How much to shave off the cylinder head.

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Princess Valiant

Princess Valiant

A.K.A. Rainy Day Auto
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So I have a 68 225 slant apart for re- ring.

Engine had minimal ridge and seems to be in very good shape.

I had a thought that I can take the head in to shave it and raise the compression.

Is .090 too much for an engine that I'm not planning to change the cam or much other than putting a 2 barrel on it.

Am I right in thinking it never hurts to raise the compression whenever possible or should I not mess with shaving and leave it??

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No, in fact, I'd make it an even .100. The one on Vixen's engine went like .178-.185. It was an accident....but it worked out. lol You'll end up in the 9:1 area. Perfect.
 
It would benefit WAY more than you think with a small performance cam and better exhaust. I'd think about it if I were you.
 
Wouldn't it be wise to deck the block and if you are going to shave the heads that way both would be good and flat?

Also aren't there thinner head gaskets?

After shaving or decking or both doesn't that affect pushrod length, valve to piston clearance piston to head clearance etc. ?

I know nothing about /6 but the principals should be the same
 
Dana67Dart said:
Wouldn't it be wise to deck the block and if you are going to shave the heads that way both would be good and flat?

Also aren't there thinner head gaskets?

After shaving or decking or both doesn't that affect pushrod length, valve to piston clearance piston to head clearance etc. ?

I know nothing about /6 but the principals should be the same
Click to expand...
That's a good idea of course. Those thin stamped steel head gaskets are getting hard to find now, though.
 
I typically don't mess around with head gaskets on classics. I use Cometic. Yes they are spendy. But always been happy.

JMO
 
My opinion: Measure what you have, then take off the needed amount (either deck, head or both) to get between 8.7 and 9-1. Use the numbers for an "aftermarket" head gasket, (as the OEM stamped steel gasket is getting hard to find). There is absolutely no downside to raising the CR of a slant, within reason. Helps with power, and fuel milage.
With a 225 engine there is no issue of piston to vale clearance, unless using aftermarket "race" pistons, or are doing excessive milling, and using a big cam.
With a 170 engine you need to be careful, as the pistons come to the top of the cyl in stock form.
With .100 off the head/deck should be ok on pushrod length, but should still be checked.
 
I took 0.070 off the head and another 30 off the block, wish I'd have done more. Especially since damneer any head gasket you're gonna find will be at least double the thickness of the original. So the first 20 or so you have milled will only get you back to where it was from the factory.
Those prices you showed for the mill job seem a little crazy, but I dunno the machine shop you 4 using or what part of the country you are in.
Even if it took a little bit longer to complete the job id definitely do the cam while it's apart this time. Alot easier to do while it's apart for the first (and hopefully only) time.
It will cost more to put a cam in later as well. More time wrenching, more more gaskets, more everything.
What cam did you have in mind? New? Reground? I see people that have cams for sale here and on the /6 site now and then, you might be able to save some money.
 
We went with .100 on a stock 1967 225 head shave. Block was checked with a straight edge and was good.
No problem with push rods plenty of adjustment. Most we ever did was .125 off the head.
In the old days we did triple .100. Block Head and Bore.When doing a total rebuild.
 
Darter6 said:
We went with .100 on a stock 1967 225 head shave. Block was checked with a straight edge and was good.
No problem with push rods plenty of adjustment. Most we ever did was .125 off the head.
In the old days we did triple .100. Block Head and Bore.When doing a total rebuild.
Click to expand...
What piston did you use at .100 over?
 
I still say Measure what you have then figure what you need to do to get 8.7-9.0 CR. After 9.0 tuning can be a PIA, if wanting to run 87-89 octane.
Don't just go milling willy/nilly.
 
Charrlie_S said:
I still say Measure what you have then figure what you need to do to get 8.7-9.0 CR. After 9.0 tuning can be a PIA, if wanting to run 87-89 octane.
Don't just go milling willy/nilly.
Click to expand...
I completely agree with Charrlie. Measure and calculate first, then machine it. I took .060 off my head and now wish I'd done another .030-.040 off the block. I wanted to run regular swill in it so shot for 8.5 SCR. I got 8.4 but wish I was closer to 9.0.
 
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