smokinHawk

iTrader: (48)

Ok over on ls1.com I read up that you can change the compression ratio with just the head gaskets. This is good news to me seems like a cheap way to get the cr down with out the expense of new heads.

Ok now what C/R should i get??Choices below

How much do you think labor is? you dont have to drop the motor to do this do you??

My goals are 500rwhp on pump gas (93-94)with the T-76 kit.

1.7mm/.067" = 9.85:1
2.0mm/.078" = 9.6:1
2.5mm/.098" = 9.25:1
2.8mm/.112" = 8.95:1
Stock 1.3mm/.054" = 10.1:1

Cablebandit this might be a good way of getting rid of detonation cheaply.

y2khawk

iTrader: (5)

Lower is better <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

FWIW, i'm going to a hair under 9:1 and the plan is to attempt 600 RWHP on pump gas <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> if i get there is the question.

With the heads and cam i think i can do it. We shall see.

But, i say go 9:1 and run 12 psi <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" />

Cool28

iTrader: (2)

Thats well and good but I would think it would make it easyer to blow a gasket.

SJH

It may be cheap and easy but it's the WORST way to do it.
This type of head greatly relies on the tight squish area for power, response and mixture motion.
The tighter the better. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
A thick gasket kills this area and you'll be much more prone to detonation compared to doing it right with pistons.
Steve

<small>[ March 15, 2002, 07:52 AM: Message edited by: SJH ]</small>

smokinHawk

iTrader: (48)

Now im confused, I though by lowering th CP you would get rid of more detonation. I know that changing out your pistons is the best way of doing it rather then heads or gaskets, but will changing out gaskets help at all for runnig pump gas at higher boost?

SJH

The area between the piston and the flat portion of the chamber is called the squish or quench area.
<img src="http://www.aera.org/Members/EngineTech/G597.gif" alt="" />
Opening this area up will increase your octane requirement.Now will the lower compression vs the trade off a a less effective squish area be worth it? I don't know.
I personally would not do it that way, but that's just me
Steve

smokinHawk

iTrader: (48)

Anyone else what to chime in on this question? <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

Blackbird

This says it all. SJH knows his shiznit. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

http://www.ralphsmachine.com/Compression_2.ivn

SJH

Blackbird, That is a very good tech article and well worth reading. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

This quote from that article should get the attention of anybody looking to run thick headgaskets for a bandaid compression drop."This is why the piston manufacturers tell you that a 10 to 1 engine is less likely to detonate with an 0.035 quench height than a 9 to 1 engine with .060 inch of quench. And, they are of course absolutely spot-on-the-money right.
"

Steve

MelloYellow

Yes, the quench argument comes up.

All I know is that real world, the LT1 Supercharged guys experimented a lot with thicker gaskets. The quench argument came up but was never an issue. Noone using thicker gaskets ever saw any detonation. A lot of them used double size or larger gaskets. I'm only adding 40% to the thickness of my gasket. .7mm

I know Nick at ARE has no problem going from stock .054" -> .067" or +20%. He didn't mention any reservations when I brought up the .078" +40% thicker gasket.

LT1's ran gaskets up to double with no probs. So even the LS1 .112" might be ok.
http://forums.corvetteforum.com/zero...376253#2376253

<small>[ March 17, 2002, 10:04 AM: Message edited by: MelloYellow ]</small>

MelloYellow

Btw, what is the stock quench measurement?

Where would you end up w/quench using a .024" thicker gasket?

TIA

SJH

stock is about .045" - a stock graphite compressed gasket is about .052" and with a positive .007" deck height.

smokinHawk

iTrader: (48)

I would think that the reason you drop compression is to lower the chance of detonation so you can use pump gas.
<img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Has any one seen if this actually works?