[bradleyc309]

Would it be worth it or can you install #13 heads on a 1964 389 engine with Tri-Power using a 1965 Tri-Power Intake and Card's?

[Dick Boneske]

You can do that. The '64 GTO engine was the first to oil the rockers through the pushrods instead of the rocker studs. I don't know how much better the #13 heads are than the 9770716 '64 heads, but likely easier to find.

[b-man]

The #13 heads will work no problem. One thing you need to do is make sure you have the correct pistons. The 1966 (and some 1967) and earlier pistons have the valve reliefs located differently than the later pistons.

If you’re running a high lift cam there could be interference between the valves and pistons using later heads with early style pistons. With a factory cam like the 068 Tri-Power that only has .406” valve lift then there’s usually no problem.

You’re not going to see any really noticeable horsepower increase going from the 1964 9770716 GTO heads (used in all GTO engines both 4-barrel and Tri-Power) to the 1970 #13 heads in a mostly stock application.

You might gain 5 or 10 horsepower at the most in my estimation, however the later big valve 2.11”/1.77” #13 heads give you more future upside performance potential and the superior screw-in rocker studs for superior valvetrain stability (especially if upgrading to ARP 7/16” studs) and greater reliability.

The later heads also greatly open up your ability to use aftermarket intakes if you so choose, 1964 and earlier heads limits your choices as you probably already know.

[bradleyc309]

Here are the current engine spec's; 267(HP), 389 (engine), 11H (engine code), 10.5 (compression), 640 (cam), 9773345 (heads), 2 (carb).

[b-man]

If that’s an untouched original engine then you’re pretty much limited to using a low-lift factory cam. The factory 068 cam that was first offered in GTO 389 engines for 1965 Tri-Power applications would be the best choice in my opinion.

The 9773345 heads are a low performance head with very small valves (1.88”/1.60) and ports, the #13 heads are vastly superior. Keep in mind that you must use the pushrods and rockers that match the new heads, the parts from the 1964 heads are not compatible.

[25stevem]

Bradly here is more detail into what your asking about.
Your stock 716 heads flow tested at .400” lift which almost as much lift as the stock cam has flow these numbers.
Intake 160 cfm@28”

Exh 131 cfm @ 28”

A stock #13 casting tested at that same .400” lift produced the following numbers.

Intake 198 cfm@28”

Exh 150 cfm @28”.

Even if you only care to apply one half of that 38 cfm gain into a Hp formula then the usage of the 13 casting will provide you with I minimum 20 Hp gain over what you have taking place now under your right foot.

Just note that you can not use your 389 push rods or rockers .you need to get the 67 and later push rods which are about 9.130” long, and of course the later rockers.

You will also be rewarded with a chamber that’s less likely to detonate on todays fuel while running a more power productive timing curve.

[Goatracer1]

Just a correction. The 9773345 heads are not push rod oiled. They oil through the rocker studs. You do not have to plug the oiling hole in the block that goes to the head. Use a 400 head gasket and it and the cylinder head will block the hole. Also you will need to use the 400 rockers (they have the oiling hole in the tip) and the 400 push rods (they are longer). Using one of the stock spec (non Ram Air or non SD) cams will prevent valve to piston problems. I have done this type of swap dozens of times over the years with good results.

[bradleyc309]

Thanks to all for your input.