Machine shop took 0.35mm off block and 0.1mm off head. The head has been rebuilt once with an unknown amount taken off. I got my machine shop to measure the head but it didn't match up to the size listed on here at all so I don't know what points were used to measure. I've heard 116mm on here and my machine shop measured around 140mm. So that will be of no help.
I'm going to have to assume around 0.1mm was taken off the head during the previous rebuild. A compression test on my previous setup with a stock HG gave me between 140psi and 145psi with #6 at 150, so there couldn't have been too much taken off.
I'd like to keep as close to stock compression as possible... but I can't find a good answer to what the stock gasket thickness is. I know that according to IJ, it is 1.37mm compressed. But according to HKS, a MHG size of 1.0mm gives you the stock 8.4:1 compression. Which then makes sense why they make a 1.2mm gasket. And a thread in the SupraForums MK3 FAQ claims the stock HG thickness is 1.2mm. And then on the titanmotorsports website, they describe using the 1.2mm to keep stock compression after cleaning up the stock head and block (suggesting 0.1mm off the top and bottom each).
So my choice of head gasket is between a Greddy 1.5mm and an HKS 2.0mm. If I am to use 1.37mm as the starting point of the HG thickness, then I would go with the 2.0mm. But if the starting point is 1.0mm I should go with the 1.5mm. .... but THEENN if I go with the 1.5mm, and the gasket was actually 1.37mm to start, and maybe i'm wrong about the 0.1mm off during the last head rebuild, I could be increasing my compression quite a bit.
So whats a guy going to do? I'd rather have my compresion a little higher than stock rather than a little lower... But I can only get 91 oct in most places around here so I don't want get too high of compression. And I'm going to be boosting 10psi to start.
Am I overthinking this? does it really make that much of a difference?
I'm going to have to assume around 0.1mm was taken off the head during the previous rebuild. A compression test on my previous setup with a stock HG gave me between 140psi and 145psi with #6 at 150, so there couldn't have been too much taken off.
I'd like to keep as close to stock compression as possible... but I can't find a good answer to what the stock gasket thickness is. I know that according to IJ, it is 1.37mm compressed. But according to HKS, a MHG size of 1.0mm gives you the stock 8.4:1 compression. Which then makes sense why they make a 1.2mm gasket. And a thread in the SupraForums MK3 FAQ claims the stock HG thickness is 1.2mm. And then on the titanmotorsports website, they describe using the 1.2mm to keep stock compression after cleaning up the stock head and block (suggesting 0.1mm off the top and bottom each).
So my choice of head gasket is between a Greddy 1.5mm and an HKS 2.0mm. If I am to use 1.37mm as the starting point of the HG thickness, then I would go with the 2.0mm. But if the starting point is 1.0mm I should go with the 1.5mm. .... but THEENN if I go with the 1.5mm, and the gasket was actually 1.37mm to start, and maybe i'm wrong about the 0.1mm off during the last head rebuild, I could be increasing my compression quite a bit.
So whats a guy going to do? I'd rather have my compresion a little higher than stock rather than a little lower... But I can only get 91 oct in most places around here so I don't want get too high of compression. And I'm going to be boosting 10psi to start.
Am I overthinking this? does it really make that much of a difference?
