360 heads on a 318 of any benefit?

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DQ81

'73 Dart
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My 318 is close to running right. There's the small issue of vac advance and the cold start issue.

This 318 is equipped with hooker performance headers and will be getting a dual plane edelbrock with 4bbl 600 cfm edelbrock carb in about a months time.

While the intake is off I'll be putting in either a stock 340 cam or an MP equivelant, maybe 1 step choppier, it still needs to run right for the street.

Will the engine benefit with 360 heads? I just came across a set cheap.

Either way I'm going to bust out the dremmel and flow the heads in any case.
 
The 360 heads can flow more due to larger valves. They also have larger runners, so the stock 318 stuff will create bad flow characteristics in the runners. Aftermarket intakes, and a stock 360 intake will work and will avoid this problem. The other issue could be compression ratio. Much of this depends on the configuration of your engine. If its stock, it may lower the CR a bit.
 
I have a 318 with 360 heads & intake. Without upgrading your pistons or milling the head you will have a low compression ratio, somewhere in the range of 7:1. This is assuming your 318 makes good compression now.
 
Forgot to mention... some people think that with the lower cubic inch a 318 has that you can't get good port velocity. Meaning, the fuel/air mixture can't get moving quickly into the combustion chamber, thus producing less HP. If this is true (and it probably is) then porting your 360 heads might actually hurt the performance on a 318.
 
I wouldnt touch either set. the 360 heads will lose you some compression because the chambers are larger. Plus, the ports on the 360 are larger. I would just leave the 318 heads, run a 318/360 Performer (not rpm), and run the summit brand smaller cam. It's made by Crane for Summit Racing, and it is cheap. MP cams are not wrth the time IMO unless you can and plan to degree it upon installation..
 
Max340 said:
The 360 heads can flow more due to larger valves. They also have larger runners,.
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While this is true, the 318 gobbles down air and fuel at a much lower rate. The potentail flow of the 360 head is not fully realized on a 318 until much much later in the rpm band. Until you get to the area where the engine can make use of the air flow ability of the larger port, the air moves slowly in the intake and head track. This drops fuel out of suspension and creates big droplets of fuel that will not burn so well once in the combustion chanber.


so the stock 318 stuff will create bad flow characteristics in the runners.
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This is simply not true of the heads. This is a mistake. It should read 360 instead of 318. I'm going to assume this is a typo. The smaller 318 head port will keep velocity up instead of droping it. Velocity is the key to makeing HP in any engine. The 318 suffers greatly from a lack of it.
Between the smaller bore and shorter stroke, the engine needs a smaller port so it can draw on the air and fuel well and really, the small port is an ideal set up.



Aftermarket intakes, and a stock 360 intake will work and will avoid this problem. The other issue could be compression ratio. Much of this depends on the configuration of your engine. If its stock, it may lower the CR a bit.
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On the cheap, a 360 head , intake and a T-Q are the best hop up parts for a 318.
However, if you want to do better and take some time and money spent well and not just spent......

Add a 1.60 valve to the 318 head, port the stock 318 head and back cut the valves. Add the Edel. Performer intake. The head and intake's ports should match. Carb of your choice. I like the T-Q for a dual performance carb, but add what ever carb you like.
 
Thanks for all the input. Something to think about in other words. Getting my 318 heads to flow with new valves and springs etc.,

Rumblefish if I replace the valves with the ones you mention and mod them as such do I need to change the rockers or pushrods to compensate at all?

Also what your saying on the cheap is: Top end of a 360 on a 318...should my cam choice be adjusted if I end up going that route (i.e. to simulate what one might choose for a 360 as opposed to a 318?

Also, I can get my hands on a T-Q and I'm tempted but it's a stock F*rd model so the linkage isn't correct, is that doable?

Last but not least, how can the Edelbrock intake be a 'one size fits all" if the intake ports and the 318 heads and 360 heads are different sizes. They just make them big enough for a 360? Wouldn't that impare the performance that intake would give on a 318?

