Best heads for 318 with light mods

[btceng]

I have a 71 date coded 318 in a 72 Challenger. Have added an Elderbrock Performer carb, 360 manifold, .284/.484 purple cam, electronic ignition, duals, 904 with shift kit. I would like to match the heads to that cam and add headers. Suggestions? Also, very rough idle when the trans loads up. I need to add a stall I guess. Would polishing the stock heads be worthwhile or should I go in a different direction. Definitely not trying to build a race car but want the sound of a musclecar. It does run good at upper rpm range but barely stays cranked at idle, even at 800-900 rpms. Help.

 

[toolmanmike]

Depending which purple shaft you have installed it is probably too much for your stock converter. I would recommend some mid 80's #302 castings from a Diplomat. Those should raise your compression a bit and they have hardened seats.

 

[btceng]

A friend suggests finding a set of 360 stock heads but I've heard about the port mismatch. Thinking about a 2500 stall. BTW, .284/.484 shaft.

 

[Rob C]

He allready has a port mismatch with the 360 intake manifold, so 360 heads would fix that.

The one tihng you'll have to do is mill the heads down alot to get some decent compresion out of it. That cam is a bit stout for a 318 and IF it has stock internals, your way to big on cam.

Duals? Headers or manifolds. If you don't have headers, your engine is a big mismatch and time and money are being wasted.

Depending on gear ratio and intended purpose of the car, 2500 isn't enuff for that cam. At 241 @ .050 duration, you'll need another thousand rpm stall to get that thing working decently.

 

[btceng]

How much would you think I would need to mill off of a stock set of 360 heads? The idea on the camshaft was to invest in parts that would crossover to a 360 block if I could find one. I really am not an engine guy and went on the opinions of a mechanic friend. He did say that it was going to be a little much but I wanted that chop. The car drives okay but the fact that it wants to choke down while idling in gear is frustrating. The gear is the stock 2.7? and he suggests going to 3.91. We just want something fun, not to race.
I took the 4 barrel as step1, cam step2, headers step3 approach. May have gone wrong with cam greed. Must confess that the car ran better before the cam replacement.

 

[burdar]

That cam is way too big for a 318. I've got that cam in a 360 with ported heads and a high stall convertor. I ran it with 4.10 gears.

I've heard that the 302 castings are good but are prone to cracking between the valves. They still have small ports so they wouldn't work well if you swapped them onto a 360.

The 318 that's going in my Challenger has a 340 cam in it. I've heard that the 340 cam runs pretty good in the 318. I think the specs are 268/276 duration...430/444 lift.

You can get a cheap set of Keith Black hyperutectic pistons for a couple hundred bucks that would raise your compression. THen you wouldn't have to mill a set of 360 heads. If you ever upgraded to a 360, you could swap the heads onto the new engine.

Your stock gears will either be 2.76's or 3.23's. Those were your only choises on a 318 car.

 

[btceng]

That's the cam that I was going to get before the recommendation of the mechanic friend. He is a long time Mopar fanatic. He is also a lifelong Chrysler mechanic at a local dealership. He does tend to be on the ragged edge sometimes. Trying to talk me into boring and stroking the little 318 to 392. I can't see that happening.

Should I be looking for some 360 heads or the 302 castings or is the stall converter what I should do first?

I was hoping to add headers, change the gears and be done with the drivetrain.

I have a lot of body work ahead but was hoping to get it in a good driveable state prior to doing the big work.

 

[blackcuda]

run from that 318 and get a 340!!!

 

[burdar]

I have a lot of body work ahead but was hoping to get it in a good driveable state prior to doing the big work.

Save most of your money for bodywork. It adds up really fast. This is what I'd do if I were you.

First, remove the 284/484 cam and save it for a 360 down the road. Either research some better 318 cams or put the stock cam back in. The 484 cam requires stiffer valve springs anyway...you didn't say that you replaced the springs so my guess is that you didn't.

Just run the stock heads and install headers. That plus the 4-barrel you already added will wake up the 318. (the intack/carb and headers can be swapped onto a 360 so there is no waisted money there)

Rear end gears would also help as well as a slightly higher stall on the convertor. Both of those things aren't going to be cheap though. I'd save my money for the bodywork. Once that's done, get a 360 and you can swap your cam, intake/carb and exhaust onto it. My $.02

 

[ramenth]

I'd save my money for the bodywork. Once that's done, get a 360 and you can swap your cam, intake/carb and exhaust onto it. My $.02

That's what I was thinking.

I know you're looking to make the 318 run a little better than what you have now, but since you're looking at body work, why not just put the money into the body and get the stock 318 running as good as you can in stock form? Sure, it won't have the horse your after, but as you're experiencing, your really not gaining a lot, other than buying 360 parts for an eventual 360 build.

My two cents (for whatever it's worth), is put the money into the engine when you have the 360 in your hand.

 

[Rob C]

run from that 318 and get a 340!!!

Nothing like having this guy spend more money on expensive parts that need more money to get it to work.

That's what I was thinking.

I know you're looking to make the 318 run a little better than what you have now, but since you're looking at body work, why not just put the money into the body and get the stock 318 running as good as you can in stock form? Sure, it won't have the horse your after, but as you're experiencing, your really not gaining a lot, other than buying 360 parts for an eventual 360 build.

My two cents (for whatever it's worth), is put the money into the engine when you have the 360 in your hand.

YEP!

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To the OE poster.

IMO, a basic run better set up for a 318 that is inexpensive but will yeild a decent result while things get done would be a;

A Comp cam. 265 DEH (Builds compresion for low ratio engines like you have. )
OE 318 heads with headers
4bbl. intake and carb (600 cfm is fine)

The above parts will work well with the gear ratio you have now without any issues or cave eats.

 

[btceng]

Rumblefish360, thanks. Your suggested setup is what I was going for. I got too much cam. I wish that I had gone with the 340 cam. I have the 4 bbl and intake and am planning on headers. The car runs okay but is definitely weak on the bottom. I'm going to try the stall converter route to get the idle right. I do enjoy the sound. Maybe I'll pull the stock heads and polish them up a bit. Maybe I can find a deal on that 360 while the car comes together.

 

[Aussie Challenger]

The 318 is a worthwhile little screamer but does need the right parts to make it move well, after all there is nothing like cubic inches so a 360 makes sense and will be cheaper to build anyway. Your idle speed with your current combo is a little slow, should be around 1,000 rpm, that will take some of the lope out but should stop the motor wanting to stall. The std 340 cam works well with a 4 bbl & headers in a 318.