Which heads?

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318willrun

318willrun

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I have 318 that's stock except with the addition of a 600 eddy on a weiand action plus intake. Runs great with surprising spunk!
Here is the future project:
I know the ports on the intake are larger than the stock 318 heads. So, should I try to come close on gasket matching the 318 heads and while they are off, perhaps a little bowl hogging? Or, my other option is a set of 308 360 heads I have off of a '89 360. These ports would match the intake, give me bigger valves, but cost me some compression. I can afford 65.00 bucks to have the 360 heads milled .040 to help get back some compression.
Please, Please do not suggest I install bigger valves in the 318 heads and have them professionally ported. I'm not going to stick hundreds into this project. Any bowl hogging or gasket matching will be done by me with a dremel. I have done this before. Oh, I may add a 340 size cam to it also at some time, but not headers. I do have older 360 exhaust manifolds that will be a direct replacement if I should use the 360 heads.
I have done both to other 318's and both ways have made the 318 respond. However, I have not used the so-called "good" 308 heads.
 
I think the gain in air flow with the 308's will make up for the slight loss in compression you may see. Do a little bit of clean up on them and you should be happy!

Which 318 heads do you have? The 302 was a decent head with it's quench pad although it was a smaller port and valve.
 
Depends on what a "340" sized cam is and the actual compression height of the piston. aka, year of the 318 since some years use a taller piston. Also the actual use of the car as well.
 
Haven't checked my 318 heads to see if they are the 302's. My 318 is a '85. I got it out of a Dodge truck thinking it would have the roller cam. NOPE! When I installed the intake it had flat tappets. I researched and learned that not all '85's had rollers. I wanted the roller for todays oils. 340 sized cam would be one that's a stock replacement or something around that .450 lift and 268 duration (advertised). Car is just a cruiser with the wife and kids, however, I will take it to the drag strip at least once a year. And, of course, a little horse'n around out of town, ya know?? Trying to keep my gas mileage too. Started at 20 mpg with the 2bbl, and ran 15.90's at 84 mph. The 4bbl has me down to 18 mpg and I don't want to go much less, if any. Haven't got an E.T slip with the 4bbl yet, but the car has more off line punch and pulls a little harder the whole way through.
 
Go to the big block section and look at IQ52's low compression 440 dyno pulls. After reading that, I think you would be miles ahead to use the 308 heads mildy ported. Use the .025" head gaskets and mill the heads .025". The intake will still line up and you'll get a little compression back, but the 308 heads will add a lot.
 
I looked, not sure if the big cubes test automatically holds true to the 318, but worth considering. I know I can gain both ways, I just want the biggest gain. Leaning towards the 308 heads. I know 8.5 compression will run real nice on todays gas and perform very well. Last time I used 360 heads on a 318, we milled them .045 and used a fel pro head gaskets, but they were late 70's heads.
 
318willrun said:
I looked, not sure if the big cubes test automatically holds true to the 318, but worth considering. I know I can gain both ways, I just want the biggest gain. Leaning towards the 308 heads. I know 8.5 compression will run real nice on todays gas and perform very well. Last time I used 360 heads on a 318, we milled them .045 and used a fel pro head gaskets, but they were late 70's heads.
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Why on earth would it not hold true to anything? To me it's proof positive. An engine is simply an air pump. The 318 and 440 both work the same. Good luck.
 
318willrun said:
I looked, not sure if the big cubes test automatically holds true to the 318, but worth considering. I know I can gain both ways, I just want the biggest gain. Leaning towards the 308 heads. I know 8.5 compression will run real nice on todays gas and perform very well. Last time I used 360 heads on a 318, we milled them .045 and used a fel pro head gaskets, but they were late 70's heads.
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It's still relevant, think principle, don't focus so much on exact detail :thumbup:
 
318willrun said:
I looked, not sure if the big cubes test automatically holds true to the 318, but worth considering. I know I can gain both ways, I just want the biggest gain. Leaning towards the 308 heads. I know 8.5 compression will run real nice on todays gas and perform very well. Last time I used 360 heads on a 318, we milled them .045 and used a fel pro head gaskets, but they were late 70's heads.
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Worth considering - yes. But based on what you list - I don't think so unless you start thinking of using a cam that will make use of that port. The test referenced uses a cam with 240°+ of duration at .050. Not 214. it also used ported heads - not just bowl cleaned up. In terms of a street car it had weak torque until 3K+ and that was with a 3.75 stroke. As far as I'm concerned - totally wrong choice for a test model.

