[n2ogpsj462]

Doing some research and I've seen a few guys for the other brands and our own Luhn utilizing a 'soft' chamber. I do better with pictures and it looks they're just leveling everything out evenly with a generic looking bowl like chamber. This would also allow me to get a few extra cc's as I'm currently sitting at about 9.4:1. Could I just lay the shroud down completely even and just kinda go to town considering boost doesn't seem to care what shape the chamber is? These are the 6x

[Tom Vaught]

You have a whole different combustion process when the air density is higher (15 psi) vs atmospheric pressure. That being said I am not a big swirl fan with boost as the fuel tends to separate from the charge easier. You would be fine if you just knock off the edges in the chamber and can get down to around a 8.75 compression ratio. Then you can run 27 degrees of timing in most cases.

Tom V.

[n2ogpsj462]

Thanks Tom that's my main goal. Need to knock compression down without compromising other areas (i.e. Thicker headgaskets etc).and research turned up guys doing this. I can't remember exactly how my head porter left my chamber but if necessary could I lay back the quench pad a bit for a few extra cc's? I need to get about 7-8cc. Is this unrealistic with a dremel?

[wreckmastr]

Curious why do you feel that you need to drop the compression?

[n2ogpsj462]

I dunno. That's a great question! I guess because everyone says with iron heads to be somewhere in the high 8s? I've got my motor out to freshen and figured now is the time to address what I didn't do the first time around. This is strictly street car to have fun with. Wallace calculator has me right at 9.34:1. Could I stay here without having to run conservative timing?
When I first built this blow thru nearly 10yrs ago I knew I needed lower comp but figured I'd build everything and learn how to tune and then pull it apart and change what's necessary so all I did was check my bearings, pulled out the nitrous cam and slapped it back together. Kids and house have the car off the road the last 5 yrs. Now have a little time back.

[Tom Vaught]

Many years ago a Turbo Expert (Don Hubbard) wrote in a Crane 'How to Turbocharge your engine' book that it was better to be two compression ratios low vs 1/2 of a compression ratio too high and kill parts. Always thought Don was a real common sense guy. 8.75 to 1 seems to be a safe number (as Charlie 66 can confirm) even at 38 psi of boost on his 4 cylinder Pontiac engine. And he was never going over 20 PSI in the beginning (right Charlie)!

Tom V.

[n2ogpsj462]

Originally Posted by Tom Vaught

Many years ago a Turbo Expert (Don Hubbard) wrote in a Crane 'How to Turbocharge your engine' book that it was better to be two compression ratios low vs 1/2 of a compression ratio too high and kill parts. Always thought Don was a real common sense guy. 8.75 to 1 seems to be a safe number (as Charlie 66 can confirm) even at 38 psi of boost on his 4 cylinder Pontiac engine. And he was never going over 20 PSI in the beginning (right Charlie)!

Tom V.

Hey Tom are you just quoting that because I'm about a half point higher than you said?! J/K I've always taken advice from smart people who know more than me. I'd rather leave a few on the table then have to be spot on with this tune every single outting. It was already to much on the street and These changes I'm making should make that worse

[charlie66]

Originally Posted by Tom Vaught

Many years ago a Turbo Expert (Don Hubbard) wrote in a Crane 'How to Turbocharge your engine' book that it was better to be two compression ratios low vs 1/2 of a compression ratio too high and kill parts. Always thought Don was a real common sense guy. 8.75 to 1 seems to be a safe number (as Charlie 66 can confirm) even at 38 psi of boost on his 4 cylinder Pontiac engine. And he was never going over 20 PSI in the beginning (right Charlie)!

Tom V.

That's right Tom.

[Tom Vaught]

By the way, Don Hubbard passed away a few years ago from Parkinson's disease, May he rest in peace. He was a personal friend who worked in Jackson Michigan for a few years and then retired back to Ft Myers, Florida. I had a chance to visit with him there, before his passing.
So I quote the people, who I know, and have great respect for: Don Hubbard, Gale Banks, Dave Austin, Bob Keller, Hugh MacInnis, and others. Macinnis and Keller were doing turbocharging in the 1950s.

Tom V.