappet. In fact, looking at those specs you have the flat tappet is likely going to clean house on the roller comparing those two profiles. Roller cam is not always the best choice.

068 Pontiac cam like you have runs in the mid to low 270s at .006 lift on the intake. Most hyd rollers will be in the 220s at .050 that seat spec. Even at that level, the durations are a bit short to make the roller cam profile work great. Acceleration off the seat effects the rest of the profile a great deal. On a little roller cam by the time the roller profile is caught up the profile is starting to deaccelerate to go over the nose. They have a lot more dwell over the nose though. Jay

Edited by - Corncob2061 on 11 Jan 2019 1:53:54 PM
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 11 Jan 2019 :  1:38:23 PM  Show Profile  Reply with Quote
Two links related.....

https://forums.maxperformanceinc.com/forums/showthread.php?t=799450&highlight=Marketing+tool

https://www.chevelles.com/forums/13-performance/883913-marketing-created-050-cam-number.html


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Steve C.
Chief PONTIAC

1953 Posts

Posted - 11 Jan 2019 :  1:49:51 PM  Show Profile  Reply with Quote
"I would like to have someone find me a cam that reads more like this
"advertised duration" 256 duration at .050" 222"

You did not state hydraulic flat tappet or hydraulic roller. That said, you will be able to find a HFT with 270 advertised and 222 @ .050 and a hyd roller with 273 advertised and 222 @.050. But finding less seat (advertised) duration probably won't happen.


EDIT: Also within the advertised durations mentioned above the lobe lift can, depending on the manufacture, vary in number considerably. Thus affecting the amount of IMPORTANT valve lift.



Edited by - Steve C. on 11 Jan 2019 2:47:24 PM
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Corncob2061
Cochise

USA
346 Posts

Posted - 11 Jan 2019 :  5:31:15 PM  Show Profile  Reply with Quote
Here are some examples of things you can do with hyd roller cams that you can not do with flat tappets when you get farther down this list.

I do not know the exact .006 tappet specs for a Pontiac 068 ra 3 cam. I do know there is 12 degrees difference on a 041 ra 4 cam from the SAE to the .006. I am sure it has more difference than that, but for these examples I am going to use 12.

068 ra 3 melling approximately 273/285 at .006 tappet, 212/225 at .050. 113 Icl 118 ecl 115.5 LSA

First example from the Bullet, would have the manors of a 068, with more power everywhere. It is a symmetrical cam

HR273/330 CTS intake. HR286/347 CTS Exhaust
273/286 adv, 222/234 .050. ,142/155 at .2, .495/.520 lift with 1.5 rockers
115.5 lsa, 112ICL

Second example is a Ultradyne, it is asymmetrical. It allows the engine to run more overlap to manage reversion than the symmetric cam above, very little change in street manors, slightly worse, but more power and torque almost everywhere.
284/292 adv 230/238 .050 .530/.530 lift 1.5 rockers. 111.5 lsa 109 Icl

Third example is another Bullet, another asymmetrical profile with more area under the curve yet, it would still be similar in street manors, but would again bump up the power.
HR284/380 CRA intake, H2293/3823 CRA exhuast
284/293 adv, 230/238 .050 154/160 .2, .570/.573 lift. 111.5lsa 109icl

Fourth example is from comp cams QXI series cam. It is another example of the CRAZY things you can do with a hyd roller cam. I think it is more similar to the first bullet cam listed as far as symmetric, the specs I listed reflect that:
QXI 273/285 adv, 221/233 @.050, 142/152, .569/.587, 114lsa, 113icl

Just some examples, small fish in a big ocean :)
Jay



Edited by - Corncob2061 on 11 Jan 2019 5:33:32 PM
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DanM
Sitting Bull

139 Posts

Posted - 14 Jan 2019 :  1:06:37 PM  Show Profile  Reply with Quote
Thanks guys. Great links.

Summary: rule of thumb, flat tappet cams with less than 273 duration at 0.006" will have more area under the curve than roller cams

Reason: flat tappet cams can be accelerated more than roller cams. Roller cams can have higher velocity than flat tappet cams.

Personal note: I'm using the Comp Cams Extreme Energy version of the 068. It has hydraulic intensity value of 44 on the intake which is super fast.

Next up: considering Rhodes lifters. My goal is to maintain my current driveability but add approximately 10 degrees more duration. (go from 215ish to 225ish)
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 14 Jan 2019 :  1:18:54 PM  Show Profile  Reply with Quote
A 225 degree cam is not a 'big' cam in a performance 400 engine. Not a specific cam recommendation on my part but only as an example, the Crower 60916 hyd flat tappet cam is often touted for a 400 combo and it has 221 degrees at .050". I will suggest not necessary with the use of Rhodes lifters ! And Cliff Ruggles has often touted the Crower 60243 with 228 degrees duration for use in a 400 combination.


