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Discussion Starter #1
Does the stock cam plus 1.7's like added compression? For instance moving from 9:1 to 10:1 ? Or is a new cam really needed to realize significant gains from additional compression?

Just wondering and considering options. I know the stock cam works well with the S/C crowd.

Thanks
Paul
 

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Hi Paul - I guess it depends on what you mean by "significant". The stock cam will work fine with 10:1 and you'll probably notice the difference. One thing to watch though is that with the stock cam cylinder pressures especially at lower rpms are gonna be higher, and so detonation can occur more easily than before, especially with your iron heads. Easily remedied by easing back on your initial timing. With aluminum heads you'd probably get away with 10.5 or maybe even 11:1 on pump gas with careful timing. And, you'd be able to change your sig to say 2350 lbs. :)
 

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Discussion Starter #3
Michael- Significant gains are relative to effort/cost. I would think that 15hp is significant. Yes 2350lbs. would be great, and Al. heads were the original plan. Then I found these GT-40P's for a great deal. Some people are making good numbers with them, they use my existing pushrods and RR's, so I'll give them a try.

I haven't put them on yet because I might get them milled .020 to bump the comp. ratio. I do not want to go too much because I want the intake to seal properly. They are 60cc which I think is about 3-4cc less than E7's. I have already ported these heads myself, focusing on the exhaust side.

I know that GT-40p's do not need much timing as they are a fast burn type combustion chamber. I run a safe/sane 16* with my E7 (don't think I could hear detonation with the side pipes if I had it) so I'll go with about 12* with the P's.

Who burned your Autologic chip? What does it do for you? I have one that only extends the rev limiter and allows me to use the soft rev limiter in my Crane HI-6 box.
 

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A local fellow - Scott Noe at Noe Performance in Morristown, TN burned the chip for me. I picked him because of his reputation, and because I can physically get the car to him so we can tune, drive, tune, drive, etc. That's what I recommend - I wouldn't have done a mail order deal. We adjusted the idle, we turned off the egr and thermactor (air injection) functions, we revised the part throttle and wot timing curves to take advantage of running more advance with my aluminum heads, and we altered the cold start parameters so that 95F or 5F, you hit the key and it starts right up and settles into an 850-900rpm idle in about 15-20 seconds. And you can drive right off - cold or hot. I think you'd be ok with a .020" cut - and that's pretty cheap to do. Whether or not it will net you 15HP - I doubt it will.
 

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I know this thread is old but I was about to post the same question. Anyone else have more feedback on this? Just crunched the numbers and my stock cam, alum head combo would be ~ 8.9:1 static. I want to mill my tw heads down from 60cc to 54cc to hit something close to 10:1 but worried about high dynamic compression and possible pinging.

Any advice on quench distance for a combo like this?

thanks,

Drew
 

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I took 40 thousand off of some e7s which should give 57cc or so, (I didn't cc the heads) for my 85 and it woke it up pretty good. I run 12 degrees initial with no ping but tried 14 and lost power, probably from detonation. The e5ae stock heads were about 67cc and gave it 8.4-1 compression so the e7 shaved get me around 9.5-1. Stock cam, bbk shortys 2.5 off road h pipe and 3.73 gears. I run 91 octane.
 

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10:1 with aluminum heads shouldn't pose a problem with pump gas. You should be able to run the timing where you want it.
 

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How about milling the tw heads down that much? Aside from intake port alignment, wil it hurt chamber efficiency?
 
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