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In the '78 and '79 motors, the head was a bit different in the valve relief space. If you look at this pic..
The piston on the right is from a '78 motor, the one on the left is an '82. As you can see, the later model has a considerably higher dome than the '78 does which should equal more compression on the later models... if all things else were equal. The '78 and '79 motors had HIGHER compression ratios than the later models. This is due to the larger valve relief space in the later heads. I call it valve relief space.. which is what it's called on the piston... sorry if I named it wrong.
I think Dan Hodges stated, probably the best performance from these motors in a stock setting, would be later model pistons with an early model head and cams,. The only question in this setup would be to check the valve clearances. I don't remember what the minimum was supposed to be, but I did check mine. I am running an '82 head with the 78 cams. The cylinders are a mute point since they basically all have the same internal measurements when stock. So, whatever the minimum piston to valve clearance was I was supposed to be checking, it was somewhere between 2-3 times more than what was called for... MORE than enough room. What would be even better, would be to shave the head some in the later model to boost compression with the early cams. *Coming soon to my next motor!
Cody, I have never actually done a rebuild really... just pieced old parts together to make one work. I did hone the cylinders this last time and was getting somewhere in the high 150's on compression. I have put a couple hundred miles on this setup I have and will check compression in a bit and get back.
And from discussions on here from before, it was stated that the valve clearances stay with the head used, not the cams??
Tod
The piston on the right is from a '78 motor, the one on the left is an '82. As you can see, the later model has a considerably higher dome than the '78 does which should equal more compression on the later models... if all things else were equal. The '78 and '79 motors had HIGHER compression ratios than the later models. This is due to the larger valve relief space in the later heads. I call it valve relief space.. which is what it's called on the piston... sorry if I named it wrong.
I think Dan Hodges stated, probably the best performance from these motors in a stock setting, would be later model pistons with an early model head and cams,. The only question in this setup would be to check the valve clearances. I don't remember what the minimum was supposed to be, but I did check mine. I am running an '82 head with the 78 cams. The cylinders are a mute point since they basically all have the same internal measurements when stock. So, whatever the minimum piston to valve clearance was I was supposed to be checking, it was somewhere between 2-3 times more than what was called for... MORE than enough room. What would be even better, would be to shave the head some in the later model to boost compression with the early cams. *Coming soon to my next motor!
Cody, I have never actually done a rebuild really... just pieced old parts together to make one work. I did hone the cylinders this last time and was getting somewhere in the high 150's on compression. I have put a couple hundred miles on this setup I have and will check compression in a bit and get back.
And from discussions on here from before, it was stated that the valve clearances stay with the head used, not the cams??
Tod
), > ? not enough valve clearance? right??
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