In that case I might just go for the stock 360 dual plane I've got, it may be heavy but if that's the only difference. Seems to me the Edelbrock probably flows better but how much. Put it this way, if you have a stock 360 intake on your 318 would you prefer an Edelbrock?
 
Best option IMO for a street 318 is a pair of #302 heads with 1.88" intake valves and some porting. 360 heads should only be put on a 318 if you're going to do some massive milling and/or swap to zero-deck pistons and build the engine for high HP and RPM.

The Performer intake works best on the 318 but can be bolted to a 360; mind you it would probably only benefit low-end torque for something like a truck. I also have a factory iron 360 4-bbl. intake and I'm looking for a Performer to put on instead. I haven't run either but the better port match-up and much lighter weight would be big benefits (for me at least) on a 318.

Also unless you really want to spend as little cash as possible you might want to check out a modern fast-ramp cam such as the Comp XE line or Lunati Voodoo line. They might be more expensive than the Summit-brand or old-style repro cams, but the increase in torque and efficiency might pay off.
 
DQ81 said:
Thanks for all the input. Something to think about in other words. Getting my 318 heads to flow with new valves and springs etc.,

Rumblefish if I replace the valves with the ones you mention and mod them as such do I need to change the rockers or pushrods to compensate at all?
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No, since you didn't mill the head or block. But it may be so if the cam is large. The lifter has approx..080 total adjustabilty and if the cam is getting larger, thats moving the space left over downwards. That turns into approx. .040. Somewhere around the .500 lift, this should be checked.

Also what your saying on the cheap is: Top end of a 360 on a 318...
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Yes

should my cam choice be adjusted if I end up going that route (i.e. to simulate what one might choose for a 360 as opposed to a 318?
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Not really. Don't worry about it.

Also, I can get my hands on a T-Q and I'm tempted but it's a stock F*rd model so the linkage isn't correct, is that doable?
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That would be a good carb to get because it has an electic choke on it. I don't know what it will take linkage wise to get it to work on a MoPar, but a little fiddling around and car crafting will get it working.
I made an adapter plate (Ugly as fido shaved *** after a drunken hinght with horny sailors) that used a AFB electric choke set up on a T-Q. Again, it was butt asss ugly, but it did turn a choke well T-Q into a electric T-Q.

Last but not least, how can the Edelbrock intake be a 'one size fits all" if the intake ports and the 318 heads and 360 heads are different sizes. They just make them big enough for a 360? Wouldn't that impare the performance that intake would give on a 318?
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The performer with it's smaller intake runners are matched to the 318 head. You can use this on a 360. The larger ports on the 360 just draw off the small port window of the head well.

It does compromise the 360's performance some, just realize trhat it is build dependent. Mild builds are fine with a performer. But IF I was doing a 360 and had the cash for an intake and was useing a bigger cam than a stock 2bb. cam or 340 cam, I'd use a RPM or Stealth etc......
A performer will produce very high torque on a 360.


In that case I might just go for the stock 360 dual plane I've got, it may be heavy but if that's the only difference. Seems to me the Edelbrock probably flows better but how much. Put it this way, if you have a stock 360 intake on your 318 would you prefer an Edelbrock?
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Hi velocity is the difference in the intakes and could be an easy tune of 30 ft. lbs without breaking a sweat.

Build dependent, yes, I'd go for a performer on a 318 without a second thought. Depending on how fast I want to go and what I'm willing to sacrifice in getting there is a different story compared to a street ride.

And that's alot of info you left out.

Here, food for thought ; http://www.geocities.com/alwest_83/318
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IMO port the 318 heads,I would keep the valves stock and go 1.51 on the bowl and port match to these gaskets http://store.summitracing.com/partdetail.asp?part=FPP-1243&autoview=sku with this and typical exhaust mods you can gain a ton of power while having a ton of low end and high velocity.I did this to a 360 (kind of an experiment) that wound up at a true 8.7 comp.,xe 274,port matched performer,1in. spacer and headers with stock rocker gear.This engine ran like an animal and made low end like a 383,it pulled cleanly to 6k and made a ton of power,with 3.23s and a 904/2,500 stall it easily ran high 12 cars so I have no doubt it was a 12.80-12.70 combo with 3.91s at the track.
 
