Are thicker head gaskets weaker?
05-22-2011, 10:11 PM
#1
Are thicker head gaskets weaker? Standard LS head gaskets are commonly 0.054" thick.
In the import world that is considered quite thick. Import turbo guys quite often install "thick" 1.2-1.5mm (0.047"-0.059") gaskets in vaine attempts to lower compression.
Cometic stocks MLS gaskets up to 0.125" thick for our motors!!! Two to three times thicker than stock head gaskets! I have a very special set of rods that are a little longer than ideal, and I really want to run them in my new 404 LS2, but they would require a set of these thicker head gaskets. This is for a naturally aspirated, 11.8:1 road-race engine, that will see some street miles.
Any reason to shy away from head gaskets over 0.100" in thickness?
In the import world that is considered quite thick. Import turbo guys quite often install "thick" 1.2-1.5mm (0.047"-0.059") gaskets in vaine attempts to lower compression.
Cometic stocks MLS gaskets up to 0.125" thick for our motors!!! Two to three times thicker than stock head gaskets! I have a very special set of rods that are a little longer than ideal, and I really want to run them in my new 404 LS2, but they would require a set of these thicker head gaskets. This is for a naturally aspirated, 11.8:1 road-race engine, that will see some street miles.
Any reason to shy away from head gaskets over 0.100" in thickness?
05-23-2011, 04:48 AM
#3
The main purpose of the thicket head gasket is to allow you to set your proper quench (.035-.040") for best burn and less knock prone...the fatter out of the deck your pistons stick out the thicker gasket you need...be sure that with these rods your top ring on the piston is still down in the block, I'm not sure how far below the deck your top ring is supposed to be, but I'm sure there is a minimum requirement
05-23-2011, 10:03 AM
#4
Found this here on ls1tech about variances in LS2 deck heights by ChucksZ06 back in 2006
https://ls1tech.com/forums/ls1-domes.../t-543708.html
"My first ls2 block with 4" eagle crank and rods was .005 in the hole. I am now doing an ls2 block with a stock crank and 6.125 rods( same length as 402 build), same piston manufacturer and the pistons are .008 out. I think the stroke on the 4" crank was not quite right. So from my experience you pretty much have to mock up the parts or it is guessing. Good luck."
Keeping the top ring below deck seems like common sense. It's common for the crevice height (top of piston to top of top ring) on performance pistons to range from about 0.180 - 0.320". So presuming (what I consider) a loose quench of 0.035" and super tall 0.125" gasket you should still be safe with low crevice volume pistons all the way down to a crevice height of 0.160". Still that's a little too close if you're running a low crevice height pistons near 0.180".
9.240" Deck height
2.000" less 4" stroke/2
1.115" less my manley piston's compression height (was designed for a 6.125" rod)
6.200" less my lube-tube oliver pistons
puts me 0.075" out of the hole.
for a tight 0.030" quench I'd need a custom 0.105" thick gasket.
I also found Lingenfelters book on google. He mentions that he reccomends 0.250 crevice height for street engines, but has seen all the way down to 0.100" on all out N/A drag engines!
John Lingenfelter on modifying small-block Chevy engines: high performance ...
By John Lingenfelter
http://books.google.com/books?id=GUC...height&f=false
https://ls1tech.com/forums/ls1-domes.../t-543708.html
"My first ls2 block with 4" eagle crank and rods was .005 in the hole. I am now doing an ls2 block with a stock crank and 6.125 rods( same length as 402 build), same piston manufacturer and the pistons are .008 out. I think the stroke on the 4" crank was not quite right. So from my experience you pretty much have to mock up the parts or it is guessing. Good luck."
Keeping the top ring below deck seems like common sense. It's common for the crevice height (top of piston to top of top ring) on performance pistons to range from about 0.180 - 0.320". So presuming (what I consider) a loose quench of 0.035" and super tall 0.125" gasket you should still be safe with low crevice volume pistons all the way down to a crevice height of 0.160". Still that's a little too close if you're running a low crevice height pistons near 0.180".
9.240" Deck height
2.000" less 4" stroke/2
1.115" less my manley piston's compression height (was designed for a 6.125" rod)
6.200" less my lube-tube oliver pistons
puts me 0.075" out of the hole.
for a tight 0.030" quench I'd need a custom 0.105" thick gasket.
I also found Lingenfelters book on google. He mentions that he reccomends 0.250 crevice height for street engines, but has seen all the way down to 0.100" on all out N/A drag engines!
John Lingenfelter on modifying small-block Chevy engines: high performance ...
By John Lingenfelter
http://books.google.com/books?id=GUC...height&f=false
