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 Crower 60918 or 60916?

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Rearwheelmaniac Posted - 14 Nov 2017 : 10:44:00 AM
I'm building a .030 over 400

-10 domes
6x-4 (9.7:1) or 6x-8's (9.3:1) not sure which yet.
.005 deck
.039 gasket
Currently have a 60918 cam on the shelf.
68404 springs
Camsaver Lifters

Running the Wallace racing DC calculator and it's giving me a DC of ~8.5:1 with the 60918.

Isn't this too high?

Secondly, I'm second guessing the 60918 and using the 60916.
I do have power brakes, and A/C. I also plan on a 200-4r this coming summer.

I do not expect much track time.

I'm having MadDog make me a set of headers this winter.
3.73 gears.
Stock Dual Plane

22   L A T E S T    R E P L I E S    (Newest First)
67drake Posted - 17 Feb 2018 : 10:12:09 AM
Reposted by accident
pitts64 Posted - 05 Feb 2018 : 08:48:53 AM
I'd put the 60918 in and not listen to these people that get off on over camming Pontiac motors and turning them into slugs on the street.. The 068 was the best cam for the street.. You are not going to be racing against any of these new performance cars anyhow unless you like to loose..

I had a 462/041/6X in a 64 Pontiac. One night I pulled up to a red light next to a new Mustang, when the light turned green he left me like I was in reverse and stopped at the next red light even faster. Make your car nice to drive with a smooth idle with good brake vacuum and enjoy going to car cruises..
mkpontiac Posted - 27 Jan 2018 : 9:17:20 PM
Most of what I understand about cams comes from this forum, the performance years forum and other reading not direct experience so I am not an expert. When comparing the 60916 to the 60918 in a 400 I think the higher compression is required with the 60916 because of where the 0.050 duration puts the engine in the rpm range and the additional overlap at 0.050. This will be especially negatively noticeable at lower rpm. The 60918 has longer advertised duration numbers, which results in a later actual intake closing, which allows for a greater compression ratio without pinging. Even though the 60918 allows for a higher compression ratio without pinging and would run better with a higher compression ratio I do not think the higher compression ratio is required for reasonable operation compared to the 60916.
Note that the 60916 has at 0.050\advertised duration of 221/278 vs the Pontiac 066 cam at 200/273. 21 degrees different at 0.050 but only 5 degrees different advertised. The 066 cam was used effectively in 400's with advertsied compression ratio of anywhere from 10.5:1 all the way down to 7.8:1.
phil400 Posted - 24 Jan 2018 : 07:07:44 AM
Lee thanks for the info, trying to learn as much as I can about this stuff.

Steve thanks for the link.
Steve C. Posted - 23 Jan 2018 : 9:38:49 PM
It can get real dizzy fast. I don't even pretend to understand it :)

"For the past 25 years I have based my cam design on one theory.
What happens before TDC in the intake cam is bad, and minimising the bad helps the engine breathe its maximum.
All the work done by the piston in starting airflow is done in the 1st 75* ATDC, up to the point of maximum piston velocity. From the point of maximum piston velocity on, the piston is progressively slowing down and pulling LESS hard on the intake port with every degree of rotation. Yet because of inertia, the velocity in the intake port is increasing, up to a max at BDC. If everything is done right, the cylinder is still filling when the initake valve shuts after BDC.
By minimizing Reversion before TDC, the piston starts airflow earlier, vs earlier intake valve openings which let in more and higher pressure exhaust gases. The less reversion, the earlier airflow starts after TDC. By having a cam with lots of mid-lift and high-lift area, the valve has more time(duration) to fill the cylinder with harder-flowing air/fuel(inertia ram).
The exhaust cam has its own part to play, I'll cover that later.
This has been my intake theory for 26 years."
(UltraDyne Cams)

"The only time that low lift flow is important is with a stock or very small cam. The Vizard book is all about real low buck, near stock engine buildups. that has NOTHING to do with serious race engines. I think along the same lines as Larry, the flow up near max lift is the most important for max HP."

