Why reinvent the wheel? There are lots of strong running 318 builds. just follow a tried and true build like RRR suggests. My built on the cheap runs real good using help from RRR. :burnout:MT
318 with 340x heads sluggish
- Thread starter tmat26
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You cut both sides of the head, block side and intake side. You can use any intake as long as no one has Dorked with it. Since uncut 318 heads are 68 cc's and you are running 65 cc 360 heads, where is the big compression loss? Yes, we are talking 4 passes on the machine. But I always go at least 2 if they have never been cut anyway. You also go from 170 cfm to 210 cfm intake flow, unported. If you want more compression, get pistons.
nm9stheham
Well-Known Member
I had not heard that milling over .040" from 360 heads would cause warping issues.....can someone comment further on that?
Once you mill about .090" off the open part of the 'open chamber' is gone and you get a much tighter closed chamber. But the stock 318 pistons will still be .080" to .090" 'in the hole' and you still won't have improved CR that much. Rahter than a lot of head work, I would not hesitate to change pistons; there are plenty of choices out there ready to go to that will get the CR right up to a nice 9:1 range. If the engine does not have a lot of miles on it, then you can probably get by with a re-hone and avoid a re-bore.
Once the heads are off, a cam change is easy, and a torque converter change is not that much more work.
BTW, I have been sick with a damned cold and sinus infection....but RRR's first post here made me laugh and I feel all better now! LOL Tnx, RRR
Once you mill about .090" off the open part of the 'open chamber' is gone and you get a much tighter closed chamber. But the stock 318 pistons will still be .080" to .090" 'in the hole' and you still won't have improved CR that much. Rahter than a lot of head work, I would not hesitate to change pistons; there are plenty of choices out there ready to go to that will get the CR right up to a nice 9:1 range. If the engine does not have a lot of miles on it, then you can probably get by with a re-hone and avoid a re-bore.
Once the heads are off, a cam change is easy, and a torque converter change is not that much more work.
BTW, I have been sick with a damned cold and sinus infection....but RRR's first post here made me laugh and I feel all better now! LOL Tnx, RRR
now put those heads back on a 340. Just about anything can be achieved with enough money and time.the problem here was not enough research in the beginning. Now we are throwing more money at it_-no point!318-340-360 completely different engines from the factory but mix and match? Lots of research needed or spend lots of money.
moper
Well-Known Member
You can mill a lot off them. Past .100" - been there - done that. But - you can;t cut the intake flange more than about .040 before you get into the valve cover bolt holes. So if you cut that far you HAVE to cut the intake to fit too. Plus you need custom pushrods so factor that in too.
Personally - compression ain't that big of a deal on this build. Put in a cam that works and the rest will be fine.
Personally - compression ain't that big of a deal on this build. Put in a cam that works and the rest will be fine.
.040 will not cause warping. Not sure when that occurs or what compression ratios. A set of untouched heads and "10.5" compression ratios would blow OEM head gaskets, and we would just mill them .020 block side and .019 intake side and be done, when rebuilding. While you were at it you could go .040 and get down to min NHRA cc's. I never went farther than that and never blew head gaskets.
I don't know where you got "360 heads are 68cc" but few and far between that I have measured have ever come in that small. They are all usually in the 72-74cc area. What they are supposed to be and what they are, are two different things.
All of these are moot arguments anyway, since we don't know real numbers.
And I also agree compression is not a huge deal here.......BUT if it is in the 7s and I am pretty sure it is, plus that cam......well........something needs to be done.
JMO.
All of these are moot arguments anyway, since we don't know real numbers.
And I also agree compression is not a huge deal here.......BUT if it is in the 7s and I am pretty sure it is, plus that cam......well........something needs to be done.
JMO.
Did it all the time. Put the best factory heads on, good valve train to match, good intake and Carb, open up the exhaust, and away you go. Doesn't matter if it is a MOPAR, Ford, or Chevy. Do you think 22 cubic inches is gonna make a difference? Same stroke, same rods as a 340, 7 % increase in displacement? Really?? I've run J heads on a 273, cammed right with a 71 TQ, it was killer. He already has the heads.
I agree with you about the OP combination. I never ran someone else's combination. There are too many unknowns. Good ring seal? Good valve job? Where is the timing mark at TDC? What cam is in there and where is it installed? Let alone everything else you guys are pointing out. I'm just not going to buy the 340 X head theory. It is in the combination, and what rpm you want to run at. As you said, you can't just throw a bunch of parts together and expect them to play nice. Any poor machining, or any bad part, let alone a bad combination, can cause the outcome described by the OP. I've seen it over and over again.
Your numbers are correct. 68 cc's were unmilled 318 heads. 65 cc's were J heads milled .040. I also agree that all of these are moot arguments anyway, since we don't know real numbers. You and I are talking about a good pair of heads with quality machine work done.
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