If it were me I'd keep the 318 heads. I would have stock 360 valves installed. For the price of a valve job you get the seats moved out and cut fresh, a larger curtain area for the given cam, and a port that is small and fast enough to work well in a mild 318 street car. Gasket match them and blend in the new valve job and you're done.
Another thought (and perhaps the best option) would be a set of used magnum heads. They can be bought cheap from the pick-a-parts with the rockers, you need to buy pushrods, and redrill the intake pattern (which if you can dremel a head, you can redrill and tap yourself).
 
All though IQ52's test shows very interesting results, I agree that the difference between a 318 and the big block he tested IS NOT PROOF POSITIVE or indicative of the small block to show the same results, though is love to try it myself.

I'm with Moper on the 360 valves in the teen head. Smaller higher flowing velocity port that should (IMO any way) be bowl ported. A cam at 214 intake and (again, IMO) a least 8*'s more in exhaust duration will put this car into the mid 14's without really trying hard, or should I say maximizing everything.
 
You are right, ratrod, in that motors are air pumps. However, power bands and torque cannot be ignored in a family cruiser. Power bands of 3000-7000 require headers, 3500 stall converters, 4.11 gears.. etc. I've been down that road, and it leads to nice E.T slips. But this car is a quiet ride that cruises 60 mph all day and idles at 600 rpm's. I would like to touch high 13's without sacrificing the driving of this car and without spending hardly any money, and I mean next to no money. I've had 318's go fast but not in the way I'm trying now. I'm guessing (?????) that I must be in mid to lower 15's with the 4bbl. I need a little better than a full second to be knocking at the door.
 
So, even though it IS on a big block, we have SOME PROOF that head flow makes more power than compression, yet ZERO proof that compression makes more. Seems stupid to me to discount that, but go ahead. Over and out.

To simply sit there and say "not sure if the big cubes test automatically holds true to the 318" or "IS NOT PROOF POSITIVE or indicative of the small block to show the same results" to me is unfounded.

There IS proof. An engine is an air pump. Simple as that. Flow in and out is what is important. The test Jim did is far more than armchair quarter backing. Big block, small block, my money says the results are the same. There is ZERO proof that it WON'T work, yet there is SOME proof it will. To ignore that is absolutely stupid.
 
318willrun said:
You are right, ratrod, in that motors are air pumps. However, power bands and torque cannot be ignored in a family cruiser. Power bands of 3000-7000 require headers, 3500 stall converters, 4.11 gears.. etc. I've been down that road, and it leads to nice E.T slips. But this car is a quiet ride that cruises 60 mph all day and idles at 600 rpm's. I would like to touch high 13's without sacrificing the driving of this car and without spending hardly any money, and I mean next to no money. I've had 318's go fast but not in the way I'm trying now. I'm guessing (?????) that I must be in mid to lower 15's with the 4bbl. I need a little better than a full second to be knocking at the door.
Click to expand...

As usual, yall are overthinkin it. Keep on keepin on.
 
Actually, I'm agreeing with you, ratrod. Low compression cars that high flow will out run high compression cars that flow low. That is why I'm leaning toward the 308's. I just want to be sure I won't have to always hit 5500 rpm's to see the real benefits while having my low end torque be flattened, and it don't take much to flatten a highway geared, factory torque converter 318. I posted this question because I want the right combination for this particular car.
 
In My post I was trying to make a ref to the power gains being similar. The cubes and combo are completely different.

We have no one showing proof positive here that more compression makes more power but it has been done but not to the tune of more air flow. I'm not sure or sold on the 308 being a better way to go about this. Since from what I gather, the Op has both heads on hand, try them both out!
 
High velosity is torque (small ports) think low end power. High volume is HP. think RPM.

The small port of the "teen" will get you moving from that stop sign/light.
I thing you will loose the spunk, or take off power, with the 360 heads.

with your combo i would do some bowl clean up and a high energy cam or a small voodo cam.

should wake it up nice with out killing the bottom end.

If you want to spend a little bit more.....put a 1.88 intake valve in it.

The 360 head will make more power but loose some of that bottom end, that it sounds like you want to keep.:-k

Internal combustion eng, like was build back it the day have a 2500 rpm window. you can have a eng that pulls from 1500-4000 rpm or make more hp and have a 4000-6500 rpm eng

That 2nt option would cause grate anger in a combo like yours.

the 360 head WILL WORK! but you will need do some changes to your combo (aka converter and gears) to get the most out of it.
 
