Moparblake33
Member
I have a set of 360 J-heads cast number 3671587-A id like to do a quick and dirty compression bump how much can I take off without intake fitment issues
How far can i mill my heads without intake issues
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PRH
Well-Known Member
.030” on uncut heads is usually safe, but as with all this stuff……. “Ymmv”
Test fit with no head gaskets and see how close it is for the intake to fit.
Test fit with no head gaskets and see how close it is for the intake to fit.
Moparblake33
Member
Ill make up the difference with gasket if I have too I guess haha
When ever you cut the heads or deck always have the intake fitment checked. Height and angle. never assume its correct.
That's same as cutting the heads. If you cut the heads .030" and use a .030" thinner gasket, you just basically cut the heads .060". The proper way is to cut the intake as well regardless. A lot of people don't
I love how they always leave the slant 6 outta this kinda stuff. lol
many shops can cut your heads
how many can mill things to match?
Shop: "we can mill the head 0.080"
can you match the intake"
Shop: we don't do intakes
a shop that doesn't understand, or provide all your solutions
find another shop
Exactly.
Don't cheap out. Mill both sides of the heads, block and intake. Then you will be done without problems.
Well, I have milled two different small block pairs of heads - one a 340, other the 360 in my 67 Barracuda now - .030 without alignment issues. However, in both cases I replaced the original steel shim head gaskets with Felpro .039 thick head gaskets on because at the time (1979 and 1990) I didn't think about how much thicker they were than the originals - almost .020 thicker. So effectively I only milled them .010.
Not too long after putting the 360 together, I replaced the Fel Pros with some composition head gaskets that were supposed to be .024-.028 thick. About .005 thicker than stock. Still no alignment issues with the .030 mill.
.030 mill would be worth about half a point if the head gasket thickness is the same before and after.
Edited to correct that the 360 got the thinner head gaskets after the .030 mill to the original heads. It now has un-milled Indy LAX heads with the same thinner head gaskets.
Not too long after putting the 360 together, I replaced the Fel Pros with some composition head gaskets that were supposed to be .024-.028 thick. About .005 thicker than stock. Still no alignment issues with the .030 mill.
.030 mill would be worth about half a point if the head gasket thickness is the same before and after.
Edited to correct that the 360 got the thinner head gaskets after the .030 mill to the original heads. It now has un-milled Indy LAX heads with the same thinner head gaskets.
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MOPAROFFICIAL
Well-Known Member
When you mill the head over .030, the bolt hole alignment with the manifold starts to reach its limit. The holes are moving inward 'center' and lower. Anything port matched must be mocked up for milling ,if necessary , and based on those thingers called gaskets.. even modified ones, they center off the bolt holes.
Aka final mock up for correct intake fitment is necessary to get it right to maintain any hope for a nuts on port window alignment .. etc.
Aka final mock up for correct intake fitment is necessary to get it right to maintain any hope for a nuts on port window alignment .. etc.
I think I've done .045 without cutting the intake. Bolt holes aligned even better than they did from the factory
MOPAROFFICIAL
Well-Known Member
Because you put a .047-.054 head gasket on it duder...
MOPAROFFICIAL
Well-Known Member
Sometimes people forget that these things came with like .019-.021 steel gaskets, and on the intake as well.
bottom line is there is no real cut and dried answer because we don't know the deck height, exactly what gasket everyone uses, what the heads and intake were precisely before any milling. I can tell you I cut several small block heads and never an issue.
sometimes... and sometimes I ran the MP thin head gaskets.... and what's a duder ?? lol
Slantsix64
Well-Known Member
Yea I have done .045 on a 360 with stock heads. I knew they were stock because I pulled them out of a low miles dodge van myself. If you don’t know that’s another story.
I have also cut .045 off of some stock 302 heads as well.
MOPAROFFICIAL
Well-Known Member
I've cut them J's down to 59cc...
... or did i....
... or did i....
I cut a slant head to 34ccs. lol
MOPAROFFICIAL
Well-Known Member
...Or was it those bigger valves I put in and where I set valve job...
MOPAROFFICIAL
Well-Known Member
If it were a high miles Magnum engine the compression would be raising as you drive it.. till the carbon turned into a glow plug..lol
You were probably stickin your little pecker in the spark plug holes.
MOPAROFFICIAL
Well-Known Member
Are you typing one handed again?
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