383LQ4SS

iTrader: (33)

What is the stock dimension between the piston at TDC and the flat portion of the head. I read somewhere that .035 is ideal. I believe the LS1 stock has alot more than that. What would happen If I took 6.0 truck heads and put them on a stock LS1 bottom end with .078 Cometic head gaskets? Would the quench are be too large and cause detonation problems? That combo above seems like a great way to lower compression...but will it cause problems?

On the flip side..If on my 11.5 to one motor..if I got head gaskets to get a dimension closer to the ideal .035 quench area....yes..compression would be bumped..but would the smaller more active quench area help fight the detonation associated with a higher CR engine?

Anyone out there have knowledge on this and the benifits of quench and how it relates to LS1s?

guadofreak

iTrader: (1)

<img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

MelloYellow

I think it's all BS sweating about .054->.078

I just added them to my new engine @ .078
Will post if I have any detonation issues. My mechanic laughed about it too. People prefer to sell complete engines rather than just a gasket I guess.

Sometimes analyzing numbers too closely is just ****. It's only a 30% increase in thickness. LT1's have run up to Double thickness without any detonation issues. Whereas the SC'd LT1's that were using double thick gaskets listening to quench arguments went back to a single that improved quench but raised the compression. With the single and higher C/R the detonation returned. With the double gasket and lower C/R and worse quench, detonation disappeared.

I wouldn't go past .078 tho.

<small>[ April 13, 2002, 12:22 AM: Message edited by: MelloYellow ]</small>

ChrisB

"Quench" is not a fairy tail - it is *very* real. I would shoot for a 0.035 to 0.045" quench. On the LS1 you also have to consider the positive deck height of the piston at TDC and subtract that from the head gasket thickness.

I have *never* seen anyone use headgasket thickness to lower compression and have good results, I would be interested in any evidence. I have seen quite a few motors run on compression ratio's and pump gas higher than you would think possible (12.3-12.5:1 LT1's) - and they all shared excellent quench characteristics.

The headgasket is not the place to lower compression - piston dish and chamber volume are where you need to do that.

Chris

383LQ4SS

iTrader: (33)

Thanks for the replies so far. So if a head gasket is not the "ideal" way to lower compression...what about increasing compression with a head gasket and at the same time improving the quench area to a near perfect .035. Is that a common practice?

And does anyone know the stock LS1 dimensions?

LS1derfull

are you adding forced induction? Because i believe motor is better off with hi compression in almost any circumstance, it will just run better and less prone to detonation with small quench area. If your not running F/I i would rather adjust throttle to less than WOT to cure detonation than give up tight combustion package. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

VINCE

iTrader: (1)

Al you thinking about doing what I am doing? I am going with the 6.0L heads next and I am having them opened up for lower compression secondary to others recommendations. I am not playing around with the head gasket thing.. I just want to get around 9.1:1 for my next setup.. Next year is the new setup..

383LQ4SS

iTrader: (33)

No Im not going forced induction. Im just trying to learn a little more as it relates to my ARE motor build up. This subject is rarely talked about and wanted more info on it.

Im looking through my build sheet right now trying to determine what the quench area distance would be. Is "deck clearance" the distance between the piston top at TDC and the block deck? If so then that would be .002 on my engine, combined with a .054 head gasket would give me a .056 quench dimension...is this correct? My compression is 11.5 to one. Would a better quench dimension of .035-.040 be a step forward in detonation fighting even though compression would be bumped up?

VINCE

iTrader: (1)

To deep for me..

MelloYellow

Does bowl porting affect the quench distance?

I believe the stock pistons come +.006 out of the hole if that helps. But a couple people joked about GM production line tolerances, so +.006 is pretty exact. Dunno what production variance would be.

Also, does the stock .0524" gasket compress when TQ'd down?

Milling heads would reduce quench height, eh? but how does bowl porting offset it?

FWIW, I'll post my results. Won't be blown for another 3-4 months, so might run 89 Octane and ATAP the results with my .078" Head Gasket too.

TimZ28

Milling the heads won't effect the distance but decking the block will.

LS1derfull

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 383LQ4SS:
<strong>No Im not going forced induction. Im just trying to learn a little more as it relates to my ARE motor build up. This subject is rarely talked about and wanted more info on it.

Im looking through my build sheet right now trying to determine what the quench area distance would be. Is "deck clearance" the distance between the piston top at TDC and the block deck? If so then that would be .002 on my engine, combined with a .054 head gasket would give me a .056 quench dimension...is this correct? My compression is 11.5 to one. Would a better quench dimension of .035-.040 be a step forward in detonation fighting even though compression would be bumped up?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Your quench is close to stock, i would leave it that way, not reduce it or raise compression. You should be ok, thats what knock sensors are for, or program setup for less timing advance with 11.5 to 1. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

ChrisB

Yep, I agree with LS1derfull - I would take the increase in comp. level to go with a 0.035-0.045" quench. Have the head worked but not milled (just surfaced true - take off as little as you can)- you should be able to get the comp. ratio decently low that way - and when you rebuild your bottom end just select an appropriate piston to complete the package (when the time comes)

Chris

MelloYellow

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by ChrisB:
<strong> I have *never* seen anyone use headgasket thickness to lower compression and have good results, I would be interested in any evidence. I have seen quite a few motors run on compression ratio's and pump gas higher than you would think possible (12.3-12.5:1 LT1's) - and they all shared excellent quench characteristics.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Have you ever seen bad experiences with thicker headgaskets? Specific examples?