Pontiac Street Performance
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password

 All Forums
 Pontiac Performance
 Cams / Heads & Valve Train
 More mismatched heads
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  

davidwyby
Tribal Scout

14 Posts

Posted - 17 Apr 2017 :  8:42:38 PM  Show Profile  Reply with Quote
Hi, I just got a '71 LeMans with a recently rebuilt 350, about '73 I think based on the numbers. I did a compression test because I couldn't get it to run very well and discovered one head, number 17, cranks about 160 psi and the other, a 46, 180. I pulled them off and CC'd them and the 17 is 80cc and the 46 is 76cc. Both date codes end in 8. Both have 1.96/1.66 valves. I am not an engine machinist but run a general machine shop. Where can I measure the heads to determine if they've been milled?

Also, I haven't been able to find flow numbers for them. Thinking about trying to make them work if it's feasible, but I know it's not recommended. I want to wake the engine up a bit and daily drive it. Probably a mild XE comp cam on the recommendations I've seen for them by Mr P-body. I'm know I should probably look for a matched pair of heads. I have a line on a set of 16s and 13s which both should be 72cc and help get my compression up a little. Pistons .030" over zero deck. Any and all advice is appreciated, I'm new to Pontiacs, doing my best to learn as much as I can.

Edited by - davidwyby on 17 Apr 2017 9:40:24 PM

davidwyby
Tribal Scout

14 Posts

Posted - 17 Apr 2017 :  10:45:45 PM  Show Profile  Reply with Quote
I found a thread where Mr PBody said the 350s actually like the smaller valves because the larger ones get close to the cylinder bore. Thoughts? I have a line on a set of ready to run 13s, 2" intake, 72cc for a good price.
Go to Top of Page

Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 18 Apr 2017 :  1:27:48 PM  Show Profile  Reply with Quote
4 cc's could be within standard deviation of an average rebuild valve job. Check left and right piston to deck height. Could be a substantial difference. Then we could confirm the 9 to 1 compression at 76 cc's.
Yes there is a lift limit for the big valve head. I dont recall the number. Yes flow is disrupted with the small bore size and large valve heads.

There have been many complaints of annoying valve train noise with the comp cams. Test show they can make good power but in a narrow rpm range.
The VooDoo and Crower off the shelf cams have had some positive reviews.

Significant power gains can be made with fine tinning of the distributor advance mechanism, the 750 cfm Q-jet, and the exhaust system.

Mr Cliff was surprised how small the power loss was, when some small valve heads were substituted on a known race engine combo he was involved with.

Tell us more about your car.





Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 18 Apr 2017 1:48:32 PM
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 19 Apr 2017 :  01:25:42 AM  Show Profile  Reply with Quote
I'm working on uploading pics. 3 spd auto, 3.08 10 bolt. Goal is fix the AC, it's hot here and have a strong daily driver. It was running pretty bad when I got it. Lots of stuff out of adjustment. I cleaned out the Edelbrock 1403 carburetor and converted it to HEI ignition, new wires and everything. Parts from Oreilly, should have gotten DUI or something. Having some run-on and long cranking when hot, need to work on that, maybe colder or non projector plugs. Had an exhaust leak at the heat riser, planning to block that. I just found out that cruising grand is Pontiac night this Friday so now I'm going to try to hurry and put it back together. Even out the combustion chamber CCs. Anyone have any idea if the 46 and 17 are otherwise the same? The combustion chambers are slightly different.
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 19 Apr 2017 :  01:29:48 AM  Show Profile  Reply with Quote
http://s142.photobucket.com/user/DavidWhymore/library/LeMANS
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 19 Apr 2017 :  01:39:00 AM  Show Profile  Reply with Quote
Planning to change out the wheels and tires, meaty BFG T/As on 15s. Of course, eventually, paint it.
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 19 Apr 2017 :  01:39:30 AM  Show Profile  Reply with Quote
Can this forum be configured to notify if replies by email? Thanks
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 19 Apr 2017 :  3:22:17 PM  Show Profile  Reply with Quote
[URL=http://s142.photobucket.com/user/DavidWhymore/media/LeMANS/787E40CD-AB9E-4B89-9927-E919998EF41A_zpswengoegg.jpg.html][/URL]
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 19 Apr 2017 :  3:23:00 PM  Show Profile  Reply with Quote
Thanks so much for the help! Been banging my head against a wall.

