toofast928

So if the fuel system could supply, what's the max horsepower a USA 4.5L could deliver and still be streetable.

If 225 is stock, then easily 325 (SC). Push a little more 350. Could the pistons and head gaskets handle the 400 mark?...........

BC

I'm shooting for 300hp at the crank from a 4.5 NA. NO MAF, but heaters, Euro intake and TB. 78 Cams with some head porting, etc.

SharkSkin

I've heard it said that the 928 CIS system can support 400hp. Under what circumstances, with what mods, I don't know.

toofast928

I'm planning on adding a SC and convert to MAF. That should give me 340 at the crank. But I was just wondering at what HP the bottom end begins to break?

Fastest928

we managed 310 rwhp with cats and stock manifolds from a 2v euro

BC

5.0 or 4.7 or 4.5?

FlyingDog

If you have an 8.5:1 4.5L 450+HP should not be a problem with a supercharger... if you can supply the fuel. The problem the newer engines have with SCs is the high compression increases the likelyhood of detonation. A lower CR allows the SC to pump more air in without risking detonation. If the CIS system, or whetever you replace it with, can keep up getting over 100HP/liter shouldn't be a problem.

John Struthers

Your talking a 4.5L, AFC-L injected, right?
If it's an 80' thru 82' you should be nearer 9.0 : 1 .
Perhaps a fatter/metal composite gasket to lower the CR would be in order.

John Veninger

To bad you didn't try it with headers or were those stock manifolds from an 86?
I can't seem to get more than 305rwhp with headers and CIS injection

Lance J

what about my 1979 4.5 liter with cis. think of have a blown beast soon as well i know our cam are more agressive than the 80-82. first stage for me is getting my gauges to monitor the system, fuel pressure, a/f ect. by then andy should have twin screw kit out. i'll drop him 3k start. i was honestly thinking off trading my near perfect 928 for a turbo those guys make hp alot easier because there already turbo.

Lance J

are there any piggybacks for cis. not to tune but just to monitor the system in a neat little spreedsheet data log. to help tune by hand to get opt. tuning

Joe F

John, is that with a 4.7 or are you taliking about the 5.0 ltr block? If it is with a 4.7, then what else are you changing to get those numbers?
Thanks in advance

JF

John Veninger

It's a 5.0L using Euro top end. Dave Lloyd hit 307rwhp, but I have a bit more torque.
Click the link to the EuroS in my sig. You can see my dyno and Dave's at the racing site. Waiting to see what Stan's new motor does!

hacker-pschorr

Any stroker 16V's out there? I know many people will squak at this idea being a waste with the S4 heads out there. Chevy is proving over and over 32 valve's are not needed for big hp numbers.

FlyingDog

Sorry, I looked at the wrong sig line. Even at 9:1, compression isn't very high. Saab uses 9.0-9.5:1 on their turbo cars. I think SC GM 3800 Series II engines are 9.3:1.