I'd like to throw my 2 cents in here, use the magnum heads! I just went through this with my 360 with 308 heads. For about the same money I got new castings and better ports. You'll have the smaller chambers and decent valve size. Dodge ran them on 318's with no problems. Better breathing and bigger valves, smaller chambers, newer casting...whats not to like??
 
If I was to use magnum heads, I would just put the whole magnum motor in the car. I have a pair of good 318 heads on the car and a good pair of 308's on the bench. I know there is gain going either way, but I'm trying to reach high 13's on a very mild 318. Every tenth counts, that is why I'm interested in different perspectives. Keep in mind, I'm using manifolds instead of headers, and that will help low end torque if I was to use the 308
 
My post wasn't meant to be insulting or argumentative......BUT, the point I was trying to make is, on the one hand, we have a professional engine builder with several dyno pulls showing what head flow can do on a low compression engine. Yes, it's a big block.

On the other hand, we have several people giving their opinions (and experienced opinions I am sure) of what they believe the case to be. One is based on fact (although again, it's not a small block) and the other based on opinion.

Yes, I agree with Rob......there is NO definitive proof this will work for a small block, BUT, common sense says it probably will. IMO, there's a stronger case for the 308 heads. But again, that's just another opinion, although with some "loose" proof that it might be the right opinion. Maybe Jim (IQ52) has done a 318 before. Maybe he intends to. It would be nice to see how the small block would react. I THINK that the head with the best flow will win out every time. And I BET that the 308 has the best flow.

Of course as Rob has pointed out, all of this, BOTH sides is merely speculation.
 
O.K, ratrod, lets just say we were talking cams instead of heads. Would a .600 lift cam with a 320 duration be recommended for this particular project??? Why not?? A cam this size will outflow a 340 size cam?? If more flow is better, then why not a cam of .600 lift and 320 duration?? If you say "too much" cam for a stock 318 and stock converter, and will kill performance, I will say why?? More flow, right?? This is why I want the right head choice, and the 308's may end up being the right choice. I just want more perspectives before I start tightening bolts.
 
don't retrofit. your return on investment will be bad. unless you patch up the comp ratio you are gaining little or nothing. gain some flow but lose some hp due to compression loss.

your best investment would be to drive it like it is. get a 360 somewhere. tear it down in your spare time build it right. get 9.5:1 and the 308 heads or better even.

that way you can drive now, will see good improvements from your money. everyone is happy. after the 360 is done and in, you can save the 318 for a later project or sell it. >>> best bang for the money

I've put 360 heads on a 318 before and the improvement is minimal.
 
I think that can only be answered on a flow bench. I "would" say that with that much cam, you're getting out of the head's port volume range......BUT, Jim has proven some pretty incredible things on the flow bench, so I don't know. I would imagine though that if everything else was matched to the cam it would work pretty damn good.
 
318willrun said:
If I was to use magnum heads, I would just put the whole magnum motor in the car. I have a pair of good 318 heads on the car and a good pair of 308's on the bench. I know there is gain going either way, but I'm trying to reach high 13's on a very mild 318. Every tenth counts, that is why I'm interested in different perspectives. Keep in mind, I'm using manifolds instead of headers, and that will help low end torque if I was to use the 308
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When I was 19 I had bought a '74 E body with a 3sp stick, 318, 4bbl, headers, etc. I replaced the 318/3sp with a bone stock re-ringer '69 340 and 4sp. The only change to the engine was the cam to a Comp High Energy 268H, a double timing chain, and a Thermoquad intake and carb. In that shape the car would run mid 13s with 3.23s. The 340 lost some ring lands due to a nice lady who helped me after I ran out of gas one day. I pulled the 340, swapped the X heads and racey parts onto the bone stock '74 318 shortblock and stuck it back in the car. On follow up runs that car would go no better than 14.0s. I then replaced the X heads with the 318 heads in order to sell the 340 as complete core. With the 318 heads, a set of MP valve springs on them, and everything else the same including the mismatched thermoquad intake, then car picked up and went 13.8s. I've had a few years of R&D and learning since then and all the fancy tools and equipment has evolved. If you want a torquey 318 and don't muddy the waters with talk of porting, fresh machining, replacing core parts, or much for HP parts - my advice is don't put 360 heads on it.
 
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