I posted on Wallace Racing's FB page, and he thinks they're similar and good to go by matching. Here's a better pic.

I think I'm going to open the chamber on the 76cc #46 head, and maybe polish off some sharp edges to reduce hot spots, area B, but I'm afraid that may introduce a head gasket leak there...?

Where would you suggest taking the meat out? I'm thinking A and/or D seem likely candidates.

The smaller chamber is slightly deeper, but has more metal inside the gasket at area C.

Looks like these heads have hardened exhaust seats installed.

Thanks again!
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 20 Apr 2017 :  01:48:38 AM  Show Profile  Reply with Quote
Thanks so much for the help! Been banging my head against a wall.

I posted on Wallace Racing's FB page, and he thinks they're similar and good to go by matching. Here's a better pic.

I think I'm going to open the chamber on the 76cc #46 head, and maybe polish off some sharp edges to reduce hot spots, area B, but I'm afraid that may introduce a head gasket leak there...?

Where would you suggest taking the meat out? I'm thinking A and/or D seem likely candidates.

The smaller chamber is slightly deeper, but has more metal inside the gasket at area C.

Looks like these heads have hardened exhaust seats installed.

Thanks again!
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 25 Apr 2017 :  01:43:47 AM  Show Profile  Reply with Quote
Did I say something wrong? Lots of reads and no replies... :-/
Go to Top of Page

Admin
Ye Olde Webmaster

844 Posts

Posted - 25 Apr 2017 :  05:46:30 AM  Show Profile  Reply with Quote
Did you say something wrong? Not that I know of.

It's not unusual for people to read what a person posts but not jump in and reply to that post. There are many reasons for it and it's something that I've seen over the past 20 years or so monitoring this website and forum.

The different size of your two heads, may not be troublesome for most, however, I find a 4 cc difference to be something I'd want to personally fix by finding a head that matched one of the chamber sizes...probably the 76 cc, 46 head. Simply grinding a bit of metal from the smaller head to make it close in size to the larger one could change the efficiency of the head. Consequently, I'd be reluctant to try it. You should be able to find a sole 46 head to match the one you have.

"Dedicated to keeping the classic Pontiac engine alive."

Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 25 Apr 2017 :  09:32:09 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Depending on your goals with the car, it wouldn't bother me as a driver or a driver i was going to sell after a couple years. But, as all these projects go, once the heads are off, you might as well...

Next thing you know, 20k resto project :)
Go to Top of Page

Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 25 Apr 2017 :  11:30:37 AM  Show Profile  Reply with Quote
If 4cc's leave's your sleepless, you may be able to find a single matching head on E-bay for not allot of money.
If some extra car budget shows up, a new pair of Edelbrock or Kauffman heads could be an option.



Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
Go to Top of Page

DanM
Buffalo

80 Posts

Posted - 28 Apr 2017 :  10:32:14 AM  Show Profile  Reply with Quote
David,

I can be wordy sometimes then disappear for weeks, so here you go.

I am not a machinist but I've smashed my knuckles loosening plenty of bolts. That should count for something. Here are a couple thoughts.

If you put much time and thought into the rebuild then you should not bother with the 350 and get a 400. Almost all the rest of the engine parts will swap over (ex manifold, int manifolds, brackets, distributor, timing cover, rocker cover, etc.) You'll be very happy with the results without a ton of money.

Meanwhile, if you want to get this thing back on the road quick then just clean up the heads, eliminate gross problems and put on the miles.

Re: gross problems. 17 and 46 heads the same? Hmm. Wallace website itself shows the 17 as 1968 and 46 as 1969 or 73-74. You said the date codes are the same. Ok so maybe they are from 68/69. Between 68 and 71 there were changes in the accessory mounting brackets. The previous owner must have run into this problem and got new brackets where necessary. If you decide to get the correct year heads then this may pop up on final assembly day.

