shaving iron heads.....how much?
10-22-2014, 02:36 PM
#1
Safety Car
Thread Starter
shaving iron heads.....how much?
Along with an intake manifold change out (Edelbrock EPS) I'd also like to install thinner heads gaskets for a bit more compression. I have a set of Fel Pro 1094's and was thinking to go with those.
From what I gather it is advisable to have the heads shaved to insure flatness. .. How much to shave? .. How much is considered too much before running into problems with intake manifold seating along with bolts and threads not lining up properly?
Thanks
From what I gather it is advisable to have the heads shaved to insure flatness. .. How much to shave? .. How much is considered too much before running into problems with intake manifold seating along with bolts and threads not lining up properly?
Thanks
10-22-2014, 03:44 PM
#3
Safety Car
If you're going to use thinner head gaskets, for that matter even if you aren't, check the piston to head surface clearance in the quench area (the flat part of the piston top and the flat head surface away from the combustion chamber). The clearance with the head gasket you use should be about .040 inches.
You can usually mill .025 inch off the heads without any need to mill the intake manifold. If you want to mill off more than that, you can adjust for the new intake port position by milling the intake manifold surfaces by 0.5 to 0.7 times the amount you milled the heads (because the intake ports are at 30 to 45 degrees angle with respect to the block deck). You may have to put a same thickness spacer under the distributor to avoid interference between the oil pump drive blade on the distributor and the oil pimp drive shaft. It would be a good idea to check piston to valve clearance after milling particularly if you have a big cam with a lot of valve overlap.
Just be aware that some original head castings didn't have much metal on the deck surface. It's too easy to mill into a water jacket or make the head so thin it will warp or crack from heat expansion.
You can usually mill .025 inch off the heads without any need to mill the intake manifold. If you want to mill off more than that, you can adjust for the new intake port position by milling the intake manifold surfaces by 0.5 to 0.7 times the amount you milled the heads (because the intake ports are at 30 to 45 degrees angle with respect to the block deck). You may have to put a same thickness spacer under the distributor to avoid interference between the oil pump drive blade on the distributor and the oil pimp drive shaft. It would be a good idea to check piston to valve clearance after milling particularly if you have a big cam with a lot of valve overlap.
Just be aware that some original head castings didn't have much metal on the deck surface. It's too easy to mill into a water jacket or make the head so thin it will warp or crack from heat expansion.
10-22-2014, 06:45 PM
#4
Safety Car
Along with an intake manifold change out (Edelbrock EPS) I'd also like to install thinner heads gaskets for a bit more compression. I have a set of Fel Pro 1094's and was thinking to go with those.
From what I gather it is advisable to have the heads shaved to insure flatness. .. How much to shave? .. How much is considered too much before running into problems with intake manifold seating along with bolts and threads not lining up properly?
Thanks
From what I gather it is advisable to have the heads shaved to insure flatness. .. How much to shave? .. How much is considered too much before running into problems with intake manifold seating along with bolts and threads not lining up properly?
Thanks
10-22-2014, 07:51 PM
#6
Team Owner
But doing that!
If you're going to use thinner head gaskets, for that matter even if you aren't, check the piston to head surface clearance in the quench area (the flat part of the piston top and the flat head surface away from the combustion chamber). The clearance with the head gasket you use should be about .040 inches.
You can usually mill .025 inch off the heads without any need to mill the intake manifold. If you want to mill off more than that, you can adjust for the new intake port position by milling the intake manifold surfaces by 0.5 to 0.7 times the amount you milled the heads (because the intake ports are at 30 to 45 degrees angle with respect to the block deck). You may have to put a same thickness spacer under the distributor to avoid interference between the oil pump drive blade on the distributor and the oil pimp drive shaft. It would be a good idea to check piston to valve clearance after milling particularly if you have a big cam with a lot of valve overlap.
Just be aware that some original head castings didn't have much metal on the deck surface. It's too easy to mill into a water jacket or make the head so thin it will warp or crack from heat expansion.
You can usually mill .025 inch off the heads without any need to mill the intake manifold. If you want to mill off more than that, you can adjust for the new intake port position by milling the intake manifold surfaces by 0.5 to 0.7 times the amount you milled the heads (because the intake ports are at 30 to 45 degrees angle with respect to the block deck). You may have to put a same thickness spacer under the distributor to avoid interference between the oil pump drive blade on the distributor and the oil pimp drive shaft. It would be a good idea to check piston to valve clearance after milling particularly if you have a big cam with a lot of valve overlap.
Just be aware that some original head castings didn't have much metal on the deck surface. It's too easy to mill into a water jacket or make the head so thin it will warp or crack from heat expansion.
Last edited by TCracingCA; 10-22-2014 at 07:53 PM.
10-22-2014, 09:25 PM
#7
Le Mans Master
I usually have the shop take a very light cut on the heads, .003 will show if you have any high or low spots and you can decide what to do from there. Unless you are talking about Angle cutting for more compression, if that is the case sealing will be difficult.
I have seen the heads clean 100% with .003 and I have seen it take .007 to .010 but then you know they are perfect. Make sure the shop you choose has great equipment.
If they tell you the job will be done on a belt sander take your parts and RUN.
I have seen the heads clean 100% with .003 and I have seen it take .007 to .010 but then you know they are perfect. Make sure the shop you choose has great equipment.
If they tell you the job will be done on a belt sander take your parts and RUN.
10-22-2014, 09:30 PM
#8
Team Owner
And if you can't find a good machine shop!
I usually have the shop take a very light cut on the heads, .003 will show if you have any high or low spots and you can decide what to do from there. Unless you are talking about Angle cutting for more compression, if that is the case sealing will be difficult.
I have seen the heads clean 100% with .003 and I have seen it take .007 to .010 but then you know they are perfect. Make sure the shop you choose has great equipment.
If they tell you the job will be done on a belt sander take your parts and RUN.
I have seen the heads clean 100% with .003 and I have seen it take .007 to .010 but then you know they are perfect. Make sure the shop you choose has great equipment.
If they tell you the job will be done on a belt sander take your parts and RUN.
Just Kidding!
PS if anyone hints that they have done this, you are banned!
10-23-2014, 02:08 PM
#10
Safety Car
Thread Starter
The pistons are flat tops. With the thinner head gasket and shaving the heads it looks like doing this would be worthwhile to gain about .5 in compression ratio. Not expecting any cam lift issues as it's an LT-1. I'll check clearances to make sure.
Thanks, guys.
Thanks, guys.