I picked up a set of these heads fresh from the shop for 300 bucks. My old heads needed completely redone. Figured I would save some and get the benefit of the closed chambered heads. First of all, in a perfect world how much power should I expect to gain from these heads? I understand they are swirl port heads, would I see a fuel mileage increase with them? The goal is basically a fresh engine able to run on 87 octane. Stock pistons are .075 in the hole and I will be using just a regular felpro gasket in a master gasket set. Even with the lower compression will I see benefit from just the heads?
closed chamber 714 casting 318 heads
- Thread starter alpha13
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txstang84
Well-Known Member
Somewhere around 60cc sounds right...
txstang84
Well-Known Member
On the CR calculator I use, I see 8.8:1...and that's with an .040"x4.15" gasket...typical for an OTS gasket set, and 0cc valve reliefs, stock bore/stroke 318.
Gas mileage is more dependent on your tuning, the type of vehicle, and how much lead is in your right foot.
Any benefit you feel will likely be on the off idle from fuel/air charge velocity.
Gas mileage is more dependent on your tuning, the type of vehicle, and how much lead is in your right foot.
Any benefit you feel will likely be on the off idle from fuel/air charge velocity.
I just finished CC'ing a set of these. 58cc ! MT
I think there should be a noticeable (seat of pants) gain in power. 714 / 302 heads will raise compression, I have to run premium gas but have 9.5 - 1.
Holy crap, 58? I might be in trouble lol. I was hoping to be at just 8.5 CR I guess we will see. Gas is getting more expensive so I want to run the cheap stuff. I've read good builds that make good power on 87 octane. I suppose if it pings on 87 I'll.go up to 89. Hopefully no more haha. I was hoping that the swirl design would atomizer the fuel better for mileage. I'm hoping to break into the low 20 range. In the future I might bump the compression up and run E85.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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You will be bumping the Scr up from about 8.36 to 9.35sealevel.
And the Dcr from about 7.7 to 8.61.......(assumes an intake closing angle of 40*atdc)
8.6 is on the edge for full-load/WOT with iron and 87. It should work just fine every where else. You may have to delay max timing a bit, but not reduce it. Time will tell. I would do it.
If it does knock at PT, that cant be cured with slightly delayed advance,or a higher octane fuel,then retarding the cam a few degrees might help, but a swap to a one-size-bigger cam might be the answer.
The higher compression is very desireable for fuel-efficient cruising, with the smaller cam. I would try everything possible to make it work without changing the cam.Even if that means installing a dash-mounted, dial-back, timing device.
And the Dcr from about 7.7 to 8.61.......(assumes an intake closing angle of 40*atdc)
8.6 is on the edge for full-load/WOT with iron and 87. It should work just fine every where else. You may have to delay max timing a bit, but not reduce it. Time will tell. I would do it.
If it does knock at PT, that cant be cured with slightly delayed advance,or a higher octane fuel,then retarding the cam a few degrees might help, but a swap to a one-size-bigger cam might be the answer.
The higher compression is very desireable for fuel-efficient cruising, with the smaller cam. I would try everything possible to make it work without changing the cam.Even if that means installing a dash-mounted, dial-back, timing device.
I realize that fuel mileage will increase with efficiency. I probably should just shoot for about 10:1 and use premium, but every time I would hit the pump I would curse. lol decisions, decisions.... thanks for the positive feedback AJ. Also, thank you Mopar Tim for a real world measurement!. I decided to swap the 360 in favor for the 318 with future plans of a 408. But that one is going to be a street strip car only. I'm hoping to find myself a Volare or aspen to swap this 318 into with an overdrive transmission and make it my daily driver.
If you maximize the tune, (Key words just spoken) the higher compression and higher octane fuel should out power and out mileage the low octane build. The cost offset should be favorable.
I do not see a problem getting into the 20mpg range. I did it in a '79 Magnum with a stock low comp. 360 & bolt on parts, no headers or cam change. 904 trans and 2.76 gears. 26 inch tire.
I do not see a problem getting into the 20mpg range. I did it in a '79 Magnum with a stock low comp. 360 & bolt on parts, no headers or cam change. 904 trans and 2.76 gears. 26 inch tire.
AJ/FormS
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If you travel 10% further on a tank of gas that costs 10% more,thats still a break even.
But typically,with a heavily throttled engine,under cruise conditions, that is pulling in just a fraction of air that it is capable of, the octane requirement is in the basement.And that is where the the well tuned vacuum advance device will pay big dividends.
You have to think outside the power-timing box.
If you are pursuing economy, there is no reason to walk the the detonation-line under full-load/WOT.So what if power timing has to be backed off a few degrees, due to too much Dcr for WOT conditions with 87 gas. So what if the rate of centrifugal has to be slowed down a tad for 87, to prevent rattle under heavy PT acceleration. Get that V-can tuned to provide what the engine needs under PT and cruise, and it will save you $$ at every fill-up.
Perhaps, to satisfy your urge for WOT, a smaller carb than normal, would be all thats required to prevent the dreaded rattle, or simply burning 91 on Funday.I once had an engine like that. I used to disconnect the secondaries all the time during the week,and burn Regular.Then on Friday,in went the Hi-Test, and pop the link back in and it was Go-Time.
