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1974GP
Tribal Scout

9 Posts

Posted - 22 Sep 2016 :  9:17:03 PM  Show Profile  Reply with Quote
I have a 74 GP with a freshly rebuilt 455, .30 over. 4X heads (98cc version), completely rebuilt as well. The engine equipped as follows- Holley 750 vac sec, edelbrock performer intake, Rhoads lifters, Harland sharp roller rockers, crower 60919 cam (231 int/240 exh, .470/.470 lift, 112 LSA), speed pro pistons, stock rods (prepped), stock crank (.10 under), ram air exhaust manifolds, 2 1/2 inch exhaust with X pipe. TH400 with a shift kit, and a Neal Chance 11' converter (2000-2800 stall).
Currently I am running the car with a 3.08 rear, but I am getting a lot of heat building in the converter/trans, I believe because the rear is not well suited to this set up. I am told the converter is constantly slipping and not equalizing which causes the temp to rise. I plan on adding a tranny cooler this weekend, but I had planned on that anyway even before this problem arose.
The engine is running beautifully, with about 450 miles on it since the rebuild, and doesn't get above 190 when cruising, (I put some time in on fitting the separator plate to the impeller in the water pump that seems to really be paying off.)
I originally set out to use a 3.23 or 3.42 rear when planning the drivetrain, but came across this 3.08 in great shape this winter for a song and gave it a shot, seems not to be working out. I thought I had a converter issue, but after talking to guys from continental converters he suggested a rear end change to get the most out of the engine.
I used to run a 76 grand prix with 4.10s and then 3.73s and it rev'd like crazy, which I wanted to avoid.
My question is or anyone out there with a big car/similar combo....what gears would be better suited to my combo here and give me the most umph....3.23, 3.42, or 3.55s?

Blued and Painted
Chief PONTIAC

USA
3409 Posts

Posted - 23 Sep 2016 :  10:16:51 AM  Show Profile  Reply with Quote
Have you added an external trans cooler?
There are some internal trans mods to get more fluid flow through the converter. Mods seem to vari with builder.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Blued and Painted
Chief PONTIAC

USA
3409 Posts

Posted - 23 Sep 2016 :  10:39:58 AM  Show Profile  Reply with Quote
How will the car be used?
The 3.08 splits the difference between a hi-way and a street race gear.


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

Edited by - Blued and Painted on 23 Sep 2016 10:41:16 AM
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1974GP
Tribal Scout

9 Posts

Posted - 23 Sep 2016 :  4:40:22 PM  Show Profile  Reply with Quote
Thanks for the reply. I was planning on adding a cooler before this became an issue, prob will do so this weekend. I am still left with the converter vs rear end, which one to I change? I like the way the car goes down the highway with the 3.08s, but it is a weekend cruiser that I would like to take to the track so giving it a little more umph off the line would be great. Would I be wrong in thinking that the 3.42s would still be decent on the highway (and by that I mean spinning the converter enoug to keep it from slipping) and keep the engine in its powerband off the line?
I talked to the folks at continental converter yesterday and he said if I stay with the 3.08s he would recommend going with a 13" converter, but he thinks I would be better served by a rear end change. The larger converter would not help with speed, only with matching up to the 3.08s better.
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tjs44
Cochise

USA
413 Posts

Posted - 23 Sep 2016 :  8:11:13 PM  Show Profile  Reply with Quote
There are MANY guys running good numbers with 3.08s and that size engines!Figure out how to take care of the trans and you should be good.I really think a properly prepped QJ and factory intake would be better than what your running.JMO,Tom
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Phil
The Great White Buffalo

USA
7222 Posts

Posted - 23 Sep 2016 :  9:19:37 PM  Show Profile  Reply with Quote
What's your compression with that combo? Something tells me it's not as high as it needs to be with that cam. Also, that existing converter may be the problem.
And as pointed out by others, there are plenty of other people running 3.08 gears successfully in similar combos (with even a good quality tight 10 inch converter).
Do you have a stock 350 (preferably) or 400 convertor you could try? You may be surprised at the results vs. your current convertor.

The 3.08 is an excellent all-around gear for 455 on the street. What is your rear tire diameter?

I've never had a lot of luck with the 750 VS Holley carbs. I've used Perforner intakes over the years and found they work best on 350's and mild 400's. I wouldn't use one on anything more (CID) than that. They are sold as direct replacements for the stock intake but they are inferior. It's even apparent by a cursory look at the shape of some of the runners. They are also smaller.

Agree with Tom about the Qjet and stock intake.

If you must have an aluminum intake and Holley, at least go with the Edelbrock RPM & 750-800 mech sec Holley.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.

Edited by - Phil on 23 Sep 2016 9:22:29 PM
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Blued and Painted
Chief PONTIAC

USA
3409 Posts

Posted - 23 Sep 2016 :  11:17:26 PM  Show Profile  Reply with Quote
Neal Chance converter
http://www.racingconverters.com/



Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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1974GP
Tribal Scout

9 Posts

Posted - 24 Sep 2016 :  09:25:33 AM  Show Profile  Reply with Quote
So I'm gathering that a change in torque converter is how you guys would go? (And the tranny cooler of course) I actually to have an original 400 torque converter I could swap in, I'd be willing to give that a try first. I really do like the way the 3.08s run. I feel like the car would never stop accelerating. When I get on it at around 40, it lifts off and keeps going and going and going. I have yet to get the engine close to 5000 rpm, in fact I only came close to 4500 one time and I had to back off.
Regarding the other issues, I do have access to a stock 455 manifold, but who would you guys use to set up a QJ? There is no one locally I know of who works on Pontiacs, been tough for me to get reliable info as I've been putting this together. Those could be good winter projects for me.
The compression is around 9.5-1, and when selecting the cam I called crower and gave them all my info. The tech guy gave me the 60919, I thought it may be a little much but he assured me the 455 could handle it. I used the rhoads lifters to make sure I had good idle and vacuum, and I definitely do. Seems to be working so far.
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cortcomp
Coyote

USA
5338 Posts

Posted - 24 Sep 2016 :  09:30:06 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
When looking at trans coolers, i liked to put a big aluminum finned tube one alone the frame rail, it dissipates heat not just to the air but the frame it's bolted to sucks it out of it as well. As far as the one you'll be likely ziptying to the radiator, i've read that the "stacked" plate ones are better at their job than the "tube and fin ones".

