pettybludart
Well-Known Member
Hi,don,t know much about 73 318 and am looking at j heads.Will they work on this 318 and how much will it help??Thanks
73 318 will J heads work???
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Burntorange70
Well-Known Member
From what I understand J or X heads have to big of a combustion chamber for a 318 and it is really hard to get the compression up unless you mill them a lot. Which causes other problems and is not usually recommended. Unless you are building the motor up and are redoing the pistons and rotating assembly with maybe a set of dome pistons it is best to go with a set of heads with smaller chambers like 302's.
Unless you are 1. turbocharging, 2. supercharging, or 3. willing to part with a lot of cash for some custom made pop-up pistons, I don't think J heads will improve the output of a 318 BECAUSE.... the combustion chamber is too big and will lower your compresssion ratio to a point that it's really detrimental to cylinder pressure.
Those heads would work great with a blower, though...
Might consider a Vortech, Procharger, Paxton, or Powerdyne unit. Not a cheap way to go, but adding power in significant amounts is never cheap or easy.
A centrifugal blower setup will usually add about 100 hp and run on pump gas if you add an alky injector to stave off detonation.
Just a thought.
Failing that, the heads with a casting number ending in "302" seem to be the best choice for a mild 318 street build. They're cheap at junkyards and on a lot of mid-'80s 318s.
Good luck!!!
Bill, in Conway, Arkansas
Those heads would work great with a blower, though...
Might consider a Vortech, Procharger, Paxton, or Powerdyne unit. Not a cheap way to go, but adding power in significant amounts is never cheap or easy.
A centrifugal blower setup will usually add about 100 hp and run on pump gas if you add an alky injector to stave off detonation.
Just a thought.
Failing that, the heads with a casting number ending in "302" seem to be the best choice for a mild 318 street build. They're cheap at junkyards and on a lot of mid-'80s 318s.
Good luck!!!
Bill, in Conway, Arkansas
71dmn
cvillarreal
hey bro!! i have a 71 demon with a 318,j-heads,yes a stock block,cheap 100 dollar hooker headers,3800 stall converter,3.91 gears w/spool,superstock leaf springs,drag shocks,adjustable pinion snubber,750 dbl pumper holley,old weiand intake.....and what? oh yeah 100 shot nx stage six nitrous system!!!!! check out my video on www.youtube.com/chrisdottie and you tell me...do you think j- heads work? don't let noone tell you otherwise....have a great day....!!!
71dmn has a set up that takes advantage of the J heads and has a shot of N02 to get going. Are you going this route?
What is your build and target? This is the question we need answered so we know what exactly a good recomendation is.
Heres the thing. Most people are not going to use a preped 318 head on there 318 when a 360 hed is cheaper to use dispite the fact that it will not work as well. Porting a head, even just a good bowl prep and valve cut back and job will out spend a stock J head. So people will opt.for a set of 360 heads @ around 2 - 3 hundred and go from there.
If your 318 is rebuilt new with zero deck or taller pistons and your caming it up with a higher stalll and gears to match, the 360 heads will do a better job than ported 318 heads. But ya better be willing to run this pup due to the huge port window and cc amount the 360 head has.
Look at this way as well. If a stock X head can get a medium weight car into the mid 12's easy, with zero porting, don't you think that is a bit much for an engine down 20+ cubes in bore alone?
Why did MoPar offer a ported 318 head over a 360 head? Hummm, They did state right up front in the catolog that there ported 318 head made 55 more HP than the 360 head.
The real question is not will it work, but, will it work well and what is a better path to take?
What is your build and target? This is the question we need answered so we know what exactly a good recomendation is.
Heres the thing. Most people are not going to use a preped 318 head on there 318 when a 360 hed is cheaper to use dispite the fact that it will not work as well. Porting a head, even just a good bowl prep and valve cut back and job will out spend a stock J head. So people will opt.for a set of 360 heads @ around 2 - 3 hundred and go from there.
If your 318 is rebuilt new with zero deck or taller pistons and your caming it up with a higher stalll and gears to match, the 360 heads will do a better job than ported 318 heads. But ya better be willing to run this pup due to the huge port window and cc amount the 360 head has.
Look at this way as well. If a stock X head can get a medium weight car into the mid 12's easy, with zero porting, don't you think that is a bit much for an engine down 20+ cubes in bore alone?
Why did MoPar offer a ported 318 head over a 360 head? Hummm, They did state right up front in the catolog that there ported 318 head made 55 more HP than the 360 head.
The real question is not will it work, but, will it work well and what is a better path to take?
71 DMN,
How does it run on the motor? The high cylinder pressure created by the nitrous effectively cancels out the low compression.