"The words "Low-Lift Flow" are relative; what is low-lift in a .450" max valve lift cam is different from that of a .750" max valve lift cam.
However, whatever valve lift occurs BEFORE TDC is bad. The piston is moving upwards, pushing burned exhaust gases out the exhaust port, not moving downward, sucking intake charge into the cylinder. The only time intake charge enters the combustion chamber BTDC is in supercharged or turbocharged engines, when it starts entering with only .001" valve lift.
The intake portion of the overlap, the part BTDC, exposes the intake port to exhaust gas reversion, both pressure and volume of exhaust gas, until TDC, when the piston reverses direction and starts down on the intake stroke. The reversion that exists, and blocks the intake charge, must be cleaned out before clean air and gas start in. The less reversion present, the quicker the reversion is cleaned out, the sooner the good flow starts. The sooner good flow starts, the higher port velocity is at every degree of crank movement, and the better the cylinder filling.
The more high-lift duration a cam has, and the higher the inertia ram velocity is, the more charge gets into the cylinder.
Although low-lift flow helps fill the cylinder at the end of the cycle, I always prefer having bad reverse-flowing ports to hinder reversion vs having good normal-flowing ports, in terms of low-lift flow. Preventing reversion at the start is a lot more helpful than a few more CFM at intake valve closing,IMHO."

MUCH more here:
Area under the curve


Steve C. Posted - 23 Jan 2018 : 9:30:42 PM
"Personally, I compare the .050" duration to the .200" duration."

Excellent point !

Lee Posted - 23 Jan 2018 : 8:42:10 PM
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".
Steve C. Posted - 23 Jan 2018 : 7:11:54 PM
This is not technically correct, but here for conversation only it is similar to Harvey Crane's Hydraulic Intensity Formula. Take a look at the difference in 'intensity' between those two hydraulic flat tappet Pontiac intake lobes by subtracting the amount of duration at .050" lift from their advertised duration.

From this you can get a good indication of how aggressive the lobe is with this intensity number. The lower the number the more aggressive the lobe.

And also related, David Vizard's comments here regarding hydraulic intensity might be of interest....


phil400 Posted - 23 Jan 2018 : 5:27:13 PM
Yeah I know the difference in .50 numbers but if you look the 60916 is 278/221 and the 60918 is 288/214, when you look at it like that it seems the 60916 has a "faster" ramp so why wouldn't it run good in 9-1 400?
67drake Posted - 23 Jan 2018 : 12:12:15 PM
Originally posted by phil400

The 60916 has less advertised duration them the 60918, how is it that the 60916 needs more compression then the 60918?

Sincerely asking, not trying to start a cam debate or anything like that.

Sorry for high jacking, Ive been looking at the sum-2801(mainly due to budget) which has the same specs as the 60918

. Look at the duration @ .050 specs. 60916 is 221/229. 60918 is 214/224
phil400 Posted - 23 Jan 2018 : 07:33:18 AM
The 60916 has less advertised duration them the 60918, how is it that the 60916 needs more compression then the 60918?

Sincerely asking, not trying to start a cam debate or anything like that.

Sorry for high jacking, Ive been looking at the sum-2801(mainly due to budget) which has the same specs as the 60918
Matt H Posted - 21 Jan 2018 : 11:59:39 AM
IYears ago i ran the 60916 cam in my low compression 400. PWH 400 with 6X4 heads, Big mistake for my combination. Poor performance to say the least. That cam needs 10.1.1 compression or better to make power . Great cam but not for my application back then.

Current car - 1981 Pontiac TA Pace Car 461 stroker
1979 Pontiac TA 400 4spd - sold
Blued and Painted Posted - 20 Nov 2017 : 5:04:29 PM
Nothing soggy about it. Hi back bucket seats is recommended.
It's considered small for a 455 race app. I wanted a street cam that was easy to tune and drive.
It would be a nice bracket race cam in a 400.
U would need a torque converter that will stall higher than stock in either.
I might use the solid version 60310 to do again.
Rearwheelmaniac Posted - 19 Nov 2017 : 11:41:50 AM

You still run the 60243? I saw in a post you had mentioned it was a big soggy in a 455. What are the stats of your car? I'm not considering for this build but I have a 455 this may work for. Thank you sir.