Edited by - Steve C. on 14 Jan 2019 1:23:07 PM
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 14 Jan 2019 :  1:40:31 PM  Show Profile  Reply with Quote
In part within another thread. Material posted by Cliff Ruggles....

Head porting for 1hp/CID really isn't money well spent. I've dyno'd pretty "basic" 400's with unported big valve heads and they will make a little over 1hp/CID with cams as small as 221 @ .050".

A 400 with tight squish, unported big valve heads, Crower 60916 cam made 419hp/453tq.

With a larger Crower 60243 cam it made 424hp/465tq.

I helped a customer out recently with his 400 build, he opted to have his #62 heads professionally ported, Crower 60243 cam, HS 1.65 rockers, Rhoads lifters, factory iron intake, factory Q-jet, stock distributor. I set up the carb, distributor, rebuilt the transmission and supplied the converter. He has 3.73 gears out back, car will weigh around 3400 lbs and change with driver.

Initial track runs were 12.0's at 114mph with limited traction. He worked on that deal and now runs solidly into the 11's in full street trim on DOT's, with good street manners.

.
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Corncob2061
Cochise

USA
346 Posts

Posted - 14 Jan 2019 :  3:17:33 PM  Show Profile  Reply with Quote
I would not necessarily say the small roller cam less than 273 always has less area under the curve than a small flat tappet. I would suggest when the cam is smaller than that it is not much extra hp for the $ spent

Comp cams does not have any xe profiles that have much in common with a 068. The comp XE is a totally different cam profile with very different engineering in their design. A comp XE has much less seat timing for the same .050 specs. Jay

Edited by - Corncob2061 on 14 Jan 2019 3:26:58 PM
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 14 Jan 2019 :  3:43:28 PM  Show Profile  Reply with Quote
One cam source will tell you a quick opening and closing cam will provide better low end performance than one that is slower opening. It all can get quite dizzy. Here is a topic introduced by Lee Atkinson on this site in a related conversation about a cams intensity....

Personally, I compare the .050" duration to the .200" duration.
Let's look at Bullet Cams' HFT offering with 224 duration @ .050". I count 17 different 224 lobe designs, and their .200" durations vary from 109 degrees to 136 degrees - a 27 degree spread. Looking at the gross duration, the spread is 268 to 290 - a 22 degree spread. IMHO, the .050/.200 comparison gives me a better feel for lobe aggressiveness than does gross/.050".


Edited by - Steve C. on 14 Jan 2019 3:46:02 PM
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 14 Jan 2019 :  4:27:22 PM  Show Profile  Reply with Quote
I personally have nothing against Crower, but I mentioned a few of their cams only to make a point regarding intake duration numbers as it might relate here. And I mentioned Cliff Ruggles material because he like and uses them. That said, my choice would gravitate towards Lunati Voodoo or Ultadyne lobes.

But as it relates to cam intensity I have noted that people often think these two lobe families are too aggressive, and both were designed by Harold Brookshire. Also mentioned has been Paul Carter who likes and uses Voodoo cams. Paul had good contact with Harold before he died and on the subject of voodoo cams intensity I asked Paul about it. His reply to me, and it relates...

"Steve, the Voodoo lobes have the same closing velocity as stock GM. They are quiet. Harold split the duration on them as 57.5 percent on the opening side, and 42.5 percent on the closing side. Or there about. They open fast, and close slow."

And a similar situation as above would also apply to UltraDyne lobes.

Subtracting the .050 number from the advertised duration does not tell all because of the different opening closing rate of the specific cam.


.

Edited by - Steve C. on 14 Jan 2019 4:33:27 PM
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DanM
Sitting Bull

139 Posts

Posted - 14 Jan 2019 :  5:08:52 PM  Show Profile  Reply with Quote
Steve, et al. Thanks again for the info. This is great.

A couple things to note how my application departs from Cliff's.

Those guys driving a 400 with a 230 degree cam in it are not commuting to work year round in that car. I've been to the track and have heard those cars. They only need to idle long enough for the tree to go Amber Amber Amber. I need to idle in stop and go traffic at 95 degrees in summer. A 230 degree cam would be death.

Similarly, the big HP for big cams is above 5000 rpm. I shift at 5200. Without variable valve timing it's very hard (or not possible) to have a useable rpm range from 600 to 6000. When my car shifts into OD at 40 mph and the torque converter locks I see about 1200 rpm. This happens a lot during my commutes. So that sets a bound on what I can tolerate.

So, given those limits I am right on the edge. I feel that 224 degrees might even be too much. But with Rhodes lifters I could be balancing the tight rope perfectly.

