[lethalgto]

I have a set of 46 head and I just picked up a pontiac 400 cubic in short block. Will they work together well and what kind of power can I expect.

Thank

[lethalgto]

I have a set of 46 head and I just picked up a pontiac 400 cubic in short block. Will they work together well and what kind of power can I expect.

Thank

[Will]

There are three different versions of the #46 head.

The first was used in '69 on 400 & 428 engines. Not sure of the chamber volume on this version. It was a small-valve, pressed stud, low compression (for the time) head. Chamber volume is probably in the 80-90 CC range.

The second was used in '73 on 2bbl 350 applications. This also is a small valve, pressed stud head. Information suggests chamber volume is around 87CC.

The third version was used on the '74 GTO, which had a 350 with a 4bbl. This version has screw-in studs, but still small valves (1.96"/1.66"). The compression was pretty low on this engine, so the chambers are also probably in the high 80cc range.

All of these heads will work fine on a 400, and if the chambers are in the mid 80 CC area, say 86cc, then you'd end up with close to 9.2:1 compression if the block is bored .030" and cut for zero deck height.

However, having pressed studs limits the cam lift and duration you can run, and having the small valves limits engine breathing and RPM range. You could have larger valves installed and have the pressed studs pulled and replaced with screw-in studs, but that of course all costs money. It might be cheaper to start with a set of big valve heads that have screw-in studs already. Research your options before spending your money.


----------------------------
'72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car!
'73 Firebird 400/4-speed Black on Black, mix & match.

[lethalgto]

Thanks for the information, So what should I be looking for in a set of heads. What I want is to be able to run my air conditioning but when a stock mustang comes along....blow its doors off. So what should I look for.

Thansk

[Will]

You want heads with screw-in studs and 2.11" intake valves. You also want an appropriate chamber volume for the compression ratio you're trying to run unless you're willing to dish the pistons you have or buy custom pistons. Achieving a pump-gas friendly mid 9:1 compression ratio on a 400 can be a bit tricky because Pontiac only produced these engines with CRs of 10:1 or higher, or 8.2:1 or lower. Sometimes a small-valve head is a good choice simply because it has the chamber volume you're after. After all, if you're buying all new stainless valves, ARP rocker studs, having hardened exhaust seats installed and are planning on paying for a porting job anyway, then the additional cost to have the pressed studs pulled and the holes tapped for the ARP conversion studs is minimal. At a shop with modern, high quality equipment (Serdi or similar head machine) it should cost no more to cut the intake seats for 2.11" valves than to recut them for the smaller valves, so the price of the valvejob is a wash if you're having all that other work done.

The one thing to watch out for is getting a chamber volume that is too big. The only way to get a good CR with big chamber heads like from a 455 or late '70s lo-performance 400 is to run domed pistons which means spending money on costly custom pistons. In theory, a domed piston doesn't work as well from a combustion efficiency standpoint either. In general, stay away from heads from '71 and later 455s, and 5C-8 or 6X-8 from 400s. Any other large valve, screw-in stud head can be made to work, depending on how much you're willing to spend and what your specific needs are.

Since I don't know what your total combination is (car, gearing, tranny, etc.), how much you're willing to spend, or what "streetable" means to you, I can't be any more specific than that.


----------------------------
'72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car!
'73 Firebird 400/4-speed Black on Black, mix & match.

[travelinscout]

Actually, the number 46 heads that were available in 69 were small valve yes. But they were 10.5-1 compression and had screw in studs, with 72cc chambers. I should know, I have a set on my 69 GP dated January of 69. Just my two cents.

[Ron Landis]

The easy way out...find a set of 6-X/4s if possible. Already has screw in studs, larger valves...etc. Cheaper in the long run. PS...'69 GP should probably have come with "62"s.

[lethalgto]

Thanks for all the info.... Im kind of new at this I have 69 Pontiac lemans....Doing a GTO conversion. I am doing a cosmetic coversion first but along the
way I am picking up things for the engine. 455's seem to be what everyone wants so I gave up on those and started looking at the 400 and they seem readily available. I have a 350 now with edelbrock carb and intake. This car will always be driven at least 2 to 3 times a week and the A/C will always run.(its too hot in Florida) So it sounds like I might have a good combo with the 69 400 short block and the 69 #46 heads?

[74Grandville]

I cc my 69 #46 heads and came up with 75cc. Also noticed they have 45 degree seats.

I plan to install screw in studs and install on a 350.

[tp's lemans sport]

where about in Florida are you?

Tom

[lethalgto]

I am in West Palm Beach....Moving to Port St lucie in 3 months.