After getting my start in the world of aircooled vw's where most of the performance to be gained is bolt on (type 1 engines) I'm loving how much more complexity there is once you get pretty deep into this stuff. It's cool that a forum like this exists to share ideas.

That said, sooo many options depending on application!

Mine is best described as shared (other cars in the stable) daily driver with severe bite, think rabies. To be honest I'll probably only get her out on weekends, bad for the car to do a round trip of 10 miles I'll beat up on the old Beetle with the Subaru engine for short trips.

So the application is: Street use, keeping the stock 904 and 8 1/4 rear. More stoplight to stoplight, I'm not looking for a high RPM machine.

Am I getting into territory here where I should be thinking about a slightly higher stall speed TC than stock? The trans is coming out in the near future for it's replacement anyway so while I'm at it...What is stock stall speed?

Rumblefish: That link you sent is what I'm trying to achieve, although with a little less headwork for now I'm just going to clean up the stock 318 heads with a dremmel for better flow, it's convinced me to go for the Edelbrock performer also (along with all the other posts in this and many a topic)
That cam he speaks of (761 MP) if I were to put something similar in, would I have to replace my valve springs on the stock heads?
 
It's going to be a PITA to try to port the heads with a Dremel. It's a good idea to get matched valve springs for the cam you end up getting, as the stock valves will most likely be worn out and soft from ~35 years of use. As far as the torque converter goes, the stock one is around 2200 RPM for a 318. Mind you your stall will increase a bit when you increase the torque from the engine. I don't think you'd really need to play with it unless you were making the engine a little more wild.
 
MOPEkidD-3 said:
It's going to be a PITA to try to port the heads with a Dremel. It's a good idea to get matched valve springs for the cam you end up getting, as the stock valves will most likely be worn out and soft from ~35 years of use. As far as the torque converter goes, the stock one is around 2200 RPM for a 318. Mind you your stall will increase a bit when you increase the torque from the engine. I don't think you'd really need to play with it unless you were making the engine a little more wild.
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I didn't realize it was that high. I'll leave that alone then. Saves cash too, always a bonus. A buddy of mine swears by porting the heads with a dremel, his experience was a days work and noticable improvement. The shop costs are just too rediculous to fathom on this side of the pond. You've gotta remember working on domestics for us, is foreign cars for them. It's a speciality field accompanied by speciality pricing. So it might be a PITA but wel worth it.

Thanks for the stock stall specs.
 
rumblefish360 said:
While this is true, the 318 gobbles down air and fuel at a much lower rate. The potentail flow of the 360 head is not fully realized on a 318 until much much later in the rpm band. Until you get to the area where the engine can make use of the air flow ability of the larger port, the air moves slowly in the intake and head track. This drops fuel out of suspension and creates big droplets of fuel that will not burn so well once in the combustion chanber.
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While it is true that the air will move slower for any given RPM, accelerating the car, and thus the rise in engine RPM, requires as easy a flow as possible. Realistically, the valve seat is the most restrictive part of the runner. Swapping the 360 heads onto the motor will allow faster cylinder fill due to larger valves. The real issue won't be airspeed in the runner as much as it will be the vacuum signal to the carb. I have done this swap, and never had a problem with it while I was running it.

rumblefish360 said:
This is simply not true of the heads. This is a mistake. It should read 360 instead of 318. I'm going to assume this is a typo. The smaller 318 head port will keep velocity up instead of droping it. Velocity is the key to makeing HP in any engine. The 318 suffers greatly from a lack of it.
Between the smaller bore and shorter stroke, the engine needs a smaller port so it can draw on the air and fuel well and really, the small port is an ideal set up.
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I'm sorry to disagree, but I must. Anytime a mismatch of port sizes occurs, there will be "reversion", which causes huge amounts of turbulance where the ports meet. It doesn't really matter if its a 318 head and 360 intake, or a 360 head and a 318 manifold. The mismatch will cause turbulance and the engine will not be making the best of the two parts.



rumblefish360 said:
On the cheap, a 360 head , intake and a T-Q are the best hop up parts for a 318.
However, if you want to do better and take some time and money spent well and not just spent......