Oh, this is a convertible. At the track if I get below 13.49 I have to install a roll bar. I'm already at 13.89. Will ten more degrees of duration take off a half second. Probably.

Jim Lehart built my heads. Knowing my need to commute and desire to race he recommended the XE262H which is 218 degrees.
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Corncob2061
Cochise

USA
346 Posts

Posted - 14 Jan 2019 :  5:35:15 PM  Show Profile  Reply with Quote
You have a xe 262 with 1.65 roller tip comp rockers then?

Kind of explains how you were getting a 400 to run that good with 8.8 compression. A factory 068 would not be super happy at that low of compression, a xe262 would be very happy. It is also insight on why the dyno work you did was a zero net gain going from 1.5 to 1.65 rocker arms. Jay

Edited by - Corncob2061 on 14 Jan 2019 5:44:34 PM
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 14 Jan 2019 :  5:56:15 PM  Show Profile  Reply with Quote
"I've been to the track and have heard those cars. They only need to idle long enough for the tree to go Amber Amber Amber. I need to idle in stop and go traffic at 95 degrees in summer. A 230 degree cam would be death."

I respectably disagree, so would Cliff :)

Only for conversation here. Much depends on the specific car and how it's set up. Certainly not suggesting it's apples-to-apples but my 600+ horsepower street car currently has a cam with 255 degrees intake duration and here in our horrid Texas Summer heat in traffic it has never overheated with this engine. Same with the transmission oil temperature with my 3400 stall converter, not an issue. I also run a overdrive transmission. But one caveat, I do not have air conditioning and my cooling system is far from being similar to 'stock' from the factory, it's been totally upgraded.


( Jim Lehart for the most part only used XE lobes, and I will suggest it was due to habit more than anything. More than a few noted Pontiac engine builders disagreed with him on that subject. But no need to go there, you can do your homework on that specific subject ! And NO disrespect by me toward him on this.)


.

Edited by - Steve C. on 14 Jan 2019 6:12:22 PM
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tjs44
Crazy Horse

USA
567 Posts

Posted - 14 Jan 2019 :  6:37:31 PM  Show Profile  Reply with Quote
a 230 on a 108 would be crap,a 230 on a 112-113 not so much in a hyd roller IMO.Tom
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 15 Jan 2019 :  07:06:26 AM  Show Profile  Reply with Quote
Ok, your 400 based combo is going to spend it's time commuting to work year round in city traffic. Your current cam is the XE262H cam Jim recommended with 218 degrees intake duration. But you want to step up a bit to probably a maximum around 225 degrees duration and I get the impression it won't be a hydraulic roller cam. And you seem to be concerned with the use of aggressive lobes, therefore said to be easy on parts by some then the Crower line of cams would seem to fit the bill just fine. And they are ground using a 112 lobe separation which should Broaden the Power Band, improve Idle Vacuum and improve the idle quality over your current XE cam with its 110 Lobe separation.

Suggested Crower examples: The 60916 at 221 degrees, 60341 at 215 degrees and the 60243 at 228 degrees.

But I'm questing the need for and use of Rhodes lifters. I have noted the company makes this statement, "Stock cams are generally not recommended as reductions in lift and duration on stock cams have very little effect on performance gains". I bring this up because in the eyes of some those Crower cams are not all that much 'bigger' than some factory cams. Hopefully someone here that has used Rhodes lifters can comment further. Jay ?


.

Edited by - Steve C. on 15 Jan 2019 07:14:24 AM
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Corncob2061
Cochise

USA
346 Posts

Posted - 15 Jan 2019 :  10:28:32 AM  Show Profile  Reply with Quote
Smallest crower cam would be a 60243 228 at .050 for Rhoads imo, it would be pretty much a must with a 8.8 compression 400. I would not use rhoads with the 60916 either. I think the 60916 with 1.65s would be a very nice daily driver cam in this engine.

Only cam I can think of that it would be worth running rhoads on smaller than the 60243 is summits 2802 which is 224/234 with a 114 lsa. Only reason for that being it has pretty wide lsa and a decent amount of seat timing.


Ultradyne, lunati voodoo, and most of the other cams that run the 110 lsa would not be worth running the rhoads until durations get into the 230s. Imo..jay
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 15 Jan 2019 :  12:30:46 PM  Show Profile  Reply with Quote
May not be directly related here but regarding a 110 lobe separation I've posted before about their use in conjunction with Voodoo cams. Some of them are 112 and some are 110.

Repeat.....

Regarding the Voodoo cam's 110 lobe separation seek out Paul Carters very specific information presented on that subject as to why they are much different than other cams, such as the Comp XE flat tappet lobes.