The owner of that 318 (Pettybluedart) may not want the added expense of a nitrous or superchager system just to make the J heads work on a 318. Dunno...
How does it run on the motor? The high cylinder pressure created by the nitrous effectively cancels out the low compression.
The owner of that 318 (Pettybluedart) may not want the added expense of a nitrous or superchager system just to make the J heads work on a 318. Dunno...
sublimeswinger
SUBLIME Senior Member
Rumble, where do they offer a prepped 318 head? Are you talking in the past? or is this new? Info?
2 Darts
A-body Addicted
The 73 models were probably the low point in terms of compression ratio. The J heads, with their larger volume, would make the situation worse. It can be helped with 67-72 stock pistons. These were flat tops with 4 valve reliefs on them. They also had the highest deck height of the 318 pistons.
I built a 318 like this with a P4452761 Purple shaft & J heads. It was a little down on power until you got it over 2500 rpm. Using a similar cam in a similar 318, 302 heads, and the same intake/carb combination, throttle response is considerably better. For a mostly street engine, I prefer the 302 head combination. I agree with those who recommend that if you want to use the J heads, the compression ratio needs to be bumped for a normally aspirated engine.
I built a 318 like this with a P4452761 Purple shaft & J heads. It was a little down on power until you got it over 2500 rpm. Using a similar cam in a similar 318, 302 heads, and the same intake/carb combination, throttle response is considerably better. For a mostly street engine, I prefer the 302 head combination. I agree with those who recommend that if you want to use the J heads, the compression ratio needs to be bumped for a normally aspirated engine.
They used to offer it and stopped offering it when the surply of standaard 318 LA heads dried up. MoPar performance can only surply performance parts, factory enhanced parts, so long as the factory makes/uses them. This is also why other parts are no longer available.
727, 904, 518 and 500 tranys. But they have parts for them since there still being serviced.
The 440 creates are slightly different stroy, but at one time offered many create versions. There down to what now? A create shrot block and one 40 create engine?
Maybe a 318/360 Magnum head might be a good choice for a normally-aspirated L-A 318. The Magnum heads have 60 cc combustion chambers, and small, but high-velocity intake ports, and a fast burn combustion chamber.
They might work as well as a 302 head and are easy to come by in wrecking yards; just be sure to have them tested for cracks, as I hear they do like to crack around the exhaust seat area.
I can't recall all the changes necessary to successfuly install Magnum heads on L-A engines, but if I remember correctly, you need Jeep lifters and pushrods with an oil hole in both ends, so that the upper end gets lubed.
The Crosswind "Air Gap" style (Chinese knockoff) manifold has both vertical (Magnum-style) attachment bolt holes and conventional, angled holes, and is pretty cheap.
Is that a viable option for a 318? My 360 Magnum has dished pistons for a true 9:1 compressuon ratio, but I've never seen what the 318 Magnum pistons look like. They could be flat top, for all I know.
One bonus might be the 1.6:1 rocker arm ratio that is stock with the Magnum valve train.
L-A headers work just fine with Magnum heads.
Food for thought...
They might work as well as a 302 head and are easy to come by in wrecking yards; just be sure to have them tested for cracks, as I hear they do like to crack around the exhaust seat area.
I can't recall all the changes necessary to successfuly install Magnum heads on L-A engines, but if I remember correctly, you need Jeep lifters and pushrods with an oil hole in both ends, so that the upper end gets lubed.
The Crosswind "Air Gap" style (Chinese knockoff) manifold has both vertical (Magnum-style) attachment bolt holes and conventional, angled holes, and is pretty cheap.
Is that a viable option for a 318? My 360 Magnum has dished pistons for a true 9:1 compressuon ratio, but I've never seen what the 318 Magnum pistons look like. They could be flat top, for all I know.
One bonus might be the 1.6:1 rocker arm ratio that is stock with the Magnum valve train.
L-A headers work just fine with Magnum heads.
Food for thought...
71dmn
cvillarreal
yeah...i know exactly how it goes for us nitrous gurus...however all motor the car runs 13.60's all day long.....if we're talkin about a backyard budget...mine definitely works! my heads have no work done to them.i simply follow what the mopar chassis and engine manuals tell you to do...with the exception of a little different odds n ends.now if your talking no money limits...then y r we even talking about factory production heads anyway? shouldn't you be talking w-2's or eddy aluminums...i mean come on guys..but back to the original question at hand! it was will the j-heads work and the answer is Y E S !
71dmn
cvillarreal
i dont mean to sound like an ahole either...thats not what im tryin to do...jus simply giving some options
pettybludart
Well-Known Member
Thanks For Responses! 71 Are You Running A Nitros Plate On A Stock Motor?other Than Yor Add On,s??and Have You Had Any Issues With The Motor??what Are Times On The Juice??you Didn,t Mention?thanks!!
