Selecting the right piston size?
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Selecting the right piston size?
1994 Del Sol Si.
75mm bore. should I go with stock size, or the bigger size 75.50mm?
Will I have to do anything else if I use 75.50mm?
Will 75.50mm increase power?
75mm bore. should I go with stock size, or the bigger size 75.50mm?
Will I have to do anything else if I use 75.50mm?
Will 75.50mm increase power?
Honda-Tech Member
Joined: Oct 2010
Posts: 1,286
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Re: Selecting the right piston size?
When you put a bigger piston in, you have to bore the cylinder. You are supposed to have a certain piston to wall gap and even if a 75.5mm piston fit, it wouldn't have the right gap so it could stick once the motor warmed up.
You can just hone the cylinder and put another 75mm piston in, but there's a risk the cylinder could be egg shaped or have an incorrect piston to wall gap and either gall the piston on the wall from being too tight a gap or get piston slap from being too loose. Proper "engine building technique" dictates boring the cylinder .5mm or .01" over to ensure a perfectly round cylinder. If you're just changing compression with the block in the car, you can just hone and drop other 75mm pistons in and plenty of people do it without any issue at all. If you have the motor out, boring to 75.5mm would be preferable.
Will boring to 75.5 increase power? It would be very minor if it does, but since you would increase displacement and compression minorly, sure, why not? It's not worth doing just for that reason though since it would be entirely too expensive for any gain made after tuning.
You can just hone the cylinder and put another 75mm piston in, but there's a risk the cylinder could be egg shaped or have an incorrect piston to wall gap and either gall the piston on the wall from being too tight a gap or get piston slap from being too loose. Proper "engine building technique" dictates boring the cylinder .5mm or .01" over to ensure a perfectly round cylinder. If you're just changing compression with the block in the car, you can just hone and drop other 75mm pistons in and plenty of people do it without any issue at all. If you have the motor out, boring to 75.5mm would be preferable.
Will boring to 75.5 increase power? It would be very minor if it does, but since you would increase displacement and compression minorly, sure, why not? It's not worth doing just for that reason though since it would be entirely too expensive for any gain made after tuning.
Honda-Tech Member
Joined: May 2011
Posts: 1,030
Likes: 12
From: Laramie, WY
Re: Selecting the right piston size?
When you put a bigger piston in, you have to bore the cylinder. You are supposed to have a certain piston to wall gap and even if a 75.5mm piston fit, it wouldn't have the right gap so it could stick once the motor warmed up.
You can just hone the cylinder and put another 75mm piston in, but there's a risk the cylinder could be egg shaped or have an incorrect piston to wall gap and either gall the piston on the wall from being too tight a gap or get piston slap from being too loose. Proper "engine building technique" dictates boring the cylinder .5mm or .01" over to ensure a perfectly round cylinder. If you're just changing compression with the block in the car, you can just hone and drop other 75mm pistons in and plenty of people do it without any issue at all. If you have the motor out, boring to 75.5mm would be preferable.
Will boring to 75.5 increase power? It would be very minor if it does, but since you would increase displacement and compression minorly, sure, why not? It's not worth doing just for that reason though since it would be entirely too expensive for any gain made after tuning.
You can just hone the cylinder and put another 75mm piston in, but there's a risk the cylinder could be egg shaped or have an incorrect piston to wall gap and either gall the piston on the wall from being too tight a gap or get piston slap from being too loose. Proper "engine building technique" dictates boring the cylinder .5mm or .01" over to ensure a perfectly round cylinder. If you're just changing compression with the block in the car, you can just hone and drop other 75mm pistons in and plenty of people do it without any issue at all. If you have the motor out, boring to 75.5mm would be preferable.
Will boring to 75.5 increase power? It would be very minor if it does, but since you would increase displacement and compression minorly, sure, why not? It's not worth doing just for that reason though since it would be entirely too expensive for any gain made after tuning.
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