[sfd771]

I've got a question about a set of SBC heads. The casting number on the heads I have are 3973487. From doing a search on www.mortec.com I found this..

3973487....71-72....350...used on 71-72 350 LT1, 75cc chamber

my question is does the LT1 mean these came on a performance engine (corvette)?

does anyone know what size the valves are or how can I find out?

Maybe I got lucky and got some good ones.

[406 ss monte]

it just means those cast # heads were used on the lt1. they should have 1.94-1.5 valves. just a plain basic head like 624's, 993's, & 882's. do they have screw in studs?

[fourbyfourblazer]

I thought I recognized those head numbers. I have the 3973487X heads that are 2.02's. Lingenfelter book says that my 487X heads are great flowing. Check out this site for the break down on some of the different head configurations for performance small block chevy heads.

Small Block Chevy Heads

This is what is says about your heads.

LARGE CHAMBER PRODUCTION "ON CAR" HEADS

"487" – 3973487, OR 3973487X. The regular casting was found on the 1971-1972 350 LT-1 engines, had 1.94/1.50" valves, 76CC combustion chambers, DO have accessory holes, intake port volume should be 161CC's, exhaust port volume should be 65CC's. The 487X had 2.02/1.60" valves.

[MI2600]

The 487s are good heavy castings and decent breathers for their age, although they have the larger chambers. I'd definitely keep them.

406 monte: I wouldn't put 624s in the same class as 487s. 624s are even worse than 882s.

[sfd771]

thanks for the input guys. I've been spending lots of time the the garage lately. I've got the bug real bad right now. I love summer.

[andymorganelli65@hot]

i too have the 3973487x number. i believe that it comes from a 70-72 camaro. the 70 is pushing 360 hp, 71 is 300hp and the 72 is only 255hp.

[steve t]

i have 1 487x, and 1, just 487, they should run alright together, shouldn't they????

[jimfulco]

Originally Posted by andymorganelli65@hot

i too have the 3973487x number. i believe that it comes from a 70-72 camaro. the 70 is pushing 360 hp, 71 is 300hp and the 72 is only 255hp.

The '71 is GROSS HP, and the '72 is NET HP. Same engine, different rating method.

[HemmiGremmie]

The X heads are good ones.
Unless your wanting every horse outta your motor, use em. HG

[ratman33]

i have a set of 487x heads on my 355 and they did not have 202/160 valves.they do not have screw in studs.i left the valves,no port work or gasket match and installed 3/8 studs and flat tops and 268xe cam.motor made 297 hp at rear wheel with 3.42 gears.ran a best of 13.45 at 109 in quarter.good heads should get 400hp with bigger cam and some port work.