Re: gross problems. 4 cc difference in chambers. sounds fine to me. Other people here think so. Don't sweat it. But I'm not an expert on this. Heck, I've built up at least 4cc of carbon crud on various cylinders. No way the engine even can tell.

If you are unsure where to machine away metal in the chambers you might consider reading Jim Hand's book. It talks about a few key locations to remove metal in order to improve flow. The goal is to keep the heart shaped chamber if possible while eliminating shrouding of the intake valve and cylinder wall. But consider this effort an adventure without any ability to confirm your results. (see previous paragraph.)

Finally, it looks to me that your exhaust valves have dug themselves into the head. It's kind of hard to tell from the photo. That could be the source of your poorly running engine. Are you burning oil? Do all the tops of the valves line up perfectly at the same height? If the exhaust valves have worn into the head those tops will be higher than the intake valves. This has happened to me even in 71 heads that have hardened seats. They're only surface hardened. '68/'69 you have nothing.

My advice? Since the heads are off and a replacement set is actually quite cheap on the web I suggest getting a pair for $150 that match and are correct for the year or at least '71 or later. Spend another $500 to recondition them with no effort for high performance short of a slight boost in CR by milling off "0.050 off the head surfaces. (Then take an equal "0.050 off the intake manifold surfaces.) Make your goal to have the engine run quietly when all done.

Then plan a rebuild for the entire engine in two years. Spend $4000 and be amazed with the results. Reuse the new heads on the 400.
Go to Top of Page

DanM
Buffalo

80 Posts

Posted - 28 Apr 2017 :  10:42:12 AM  Show Profile  Reply with Quote
some flow numbers. Don't compare from one site to the other. Flow bench setup will affect absolute values. Relative values from head to head should be more accurate though.

http://ronspontiacpage.com/reference-pages/stockflowcharts.htm

http://users.erols.com/srweiss/tablehdc.htm#Pontiac

note the SD Performance version of the 17 and 46 heads. Lot's of porting and bigger valves. Still quite a difference in flow. Stock is most likely around 200 CFF at 0.500. They were designed for low lift high flow which is great for low to mid RPM engines that last forever. The smaller valve heads will flow better at low lift and low CID engines for low-mid RPM. No real HP but good torque.


71 LeMans Sport Convertible with 310,000 miles driven year round since 1994.
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 30 Apr 2017 :  01:40:55 AM  Show Profile  Reply with Quote
Gents, thanks for lending your input! Sorry I had forgotten to keep up with checking on this thread.

Current plan is to take .020" off the 80 Cc head and bring CR to 8.89. Both heads are indeed 8 date code.

Not doing a 400 as this 350 was just rebuilt and it and car was free. Goal isn't max speed or hp, just the most power I can get from what I have and hopefully efficiency and longevity. Initial motivation was to see how close I can get to modern a V8 without buying aluminum heads with heart shaped combustion chambers. Trying to keep low and midrange power and keep torque and a widish power band. Been playing with CamQuest, studying 350 builds and Pontiac builders a lot, and talking to some. Also been reading various charts and articles on choosing a cam. GrumpysPerformance has lots of reading.

Planning to ditch the '73 smog cam and install Comp's smallest off the shelf hydraulic roller cam, which may seem like overkill for "just a 350", but it fits my goals well, I think. XR264HR. "Good for daily, strong torque". 1000-5000 rpm. 212/218@.050" .487"/.495" lift. 110LSA.

CamQuest and Mr. P-body's software put this combo at just over 300 hp at 4500/5000? and 400lb/ft -at 3000-3500 RPM depending on carb size.

Also doing roller rockers, screw in studs, and springs of course.

