Tin Indian

Friend has a Twin Turbo LS1.

The stock 10.1 compression is not boost friendly. We were just going to install low compression forged pistons, but have maybe come up with another easier/cheaper alternative.

I understand the 6.0 L heads have a larger combustion chamber than stock 5.7 heads.

If we were to have a set of 6.0 heads ported with upgraded stainless valves and 918 springs, would we get the following:

1. Would we get the compression down to about 9.0 to 1. We actually would like closer to 8.5 to 1 in order to run big boost.

2. Do ported 6.0 heads flow as good as ported 5.7 heads that have been fitted with 2.02"/1.57" valves?

Thanks,
Ron

<small>[ July 17, 2002, 03:51 PM: Message edited by: Kimchee and Rice ]</small>

verbs

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>
1. Would we get the compression down to about 9.0 to 1 (we actually would like closer to 8.5 to 1 in order to run big boost} as long as the 6.0 heads were not milled?

2. Do ported 6.0 heads flow as good as ported 5.7 heads fitted that have been fitted with 2.02"/1.57" valves?

Thanks,
Ron</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I thought compression only goes down to 9.5:1 with a set of unmilled 6.0 heads.

Also, 6.0 heads will flow better than LS1 heads.

ls1290

iTrader: (20)

Going with a thicker head gasket will drop it a little lower, but the best thing to do is inverted dome pistons. 6.0L heads and -10cc psitons will make it very boost friendly <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Tin Indian

Quick answer Verbs....

9.5 to 1 <img border="0" alt="[whiner]" title="" src="graemlins/gr_cry.gif" />

I was hoping for closer to maybe 8.8 to 1. I wonder if the CNC machine could remove a little out of the chambers in order to get the comp. a little lower without getting into shrouding problems or poor flame propagation (fancy word <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> ) within the combustion chamber?

Thanks,
Ron

verbs

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>Quick answer Verbs....

9.5 to 1 <img border="0" alt="[whiner]" title="" src="graemlins/gr_cry.gif" />

</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I aim to please <img border="0" title="" alt="[Razz]" src="gr_tounge.gif" />

Tin Indian

Verbs...
This is actually Dug's Incon twin turbo SS here in Phoenix. You may know him.
I am visiting my parents here right now. Need to go back to Korea by the end of this month.

As stated before; "I wonder if the CNC machine could remove a little out of the 6.0 chambers in order to get the CR a little lower without getting into shrouding problems or poor flame propagation (fancy word) within the combustion chamber"?

Anyone else know something about 6.0 heads? Sure would like to get the CR down below 9 to 1 for this boosted motor without changing out pistons.

Low compression / high boost IS is answer to power. With the LS1s 10 to 1 CR, it just does not lend itself to making good boosted power. You just can't run high boost with that kind of static CR on a daily driver. And if you try, you are basically fighting an uphill battle. Yes, there [IS] a reason Buick kept the CR on there GNs to 8 to 1. Same for the Pontiac 89 TTA.

Ron,

XLR8NSS

iTrader: (4)

I think you could get 8.8:1 if you put on a thick gasket, cut valve reliefs in the pistons, get dished valves(I don't know what they're really called but, the face is not flat), and have the chambers on the 6.0L heads cleaned up.

That is the only way I think you'll get lower than 9:1 with the stock pistons. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

John

PS - You could also put some spacers on the sparkplugs to hold them outta the combustion chamber a little bit. j/k <img border="0" title="" alt="[Razz]" src="gr_tounge.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Here is a neat little CR calculator to mess with.

http://www.smokemup.com/auto_math/compression_ratio.php

<small>[ July 17, 2002, 07:49 PM: Message edited by: XLR8NSS ]</small>

verbs

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>Verbs...
This is actually Dug's Incon twin turbo SS here in Phoenix. You may know him.
I am visiting my parents here right now. Need to go back to Korea by the end of this month.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">hahaha !!! I know him all too well. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> Tell him I said hi.

Has he gotten his tuning issues taken care of??

If you are here on the 27th of this month, we are having our monthly AZfbody meeting along w/ a large caravan of fbodies....we'd love for you to join.

Tin Indian

Sounds great, but I may be leaving Fri the 26th.

My TA is in storage here, but has no insurance on it. The Illinois plates on it expired in 99 <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

Its just sleeping away in the garage with a car cover on it. Haven't even takin the car cover off of it this time.

I sent you an e-mail (address in your profile) with a price list I made out from info I recieved from TEA. VERY interesting indeed.

Ron,

BTW, Dug lives only 1 mile from my parents house.