GoodysGotaCuda
Mr. Goody
I run Jheads on my 318, milled, only because they were free. I personally would have went another route. The poster above doesn't have many problems due to the 3,800 stall converter, 3.91s and nitrous...so it kinda makes up for the low velocity and lack of compression in a non-milled j-head 318.
69superbee
Pete E
I safely sprayed 125 hp shot of NOS with my old bone stock 68 318 and it loved it . it turned it in to a lil monster ! With never a problem. and I sprayed the dookie out it 
its tounge was hangin out up stairs so I kept the shift points low ... around 5200 to 5400
getting the pressure up with the spray and the J's will work nice but, it will be a little lazy down low off the spray. being a stock piston combo then the max would only be 125hp of spray safely. So, I do not really see much benefit by bolting on the J's . you could toss in a nice set of pistons ( expensive ) then maybe hit it with a 250 shot ? using the J's ..... humm..... getting into the land of trashed and expensive parts. but it would pretty amazing to see a 318 all setup for that kind of spraying just to see what it could do.
My point is........
you can make very good power with a stock combination with spray if you keep fat and happy, lower your shift point and take some timing out.
with a little homework and common sense, a solid stock build will work very nice with little sauce. the power is there when you need it in a bottle in the trunk. if I was going to build a 318 I would do a little more than stock cam and some mild port work on the heads. yes I would use the small heads but, that is my personal choice. just because I drive on the street as much as I can in the summer.
I have been sorta planning the my next build for my pickup and I am thinking along this combination . but, with a 360. a small just over stock 318 cam and the small heads with the small 2bb 318 intake/carb.
should make a ton of bottom and get pretty decent milage in the old Ram 150 with a 3.21
I have a set of J heads on my 360 that have had some work done to them and I have to say that I really enjoy my 360 on motor. the 360 on spray is awesome !
The 318 was even a bit more fun just because it was sneaky to have it on the spray and it was pretty close to my 360 when I run it on motor.
When I would go and tear off a 13:80 pass on street tires and a 2.76 gear I would laugh my butt off ! was just fun
I will be upgrading heads soon with a set of E heads and a cam change my goal is to get into the mid to low 11's and have a totally streetable combination.
There is a ton of good info here on FABO it all boils down to what ya want to do with your stuff. we all have tried different stuff and had success and failures. it is great to have all of this information to draw on. back in the old days I would have saved a lot of cash and good parts if I would have had this great resource to draw from.
good luck
its tounge was hangin out up stairs so I kept the shift points low ... around 5200 to 5400getting the pressure up with the spray and the J's will work nice but, it will be a little lazy down low off the spray. being a stock piston combo then the max would only be 125hp of spray safely. So, I do not really see much benefit by bolting on the J's . you could toss in a nice set of pistons ( expensive ) then maybe hit it with a 250 shot ? using the J's ..... humm..... getting into the land of trashed and expensive parts. but it would pretty amazing to see a 318 all setup for that kind of spraying just to see what it could do.
My point is........
you can make very good power with a stock combination with spray if you keep fat and happy, lower your shift point and take some timing out.
with a little homework and common sense, a solid stock build will work very nice with little sauce. the power is there when you need it in a bottle in the trunk. if I was going to build a 318 I would do a little more than stock cam and some mild port work on the heads. yes I would use the small heads but, that is my personal choice. just because I drive on the street as much as I can in the summer.
I have been sorta planning the my next build for my pickup and I am thinking along this combination . but, with a 360. a small just over stock 318 cam and the small heads with the small 2bb 318 intake/carb.
should make a ton of bottom and get pretty decent milage in the old Ram 150 with a 3.21
I have a set of J heads on my 360 that have had some work done to them and I have to say that I really enjoy my 360 on motor. the 360 on spray is awesome !
The 318 was even a bit more fun just because it was sneaky to have it on the spray and it was pretty close to my 360 when I run it on motor.
When I would go and tear off a 13:80 pass on street tires and a 2.76 gear I would laugh my butt off ! was just fun
I will be upgrading heads soon with a set of E heads and a cam change my goal is to get into the mid to low 11's and have a totally streetable combination.
There is a ton of good info here on FABO it all boils down to what ya want to do with your stuff. we all have tried different stuff and had success and failures. it is great to have all of this information to draw on. back in the old days I would have saved a lot of cash and good parts if I would have had this great resource to draw from.
good luck
71dmn
cvillarreal
i run an nx system...stage six dual stage plate sytem...i only use one stage...i still have to buy the other two solenoids....as far as times at the track...off the juice= 13.60's all day long....on the dope=11.94
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