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Quote:

Originally Posted by wjb21ndtown (Post 3342837)

I can't get a straight answer on compression ratio of the 330. I hear everything from 8.1 - 1, to 8.8 - 1. That said, they generally use a 118 cc combustion chamber in peanut port heads on the motor. The 781s generally have 113 cc combustion chambers:

http://outintheshop.com/faq/casting/castings2.html

That list was taken from Mortech, who for some reason took down the casting number search from their website. They were an online "go-to" authority on GM casting # research.

Delete that page from your favorites, that is very incomplete and has a bunch of wrong info. I found the old Mortec page after doing a little research. Hope this helps everyone out.

Quote:

Originally Posted by strega (Post 3342701)

Thank you all so much for your help, I would be lost with out you.
I will strip the engine down and fit these heads after a little freshen up as it will make it easier in the future to upgrade. Trying to find decent exhaust manifolds in the UK is a joke but I will keep looking. Once I have those then it's time for a new cam, oh.....and a bravo one!!!!!!

If you can find them in the UK, the stock exhaust from a Merc 496 are an upgrade over your 330's (better flow, much lighter weight). I bought a set for my 330 for $400. I changed the heads to 781s and intake to a Performer and picked up a little bit of top end and fattened up my mid-range. Not a dramatic change, but certainly noticable. I made the change due to a cracked head that had to be replaced anyway. At the time I was on a tight budget so didn't have cash to put into it.

If I would have had a little more cash in my pocket, I would have upgraded the pistons to forged, ported those heads, put on a Performer RPM Air-Gap intake and a bigger cam. That, I think, would have made a substantial difference.

Quote:

Originally Posted by strega (Post 3343035)

Great info there, thanks.

Hey strega, I have everything you need, I did the same thing a few years ago and have all the parts you need for around 425 hp out of that bottom end....VERY AFFORDABLE. Pm me or call Robby