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Pontiac 350 Motor/Intake Manifold setup question

15K views 20 replies 7 participants last post by  LATECH 
#1 ·
I have a 1969 Pontiac 350, TH 350 automatic transmission, Pertronix ignition module inside the original distributor, a mild Comp Cam, bored .30, Edelbrock 650 4bbl carb mounted on an Edelbrock RPM Performer manifold, original exhaust manifold, dual 2.5" exhaust.

I was told this setup would be good to go and now I hear from a few different people that my "RPM" Performer will make my car a dog at the lower 0-2000 rpms. They said I should get the Performer intake not the RPM version and that will give me more torque at the lower end and for an automatic car.

What are your opinions on this? Did I screw up and get the wrong manifold?

I hate to hear it because the 69 convertible Firebird just needs an interior and top. I hate to take a step backwards.

Please let me know your thoughts...I can take it!

SAM
 
#3 ·
Sam, while I have to agree with Mr. Creech because he's one of the resident Pontiac experts, I am of the opinion that you have installed the correct manifold . The RPM will make more power from 1500 to 6000 than any other manifold you could bolt on the motor, in my experience and opinion.

And just for grins and giggles, let me ask you.....when is the last time you needed killer power under 1500 rpm's??????????:eek::rolleyes::smash::(
Tell these "few different people" to get their sheets together or shut the hell up.
 
#4 ·
Good question. I just want some good low in torque off the line. I also don't plan on changing the carb. I haven't even tuned it yet and it hums right out of the box. I was just worried because of the comments that I should swap my RPM for a stock four barrel manifold or the plain Performer.

SAM
 
#5 ·
If the cam you purchased recommends a higher stall speed converter than stock, you would be wise to use it.
If the cam says it pulls from 1300 and up, the stock would be OK.
Choose a converter with an estimated stall that is 200 rpm higher than the low end of the cams power band. LA
 
#7 ·
How does it drive? Pontiacs produce a bit more low end torque then a same size Chevrolet engine. Bleeding off a little low end torque usually isn't an issue with these motors if they are built right. Just helps them hook better...
Mark
 
#8 ·
The difference between the Edelbrock Performer RPM and the Performer manifold on a 350 CI Pontiac engine will not make any significant difference in overall performance. What little difference in performance that you will notice with a 350 CI Pontiac engine above 3,000 RPM is not worth the effort and cost it will take to change manifolds.

A Performer manifold is a replacement for a stock manifold. The Performer RPM manifold is more suited for a 400 CI Pontiac engine that has a better bore/stroke ratio and can take advantage of the short runners and larger plenum area at high RPM, as the name suggests. However, it will not operate as well at low RPM and in normal driving.
 
#9 ·
In fact, the RPM is not well-suited to the 350 Pontiac. Performer is much better. RPM is the "red-headed stepchild" of Edelbrock intakes for Pontiac. The 400 is about the only engine size that really benefits from it. The runners are too large for the smaller bore 350, and the low-end "rush" is too much with the longer strokes. This is one of the many differences in how to approach a Pontiac versus a small or big Chevy.

Conversely, Performer is no better than the cast intakes Pontiac put on there in '69, as Bill and Lynn have pointed out. But the factory intake requires the use of Q-Jet or a really good "spread bore". Adapters on these intakes are verboten. Performer will work well with your 650 E-carb.

It would be really helpful if you elaborate on the cam. "Mild" is not a good description. Numbers, please.

350 Chevy will rev to the moon. 350 Pontiac makes significantly more torque at lower RPM. 350 Pontiac is not a good revver. That's what 400s are for... :)-

Jim
 
#14 ·
You would be better off to run the 51-221-4 .
It would keep your dynamic CR down enough to run 87 In My Honest Opinion.
It is about the biggest you can run with catt wizz gas,tall gears, stock converter and 350 cubes .
Bigger cubic inches need bigger cams. Dont over do it on cam choice.
I agonized over my cam choice for almost 9 months before I finally chose th exact one. I had originally 3 different ones in mind.
 

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#15 ·
I agree with Lynn. XE256H is a very good cam for both 326 and 350. Building a 326 right now using that one. Will also use Performer and a 650 E-carb. Figures to make around 300 HP and 400 lb. ft.

The old Magnum grinds (what you list) are basically similar to Chevy small block grinds popular in the '80s. They've been obsolete for some time now. Pontiacs ALWAYS "like" a dual-pattern grind (more duration and/or lift on the exhaust side).

Jim
 
#16 ·
Well, we will have to see how it all works out. The engine is built and installed. I only have the top and interior left to do. I have done everything on the car except the motor. I was recommended this cam by Summit Racing. I live North of Atlanta and that is what they recommended. I bought everything at one time and figured it would work because they deal in this everyday and I don't.

Any idea on what it costs to change out a cam if everything else is newly built?

I really hate taking steps backwards in a build. So I may just have to see how it all works out.

SAM
 
#17 ·
Better put a 2500 or 3000 stall in that bad boy if youre gonna run that cam.
You wont like it trust us. We arent a saleperson trying to sell you something. All of the guys here have built engines (especially P Body ) and we know what works.
You want to take a step backwards..put that cam in . Big step backwards next.
Do what you want. Easy to change the cam now...later...not so much
 
#18 ·
I guess it is too late now. The motor is in the car. Everything engine and transmission related is complete and working good. I just don't have a windshield or top and interior. So to change the cam now has got to be expensive. That is why I was curious on what it would cost.

SAM
 
#19 ·
Ok. Well get it running and greak in the cam. See what you have at this point.
If youre dissapointed in the low end /take off performance , that big cam will be to blame.
Like I said you could put a higher RPM stall converter in it. Which would be a quick round trip , pull the trans, swap converter and reinstall.
See what you get. Let us know how she turns out.
 
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