Add a 1.60 valve to the 318 head, port the stock 318 head and back cut the valves. Add the Edel. Performer intake. The head and intake's ports should match. Carb of your choice. I like the T-Q for a dual performance carb, but add what ever carb you like.
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Certainly the heads should match the intake, and if I did not suggest that, I should have. Given the 360 valve size of 1.88", I disagree with the valves being too big for the 318. In fact, if the exhaust valve can be enlarged to a 1.65, or 1.70" that would be very effective. But thats just my experience, YMMV.
 
Allrighty guys, let's say I tackle my 318 heads to keep compression as high as possible what angle do I want new valves cut too or can I get them precut? If done correctly I"m assuming the seat needs no work to accomodate a cut valve...thinking out loud you'd have to add material to compensate and it would nullify the effect of the back cutting right as the point of the excersize is to increase the ease of flow...

Also how much benefit in the whole P%P process does back cutting give lets say in percentage in your opinion?

I'm still on the fence on the 360 heads...If I port them properly my biggest 'issue' will be a loss in compression due to the heads being taller and increasing combustion chamber size. How is that off-set by the larger valves which in turn increase air intake and thus compression?

Am I getting it?

Now as far as valves go I realize it's a question of taste/experience. What's the stock intake/exhaust size for a 318 and what for a 360?

340: what you're saying is keep the 318 heads port em' and get my exhaust out quicker/smoother with bigger valves...? For this I'll need to enlarge the valve seat. Porting and polishing I'm comfortable doing, valve seat idk...
 
Why not ditch the 360 heads and go with a set of "J" heads or summit 318 2.02 heads? I will be building a set of roller heads from the summit 2.02 castings they are $525 a set I believe or in that area any ways.

Shawn.
 
Dart Shawn said:
Why not ditch the 360 heads and go with a set of "J" heads or summit 318 2.02 heads? I will be building a set of roller heads from the summit 2.02 castings they are $525 a set I believe or in that area any ways.

Shawn.
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Can you please provide a link? Ive never heard of Summit Mopar heads. Are the mags or LA?
 
Dart Shawn said:
Why not ditch the 360 heads and go with a set of "J" heads or summit 318 2.02 heads? I will be building a set of roller heads from the summit 2.02 castings they are $525 a set I believe or in that area any ways.

Shawn.
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J heads are 360 heads. 2.02" intake valves are also too large for a 318. Besides, I don't think he wants to spend that much money; he seems to be on a pretty tight budget.
 
They arent Summit but Summit does sell them, they are mopar performance, they are "LA" replacement head castings.

http://store.summitracing.com/partd...4294908110+400172+4294840085+115&autoview=sku

I researched the use of 360 heads on a 318 and got mixed opinion's but seems to me that the compression ratio will drop considerably, I was looking at going with a stock rebuilt set of 360 heads but I couldnt deck the block or heads enough to bring up the compression ration with out tossing off the mounting surfaces for the intake. please excuse me if I do not know what heads are what, I just base my knowledge off of research I am a Chevy guy, but that doesnt mean I dont like Mopar, hell I even like Ford I just know most about Chevy.

Shawn.

sublimeswinger said:
Can you please provide a link? Ive never heard of Summit Mopar heads. Are the mags or LA?
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In the Application notes it says.

Requiers Magnum Cilinder head Conversion Kit.

Must be Magnums then.
 
They say LA replacement, but pictured are Magnum... Also, that $500+ each... not a pair. And if the pic is reasonable, it's a bare head.
 
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