[455Grandville]

I have a good running 1968 400 with # 15 heads. Does anyone know if they are small valve (1.96") heads ?
I have some 350 type 6X heads laying around I can rebuild; thought about making them useful -

[Will]

The #15 heads are small valve but the combustion chambers may be just the right size for a good street compression ratio. CC the chambers, I bet they'll be in the low 80cc range which would be good for about 9.5:1 CR. You can easily have the small valves replaced with big ones at rebuild time (you'd buy new valves anyway, right?) and then you've got a nice set of big valve heads with nice sized chambers. Only other thing you'd have to do would be to pull the pressed studs and tap the holes for screw-ins. Sell the 6X-4s to someone with a 455 because you'd have to mill them quite a bit to get into the lower or mid 9:1 range compression wise.

[GTOGreg]

The 15's were one year only ('70) 455 heads with 87cc chambers and small valves/press-in studs. Perfect chamber size for streetable comp ratio on a 400 - just change the valves and studs and you'll be in good shape. Save the 6X's for a 455 build unless you plan to add some boost power-adders or want to go with 87 octane on your 400.

[smagnotti]

Hang on to those small chamber 6x heads as they are getting to be hard to come by!

[firebirdcrazy1959]

Originally Posted by GTOGreg

The 15's were one year only ('70) 455 heads with 87cc chambers and small valves/press-in studs. Perfect chamber size for streetable comp ratio on a 400 - just change the valves and studs and you'll be in good shape. Save the 6X's for a 455 build unless you plan to add some boost power-adders or want to go with 87 octane on your 400.

Not true Greg,68 400 big cars got 15's and then in 1970 big car 455s came with 15's.I know i have 2 sets!68 15's are about 75 CC's and with bigger valves they are just as good as big valve 68 heads.15's or #62's had the same compression on a 400.1970 15's are 87 cc.

[goatman-68]

I agree with firebirdcrazy1959, I also have a pair of 68 #15 heads with about a 75cc chamber. They came off of a 68 big car, Small valve press in studs.

[firebirdcrazy1959]

1970 #15's [87CC] are a great 455 head,give about 10:1.I have a set on a 400 i just did a stock rebuild on,haven't run it yet.The other set i'm porting and having big valves and screw in studs done to them.

[PONTIAC LARRY]

'68 340HP 400 #15's , nice , cheap street/strip head , small valves don't hurt mild combo's , easy mid-low 13's in a very mild 2nd gen F-body setup , good big valve/porting potential when the other heads are too pricey or not available .