[Zooguy]

I got a 66 star chief executive 389 2barrel carb

I found a 1966 Bonnie at the junk yard and it had a 66 4barrel intake manifold. I snagged it thinking it could be an upgrade for my car. Any one know what kind of power I could get with this intake manifold?

[61-63]

There are too many variables to know for sure but McCarthy's book says a '66 389 2bbl big car originally had 256 or 290hp depending upon transmission and compression ratio where the 4bbl big car car had 325 or 333hp.

[sdbob]

I'm not sure of that. I had a 1965 421. Initially had a cast iron stock 4 bbl for afb carb. Then went to edelbrock aluminum for same carb. Then tried a square bore small Holley then went to PMD qjet cast iron intake with Holley spread bore. Then 1970 PMD qjet. All around performance , mileage the PMD qjet was the best for me and my abilities at the time,about25

[b-man]

Probably about 20 horsepower compared to the 2-barrel as long as you have dual exhaust.

[Zooguy]

Originally Posted by b-man

Probably about 20 horsepower compared to the 2-barrel as long as you have dual exhaust.

It's just a single exhaust but whenever I was getting the motor running again after sitting since 1993 I had a couple backfires and it completely blew apart the muffler so it's going to have to have exhaust work done on it anyways. I've read putting headers on it even the cast iron ones could be a really big project compared to the performance increase.

What size exhaust is recommended when switching from a single exhaust to duals keeping the stock manifolds?

[b-man]

The exit size on the manifolds fits 2-1/4” pipe nicely even though most were equipped with 2” pipe.

There are head pipes (or down pipes) sold that are 2-1/4” right at the manifold and after a few inches flare out to 2-1/2” from there. I have a set sold by PYPES on my Le Mans exactly like that, they’re probably the best way to go for a good flowing exhaust while retaining the stock exhaust manifolds.

Any good exhaust shop cam fabricate them as well, I made a set myself many years ago before they were available from the aftermarket.

Good thread on this subject:

http://forums.maxperformanceinc.com/...d.php?t=630943

[Zooguy]

Finally about damn time I got around to doing something with the car. Found the correct gaskets to block the exhaust crossover and did some electrolysis on the intake manifold to try and remove as much rust from the cast iron as I could. Picked up a carburetor and got it all bolted in ... Hopefully the gasket at the front of the intake manifold where you put in that large o-ring seal doesn't leak I didn't put gasket maker on it before installing it and I read that is as advisable.

[25stevem]

Sometimes that’s all you can do is put things on hold until the clock is in your favor!

[F ROCK]

good job on getting a factory 4bbl intake.
There is actually a bolt tightening sequence for the intake. I cant remember off the top of my head, but i think you'll set all of the bolts in the intake, hand loose, then tighten that timing cover/ water pump/ O ring before the others. Do a search on here, the info is here. Hopefully someone will chime in on that.
Manifolds are fine. Ran them on my GTO for twenty years. The Iron Ram Air headers install easily and work great if you can get your hands on a set.
I didnt like tube headers on my car.
Good luck!!

[mgarblik]

Not sure how you tightened the intake manifold to the heads. But your best chance for not having that annoying leak at the bypass O-ring is to do the following. Loosen all the intake mounting bolts about 1 turn. Then tighten the draw bolt in front of the timing case to pull the intake all the way forward and pinch that O-ring. Then tighten all the manifold bolts to specs. to the heads. If you already did it that way, your as good as you can be without sealer on the O-ring. For future reference, Butler Performance sells an O-ring that is .020" thicker than the other ones commercially available. They work the best from my experience.