how much can you shave an L98 head before its done

turtlevette

turtlevette

The Turdle
Joined
Mar 24, 2008
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1,492
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Marshfield, MA
i'm up to 20 thous after overheating them again.

the lowpoint is between the middle cylinders every time on both heads.

it takes about 10 thous to level it out.

anyone know how thick the deck is to begin with. The fast burn are 0.4"
 
That's the problem with those lightweight castings, they are pretty thin and therefore warp easily (much easier than heavier aftermarket heads), if you have the heads off you can easily measure the deck thickness in some of the coolant ports. 20 thousand, don't think there's a whole lot left there.
 
And that's where you might have a problem. What's your deck height? Stock? Probably 9.025 or thereabouts. Piston will be down the hole from 9.000 so assume you have it at least .030 down the deck, add a .051 gasket to it and you have a quench height of around .080 or in other words, no meaningful quench at all. Above about .060 it's pretty much worthless. With those small chambers you need to have good quench to keep the engine from detonating. Maybe that's why your fire ring is messed up.
 
Twin_Turbo said:
And that's where you might have a problem. What's your deck height? Stock? Probably 9.025 or thereabouts. Piston will be down the hole from 9.000 so assume you have it at least .030 down the deck, add a .051 gasket to it and you have a quench height of around .080 or in other words, no meaningful quench at all. Above about .060 it's pretty much worthless. With those small chambers you need to have good quench to keep the engine from detonating. Maybe that's why your fire ring is messed up.
Click to expand...


this is just a temporary situation while i'm working on the new engine.
 
I had a set of CI heads off my early 86 Vette angle milled .080 and didn't have a problem. I wanted to go more (looking for more CR), but any more of a cut would have interfered with an outboard water port.

Could be I lucked out though so I'm hesitant to recommend it. A dirt track shop in Dallas did the work for me.

I do know for a FACT that they're thin wall castings because even a rather small amount of port enlargement caused me to grind through one verticle intake port wall. I believe it was the forward-most #7.

Jake
 
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