Compression help for ls2 427?
Compression help for ls2 427? I Just got new heads for my motor and need to know the compression it will be. I have a 4.125in. ls2 sleeved block with a 4.0inch crank. Just ordered 4.125 cometic head gaskets that are .040" thick and the heads are 65cc. I have 6.125 rods and wisco pistons with -8 dish. I do not know the deck height so is there any way to figure it out?
Thanks,
Matt
Thanks,
Matt
First off, your gaskets are not large enough. You should have atleast 4.130" bore gaskets, and I would recommend 4.150 (which is the stock LS7 gasket bore size). The bore is going to be larger than 4.125" remember, for piston clearance.
Secondly, without your deck height, there is no way to tell what your compression is going to be. But assuming a zero deck height your compression will be 11.73:1 SCR.
To measure your deck height, put a straight edge over the piston, and turn the piston till it touches your straight edge. Then, using a dial guage, place it at a 90 degree angle at the pin side (middle left or right) of the piston. Zero your dial guage, then rotate the motor and watch till the needle goes up and then starts to go back down. Whatever the highest the needle went is how far the piston comes out of the hole, and this is your deck height. Get this measurement, and I will get you the correct compression value.
Secondly, without your deck height, there is no way to tell what your compression is going to be. But assuming a zero deck height your compression will be 11.73:1 SCR.
To measure your deck height, put a straight edge over the piston, and turn the piston till it touches your straight edge. Then, using a dial guage, place it at a 90 degree angle at the pin side (middle left or right) of the piston. Zero your dial guage, then rotate the motor and watch till the needle goes up and then starts to go back down. Whatever the highest the needle went is how far the piston comes out of the hole, and this is your deck height. Get this measurement, and I will get you the correct compression value.
I assume your using Wiseco piston part # K395X125 which has a '0' piston to deck height with a stock 9.240" block deck height.
I agree with Haans249, you should go with at least a 4.150 head gasket bore diameter.
Here's the calculation:
I agree with Haans249, you should go with at least a 4.150 head gasket bore diameter.
Here's the calculation:
