cumbustion chamber size

[icanfly]

if you have a larger cumbustion chamber in your head cant you run more boost or at least make the car more boost friendly? ex. a 58cc versus like a 76cc

[quiet_storm98]

i believe it makes it more boost friendly..a larger combustion chamber drops the compression ratio thus making it better for boost

[icanfly]

does any body know what the compression ratio on a 195 lt4 head from afr with a 76cc chamber would be

[pigpen]

Assuming your talking about a stock shortblock youd see about 8.6:1 - 8.7:1 or so...

Here's decent compression calculator you can download and use.

http://webzoom.freewebs.com/heads_up_racing/compression.xls

[GTP231]

i believe it makes it more boost friendly..a larger combustion chamber drops the compression ratio thus making it better for boost
Correct

[SiCk PuPpY]

Wouldn't increasing the combustion chamber size be a band-aid fix? And chamber shape also plays an important role in turbulance and combustion.

[mightyquickz28]

I have two weaponized Head/Cam 383 LT1s. One is in a '94 Z28 A4 3.42 while the other is just being buttoned up in my '96 Z28 M6 4.10. I would've put in turbo friendly pistons in the new motor but the (@#$%^&*&^%$%^!!!) engine builder has had motor since July/2005, jacking me around the whole time. Recently, I've paid down all my credit cards and bought myself an early Christmas present. A Turbonetics T76. The new motor is a 11:1, Solid Roller (244/.604 CamMotions) with 6" H-beam rods. I don't want to throw away the custom Probe Pistons and the Balancing expenses so a set of large(r) chamber heads is much prefered. My current Stock LT1 castings have LT4 sized stainless Ferrara Valves and they were ported to flow I/E of 275/195 @ .600 lift (Though ported and evaluated by Will Garza, the Flows were independently verified by Craig Gallant of GTP for and additional expense). These flows are better than Brodix Track 1's at the same lift. I hate to give that up but the T76 will compensate nicely for that. I see that 23 degree TFS have 60cc chambers , Edelbrock Victor Jr. have 70cc and a previous post stated some AFR's are available with large chambers too. Lloyd Elliot gave me a name/number of a machinist that can convert traditional SBC style heads to the LT1 Reverse cool format. Thanks for the compression calculator!!!



Wouldn't increasing the combustion chamber size be a band-aid fix? And chamber shape also plays an important role in turbulance and combustion.

[Zupercharged28]

bigger combustion chambers = less combustion which allows for more boost = more power with OUT a forged rotating assemble. 72cc chambers and pistons are the way to do it. drop it NICE and low and crank up that boost-o!

p.s. dont run any more than around 19 total motor compression on the stock internals no matter what! (dont forget this does NOT include the pressure from the altitude you live at cause that WILL play a factor)

[mightyquickz28]

This motor has all forged bottom end, just that it has flat top J&E Pistons.
If I go to a .060 Cometic MLS head gasket and some SBC 72cc chamber Heads (converted to LT1 Reverse cool), I think I can get to a good place in terms of compression ratio.
I've been reading some interesting threads regarding quench. It seems to imply that the smallest distance from piston to head, short of hitting them together, is the best.
But if one is to have low compression for turbo/blower, I don't see how the two (best quench/low compression) are are compatible.


bigger combustion chambers = less combustion which allows for more boost = more power with OUT a forged rotating assemble. 72cc chambers and pistons are the way to do it. drop it NICE and low and crank up that boost-o!

p.s. dont run any more than around 19 total motor compression on the stock internals no matter what! (dont forget this does NOT include the pressure from the altitude you live at cause that WILL play a factor)

[Zupercharged28]

yea, i dont quite understand it yet myself either. ive been bummin around at my local speed show asking all sorts of anoying questions about it. ill be sure to let you know if i have any new info though!

[mightyquickz28]

Doing a bit more searching, I see that AFR has some 180cc LT1 heads that can be ordered with 76cc combustion chambers. I only see them as 'assembled'. I guess I'll sell my fully ported LT1 castings (LT4 sized stainless steel Ferrara valves) to recoup some of the expense. That's down the road a bit since I'm still acquiring parts for the T76 implant. So far, I have the T76 (on it's way), the TS-38 Wastegate (on it's way here) and 60# Mototron Fuel Injectors(on their way here) so I'm over 2 grand into this already. Yuck! I don't like to think about it that way! I'm still trying to find someone with the injector offsets commensurate with the 60#'ers for programming into the PCM. Mototrons site simply states that the offset is .55 volts at 14volts but doesn't break it down to the various other voltage states that are in the PCM for the offsets.

yea, i dont quite understand it yet myself either. ive been bummin around at my local speed show asking all sorts of anoying questions about it. ill be sure to let you know if i have any new info though!

[94 6-speed]

Just wondering who can convert gen 1 heads to work on the lt1?

[Zupercharged28]

that will be sort of hard to do and expensive as well youre better off selling them and buying LT1 heads. they will have to be ported and new holes drilled in them since they are reverse flow. LOTS OF MOOLAH!

[CKJ]

that will be sort of hard to do and expensive as well youre better off selling them and buying LT1 heads. they will have to be ported and new holes drilled in them since they are reverse flow. LOTS OF MOOLAH!

Its not to awful bad, lets face it, 23 degree heads arn't the greatest when it comes to performance wise thats why people convert lets say 18 & 15 degree to take the place of them :thumbsup:

[Zupercharged28]

hahahah true this. but realize as well that to me $50 is expensive! im only a college kid here guys!!! you know your stuff alot better than i do CKJ

[CKJ]

Hey man, we all learn through stuff we have done before. I'm going through the process of converting heads to the LT1 style. I think its costing me close to 400 for just converting the heads. Thats not even the tip of the iceburg :cool:

[Zupercharged28]

damn man! youve got way deep pockets!!! thats about.... 400 times my bank account right now!

[CKJ]

damn man! youve got way deep pockets!!! thats about.... 400 times my bank account right now!

ha! you would hate to have my build up then.. for the cost of porting, converting and all that good stuff. I paid 600 just for digitization! Thats when the guys who's doing the porting puts the info into a CNC machine to machine parts of the heads. 1500 just for shaft rocker arms..:eek: yeah..i could go oooon and oooon and oooon... The price to play the game of lets go fast iiissssssnnnnnnnn'tttt cheap :werd:

[snakeoilperformance]

Just wondering who can convert gen 1 heads to work on the lt1?

its a real real real pain in the ass.. and if a shop actualy decided to do it, your gonna pay out the ass. u can get a set of lt1 heads cheap and port them yourself.

[Zupercharged28]

ha! you would hate to have my build up then.. for the cost of porting, converting and all that good stuff. I paid 600 just for digitization! Thats when the guys who's doing the porting puts the info into a CNC machine to machine parts of the heads. 1500 just for shaft rocker arms..:eek: yeah..i could go oooon and oooon and oooon... The price to play the game of lets go fast iiissssssnnnnnnnn'tttt cheap :werd:

ohmagod! youre a crazed man sir!! holy McCrackel! you know what i paid for my rocker arms? theyre stock. hahahah but i dont have the car anymore my friend is going to forge it and boost it more. thank goodness its gone we just got snow. its actually still snowing and its going to ice storm over night. trusty tahoe.... ATLEAST IM STILL CHEVY!!