How do you figure ? Based on what ?
Basically if the OP is fine making 200-300 hp then the stock heads are fine but if wants to make over 300 hp he needs to do something about the heads needs more air flow.
318 build
- Thread starter ryan1964
- Start date
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You really need to know what you have. J heads are great with the right combination on a 318. If they have not been milled before, you can have them milled .040 and .038 on the intake side. That should get you down to 65cc per chamber. Do yourself a favor and call Jim at Racer Brown and get a custom cam for your combo. You will need to know a lot about your car for him to know what will work best, gear ratio, tire size, compression. You also need to be honest with yourself about what you want.
You dont have a clue
340 heads on a 318 have been done thousands of times
Was also in the direct connection bible under 13 sec 318 build
quit while your behind
Newbomb Turk
Well-Known Member
You know Dan, the first engine I built was a 318 with 360 heads. We didn’t mill the crap out of them either.
Strip Dominator. Hooker 5204 headers. And a 284/484 cam.
And you know what? He took money from a lot of fools who underestimated that little 318.
I do not know what math you are using or what experience you have but it clearly is wrong.
That engine didn’t need rpm to make power. The idea that ANY production cylinder head is too big for a 318 is silly and wrong.
These things are under valved and under headed severely. You can’t hurt a 318 with a W2 head. And you don’t have to spin the engine to the moon.
This idea you can get the heads too big on one of these engines is nonsense.
A 273 is 80% the size of a 340 if you look at the port cc and cfm there on par with there cid ratio with each other in other words a 273 head is about 80% the cfm and cc as a 340 X head.
A 318 is 93% the size of a 340 but basically comes with 273 head a j head is more inline with what a performance 318 should come with.
No one considers the 273 and or 340 be over headed.
P.S. If you hold the 360 to the same ratio it should of came with something like Edelbrock Rpm heads. Probably why the 273/340 are considered the revver's of the family.
A 318 is 93% the size of a 340 but basically comes with 273 head a j head is more inline with what a performance 318 should come with.
No one considers the 273 and or 340 be over headed.
P.S. If you hold the 360 to the same ratio it should of came with something like Edelbrock Rpm heads. Probably why the 273/340 are considered the revver's of the family.
Newbomb Turk
Well-Known Member
Every time My uncle or cousin or me have swap a 340/360 top end on a low cr 318 has worked fine, my cousin had to run one in his late model stock car for a few weeks cause his 360 spun a bearing, he was down some power but still kept up with the leaders.
Dan the man
Well-Known Member
So, from what you're saying, 190cc intake runner size cylinder heads wouldn't be to much for a 318? Especially a mild build as it seems like the op is doing?
They also work great on 273's if you are careful.
Dan the man
Well-Known Member
Thanks guys for bringing to light the real benefits of having 360 heads on the 318's. I do have a question, if the heads are milled like 0.040" and the block is zero decked and if I remember correctly it takes 0.012" for the KB pistons and the use of a thinner head gasket wouldn't that affect the actual torque reading of the cylinder head bolts? What about lifter preload? I guess that I didn't realize just how bad the 318's were under cylinder headed as well as the cr and the small cam.
PRH
Well-Known Member
I sense this coming on…….. or has it happened already?
Torque is the same for head bolts. You want the same clamping force on the gasket. Lifter preload should be acceptable, but that is a big can of worms depending on how well you want to run.
Dartswinger70
Well-Known Member
I knew a feller who ran the 360 head on a 318. he said "it ran good" now I'm not too sure what he meant by "ran good" though...
Dan the man
Well-Known Member
I don't think that I made my question very clear. If the cylinder heads are milled 0.040"-0.050" and the block has been decked for a zero deck height which would be around 0.012" for the kb pistons and then if they use a 0.021" thick head gasket instead of a 0.028 " thick gasket that's a total of 0.059". That has to affect the cylinder head bolts length making them to long by 0.059" is this correct?
Correct. One mark on a 1/16 ruler. I always bottom tap the block for the head bolts anyway.
Dan the man
Well-Known Member
I do too. Most small blocks have " blind" cylinder head bolt holes and almost a 1/16" of a inch could cause problems. I'm the only one who has ever mentioned this.
You really need to stop. Just stop. Someone will eventually take your stupidness as gospel and follow your ridiculous instructions and lead themselves down a dismal non power making path. Just stop. You don't know WTF you're talking about.
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TT5.9mag
Two atmospheres are better than one
I think the second engine I built when I was 16 was almost exactly the same as your first. 318, 360 heads, 284/484, same headers, but I used an rpm dual plane and a 750vs Holley. Ran pretty good. Sounded awesome through cherry bomb header mufflers.
If you want a 318 hit the easy button and get a 5.2 magnum. Better compression and heads, as well as a roller cam on the cheap.
Dan the man
Well-Known Member
This may very well be the time that you are wrong. The op hasn't really said anything about how the car will be used. The cam choices that he originally listed are mild at best. Bigger valve's and ports are better for higher rpm's, making power and I agree but with his cam choices the bigger valve's and ports will hurt low rpm velocity which affects throttle response and low to midrange torque. From what little information that the OP provided he would probably be better off with cleaning up the bowl area and a good competition valve job. As you should know, bigger valve's and ports move the power band up as they improve flow and high rpm breathing. I also mentioned above milling the cylinder heads and having the deck milled for a zero deck height, the small block mopars that I've dealt with all had "blind " cylinder head bolt holes and when there had been almost a 1/16" removed that makes the heads bolts that much to long and could cause inaccurate torque reading of the head bolts as possible causing the block to crack between the bolt holes and the outer part of the block ( exhaust manifold side ). These are things that you yourself probably never thought about. You probably can't stand it that it's possible that I could be correct for a change.
Is that the summary you got from 3+ years of asking others on this forum like Rusty how to build a mild 318 that someday you may own, now your telling him how to do it lol.
Dan the man
Well-Known Member
He may have to be told as it's appent to me that he doesn't understand that bigger valve's and ports affect port velocity plain and simple and that the bigger valve's and ports move the powerband up. Am I wrong that those same bigger valve's and ports hurt port velocity which hurts both throttle response and low to midrange torque, is this correct or not.Is that the summary you got from 3+ years of asking others on this forum like Rusty how to build a mild 318 that someday you may own, now your telling him how to do it lol.
Newbomb Turk
Well-Known Member
Horseshit Dan. If you think a 2.02 valve kills velocity in a port that’s already too small and fast you will never get it.
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