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Old 06-19-2013, 04:54 PM
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Pontiac 350 Motor/Intake Manifold setup question

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
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Old 06-19-2013, 05:08 PM
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Sam,
Like I've told others, the best bang for the buck, on the street, would be a factory cast iron manifold. A '69 spread bore manifold and a quadrajet would be my choice.

Bill

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Old 06-19-2013, 05:25 PM
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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??????????
Tell these "few different people" to get their sheets together or shut the hell up.
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Old 06-19-2013, 07:52 PM
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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
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Old 06-19-2013, 08:25 PM
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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
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Old 06-20-2013, 03:16 AM
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I will have to check on the Stall speed for the cam. When I had the tranny rebuilt, he put in a mild shift kit and I did end up with a new torque converter. As for specifics, I am not sure.

SAM
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Old 06-20-2013, 04:17 AM
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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
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Old 06-20-2013, 06:58 AM
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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.
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Old 06-20-2013, 05:10 PM
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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
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Old 06-21-2013, 04:56 PM
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I am not sure what Information you need but here is what came with the camshaft. Also, my Carb is a Edelbrock 600 cfm.
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Old 06-21-2013, 06:16 PM
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That cam is way too big on duration for the 350. You are gonna hate it.
It will be a dog getting off the line.
You need more cubic inches, more compression, a stall converter and most likely some more rear end gear.
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Old 06-21-2013, 06:20 PM
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Comp Cams 51-221-4 would be a much better and more optimum choice for your 350.
It would do well on 89 octane and probably just as well on 87 with that cam and the rest of your build recipie.
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Old 06-21-2013, 09:31 PM
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Originally Posted by LATECH View Post
Comp Cams 51-221-4 would be a much better and more optimum choice for your 350.
It would do well on 89 octane and probably just as well on 87 with that cam and the rest of your build recipie.
Which cam are you saying would do well on 89 octane?
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Old 06-22-2013, 06:44 AM
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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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Old 06-22-2013, 09:46 AM
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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
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