The point is, you might have to experiment a little, to get the results you want.But in the end, it will be very satisfying.
And if you just cant get the tune right, a simple swap to a slightly bigger cam with its slightly later closing intake will drop a wee bit of Dcr, and put you back in business.
If this dilemma was mine, the heads would be on already.
But typically,with a heavily throttled engine,under cruise conditions, that is pulling in just a fraction of air that it is capable of, the octane requirement is in the basement.And that is where the the well tuned vacuum advance device will pay big dividends.
You have to think outside the power-timing box.
If you are pursuing economy, there is no reason to walk the the detonation-line under full-load/WOT.So what if power timing has to be backed off a few degrees, due to too much Dcr for WOT conditions with 87 gas. So what if the rate of centrifugal has to be slowed down a tad for 87, to prevent rattle under heavy PT acceleration. Get that V-can tuned to provide what the engine needs under PT and cruise, and it will save you $$ at every fill-up.
Perhaps, to satisfy your urge for WOT, a smaller carb than normal, would be all thats required to prevent the dreaded rattle, or simply burning 91 on Funday.I once had an engine like that. I used to disconnect the secondaries all the time during the week,and burn Regular.Then on Friday,in went the Hi-Test, and pop the link back in and it was Go-Time.
The point is, you might have to experiment a little, to get the results you want.But in the end, it will be very satisfying.
And if you just cant get the tune right, a simple swap to a slightly bigger cam with its slightly later closing intake will drop a wee bit of Dcr, and put you back in business.
If this dilemma was mine, the heads would be on already.
I feel that on 87 it will be a little more forgiving to my tune. Lol I've been playing with my timing and my 600 edelbrock. I still have to get that thing tuned. I haven't eliminated that part throttle surge yet. I talked about it in another post I brought back. You know AJ. I think you even commented on it Rumblefish. I got the tuning kit for it but I haven't had a lot of time to mess with it because of work and watching the baby. Only reason I don't have the heads on yet is I still have to get my gaskets and whatnot and I still have to pull the other engine. Just got the trans out yesterday morning. I'm going to use the cam from the 360 cuz the other one from the 318 was showing signs of wear. Some of the lobes were pitted badly. It's a HE268 comp. The original plan was to keep the stock cam but I didn't want to deal with it later and I'm going to a bigger magnum 270 in the 408. So this other one would just sit on the shelf.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Alpha,
It sounds like your plate is over full.lol
It sounds like your plate is over full.lol
just found this
The 318-2bbl heads (4323302) used from 1985 on are a swirl port design with a closed (heart-shaped) combustion chamber design with a chamber volume of between 56 and 65 cc. The 4 heads I examined averaged 62cc in volume. The 302 head has 1.78 inch/1.50 inch valves and small ports averaging 54cc on the exhaust side and 118cc on the intake side. The intake ports have a more severe dogleg than earlier heads because the holes for the pushrods are larger - 11/16 inches. Cars equipped with the 302 head have a dished piston to keep the compression ratio from being too high. Some cars left the factory with nail head exhaust valves in 302 heads, others with semi-tulip exhaust valves, which add 0.6-0.75 cc to the chamber volume. There is an interesting excerpt in "Mopar Engines", page 72, describing how such a head was ported and made to flow as well or better than other small block cylinder heads. Apparently, this experimentation resulted in the master for today's Mopar Performance P4452758 cylinder head.
Quoted from 62 to 65 mopars. MT
The 318-2bbl heads (4323302) used from 1985 on are a swirl port design with a closed (heart-shaped) combustion chamber design with a chamber volume of between 56 and 65 cc. The 4 heads I examined averaged 62cc in volume. The 302 head has 1.78 inch/1.50 inch valves and small ports averaging 54cc on the exhaust side and 118cc on the intake side. The intake ports have a more severe dogleg than earlier heads because the holes for the pushrods are larger - 11/16 inches. Cars equipped with the 302 head have a dished piston to keep the compression ratio from being too high. Some cars left the factory with nail head exhaust valves in 302 heads, others with semi-tulip exhaust valves, which add 0.6-0.75 cc to the chamber volume. There is an interesting excerpt in "Mopar Engines", page 72, describing how such a head was ported and made to flow as well or better than other small block cylinder heads. Apparently, this experimentation resulted in the master for today's Mopar Performance P4452758 cylinder head.
Quoted from 62 to 65 mopars. MT
Yes that would be the fully ported 318 head which made 55 hp more than a 360 head. Which I believe to be ported mostly in the bowl area.
And people wonder why I recommend a fully ported :18 head w/ 1.88/1.60 valves.
And people wonder why I recommend a fully ported :18 head w/ 1.88/1.60 valves.
It always seems that way... lol I suppose I'm never bored. Right now besides working on the duster, I'm fixing sticking brakes on my truck and looking for a new home. Then on top of that going to work everyday. Haha. I read about porting 318 heads with 360 valves. Sounds like a winner to me. Although I'm.just gonna stick with stock for now to see what I can get for mileage.
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