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Discussion Starter #1
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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Discussion Starter #2
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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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. :cheers
 

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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 :(
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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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.

Bear
 

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Discussion Starter #6
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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Why should I chose a Holley instead of the Edelbrock?
Oh my, that question has started wars and toppled governments... :D

(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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Discussion Starter #9
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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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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Discussion Starter #12
This gas milage sounds pretty good, would be nice but I can surely tolerate to burn more fuel if it gives more power :)

Lets say if I try to use all parts from Edelbrock... is 650 or 800cfm better? I guess 650cfm is not big enough... and will the performer manifold provide better low end torque than the performer rpm? I won't get over the 5500rpm very often and if I do, will the performer manifold be much worse than the performer rpm at my max. of 6000rpm?
 

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770 CFM is going to be marginal on your engine, in my opinion. I think it'll be happier with something around 850 (or so). As far as fitting, generally there are two kinds of carb bases: spread-bore where the front barrels are small and rear ones large (like the QJet), and square-bore where all 4 are the same size. Within those two families, they pretty much all have the same dimensions (except for the giant Holley "Dominator" series.)

I wouldn't give up on the tri-power just yet though. Now that you know it's very lean at idle, now you've just got to figure out how to convince it to pass more fuel through the idle circuits. I did a quick Google search and found this link:
Services | Pontiac Tripower

Notice the part where he says:
"I modify the carbs to your needs. For example, if you are running a 455 and using a tripower that started life on a 389, the idle circuits need to be opened up, and jets need changed. With a radical cam, the power piston may need modification."

Sound to me like that's almost exactly your problem.

The good news is, this is a problem that other people have seen and it has been solved before. All that remains is figuring out what to do about it.

The same site has a DVD that might just have the information you need:
DVD Tripower Basics, Mods, and Troubleshooting | Pontiac Tripower

There's also a discussion with information here:
Pontiac Street Performance - Tripower with KRE heads: Electric choke???

Keep cool, it's just an engine - all it needs is a proper volume of air and fuel in the correct proportions.

Bear
 

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Agree with Bear about this site. I got his DVD for my Tr-power set-up, as I was not very knowledgeable when it came to Tri-power carbs. I also got his phelonic spacers for my Tri-power and it cured some problems that I was having.

The owner of PontiacTri-power.com is very keen and friendly to deal with. He really knows Tri-power set-ups. I would think for the price of a long distance call or email, you could get some good answers.
 

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Discussion Starter #16
I have some new questions :)

1. What do you think of the Holley Ultra Double Pumper and the Holley Ultra Street Avenger? The difference isn't big.. one has mechanical secondaries and the other vacuum secondaries and I was told the mechanical version is the better choice for my engine (but will need more fuel.. I don't care about that).

2. I want either the Performer or the Performer RPM intake. If I choose the std Performer and use a spacer (0.5-1") I can make sure not to run into clearence issues and if I watch the simulation of my engine my max hp is at 5550rpm, what would fit into the power range of the std Performer. Probably the Performer RPM will give more power at mid range but I'm pretty sure it will lose some power down in the rpm range because it has bigger intake runners. On the other hand if I now try the std. Performer and feel that there should be more power at mid-high rpm's I can change to a Performer RPM later and keep the carb. I'll see if my driving style changes now with the rebuild engine plus if I first use the std. Performer I can check the clearance very easy to make sure the Performer RPM would fit if I decide to change..

3. Are you sure 770cfm is marginal if I don't rev the engine up to more than 5600-5700rpm? The Holley calculator says 750-800cfm depending on the secondaries type and what they have available with electric choke.

4. What is the rpm range of the tri-power? Because I think it doesn't look like a high rise manifold. Is it taller than the std. Performer or has bigger intake runners?

5. I decided to put the tri-power into storage for now.. I know many things now that might get it to work with my engine, but I cannot find someone who will adjust it to my needs. They are afraid of it and have no experience, so if I spend even more money for the tri-power and something won't work like in theory it might be damaged and I don't want to risk that. The rebuilded carbs would need another rebuild and testing, working, adjusting... would cost me more than a new intake and carb. The mechanic who will do the job told me he has very good experience with the Holley Double Pumper and has build some Pontiac engines with such carbs with very good results. I really like the tri-power but I need to get something that the mechanics here can adjust and are familiar with.. the best system won't help me if nobody can adjust it :(
 

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Discussion Starter #17
Hey :) I'm back with some pic's of my new Setup.. the Tri-Power was removed and is waiting for a proper rebuild. Until then I got following parts:

- Edelbrock Performer manifold (RPM would not fit under my hood, maybe if I used a pretty small filter)
- Holley Double Pumper 750cfm with electric choke

It runs great now!!! Couldn't drive it more than an hour because it's snowing now :(
I probably will use another thermostat housing and radiator hose soon, also the fuel pressure is pretty low with 4-5psi. Or do you think thats okay? Had to cut the fuel lines because they wouldn't fit.. but I'll build some nice fuel lines by my own soon.

Here are the pics:







The tri-power surely is more desireable but for now I'm really happy with the setup and in the future I'll switch to the tri-power again to see the difference. I'm curious how much it will cost me to send the carbs to the US, have them rebuild and get them back.. but I don't see another chance to get them to work like they should do.
 

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Glad to see you got your GTO up and running Chris!

We have snow here too, 13.5 inches yesterday, definitely not GTO weather.

Pics of your engine look great, very organized looking engine bay. Just get rid of that rubber line as soon as you can :willy: I know you said it was temporary. :cheers
 

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Looks nice, Chris. Like Alky said, please DO replace that rubber line asap. I'd hate for you to have to stand and watch that pretty thing burn to the ground...
:(

5 psi might be a little on the low side, but the real test will come when you have an opportunity to really run the car hard through all the gears. If there's not enough fuel to keep it fed, it'll be pretty obvious. :D I wouldn't fiddle with it until you know for sure it needs fiddling.

Bear
 
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