If you're never going to have A/C, i wonder how well an A/C condensor would work, considering it's larger and would be able to be easily and sturdily mounted usually without touching radiator?

anyways,

frame heatsink cooler:
https://www.summitracing.com/parts/der-13256?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-derale-cooling-products&gclid=Cj0KEQjwyJi_BRDLusby7_S7z-IBEiQAwCVvn9O32QcbpYErJx2yx1of6n4kiVB5MzJurGGMWCHshMkaAujI8P8HAQ

stacked plate style cooler:
https://www.summitracing.com/parts/der-51910/overview/
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tjs44
Cochise

USA
413 Posts

Posted - 24 Sep 2016 :  09:58:29 AM  Show Profile  Reply with Quote
SMI can do a QJ for you.The owner Sean owns and drives a pontiac.He has done many carbs for me,in fact he is restoring a RA V carb for me know.He is in huntington beach ca.Search SMI.Tom
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Blued and Painted
Chief PONTIAC

USA
3409 Posts

Posted - 24 Sep 2016 :  10:18:20 AM  Show Profile  Reply with Quote
Stock converter is not a good match for the ra4 camshaft.

3.42 or 3.55 should give plenty of tire smoking And keep the engine closer to the camshaft power range.



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

Edited by - Blued and Painted on 24 Sep 2016 10:21:38 AM
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1974GP
Tribal Scout

9 Posts

Posted - 24 Sep 2016 :  10:39:47 AM  Show Profile  Reply with Quote
One other thing, when I called crower for the cam recomendations, I had told them that I was planning on using either 3.23s or 3.42s. That is prob had a lot to do with why they said the 60919 was a good fit. I came across the 3.08 for next to nothing and decided to give it a try, which is why I am where I am now. Learning as I go is sometimes costly I guess.
I want to thank all you guys for the input. It's much appreciated and give me a lot to think about. I'm kind of leaning on the gear swap at the moment. I did one on my own in the garage back in the day with good results so I may try it again here. Been quoted 400 from one shop and 600 from another just in labor alone to set up the rear.
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Tub
Sitting Bull

172 Posts

Posted - 24 Sep 2016 :  11:34:42 AM  Show Profile  Reply with Quote
"... Been quoted 400 from one shop and 600 from another just in labor alone to set up the rear..."

Talk to some of the drag racers in your area. They will know who can do the gears correctly, for a reasonable price.


"...Stock converter is not a good match for the ra4 camshaft..."

We ran RA4 cam/ Rhoads, with stock converters, in several bracket cars. Used 3.55, 3.64, & 3.73 gears. Had a 750 Q-jet in all of 'em. Launched from an 800rpm idle. Ran high 1.60 & low 1.70, 60ft times.

Ran the 72-75cc heads. Don't know how much difference the lower CR would make. ?

Tried one of these cars, with hard street tires, on a rural black top road one day. Nothin but smoke and rear end walkin. Ran 13 X 30 slicks on the track. Still had traction problems on slick tracks.

Edited by - Tub on 24 Sep 2016 11:48:14 AM
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1974GP
Tribal Scout

9 Posts

Posted - 24 Sep 2016 :  3:22:24 PM  Show Profile  Reply with Quote
Here's a few pics of the project so far. It's a 74 with the nose from my first car, a 76 GP.

http://s769.photobucket.com/user/rlaporte207/library/Grand%20Prix
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RayK
Cochise

USA
925 Posts

Posted - 27 Oct 2016 :  06:25:36 AM  Show Profile  Reply with Quote
I had a 74 GP for quite awhile years ago with a similar combination as you are running, except it had 3:23 gears and a 400 converter in it. I loved it. The only thing I wanted to do was get rid of the Performer intake and Holley, which I did, and it had the Q-Jet and iron intake and it "felt" better. I ran a 1970 iron intake with a 76 Q-Jet. I ran casting #62 heads though so the compression was up higher, which worked better with the RA 4 camshaft. As far as the trans cooler, I ran mine right up against the radiator with a mounting kit (not tie wraps) that really worked well and never had a heat issue. We can build you a really nice carburetor for it at Cliffs high performance. Call the shop to discuss if you want. 740-397-2921.

1969 Firebird 461, #62 iron heads, Comp roller, Performer RPM, Q-Jet Turbo 400 w/ Continental converter. GM 8.5" 10 bolt with 3:73 gears.11.50's@ 119+ MPH
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Phil
The Great White Buffalo

USA
7222 Posts

Posted - 27 Oct 2016 :  4:43:02 PM  Show Profile  Reply with Quote
Cliff seems to be caught up right now if you want to get a Qjet reasonable fast.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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RayK
Cochise

USA
925 Posts

Posted - 27 Oct 2016 :  7:14:36 PM  Show Profile  Reply with Quote
Yes, we are pretty well caught up. A couple restorations but thats the only time consuming projects. Most are simple rebuilds or bottom plug repairs, heli coils, etc.

1969 Firebird 461, #62 iron heads, Comp roller, Performer RPM, Q-Jet Turbo 400 w/ Continental converter. GM 8.5" 10 bolt with 3:73 gears.11.50's@ 119+ MPH
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