[charlie66]

Originally Posted by Boostedbird

The Butler's 482" in this story is at 10:1 and at this point was at 44psi. They were on alcohol though. Just something to read.

Thanks. I have seen that article ...

[charlie66]

Originally Posted by v869tr6

My compression is about 8.25 maybe 8.5 with the heads having been resurfaced about 3 times.
I do have a very small cam with no overlap so that must make some difference.
I run E85 most of the time on the street and run E98 at the strip just for some insurance in the 1/4 mile.

Thank you.

I was also thinking for this case scenario a small cam with hardly any overlap would be the best way to go... I really do feel that E85 would work. That's all I've been using with my 4 cylinder even at 35 - 38 psi I have had not one detonation problem . So 10 psi on a 11 to 1 motor to me seems like a go. But what do I know really im just going off a feeling from what I have experienced ... But that's all I got, my experience's, and you guys..... and a appreciate and value all of you!

[Boostedbird]

Originally Posted by charlie66

Thank you.

I was also thinking for this case scenario a small cam with hardly any overlap would be the best way to go... I really do feel that E85 would work. That's all I've been using with my 4 cylinder even at 35 - 38 psi I have had not one detonation problem . So 10 psi on a 11 to 1 motor to me seems like a go. But what do I know really im just going off a feeling from what I have experienced ... But that's all I got, my experience's, and you guys..... and a appreciate and value all of you!

Charlie, I would think that as long as you had a larger good flowing exhaust with low backpressure a larger cam with some overlap would be the way to go. Not the same situation, but my car has 9.3:1 compression with 26 degrees of overlap on the cam. It's just a solid flat tappet. Seems to run pretty good I think. I would think that a small cam and no overlap would cause it to be prone to detonation at 11:1, especially when the cylinder pressure rises even more under boost. No expert though, just my thoughts.

[charlie66]

Originally Posted by Boostedbird

Charlie, I would think that as long as you had a larger good flowing exhaust with low backpressure a larger cam with some overlap would be the way to go. Not the same situation, but my car has 9.3:1 compression with 26 degrees of overlap on the cam. It's just a solid flat tappet. Seems to run pretty good I think. I would think that a small cam and no overlap would cause it to be prone to detonation at 11:1, especially when the cylinder pressure rises even more under boost. No expert though, just my thoughts.

Ok ill have to look into that one. Ill call Tim at bullet

[JSPONT]

Originally Posted by charlie66

Do you know this guy. I would like to talk to him if possible ..

Yes I know him well I will get text you his #.

[BruceWilkie]

Charlie run timing at say 10 degrees at 2 psi and start adding boost. READ your plugs! If ok try a 2 degree jump at 2 psi and start sneaking the boost up again. READ your plugs. (Best done on a chassis or engine dyno so you can get an accurate read). Your plugs will tell you what you need to know. (both timing and fuel)

As far as cam goes intake closing point affects cylinder pressure. Early = more, late = less.
As far as overlap goes... nothing can go in the cylinder until pressure in the cylinder/ex port is less than whats present at the intake valve. Small amounts of overlap help purge the chamber while piston is nearly parked at tdc. small amounts of unburned charge help cool exhaust valve but excessive amounts will blow-torch your turbine. Overlap in small proportion allows more undiluted charge as piston descends. No overlap or underlap creates more EGR. Exhaust doesnt reburn it adds heat and takes up space that could be fresh charge.
Mark at Bullet cams might be most helpful choosing what should work best with your combo.

[v869tr6]

I mentioned the no overlap because I bet my cylinder pressures are quite hi, with the long stroke and the low rpm making things even worse.
But it work pretty good.

[TimeWarp]

Charlie...did I miss where you said the type of heads on that engine? Can you open them up a bit perhaps?

[charlie66]

Originally Posted by TimeWarp

Charlie...did I miss where you said the type of heads on that engine? Can you open them up a bit perhaps?

They are 334 cnc Edelbrocks with 75 cc chambers...

[TimeWarp]

So could the chambers be opened up a bit? I heard SD Performance has a program to do that (open up to 100cc) and the cost is around $100....that was what I was told. No idea if its true or not. lol

[Tom Vaught]

Dave would be the one to talk to about that deal BUT I believe Charlie had his 4 cylinder head done by Dave at SD so they should be on good terms.

Tom V.

[JD311]

I think ceralli/all pontiac has a boost chamber mod as well.

[charlie66]

that's a good idea. But I still would like to see how a high compression set up would work....

[TimeWarp]

You're more daring than I am. lol I know it could just end up sacrificing head gaskets. But the thought of what detonation does is enough to send me in the other direction. I guess if its just a junkyard engine, no big deal, but...

[charlie66]

Lol! I have 12,000.00 Invested in this motor.. Its not like that. I think I can have a good try and not burn it up. Ive been tuning the 4 cyl on e85 and 44 psi and never even cam close. I like the challenge of the idea.. This I something I would do over rhe winter. I almost have all the parts together to put the 4 cyl back together so I have to do that first..

[70 bird]

Sounds like great risk for a little extra power, I would lower the compression a bit and have some fun without melting parts. JMO.

[Tom Vaught]

Originally Posted by 70 bird

Sounds like great risk for a little extra power, I would lower the compression a bit and have some fun without melting parts. JMO.

Even if the price was $800 ($100 per chamber), if you could take 20 ccs more out of your 76 cc heads and get a 96 cc head you would be in a much better area for compression ratio vs boost. I am talking about the SD combustion chamber mod.

But for basically the same money, removing the pistons and putting in a dished piston with a proper top ring location, proper ring gaps, and a stronger pin/piston design would net far better benefits.

Tom V.