<small>[ July 17, 2002, 08:10 PM: Message edited by: Kimchee and Rice ]</small>

AlonzoVersion 1.0

6.0 heads and thicker heads gaskets would be the cheapest route.If they want to play it safe have the car run a little on the fat side also.

smokinHawk

iTrader: (48)

I posted a bunch of "info about 6.0 heads"

6.0 heads have a 69cc chamber, that will only get you dwn to about 9.8:1, you could use a thicker head gasket with that and get it down to about 9.2:1 with 6.0 heads and a .078 gasket. A .125 gasket will get you even lower, but thats thick!

If your buddy is willing to do it with pistons thats the way to go.
i was going to use the 6.0's and .078 but since i had to replace the bearings i decided to do it right with forged dished pistons and the 6.0 heads i got.

Reckless

iTrader: (9)

Ron...stop trying to talk "fancy" and stick with "foul-mouthed", it fits you better <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

I think dished pistons is the way to go. I have been using 15cc dishes with the deck at set to zero (stock is .006). This nets about 9:1 with stock LS1 heads. To get to 8.5, you'll proll yneed 20cc dishes.

Have fun back in the "Land of not quite right"! <img border="0" title="" alt="[Razz]" src="gr_tounge.gif" />

Tin Indian

Folks.... Thanks for all the replies.

Well,we have talked about 6.0 heads with thicker gaskets, valve reliefs, dished valves, dished forged pistons, and of course the infamous "spark plug spacers" <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Well, I agree that new pistons is the only correct way to get the CR down to lower than 9.5 to 1.

I am still thinking that material could be removed from the chambers of the 6,0 heads with the CNC machine, but I doubt if that would be enough and/or it may cause problems with combustion. I guess Dug could talk to TEA or someone.
_______________________

Todd, your right, I should not try and talk "fancy", especially when I can't spell the words anyway <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />
Those 4 letter words are so much easier to spell and much more effective, and certainly suit my persona (there I go again with another fancy word) <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />

Ron,

<small>[ July 18, 2002, 08:23 AM: Message edited by: Kimchee and Rice ]</small>

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 smokinHawk:
<strong>6.0 heads have a 69cc chamber, that will only get you dwn to about 9.8:1, you could use a thicker head gasket with that and get it down to about 9.2:1 with 6.0 heads and a .078 gasket.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I think this is the most accurate response and the best setup to go with. The 6.0L heads will only drop you .3 pts, the .078 gaskets will drop you .5 pts on the C/R.

Black Sunshine/ 00SS

iTrader: (1)

I think you need to discusss this with Mr. Harlan.. Matt, help the guy out.. <img border="0" alt="[chug]" title="" src="graemlins/gr_chug.gif" />

verbs

I was on the phone with TEA today, and they said they could play with the combustion chambers on the 6L heads to get the compression ratio down to 9.0:1.

You could cheat a little more w/ thicker head gaskets, but then you'd have to deal with quench and more detonation which will make the whole project pointless.

VINCE

iTrader: (1)

Personally I think you could get away with between 9.1:1 and 9.5:1. I know you want to run some boost in there, but remember there are cars running 10#'s on stock compression. The key is the tuning. You can have a 600rwhp car on 9.5:1 with a bigger turbo, conserv tune, 5.7L or 6.0L heads, boost cam I think w/out any issues. Now if you are planning on running 15lbs of boost then yes I would go lower with the compression to be on the safe side.

Ragtop 99

iTrader: (7)

If you were planning on getting ported heads anyways, then have some 6.0 heads set up for a low 9s ratio and go with good gaskets from ARE. wouldn't use the gasket to achieve more than .1
However, if your really want to achieve the power level that comes from cranking the boost up using an 8.5:1 compression, go into the bottom end and do it right. Put a set of boost piston and rings in and stronger rod bolts too.

smokinHawk

iTrader: (48)

If your wanting big power id get into the engine, youll have nightmares worring if the stock bottom end can take it and for how long?
i was going to go with the 6.0 heads and gaskets, but didnt think i could take it past 500 rwhp. now since im forging it out the sky's the limit! <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" />

y2khawk

iTrader: (5)

The CR of my new motor is 8.7:1

6.0 heads, inverted dome pistons. I don't have a cc number on the dish but depth is .070

Stock deck clearance, stock gasket thickness.

I personally would go w/ pistons if Doug is serious about making reliable power. "Safest" way to drop CR IMHO. Keep your squish area on the head, stay away from the problems of really thick gaskets, etc.

<img src="http://harlan-engineering.com/eviltwin/short_block.jpg" alt=" - " />

<small>[ July 19, 2002, 07:16 AM: Message edited by: y2khawk ]</small>