new intake manifold and carb for my engine - Pontiac GTO Forum
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post #1 of 28 (permalink) Old 03-09-2013, 09:19 AM Thread Starter
 
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new intake manifold and carb for my engine

Hi!

I'm thinking of a new manifold and carb instead of the tri-power. If we cannot fix it, I don't want to wait forever until someone can rebuild my tri-power.

The question is, if my mechanic cannot repair it, which combination would be good for my new engine. I have now a 435cui with E-heads, headers, msd distributor, raiv4 cam... So I guess the 1500-6500 rpm performer dual plane intake manifold is the best choice. Carbs are 650 or 800cfm and I guess the 800cfm would be best. What do you think?

I want good power at low rpms and really good power at mid and high rpms. Nice throttle response and not the worst fuel economy would be nice too. But I don't want to lose power because of less fuel economy... dosn't matter that much.. best power and throttle response are most important.

Thank you!
Chris
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post #2 of 28 (permalink) Old 03-09-2013, 10:38 AM Thread Starter
 
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What I also need to know.. do I need new parts to connect the throttle (gas pedal) to the new carb or will the old one from my tri-power fit? Don't have any experience with that
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post #3 of 28 (permalink) Old 03-09-2013, 01:46 PM
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I'm gonna say Performer RPM (since you have the E heads) and a 750 Holley. Good all around set up and if you switch back it will be easy to resell if you want to.
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post #4 of 28 (permalink) Old 03-09-2013, 01:49 PM
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Originally Posted by Chris-Austria View Post
What I also need to know.. do I need new parts to connect the throttle (gas pedal) to the new carb or will the old one from my tri-power fit? Don't have any experience with that
Honestly you'll just have to have it all on there to see. The RPM is gonna be taller than the trips ( Have to look for hood clearance too!) so that might make up the difference. Lokar makes some nice adjustable cables that you can use also. Summit has em.
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post #5 of 28 (permalink) Old 03-09-2013, 02:08 PM
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You've got several options. If you want to avoid the chance of hood clearance problems, then you'll want to go with a manifold that was supposed to be a direct replacement for factory manifolds (or some version of a factory manifold). Something in my head just tripped... are you SURE your tripower manifold is completely covering the intake ports in the heads? I was running a port-matched factory iron intake with my Ram Air IV's and it fit, but just barely. When I put on the ported E-heads, there was no way. The factory intake didn't come close to covering the ports on the new heads so I had to use a different manifold. I wound up using an old Edelbrock Torker-I because it's what I had available, it's a direct replacement for the factory manifold (all the accessories and even the ram air system still line up correctly), and it was tall enough to cover the ports on the new heads.

Anyway, other options for you would be a reproduction factory aluminum Ram Air IV manifold or a Torker-1 (both of those accept spread bore QJet carbs). I think the Edelbrock performer (not the RPM) might also be a direct replacement but I'm not sure.

In terms of performance though, on your engine, none of the aftermarket manifolds are going to run quite as well as the factory ones if they've been set up correctly.

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post #6 of 28 (permalink) Old 03-09-2013, 02:25 PM Thread Starter
 
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I didn't ask the engine builder if the intake manifold fits the heads perfect. His job was to make it fit and I hope he did I'll contact him!
I now have the stock tri-power manifold and the rather high tri power carbs. The ram air pan and seal is about 2" high and it touches the hood like it is supposed to.

I didn't think that the Edelbrock intake may run worse than my old tri-power intake. If I chose the performer intake (idle-5500rpm) do you think this would also match my needs with the engine's camshaft?

Holley sells lots of different types of carbs, I don't have a clue which one to chose. The Edelbrock Thunder AVS looks nice to me, but I have no experience. Why should I chose a Holley instead of the Edelbrock?
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post #7 of 28 (permalink) Old 03-09-2013, 02:56 PM
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Originally Posted by Chris-Austria View Post
Why should I chose a Holley instead of the Edelbrock?
Oh my, that question has started wars and toppled governments...

(Seriously, the "best carb" question tends to generate lots of "passion"...)

I'll do my best to be "objective"...

Advantages of Holley:
They're siimple.
They're plentiful.
Lot's of people know about them.
You can get them pretty much as "big" as you'd ever want.
Parts are 'everywhere'.
Disadvantages of Holley:
They're simple (they don't have a dedicated part-throttle cruise circuit so they tend to not get mileage as good as a more finely "tunable" carb.)
Some of them like to "eat" power valves if the engine ever backfires.

Advantages of QJet:
Precise metering (they do have a dedicated cruise circuit) so they'll give better mileage than other brands of comparable capacity.
Variable CFM - they'll pass only as much air as the engine can handle, up to their limit.
Disadvantages of QJet:
Not as simple.
Once plentiful, but good, un-trifled with examples are getting harder to find.
Upper CFM capacity of 800 CFM (some models), others are 750 CFM - may not be enough for a large displacement/high rpm engine.
Not as many people know how to properly set one up (although many people "think" they do, which contributes to good carbs being effectively destroyed).
Parts sources are drying up.

I've got no direct experience with Edelbrock carbs, but I've "heard" from others that they're hard to get set up and don't run as well as a QJet.

I'm running an 800 CFM QJet on my car and I like it a lot.

Bear

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post #8 of 28 (permalink) Old 03-09-2013, 03:45 PM
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Something in my head just tripped...

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You are truly a child of the 60's Bear.
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post #9 of 28 (permalink) Old 03-09-2013, 03:46 PM Thread Starter
 
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I found a thread "Performer or Performer rpm" manifold.. and now I start to think the Performer is better for my needs as I dont want to lose low rpm power and 5500 is about my max rpm (I think 5500-6000 will be the Limit for my combination)

A rebuild qjet would need an adapter I guess? Its just that its very simple to get a nice Holley or Edelbrock and hard to get a good qjet for me
I thought of the Edelbrock Thunder AVS 800 endurashine with electric choke.. not a good deal? Which Holley should I look at?
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post #10 of 28 (permalink) Old 03-09-2013, 06:14 PM
 
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I have an Edelbrock 800 cfm thunder series with electric choke and the performer manifold on my 474 and I like it a lot. For a street car I think they are hard to beat. The car starts on the first click of the starter, idles nice, is very responsive and gets good gas mileage (16-18 mpg if I keep my foot out of it.) It took a little experimenting with jets and metering rods to get best performance with this engine, but they are simple to change. I replaced a 750 cfm Demon double pumper that was previously on the car. The motor did have more power with the Demon but used a tremendous amount of gasoline. I'll probably get a Holly for it if I race it this summer, but for a street carb I like the Edelbrock.
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