Some here:

http://forums.maxperformanceinc.com/forums/showthread.php?t=817316&highlight=Voodoo&page=2

And this comment....

"Let me make one thing perfectly clear. When I talk about narrower lobe sep cams in big engines, I am specifically talking about Harold cams. Not Comp XE or anyone else's tight LSA cams. Harold did many things differently to his lobes. Things NO ONE ELSE DID! These subtle little things created lobes that when ground on a 110 LSA, gave the power band performance of a cam ground on a 112-114 LSA. Just look at some of the Voodoo lobes."
Paul Carter


.

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DanM
Sitting Bull

139 Posts

Posted - 15 Jan 2019 :  2:33:41 PM  Show Profile  Reply with Quote
Jay and others,

I mistakenly misguided everyone by mentioning the XE262 (218/224) that Jim L suggested. I don't currently have that installed. I have something very similar to the XE256. When I bought the cam 7 years ago I knew so much less than the little I currently know. 2 years ago when I upgraded the heads by Jim I kept that 212/224 cam.

Current cam: lobes are XE lobes. 212/224 degrees at 0.050", 116 LSA, 116 centerline. I have advanced the cam 4 degrees to 112 ICL. 1.65 roller tip rockers.

I have seen various descriptions of the 068 that show it to be 116 LSA and 112 ICL at 212/224 at 0.050" so my current custom cam is identical to that. The advantage (I believe) I have over the 068 is the super aggressive lobes that minimize duration at 0.006" and thus improve vacuum and idle.

Sooooo....

Given my current setup, 8.8ish compression (90 ccs and 0 deck height and 7 cc reliefs), 400 ci, 3.55 gears, 2000ish converter, daily driving, borderline idle, I am considering 10 more degrees to 222/230ish. I feel (I feel) that that would be too much w/o Rhodes lifters.

I recently read a long article written by Jim Hand. In his wagon he uses the 041 cam in a 455. He struggled with idle quality and solved it with Rhodes lifters. Granted he was using the old style lobes with all that 0.006" duration (308 degrees I think) so his idle wouldn't be as good as an XE lobe, for instance. Still, I'm spooked against going above 224/230ish for a regular driver if Jim struggled to idle with 230 degrees in a 455 9.5:1 engine. Maybe the XE lobes eliminate all the idle problems with such big 0.006" duration.

Steve, I'm not so concerned about aggressive lobes. I already have the XE cam which is about as steep as it gets. And correct, no roller cam for me. I'm not in that realm yet.

Someday this engine will die and I will rebuild it as a 461. I would like to have more experience balancing between performance and idle on my 400 so I can be better positioned to select a cam for my future engine.

Rhodes lifters seem magical, true variable valve timing. They allow about 10 extra degrees of duration, but also will be more optimal all across the RPM range. However, surely there are some tradeoffs aside from some ticking lifters at idle. Durability?
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DanM
Sitting Bull

139 Posts

Posted - 15 Jan 2019 :  2:54:49 PM  Show Profile  Reply with Quote
I should measure my vacuum and report back. That will take away the subjectivity of what we all mean by acceptable idle.

Steve, 600+HP in a "street car"? I think we have a different view of what that means unless that car is a 2016 Dodge Challenger Hellcat or whatever they call it.

So, for now let's say I need 17 inches of vacuum at idle and want to minimize my 1/4 mile ET.
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Corncob2061
Cochise

USA
346 Posts

Posted - 15 Jan 2019 :  3:35:37 PM  Show Profile  Reply with Quote
No disadvantage running the rhoads vmaxs on a small cam that I know of. I would not use the originals though. Using the vmaxs, you can set the valve lash to the hydrualic cams lash ramp design, usually .045 to .006 x the rocker ratio. For most cams .009 lash is in the ball park. Then you can add lash to get the driving characteristic, vacuum, etc. Imo, at worst you end up with a high quality high rpm lifter, only mod required is an adjustable valve terrain. Jay
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 15 Jan 2019 :  4:45:58 PM  Show Profile  Reply with Quote
"Steve, 600+HP in a "street car"? I think we have a different view of what that means unless that car is a 2016 Dodge Challenger Hellcat or whatever they call it."

You are correct sir, I have a much different view on most that post and visit here. Quite a view of my combinations are linked within this website. This is the current one...

https://www.hotrod.com/articles/0712phr-1970-pontiac-trans-am/

The information is not up to date on that link. Second dyno session 660 hp. It now has fuel injection. It has run 10.63 but not raced, street only. Very driveable !

But I started out 31 years ago with the same numbers matching car and similar to what you are doing now.

