318 with "special" j heads?

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63dartman

63dartman

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I have a rebuilt stock bottom end 318 with flat top pistons. Pistons sit in in the hole a little and I'm going to measure for exact. My question is: I have a matching set of 360 j heads 1.88/1.6 valves that were milled to 49cc chambers. I ran them on my 360 for awhile but it was too much compression since my 360 was zero deck. Will these heads work well on the 318 since the compression will be less. I'm thinking it will be right around 10.5-1 compression. I also have the milled matching intake for it too. It is a eddie rpm. What do you guys think?
 
Without knowing exactly where the piston sits and the diamentions of the head gasket to be used, it's a shot in the dark on the ratio.

The ports are large for a 318, so, if the rest of the package is up to snuff...........it'll be fine.
 
thanks rumble. I will get the gasket dimensions and piston depth tonight or tomorrow. I just want to make sure it's a workable solution for my son in law. He is getting ready to inherit my 70 swinger as his first project. He "plans" on building a 340 or360 for it in the future but needs something to make it fun to drive for a year or two.
 
HOw big of a cam, converter and what gears?
 
LOL, I forgot the cam size, I know it's aftermarket, crane or comp. I believe it advertised for 1500 to 6000 rpm and it's definately under 500 lift. stock converter and 3.23 gears.
 
Might be a bit sluggy out of the hole. Could be worse though. Once a running down the road, it should be a fun ride.
 
hey rumble, do you think that the intake will line up ok since it was on a zero deck height motor, and matched to it? just a thought, the ports may not line back up and the intake may be either too deep, or not deep enough, to seal on both heads. i had a z/d/h 360 once, and the old head/intake setup i had was a nightmare untill i got the intake reset to the new head location.vacuum leaks, water leaks. what do you think?
 
He said he used it before. It should bolt back on without a problem.
 
Wow! J heads milled down to 49cc chambers!! That's a bunch of milling. Probably took a couple lbs. off each head.:toothy10:
 
ok, i must have misunderstood. i just figured, different block and all. they are close, but not that close. i kinda feel like it probably should be checked b-4 assembly. you know, gasket in place, bolt holes line up ok, not out of square, flanges at same angle as head. that sort of stuff.
 
the 360 zero deck was achieved with after market pistons. Ther was no machining to either block. I hope I'm using the right term when I say zero deck. I assumed it meant your pistons are level with the deck.
 
that is correct. but i've never seen a z/d/h 360 that wasn't done after the fact(by someone besides the factory). i'm not saying that there weren't, i've never seen one.they were all smoggers.low compression and stuff.
 
Z/D/H, LOL, good abr. The factory never did one.
I know a few machinest that do alot of work to the parts and make it all work with stock parts at a much higher level. But since they have the talent to work the machines and such...

Heavy block height milling, head milling, switching in pistons from different year engines.

I'll just stick with an aftermarket piston and a nice balance job.
 
rumblefish360 said:
Z/D/H, LOL, good abr. The factory never did one.
I know a few machinest that do alot of work to the parts and make it all work with stock parts at a much higher level. But since they have the talent to work the machines and such...

Heavy block height milling, head milling, switching in pistons from different year engines.

I'll just stick with an aftermarket piston and a nice balance job.
Click to expand...


Who you talkin bout? .....................Me...............Not me I don't do things like that.

LOL
 
LOL, I have heard of a few guys in the past doing such things but never found out what exactly they did or how far they went with such work. Allways a secrect and big dollors charged for it.
 
i have a z/d/h 360 block around here somewhere. from back in the day. i used to race it and it worked awesome. i bought k.b. hyperutectic stock pistons and my machinist and i put the crank in it with new bearings. we puth the rods in it with the pistons, ran them all to the top and measured the height from t/d/c on all eight, chucked the block in the mill and cut .062 off the block at the top of the cylinders. after the heads were done it came out to like 13.6 to 1. as i said it was a race motor and a sort of an experiment. it worked very, very well. thet is what prompted my question about the intake matching up with the heads. when you do it that way you have to remove some off the intake at the port ends so it will go down into the "V" between the heads.
 
Riiiiiiiight!!!! MoPar has a formula just for this in there engines book. The biggest secret is knowing how far the block/heads can go before there junk.
I know after a while, the head can't be milled on the intake side because you just simply run out of rail for the valve covers. So the intake gets done. Theres limits to everything and how it's done may require a combo of milling everywhere.

But, he said he took a working set...heads and intake ... so it should bolt on. The missing question is was the block milled ?
 
Rumble, I posted above it was achieved with aftermarket pistons on the 360 and no block machining was done. I got the numbers from the 318 and it looks like it will be sitting at 10.33:1 static compression using the thin .028 mopar gaskets. I'm not sure how the engine will react to the larger 360 and rpm runners but I'm thinking with the added compression and a good cam it should be a decent engine to run for a year or two.
 
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