[Goathead]

If you have a stock 65 GTO with tripower, 3.23 posi rear, petronix ignition, holly fuel pump and a muncie m21 wide ratio tranny, what is the best investment for improving the performance? Heads?

PS: The rear end has air bags & hop stops and the exhaust has a X pipe and I do not want to put headers on because they allways seem to spring leaks and fit too tight thus causing rattles.

[Goathead]

If you have a stock 65 GTO with tripower, 3.23 posi rear, petronix ignition, holly fuel pump and a muncie m21 wide ratio tranny, what is the best investment for improving the performance? Heads?

PS: The rear end has air bags & hop stops and the exhaust has a X pipe and I do not want to put headers on because they allways seem to spring leaks and fit too tight thus causing rattles.

[HANDSEL]

My suggestion would be to put long branch exhuast manifolds(since you don't want headers) you need more exhaust flow before you do any other performance modifications, cam and heads. What heads do you have now? What cam do you have? Maybe some bigger valves and some mild porting.

[Mr_GTO]

Gears, heads, cam, and HEADERS. Once you have the heads off, installing headers will be a piece of cake.

[larry davis]

Exhaust! Preferably headers.

[Doug]

If performance means "acceleration", the quickest best bang-for-your-buck is stiffer gears (I think 3.90 is the highest that "fits" your carrier). Of course, you have to get it to the ground. If the engine is fairly healthy now, then exhaust is next. I don't know if "long branch" will fit but I think maybe the 1967 D port HO manifolds would. I don't know. I would think about using some economy tube headers before I jumped into the HO units.

If the car is a daily driver, the 3.90 gear may be too stiff. I had an exact copy of your car, gears and all. I handled the 3.90 gear deal by buying a complete rear end housing which I put the 3.90 in. I used the 3.23 and if I needed the 3.90 setup, I would change the complete rear. In a good work space, I could switch them out completely in well under an hour.

[Tim Swain]

Little head work, not to much and maybe a cam to match. Jim Taylor did my heads and his solid lifter cams are matinance free. He personally does the work himself and takes much pride. It is a dirty job but when he's done there dimonds.Don't fall for big CFM, you need velocity. Distributer recurved by someone who knows. I think it's very important contract services to people who know Pontiacs. Beware of people who think they know or want to sell you Bigger More More$$$$$$$. Me and a friend of mine dynoed are cars together he had some HO castiron manafolds by pontiac (not longbranch).Anyways he ran 380 torque 317 HP at the rear wheels. All but stock appearing 65 lemans show car 421 engine.

[Goathead]

Nandsel, have the stock tripower cam and heads, new though, about 3K miles on them. Engine runs strong, and I know headers are the thing, but seem to be too much hassle for the street, strip kina guy I am. Seem to allways blow gaskets. Have a set of Headman's in the attick now, but trying to get around them. A friend of mine ports and polishes heads and that's the way I am leaning. I do understand that exhust flow is important, but will it help that much to have headers and keet the flowmaster 40's attached?

[Blackcat]

Install the 67 HO exhaust manifolds as a compromise. Better than the stock logs.

[HANDSEL]

Which side gaskets The head side or the collector? I found that dead soft copper collector gaskets work really well on my Hooker supercomp headers. I also cut the flanges between the pipes and WOW!!! what a difference easier to install take out and I haven't blown any gaskets. Much easier to keep the bolts tight also. I have stainless steel bolts that kept falling of the headers Because as you tighten the bolts at different tubes you are trying to bend a 3/8 inch thick flange to different angles on the head. Plus fibration fron the exhaust kept shaking the bolts loose. Now that I cut the flange they always stay tight. I now only have to tighten the bolts once a month except every week.

[Goathead]

Blackat, need help! Would you mine checking out out ebay item # 601735756 and telling me if this is what you suggest?....thanks...Danny

[Ken K]

The queston was the best investment. That would leave out headers, did you ever try and sell a used set of headers? A set of big valve small chamber 400 heads will really wake up your engine, you will defintly notice the difference. I know someone who claims the biggest single thing that added peformance to his engine is a set of HO exhaust manifolds. The only problem with that theory is he allready had all the other stuff on his engine, the big valve heads and a bigger cam so maybe it just helped the other parts work better. I have seen the real difference that a set of big valve 400 heads added to a 389 engine and no other changes.

[Old Man Taylor]

Goathead - If his description is correct, those are the ones that would fit your car. It is unusual to be able to buy them with the flanges, so that would be a pretty good deal. I installed them on my 64. I took out the butterfly and shaft and had the manifold holes welded up where the shaft came out.

['ol Pinion head]

Several thoughts...

-Leave the 35 year old rusty '67 HO manifolds for someone else to resurface, blast, & not be happy with the pitted finish. They will eventually crack from thousands of heat cycles.
-Consider building a set of '67 "061" heads, or buy some well built 670's. Mild street porting job will be fine. Ck your rebuilt "389's" piston tops & see if they are dual valve relief rebuilder style pistons or if 400 piston(?). '67+ heads had a different valve inclination. Will need later pushrods as well.
-Manifolds, again...buy new Ram Air Resto Enterprises manifolds from Performance Years. Made of much better metal than the originals & come with a fine warranty. If you want 2.5" outlets (vs stock 2 3/16") Ram Air manifolds ck with PY, or call Paul Sr at RARE in Dallas.

Sounds like a fun project. Good luck.

[Blackcat]

I agree! Purchase the repros from Preformance years! Get the 67 HO Manifolds and the collectors! The repros are much better than the orignals! Oh, also get the bolt and Gasket kit to go with them!