Edited by - Steve C. on 15 Jan 2019 4:52:00 PM
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Lee
Sitting Bull

178 Posts

Posted - 15 Jan 2019 :  7:11:55 PM  Show Profile  Visit Lee's Homepage  Reply with Quote
"My understanding of the value of a roller cam has everything to do with the ability to use a more aggressive lobe profile." A flat tappet lobe's contact point on the face of the lifter moves towards the edge of the lifter as the slope of the lobe increases. It can only go so far before it reaches the edge of the lifter, then damage occurs. If you have a larger lifter diameter (like the .904" Mopar lifters) you can go a bit more aggressive. A roller can go more aggressive due it it's design, but eventually get to side-loading which can cause lifter damage or broken lifter bores. But, as with larger diameter flat tappets, larger diameter lifter bores allow for larger diameter rollers which allow for more aggressive lobes.

What a SOLID roller cam offers, is the ability to use much stronger valve springs, which keep the valvetrain stable - both at high RPM and also at rapid changes in rates of acceleration.

"Those guys driving a 400 with a 230 degree cam in it are not commuting to work year round in that car." Untrue. Back in the late 80's my cousin had an HC-02 (232/242 @ .050) in his '78 Trans Am's 400. He drove it daily for several years, and even took it to college with him for his last two years. 3.23 gears, Q-jet, Hooker headers, a variety of intakes. It ran low-13's/high-12's back then in street trim, but that was on the crappy street tires we had back then (drag radials didn't exist for another decade) and unported "13" heads (77cc's, ran fine on 93-octane). I'm pretty sure we had Rhoads on that cam, as his power brakes worked fine.

CURRENT: '73 T/A clone, starting to get less boring!...
67 Firebird (sold) 11.27 @ 119.6 Feb. '05 issue HPP
69 Falcon wagon, 10.51 @ 130mph Feb. '10 issue PHR (sold)
72 Cutlass Convertible, first car, owned since '82, now with a 6.0 LS, mild, putting just under 400 hp/tq to the wheels.
www.LNLPD.com
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Lee
Sitting Bull

178 Posts

Posted - 15 Jan 2019 :  7:35:28 PM  Show Profile  Visit Lee's Homepage  Reply with Quote
As for Steve's car being a street car... I rode in it a few years ago. He pulled it out of the garage on a rather hot day, and it fired right up. We drove around for a half-hour or so, and got some cheeseburgers. We drove around some more afterwards, making some "exhibition" runs, then took it home. Zero issues, no hiccups, no overheating, no problems at traffic lights. That was before he installed the EFI system, so it is probably even more mild mannered now.

As a motor gets more radical - by that I mean more CR, more CFM, etc - you have less room for error. The carb needs to be properly sized AND tuned, the timing needs to be right, the cam specs have to be proper. At 300hp you can be fairly off on those and still run o.k., but the margin of error narrows as the power goes up. With over 30 years with the same car, Steve's is tuned very well. Likewise, Jim Hand has honed his combination to a fine-edge.

Also note that ".050 specs" are NOT directly comparable between solids and hydraulics. Steve's "255" solid roller is probably more like a hydraulic flat that is about 20 degrees smaller, as far as idle goes. There are other SR "255" lobes that may act more like an HF that is only 10 degrees smaller, while others may go the other way. It just depends upon how the take-up section of the lobe is designed.

My 7-liter SBF wagon had a 251 @ .050 SR cam in it. It also had an OD tranny with a lock-up converter. It would cruise the highway at 2200 rpm all day. I took it on the Power Tour in 2011, drove 4,400 miles on that trip with no problems.

CURRENT: '73 T/A clone, starting to get less boring!...
67 Firebird (sold) 11.27 @ 119.6 Feb. '05 issue HPP
69 Falcon wagon, 10.51 @ 130mph Feb. '10 issue PHR (sold)
72 Cutlass Convertible, first car, owned since '82, now with a 6.0 LS, mild, putting just under 400 hp/tq to the wheels.
www.LNLPD.com
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 15 Jan 2019 :  9:12:17 PM  Show Profile  Reply with Quote
Right here on this street performance site. Take a similar engine as this fine example linked here, port the cylinder heads to 300-305 cfm, use a port matched Torker II intake & 'worked' Holley 800-850 cfm carb. Either a Comp 320H hydraulic flat tappet cam, 268 at .050, with Harland sharp high ratio rocker arms and Rhodes Vari-Duration lifters with a bit over 0.600" net valve lift. Or a SD Performance "Road Paver" hydraulic roller cam, 246 at .050 and using Crower solid roller lifters with a 1.65 ratio. Or Butlers Comp 290 solid roller cam, 254 at .050, 0.630" lift with .020" lash. The right headers. All three cams will make 580+ easy and approaching 600 hp depending the cam and some fine points at around 5800 peak rpm. Slam dunk.

http://www.pontiacstreetperformance.com/psp/rebuild455MikeG.html

A 505 cid engine eats up a lot of duration at a similar 5800-6000 rpm. My current cam is a UltraDyne MSP solid roller with 255 degrees intake duration.