I'm still all ears. I considered lunati but their smallest cam is a little big so I ended up back at Comp.
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 30 Apr 2017 :  01:42:04 AM  Show Profile  Reply with Quote
Valve stems are even across the top, seeming to indicate good seats. They'll come out and everything will be checked of course.
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 30 Apr 2017 :  01:46:18 AM  Show Profile  Reply with Quote
Appears to have hardened seats and all was rebuilt 1 yr ago, and then mostly sat since. Poor guy wasn't very mechanical and got tired of throwing money at it.
Go to Top of Page

DanM
Buffalo

80 Posts

Posted - 02 May 2017 :  11:43:32 AM  Show Profile  Reply with Quote
Hi David,

I considered a roller cam with my recent rebuild and decided to stay with flat tappet. The issue that worried me is the springs' ability to follow the aggressive lobe. I had already picked decent springs (comp cams 995) and was still advised by a builder to be careful about the "seated" spring force. I think those springs could have worked but I was more interested in revving to 6000 to get 30 more HP than to use a roller to gain 6 more HP. Revving to 6000 with a roller seemed asking too much.

Also, there is a way to use Ford, I think, hydraulic lifters and a special guide plate and they drop right into the Pontiac block with very little effort. CVMS can advise you on that.

The roller cams lobes are more square and thus more harsh on the valve train. If longevity is your goal then flat tappet would be better.

The cam with 212 at 50 is what I use. I'm very happy. Great idle. Great mid range. Great top end. I could have gone to 218 and had another 6-8 HP at the peak but the average from 3000 and above wasn't any better. All my, theoretical, HP gains are due to mild porting and revving above 5000. (according to Engine Analyzer v3.4 free trial download.)

I'm expecting 320 HP at the wheels and will confirm in two weeks at the dyno. I would love to hear how your roller cam works in case I choose to go that route in the future.

Another consideration. If you plan to let the transmission shift on its own at the stock 4000 then there is no benefit with using a roller cam. The benefits for an aggressive cam occur above 4500 rpm. And even if you manually shift at 5000 you still spend most of your time between 3000 and 4500. So the average HP is not changed much.

I'm currently in the process of changing the modulator on my transmission to shift at 5500.

Wow I can talk a lot sometimes...

71 LeMans Sport Convertible with 310,000 miles driven year round since 1994.
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 02 May 2017 :  2:33:16 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I am not a fan of the comp springs, the ones they speced for my XE284 were way less at the seat than they claimed (like 30 lbs too light.) Others have observed the same.
Go to Top of Page

davidwyby
Tribal Scout

14 Posts

Posted - 09 May 2017 :  11:41:56 AM  Show Profile  Reply with Quote
My springs and some of the other parts are Liberty Performance Components. Hope they're good...?

How much benefit do you guys think there is to plugging the cross feed communication between the two center exhaust ports? I'm stock manifolds for now, maybe HO/Ram Airs later.

Thanks

Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 09 May 2017 :  11:55:17 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Probably nothing measurable in a street engine. Most do it to keep the manifold floor cooler, but honestly after awhile, the whole thing evens out anyways. In fact, when i separated my water crossover to keep it from soaking heat into the intake, the intake was WARMER than the crossover! So, i would guess the water crossover helps cool the intake.
Go to Top of Page

DanM
Buffalo

80 Posts

Posted - 11 May 2017 :  09:38:16 AM  Show Profile  Reply with Quote
Cortcomp, that's very enlightening info about the water crossover. Now I can stop agonizing about whether to separate it or not. I'm solidly in the "not" camp now.
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 11 May 2017 :  10:05:28 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Yeah i was surprised when i measured it. It was on a car that would run steady 210 degrees, hot or cold out, ac or not, it would just climb and sit exactly there. That's when i did the measurement. I found later i had the timing too retarded. I went from 10 or 12 degrees to 16 or 18, and it dropped to always run 190 degrees. Was like magic. I measured it then too. When it was up to temp, the water xover was, as i recall, about 20 degreesish cooler than the intake. You could touch it and tell the difference too. I would have thought the opposite honestly, that it was heating the intake.

1 car and measuring twice isn't really good science, but i'd be curious what others that have it separated could report with a laser temp gun. does make chasing down bad lifters easier, still had to pull the dist though to get the lifter cover off. I swear in EVERY set of lifters i buy, 1 or 2 is lazy or bad.
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
Pontiac Street Performance © 2006-2017 Go To Top Of Page
This page was generated in 0.21 seconds. This Site Sponsored By:
Powered By: Snitz Forums 2000 Version 3.4.05