[Badgoat64]

I have the original 389 block for my 64 GTO that I want to rebuild. It has the 4 bbl carb and intake, but my plans are to install tripower. What other mods can I do to give a bit more power and keep it easy and fun to drive?

[TPM]

I have a 1965 GTO 389 Tripower and there are a few upgrades that I am very happy with:
- ram air exhaust manifolds into 2.5” exhaust system with mandrel bent down pipes, X pipe and Pypes mufflers
- replaced 3/8 pressed in rocker studs with 7/16 screw in studs and added roller rockers & push rod guides
- phenolic carburetor spacers
In terms of fun/driveability, I installed a Tremec TKX 5-speed - a real game changer!
Disc brakes in the front and a dual reservoir master is a great safety upgrade.

In my opinion, these upgrades really enhance the overall driving experience and reliability.
Good luck

[b-man]

Lower the compression using dished pistons.

These engines were advertised as having 10.75:1 compression but were actually about a half point lower. I’d recommend dropping down to around 9 to maybe 9.5:1. A manual trans car can get by with more compression than an automatic car, also rear end gears are a factor as well. Higher rear end gears numerically will be happier with more compression, conversely if using taller highway (lower numerically) gears you’ll want to err on the lower end compression-wise.

Upgrading the cam to the the factory 068 1965 - 1966 360 hp Tri-Power cam or perhaps the Summit 2801 will give it a nice boost over the original 009 cam that was used in 1964 on both 4-barrel 325 hp and Tri-Power 348 hp engines. The 009 cam is the same profile as the 067 cam that was used in 1965 - 1966 4-barrel 335 hp GTO engines.

If you’re not spending the money to convert the heads to screw-in studs which won’t be cheap I would suggest sticking with the factory 068 cam. However after inspecting the pushrod guide slots that are machined into the head castings and finding some to be excessively worn then you should resign yourself to converting to screw-in studs and aftermarket adjustable guide plates. Once those guide slots are worn out you really have no other choice if you want to keep using the original 1964. 9770716 GTO heads.

The 1967 Ram Air / HO exhaust manifolds will buy you maybe 8 horsepower at most over the standard log manifolds so for the additional 500 dollars there’s not a lot of bang for the buck on a near stock 389 engine. A nice set of 2-1/2” PYPES headpipes and whatever mandrel-bent 2-1/2” exhaust you like will be plenty for a mildly modified 389.

[TPM]

I have the 068 cam that b-man mentioned - that cam with the exhaust system upgrades I mentioned in my previous post really make for good drive- ability with decent power for the street.

[Rich-Tripower]

When we were rebuilding the tripower in our 64 the 64 cam was not available so we went with the 068 (65 tripower) cam. Worked out just fine. However, early on we did have trouble with some rocker studs pulling out of the head a bit making it run poopy. After pounded the studs back in and put in a Crane ignition module that includes a rev limiter and set the rev limit to 5100 we never had a problem again. We also switched to Chevy rocker stud nuts as we were having some valves staying slightly open when torqued down with Pontiac rocker stud nuts. Which was odd since we didn't shave the heads or block.

But anyway, with a bit of fiddling around we got it running just fine.

[Sunfirered64]

Spotts performance makes screw in rocker studs that fit under the stock valve covers, needs to go to a machine shop it be done properly. I don't know what altitude you are it in Nebraska, but in Colorado and Wyoming you really do not need to lower compression as we are at 5k + feet in altitude, we will have a lower actual compression ratio due to the altitude density that is far from 14.7:1, so high compression is a good thing up here, and we don't have the preignition issues that they do at lower altitudes with the stock setups. My 64 that I'm in process on will have 11:1 forged pistons, and a heavy roller cam with 716 heads. I run 11:1 with 9 pounds of boost on my LS3 powered 2004 GTO with no issues on 91 octane. I am at 6,000+ feet in altitude.

[bradleyc309]

How about adding #13 heads as well a 068 cam?

[Goatracer1]

I agree with bman. Lower the compression. The engine that was in my 1962 Bonneville was rebuilt when I bought the car. Someone did a nice job but the compression was too high. No matter what I used for pump gas it pinged and wiped out the rings. Remember when you rebuild an engine stock you usually increase the compression. Boring it, decking the block and shaving the heads all increase the compression. I rebuilt another 389 for the car and had the new pistons shaved to lower the compression and could not be happier.

[Brad_bb]

In my 64 tripower engine: ARP screw in studs in the 716 heads, new valve seats. I had the pistons machined to lower compression so I could run 93 octane. I used new after market rods and I can't remember if I used TRW or Federal mogul pistons? I balanced the pistons, rods(arp bolts), and had the entire reciprocating assembly checked and balanced by Butler Performance, they also assembled/blue printed and broke in my engine on their test stand. I used original head bolts to look original. I changed my points to Petronix. When ever you change over to Petronix, you need to change the spark plug wires to the other type so you don't burn the sensor out. I believe I used a pilot bearing instead of bushing. Original rebuilt water pump and fuel pump. You could consider using electric fans instead of the original mechanical if you are not concerned with originality. If you use the original fan, I'd use a fan shroud that works well. You don't want to overheat in a parade or in summer traffic.

[scott06]

depends on what you want to do.

I have a stock 389 in my 65 now with a tripower, I am running a 2801 cam (AKA spotts 068HL) and wlaker dynomax mufflers which sound great. Love the cam very mild and driveable.

Also added a SE single wire electronic ignition. Biggest gain on this was faster starting.

I'm having a new engine built at the moment stock 65 389. Goals were to keep it stock externally and stay with the 65 tripower and #77 heads- dished pistons to lower CR. Got a eagle cast crank so stroked to 447 in, some mild bowl back cut work, RA exhaust, Spotts HCP01 cam.

Would also second the disc brakes. I put a summit kit that uses basically stock GM 11" rotors single piston calipers and a dual master, nice upgrade kept drums in back.

[trader61]

As others said, lower the compression. I refreshed mine and kept it stock with just new rings. I'm stuck blending in some 110 octane to bring me to 94-95 to keep from pinging under certain situations.