.

Edited by - Steve C. on 15 Jan 2019 9:19:41 PM
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tjs44
Crazy Horse

USA
567 Posts

Posted - 15 Jan 2019 :  9:55:59 PM  Show Profile  Reply with Quote
Steves view of a "street" car and mine have become worlds apart over the years as I get older.There in NO way in hell I would think about a 250@50 cam unless it was over 500 CI and then maybe not.I have gone down from 252-260@50 in a 455 down to a 236-242@50 in stages,245-252,236-242.BUT ALL my cars are stick shift car and again,started at 108 on a 250 and keep going down to 112-113.The one I just ordered from Comp is a 113 with no built in adv.It is 233-240 lobes 13450 and 3123 for a 428.JMHOTom
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 15 Jan 2019 :  10:16:18 PM  Show Profile  Reply with Quote
Like Tom today I'd 'downgrade a bit' given the time and resources. I started planning mt 505 about 14 years ago for peak power at or under 6000 rpm. At age 72 no more changes.

A good friends street car. Bob has used 236, 242 and 254 Comp XE solid roller cams.....

https://www.hotrod.com/articles/0804phr-bob-davis-64-pontiac-tempest-custom/

XE 242 at .050 solid street roller cam changed to a SD Performance Old Faithful 236 hyd roller cam with Crower solid roller lifters, .005-.006 lash. Not a significant track difference, the expected slightly better idle quality with the wider 112 lobe separation. A wash to most.

Edited by - Steve C. on 15 Jan 2019 10:21:23 PM
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 15 Jan 2019 :  10:32:53 PM  Show Profile  Reply with Quote
Lees previous Pontiac:

http://www.pontiacstreetperformance.com/psp/rebuild45500.html

He changed from the 231 degree hydraulic flat tappet cam to a UltraDyne solid flat tappet cam with 247 degrees intake duration, .024 lash. 16 degrees additional duration. Similar driveability. Increased 2-tenths and 4-mph if memory serves me right.

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Corncob2061
Cochise

USA
346 Posts

Posted - 16 Jan 2019 :  11:03:16 AM  Show Profile  Reply with Quote
I realize that cam has some appearences on a 068 with the lsa and Icl. Really is not very close on everything else. Running the numbers in my head I come up with about 30 degrees of overlap with the cam at 252/270 and 115.5. I do not recall ever seeing a comp XE that size ever spread out like that. Reminds of me of a cheater cam for a stock 2bbl, log manifold restricted racing class. Is there a story behind that cam? Not much scavenging going on with 30. Probably not utilizing the headers much on the cylinder scavenging. Jay

Edited by - Corncob2061 on 16 Jan 2019 11:13:08 AM
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DanM
Sitting Bull

139 Posts

Posted - 16 Jan 2019 :  12:49:22 PM  Show Profile  Reply with Quote
Hey Team,

I measured my vacuum. At idle in park it is 17.5 inches. At idle in gear it is between 15 and 17. I have the idle speed set as low as possible without it stalling. This is because as the weather changes sometimes it will run better and then idle faster. If I have the idle set a little higher it will end up racing a tad on certain days. After much adjusting and waiting I think I have it set in a happy medium.

So idling in Park is about 800-900 rpm at 17-18 inches as I said.
Idling in gear is about 600 - 700 rpm at 16 inches.

Over a period of several minutes it may idle in gear as high as 17 but will just as likely idle at 15 and be right on the edge of stalling. If I just tap the throttle ever so slightly it will recover and then idle at 17. I really like the sound and shaking when it is idling low at 15 inches of vacuum.

Conclusion: no more room for using a larger duration cam.
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 16 Jan 2019 :  12:50:23 PM  Show Profile  Reply with Quote
"I recently read a long article written by Jim Hand. In his wagon he uses the 041 cam in a 455. He struggled with idle quality and solved it with Rhodes lifters."

What would the outcome be if Jim had tried the Voodoo 704 cam today ?

Use the Crower 60919 cam that many consider as a good 041 replacement as an example. If you go by the catalog listed numbers it has a whopping 86 degrees overlap. Probably very similar to the 041 cam, no wonder he used Rhodes lifters !

The Voodoo cam has 60 degrees overlap.

At their .050" duration these two cams are within 2 degrees of each other, 241 vs 233, and on the intake the Voodoo lobe has the important additional valve lift... .504" vs .470". And if you custom order the Voodoo cam with a 112 lobe separation the idle quality might be a tad bit improved over its normal 110 LS. (which may not be necessary based on Paul Carters thoughts regarding the subject I posted above ). But if you did so with the 112 now the overlap is further reduced to only 56 degrees.

