tawd77

I recently purchased a 74 nova with a fresh 355sbc in it. It doesnt seem to have quite the power that i want, so im trying to figure out what im working with. The block is an older, drivers side dipstick block. But the heads are newer style, centerbolt valvecover heads.

So, I took the valve cover off, and I noticed roller rockers, screw in studs, and guideplates. The casting number on the head is 10239906 which makes it a 96+ Vortec head, with 64cc chamber, and 170cc runners.

Whats strange with the heads...
It has an older style intake manifold on it with 6 bolts per side instead of 4 per side like a vortec would have. So im assuming they have been redrilled.

But even stranger, they dont have the "sawtooth" spikes on the end of the head castings. Where the three teeth would usually be, there is a tall half circle, and thats it. Are these vortec heads for sure?And why wouldnt they have the sawteeth? Also, would anyone have an estimate of what my compression would be assuming the block hasnt been decked, running a flat top piston? Thanks!!

aj_wicked13

Those May be from a Vortec Engine but most likely a large truck or somthing along those lines. Like you said the good Vortec Heads you want at 4 bolts per side and have the saw tooth... after a quick search i couln't find the casting number. But i do have those heads in my camaro. If you can't find the casting number for these good heads i can go pull a valve cover and get it for you.

read this article about sbc vortec heads
http://www.chevyhiperformance.com/ho...458/index.html

"For you junkyard hunters, be forewarned that some ¾- and 1-ton trucks came with Vortec heads equipped with a specially hardened exhaust seat that kills low- and mid-lift flow. Casting number 10239906 should be avoided."

chevypeck

sounds like you have the suposily the unliked vortec heads 906 casting. the ones with the sawtooth are the 062 casting. some people say the 906 do not flow as good as the 062, who knows for sure, unless you flow them. other people say there is no difference.

mattrunner

this is quite useful. recently got vortec heads in my car and the overall power increase has been quite good. worth the money i would say.