wizkid

iTrader: (3)

Anyone know the compressed head gasket thickness?
Deck height?

Is the 67.3 cc combustion chamber volume take into account the spark plug?

I have some answers for these questions already but I am wanting to double check.

Also, has anyone milled their heads and had the combustion chamber volume measured? If so, can you post how much they were milled and the new volume.


Thanks,

Eric

2quick4u

According to GM, the stock compressed head gasket thickness is 1.33mm or 0.0523". If you use 4" diameter for head gasket hole, then the volume of the compressed open space between piston and head is roughly .657 cid or 10.77cc. Of course the LS1 piston actually sticks up above the block by about 0.007" stock, so you will need to subtract this 'piston above deck' volume. Using a 3.9" diameter piston and a negative piston deck height of 0.007", you get -.084cid or -1.37cc for the piston above deck volume. 10.77cc-1.37cc=9.40cc. But then you have to add back the volume around the top piston ring which is approx. 1.2 cc. So 9.4 + 1.2 = 10.6cc. The 67.3 cc that GM rates the combustion chamber at does include the sparkplug volume I do believe.

So 67.3cc+10.6cc=77.9cc. (709cc+77.9cc)/77.9cc = 10.1 as rated by GM.

[ November 26, 2001: Message edited by: 2quick4u ]</p>

2quick4u

Some stock LS1 dimensions per GM:

Stroke: 3.622"
rod length: 6.098"
block deck height: 9.240"
piston comp. height: 1.338"

piston to deck ht.= block deck ht. - [(stroke/2)+ rod lenght + piston comp. ht.]

9.240" - [(3.622"/2) + 6.098" + 1.338"] = -.007"

So the piston sticks up .007" above the block. The negative sign denotes the piston is above the block. Most conventional engines have the piston slightly below the block deck and would have positive piston to deck heights.

wizkid

iTrader: (3)

Thanks John for the number. <img src="images/icons/smile.gif" border="0">

I have only seen the LS1 rated at 10.1:1 on their website. When you look in their catalog every year, the LS1 is rated at 10.2:1 compression. Weird, huh?

Nick A. gave me a ring volume.

You have mail.

ERic

wizkid

iTrader: (3)

John, thanks a lot for that formula. I was just sitting here wondering how to get that number.

I get 10.12:1

The ring volume is 1.2cc accroding to ARE.

That is good info. on the deck height. I was stumped until Onfire explained that to me. <img src="images/icons/smile.gif" border="0">

Eric

2quick4u

[quote]Originally posted by wizkid:
<strong>
The ring volume is 1.2cc accroding to ARE.

</strong><hr></blockquote>

I added that 1.2 cc back into my CR calc above and got 10.1 CR on the nose.

wizkid

iTrader: (3)

I was using 1.3mm instead of 1.33.

I got 10.09:1 now and feel that is close enough.

<img src="images/icons/smile.gif" border="0">


Now, have any idea on combustion chamber volumes on milled heads? <img src="images/icons/smile.gif" border="0">

Eric

[ November 26, 2001: Message edited by: wizkid ]</p>