Would there be a good chance Jim might of seen an improvement with the Voodoo lobe ? And doing so without the need of Rhodes lifters?

From a tech article about cam.....

Less overlap increases efficiency by reducing the amount of raw fuel that escapes through the exhaust, while improving low-end response due to less reversion of the exhaust gases back up the intake port; the result is better idle, a stronger vacuum signal, and improved fuel economy.

Due to the differences in cylinder head, intake, and exhaust configuration, different engine combos are extremely sensitive to the camshaft's overlap region. Not only is the duration and area of the overlap triangle important but also its overall shape. Much recent progress in cam design has been due to careful tailoring of the shape of the overlap triangle. The most critical engine factors for optimizing overlap include intake system efficiency, exhaust system efficiency, and how well the heads flow from the intake toward the exhaust with both valves slightly open.

Edited by - Steve C. on 16 Jan 2019 12:54:51 PM
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DanM
Sitting Bull

139 Posts

Posted - 16 Jan 2019 :  12:54:36 PM  Show Profile  Reply with Quote
Jay,

I bought the cam from Comp Cams in 2011-2012. I knew nothing. The tech and I talked and he ended up with a recommendation which is now in the car. It is indeed XE lobes. I just confirmed that this morning by calling Comp Cams. 212/224 at .050 and 255/267 at 0.006". 116 LSA and 116 ICL but advanced by 4 degrees when installed.

I told the cam tech my vacuum numbers and he was impressed they were that high. I use the vacuum port on the carb which gives me vacuum advance at idle (and I've modified my vacuum advance mechanism to max at 10 degrees added vacuum advance.) If I use the other port it doesn't idle as well. I could try it again, reset my idle screw and compare vacuum of park vs drive, again,...
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 16 Jan 2019 :  12:59:17 PM  Show Profile  Reply with Quote
More information that relates to my post above if interested...

Calculating Overlap

http://members.uia.net/pkelley2/Overlap.html

And due note, take the timing overlap ranges listed in there with a grain of salt for a 455 based combo. Some suggest they are more toward a smaller cubic inch combo with less stroke than our Pontiacs. But it serves as a good example.

Edited by - Steve C. on 16 Jan 2019 1:05:09 PM
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DanM
Sitting Bull

139 Posts

Posted - 16 Jan 2019 :  1:03:49 PM  Show Profile  Reply with Quote
Steve, I was thinking the same thing. The 041 cam Jim uses is an insane 308 of advertised duration. An XE lobe of the same .050 duration (230) would only be about 275 of advertised duration. That alone would be more than equivalent to using Rhodes lifters.

Finally, I asked my engine builder's partner about Rhodes lifters. His advice is for me to not use them. He knows my driving habits and suggests that I will not like the noise. I fuss so much over keeping my car relatively quiet and smooth (while allowing for the raspy exhaust sound of headers.) The Rhodes lifters just wouldn't fit in.

So I think I may retire from this thread and resume discussion elsewhere. But my parting question is...

What is the maximum duration I can achieve (minimum 1/4 mile time) and still get 17 inches of vacuum at idle? I think the answer is 212 degrees if using something like an XE lobe.
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DanM
Sitting Bull

139 Posts

Posted - 16 Jan 2019 :  1:09:21 PM  Show Profile  Reply with Quote
Steve,

30 degrees overlap for me using your method.

Dan
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 16 Jan 2019 :  1:11:00 PM  Show Profile  Reply with Quote
Before you part. A rhetorical thought to consider about the need for 17 inches of vacuum.....


https://leedbrakes.com/i-23439163-electric-vacuum-pump-kit-black-bandit-series.html
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 16 Jan 2019 :  1:16:04 PM  Show Profile  Reply with Quote
The Voodoo 701..... 35 degrees overlap.

http://www.lunatipower.com/Product.aspx?id=1774&gid=287
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Corncob2061
Cochise

USA
346 Posts

Posted - 16 Jan 2019 :  1:36:08 PM  Show Profile  Reply with Quote
For reference: a typical factory muscle car has 16 inch of vacuum at 1200 rpm. It takes about 11 inches to run vacuum brakes properly.

