318 with 360 heads

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FrankenDuster74

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So I'm building a 74 duster it has a 4 speed and I'm trying to decide what to do for an engine my intention for the car is just a daily driver amd a friday jight test and tune car but I want some reliable power with it nothing crazy but enough to notice I have a mid 80s 318 all tore apart so it would need a re Ring kit I also have a set of j heads to go with it should I get these heads milled and use the 318 or would I be better off getting a junkyard 360? I don't plan on doing any crazy modifications I have hooker headers a weiand dual plane intake and a Holley 600 carb? What's a good cam to run with this set up? And what should I mill my heads to?

Thank you
 
Welcome to the site FrankenDuster74...get ready for a ton of different opinions. J heads on a 318 is a pretty common question. I'd recommend you get familiar with and start using the search function-not nit-picking, just trying to save you some time from waiting for replies...although this one should receive a few ;)

I'll add this much first off, if you don't have anything else, and you want to save a couple $, you can use the J heads; but you need to shave them to maintain any compression. Just bolting them on a stock 318 will drop your compression somewhere between a half and a full point. If you have some ends to rub together, I'd recommend selling the J heads to someone who wants them for a resto and buying a set of complete Magnum heads (with rockers) and buy the appropriate pushrods intake and head bolts then use them on your 318.

If you have more spare cash than that, find and buy a fully dressed out and running 360...there are members here running 10s in Dusters with 360s...lots of mods, but 360s are an easy base to build from
 
Agreed and his advice is a good way to go.
Are new pistons in the future? The 318 w/360 heads could use better pistons. Keith Black (KB) has pistons in Hyper and forged. If you have the cash for a rebuild, I would go this way over milling heads. Though it is not a bad option. The Magnum head option I'm not all that ($$$$) fond of.
 
If money is an issue, you can put your combo together as you have it with a 340 cam (or the likes) and you'll be happy. The J heads do not have hardened seats for unleaded fuel, keep that in mind. Hardened seats can be installed. If you were to sell them, you could by "308" 360 heads from a 89-91 360 and you should have money left over. Any money you have to spend on top of the basic "rings and bearings" rebuild, I would go .030 over and use KB pistons, this will give ya another 5 cubic inches and raise your compression. This will be a very smooth idling, well mannered street 318 that will run very strong! and remember, tune, tune, tune. If you have easy access to a good 360 for very little money, that will give you more performance and torque! Good luck
 
If you run 10.5:1 318 pistons and then use 340/360 heads, your compression will be 9.2.
 
With what slug, overbore, gasket and head cc?
Just enquiring
 
I was (am) in a similar situation as you, just as lots of other members here. The tired old 318 in my 70 Dart is just plain ol worn out. I have a 360 on a stand and am preparing to do the swap. If you're considering a 360, you should try to find a 1989-1991 pickup for the donor vehicle. It has a roller cam, and the larger valves, but it is still an LA block, you will need a different pan (car pan) and different torque converter, a slight modification to the drivers side motor mount, and that's about it.
 
Use the 318 mount on the 360 with a large nut that slips over the bolt to take up the extra room. Sometimes, a washer or two is needed depending on the actual nut thickness.
 
I really appreciate all the help I'm going to look into the 89-91 360 but if I decide to stay with the j heads how much should I have milled off to get decent compression ? I don't mind running a higher octane just as long as I can get it at the pump and its not race fuel lol
 
That depends on budget. I like the Scum it(Summit racing K6901 grind, it's healthy enough!), Look for 302 /Magnum heads. If you are not broke,check out RAMM's 318/347 stroked threads....
 
Abodybomber said:
That depends on budget. I like the Scum it(Summit racing K6901 grind, it's healthy enough!), Look for 302 /Magnum heads. If you are not broke,check out RAMM's 318/347 stroked threads....
Click to expand...
X2 on the 302 heads..will increase your comp and be pretty torquey even in stock form,that summit cam a good carb/intake......if you use the J-heads run the 1.88/1.60 valve[stock] milled about .050-.060 use steel shim gasket it will perf well just need a min of 3.55 gears or steeper to help get it winding...smallblks like the steeper gears...there was a fellar on here in the past Bobby[BJR RACING ] did a few combos on 318's[322's] and 302 heads that was pretty damn good and well worth reading...
 
rumblefish360 said:
With what slug, overbore, gasket and head cc?
Just enquiring
Click to expand...

Right?
I love how people just throw it out there with nothing to figure it by.

Open chamber 318 heads like the 675's have about 68cc chamber.
360 head range from 70-72 cc's with small valves.

Mill .015-.020 and the compression stays the same.

Btw the j heads chamber hangs into the 360/340 bore enough to actually end up about matched to a 318 bore size too.

Flow is power.
Flow increase will also increase the dynamic compression because you are filling the cylinder more.

People just stop thinking at a certain point and I dont know why... Sigh....
 
Abodybomber said:
That depends on budget. I like the Scum it(Summit racing K6901 grind, it's healthy enough!), Look for 302 /Magnum heads. If you are not broke,check out RAMM's 318/347 stroked threads....
Click to expand...

Magnum heads flow stock what a pair of mildly ported 318 '675/302 heads flow, but cost 4 times the money. You need to change lifters to oil through, push rods, intake, rockers, valve covers, bolts, plates
If he can find a really good deal ...then that's a good route to take, for a 318 at least.
 
So if I get them milled .060 what compression ratio should I be at? What brand re ring kit should I use ? I don't mind spending a little more for a better quality and if I get them milled .060 with stock bottom end what is a good size cam to use?
 
If your just searching for more low buck power, the 360 will be the way to go. More torque stock. Those heads will help make easy cheap horse power also.318 being smaller displacement will take more upgrades for same results as 360. Good 2 1/2 in. exhaust,3.55 gears. I would not mill j. heads.Quality rebuild, multi angle valve job. Good luck.
 
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