Bill Boyle Posted - 16 Nov 2017 : 12:34:41 PM
With pistons in place, the top of the piston is .005" below the deck, correct?

Gasket thickness between manufacturers may vary, but a good rule of thumb is .039". Ideal quench, if there really is such a thing is about .045" or a little less. So, if the piston to head clearance is truly an accurate .005", your engine quench would be .044." That's darn good.

Either 6X head will give the same quench.
Rearwheelmaniac Posted - 16 Nov 2017 : 11:11:44 AM
Last question in deciding on gasket and which heads. What quench distance do you recommend as a target. Deck is .005 but that is because the pistons require it.
Bill Boyle Posted - 16 Nov 2017 : 10:29:45 AM
The cam you already have, the 60918 with 112 LSA, 214/224 @.050", .444" intake lift, .467" exhaust lift using the 68404 springs set at 1.600 installed height.
Rearwheelmaniac Posted - 16 Nov 2017 : 07:01:07 AM
Alright. So, in your opinion, will a street car, that will probably never see the track use a 60916?'I mean it's only a few hundred RPM.
Bill Boyle Posted - 15 Nov 2017 : 9:01:15 PM
Chris--the adjustable valve train Mark speaks of works with roller rockers or stamped OEM style rockers whether they are 1.5 or higher. The rollers are designed to be more accurate on the lift when one is trying to gain that extra few pounds of torque and hp. For a mild street engine, stamped steel works just fine. Stamped steel and poly lock nuts go together and there's really no reason to go overboard with large diameter ARP studs. If using the 60918 the lift isn't so great that it puts lots of stress on the studs. When lift is over .500" that's when larger diameter studs and increased valve pressure and installed height change the equation.
Rearwheelmaniac Posted - 15 Nov 2017 : 12:20:49 PM
Thank you both for the response. MadDog is building me a set of headers next month, I guess they stopped making pontiac G body headers because they were too time consuming, when they could be making other headers. They agreed to take a few custom orders during the slower season, so those added with nice flowing pipes should work well. I just planned on static of 9.5, was gonna have 6x8's trimmed to 98,but then stumbled over a set of 4's. So its one or the other. I dont wanna use a cam as a crutch for too much compression, but I dont have 3o yrs of exp and I want a solid, usable motor with no regrets. I have the 918, but wanted input on other options as well. I understand Dynamic Compression a little more now, and realize thats what I should have been using to put this formula together. Do you guys have a "limit" to DC or Cranking compression that I could use (or you could recommend) as a target as I finish this build?

With the info you gave on an adjustable valvetrain actually answered alot of questions for me. Now I will ask, is it imperative I use roller rockers? or could I move forward with the stamped 1.5's? If I use the stock 1.5's do I still upgrade the studs due to lift? if so What Locks do I use at that point?
Bill Boyle Posted - 15 Nov 2017 : 09:48:13 AM
Chris--the Crower 60918, in a mild 400 build should easily run on 93 octane gasoline. It's built on a 112 LSA and will have plenty of vacuum for power brakes. I don't think you'll be disappointed with the performance on the street-highway with 6X-4 heads and tuned exhaust.
Blued and Painted Posted - 14 Nov 2017 : 11:48:26 PM
The 918 looks like it a mild up grade over stock and could possibly use stock valve train components . The hi DCR number could make it fuel /spark knock sensitive. But should be fairly easy to tune for good drivability.
The 916 starts to enter the race category with its longer duration. Your rear gear and compression ratio would match up better with this cam. Some carberator mods may be needed for driveability. Hard to predict how the power brakes will react. It's not a huge cam so vacuum may be ok??

A fully adjustable valve train is advised. Aftermarket cams May use a different base circle diameter creating valve lash headaches.
6x heads usually have screw in rocker studs so an upgrade to the larger 7/16" stud is easy. But not cheep when talking new roller rockers and correct length push rods.

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