17 at low idle is pretty close to the vacuum most stock non performance engines run. But if you like how the car drives there are plenty of other areas to look at to cut your E.T. That 13.5 roll bar rule is already getting pretty close. Might consider: removing 1 lb of rotating mass is like removing 4 lbs of static weight. Also every tenth you can remove off the short time removes about twice that off the E.T. I have been down to a 1.78 60 foot time with a cam 214/224 cam in a 4000 lbs car with less head flow. It sounds like you should leave your engine be, and focus on those areas. Jay

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Lee
Sitting Bull

178 Posts

Posted - 16 Jan 2019 :  1:37:46 PM  Show Profile  Visit Lee's Homepage  Reply with Quote
quote:
Originally posted by DanM


What is the maximum duration I can achieve (minimum 1/4 mile time) and still get 17 inches of vacuum at idle? I think the answer is 212 degrees if using something like an XE lobe.



It depends upon the overlap. A bigger intake lobe with a wider LSA can make the same vacuum as a smaller intake on a tighter LSA.

The HFT in my low compression 455 is 222/242 on a 116 lsa. Even with just 7.8:1 compression it idles smooth and has no issues with power brakes.

For a friend's recent 455, with a bit over 9:1 CR, I had a 226/241 ground on a 115 lsa. Even though it the cam has a bit more intake duration a degree tighter lsa, the extra CR makes this motor have about 40rwTQ more than my motor, and feels like it makes better vacuum as well (did not measure).

Also note that both of those cams use very mild lobe designs, with rather low lift. The second cam has 0.439"/0.427", the first just a slight bit more. With unported heads, I'd rather have the long-term reliability of a milder lobe, rather than an aggressive lobe that will only make a few more HP (and then LESS HP when the lobes/lifters start to fail).

CURRENT: '73 T/A clone, starting to get less boring!...
67 Firebird (sold) 11.27 @ 119.6 Feb. '05 issue HPP
69 Falcon wagon, 10.51 @ 130mph Feb. '10 issue PHR (sold)
72 Cutlass Convertible, first car, owned since '82, now with a 6.0 LS, mild, putting just under 400 hp/tq to the wheels.
www.LNLPD.com

Edited by - Lee on 16 Jan 2019 4:07:07 PM
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 16 Jan 2019 :  2:09:50 PM  Show Profile  Reply with Quote
Based on Lees comments regarding long-term reliability of a milder lobe....

The previous Voodoo 701 lobe with 213 degrees intake duration and 256 degrees advertised duration. The Crower 60918 has 214 degrees but more advertised duration at 288 degrees. Both with a 112 LS.

Just meant as tid bits for interest, as usual. Neither is not necessarily a cam recommendation by me personally.

Edited by - Steve C. on 16 Jan 2019 2:12:58 PM
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Steve C.
Chief PONTIAC

1953 Posts

Posted - 16 Jan 2019 :  2:31:50 PM  Show Profile  Reply with Quote
Dan
I haven't seen Lee post here in awhile, he seldom if ever makes statements about himself in a boastful manner. Therefore a nice tid bit to share with you, I've known him for quite some time and he knows cams and has designed quite a few for his 'customers', that and he owns a chassis dyno for his research and much of the information he shares.

EDIT.... I posted this before I read Lee's post on the other thread where he mentions some of what I said here.


Edited by - Steve C. on 16 Jan 2019 3:02:38 PM
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DanM
Sitting Bull

139 Posts

Posted - 17 Jan 2019 :  5:07:58 PM  Show Profile  Reply with Quote
EPILOGUE

I called Cliff Ruggles to ask him two fairly simple questions. It turned into a 30 minute discussion followed by me sending him a series of photos of my carb.

There were a couple things which his opinion stood alone in the community, that I agreed with. That helped align our thoughts. On the other hand it took a little patience to earn his trust that I kind of know a little about what I'm doing with this carb.

The mystery I've noticed is that my car idles at 15 inches before it stalls due to the air-fuel ratio (AFR) going lean, like 17:1. Although I have my carb tuned so well it runs like fuel injection without the slightest hesitation at any point in the throttle position it has a problem with the idle for very low rpm. And it slowly leaks out the front and makes my garage smell gasoliny.

I have his book and have measured every stupid orifice on that carb. All my numbers are in line, still it goes lean at low idle rpm. His instincts say there is just something fundamentally wrong inside the carb, like a small air leak or something.

Turns out I have a 1069 top on my 1971 main body (7041264). I don't think that is the real problem. The fact that the top is warped is the problem. It just doesn't seal right.

Sooo, I bought a 7041264 off eBay for $200. I can't wait for it to arrive in a week. I'll try it out, rebuild if necessary, and if all that fails I'll send it to Cliff.

If I can get it to idle at 600 rpm, at 15 inches of vacuum, but not go lean, and it keeps running smoothly then that might imply I could tolerate more duration in my cam!!
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DanM
Sitting Bull

139 Posts

Posted - 17 Jan 2019 :  5:09:49 PM  Show Profile  Reply with Quote
TYPO.

Turns out I have a 1967 top on my 1971 body...
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