360 heads on 318?

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67valiant

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i have a set of regular 360 heads and a set of 915 j heads i want to add more power to my 318, will putting the regualr 360 heads on add more power since they do ahve the bigger valves or am i just going to waste my time putting them on and if i do put them on should i get them shaved at all.
my 318 is .030 over and i have the 1970 340 4 barrel cast iron intake
any input would be great thanks guys
 
The 360 heads will lower your compression and port velocity. Depending on the cam you are running you could see an increase in power in the mid to upper RPM ranges but will most likely sacrifice low and midrange torque and power. I have a 318 that is pretty much stock with 915 heads on it. It was done that way when I aquired the car. I am running the Weiand dual plane for the 318 port size. It runs ok but I have no base line on it from before the head swap. I was thinking about putting the swirl port 302 castings on it for added low and midrange performance. There are some guys on here with very quick 318 cars running 360 heads though. If I recall the best results came from either milling heads or using near zero deck pistons.... Use the search utility and you will find lots of input on this subject in past posts. Also take a look at the tech archive section.
 
I guess I'm always backwards LOL!

My 360 has 318 heads on it (302 swirl ports). I wanted a tire ripping motor. The valves have been back cut is all that was done. I have no problem with low end torque and port velocity.
 
i am also putting in a new cam that is 443/465 lift and i forgot the duration and all that its and erson though and should i mill the heads and intake?
 
67valiant said:
i am also putting in a new cam that is 443/465 lift and i forgot the duration and all that its and erson though and should i mill the heads and intake?
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It's a common pratice if you mill the heads to mill the intake so they will fit together properly. I think there is a formula that when you take so much off the heads that you need to take so much off the intake. The machinst should know that.

I would go with the smaller valve 360 heads if it was me rather than the 915 for the 318. That will keep the port velocity up. Have the valves back cut while you're at it. Basically its the same thing I had done to a set of heads for a 273. Having them milled brought the compression up which was a good thing. Knowing the ccs of the heads before install will help determine your compression ratio. I used the thin Mopar performance head gaskets also. They usally compress to .020 or so.

This will help you determine your compression ratio http://www.mopar1.us/compratio.html
 
mullinax95 said:
I guess I'm always backwards LOL!

My 360 has 318 heads on it (302 swirl ports). I wanted a tire ripping motor. The valves have been back cut is all that was done. I have no problem with low end torque and port velocity.
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Hows it run ? My 360 has a set of 302s also. Mine have 1.88-1.60 valves and some port work though.
 
AdamR said:
Hows it run ? My 360 has a set of 302s also. Mine have 1.88-1.60 valves and some port work though.
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I have not did the "fine tune" yet because I drive it very little and just work on other stuff. I'll move the timing a little here, adjust the carb etc.. but have got it in the ball park. The valves have been back cut and the heads have been milled so I have 59cc chambers. That's all I had done to the heads. Everything calculated together I have 10.7 compression. The cam is just MP 474/474 so it is not really radical. Performer intake, TTI and 750 Holley HP mechanical secondaries. The car is easy to get sideways so it is fun to drive. It is there all the way to 5500 RPM but I don't tach my motor over that anyhow. The rev limiter is set at 5500 RPM lol! Another words low end and mid range is just flat awesome.

I noticed awhile back that you had 302s on your 360 so I didn't feel like I was the only one. But I still have the 1.78-1.58 valves. I guess I could always move up to the 1.88-1.60 if I like but I wouldn't dare go any larger than that. I tried to match everything rather than miss match so over all I am very happy with it.

DSC01682.jpg
 
The 360 heads are OK and fine for on the cheap upgrade. The cost of porting the 318 heads can be counter wallet productive. But it is more likly a better way to go.

The cams duration @ .050 would be real good to know as well as actual compresion ratio.



If you go via the 360 head, the small valve should be used. Ethier head, smog or J will be fine for modest upgrades. It's better to use the 340/360 head in a fairly aggressive 318. 400 plus HP is where ya might start thinking about it.

OH, if it is a true 8.0-1 engine, then adding 360 heads will drop the ratio down to 7.38-1.
What ever you come with, it's a .62 drop in the ratio. OUCH! Use a Fel - Pro .039 thick gasket, it'll drop (More than) another .28 (min) to 7.1-1 Or less. (This is due to gasket bore size being unknown from what you have to what you actually go to.) This could be an easy 60 HP lose with such a drop over the correct piston use.

This is why a few here are against the use of 340/360 heads as well as the larger port runner slowing down the velocity of the air and fuel mix. Slower movement also doesn't help the mix to atomize well and will cause the fuel not to burn as well.

Here you can see the double trouble of the bigger head. Loss of compresion, low port velocity which leads to sluggish pedal feel/response and the use of more fuel because of this while adding up to less power than a port 318 head.
 
This is what I've been preaching, and yet some either don't want to hear or don't listen. This is why I backed off on posting, thank you Rumblefish for stating what I've been trying to say all this time.

Marland, you know what I've said and it works. Because you did it.
 
Thanks Mullinax. I agree with ya Bobby. Theres various builds on the net and many of the better builds document it all with the dyno sheet. A 2.02 head or Edelbrock head looks great on the dyno, but when you put it into your car, welllll, you may not be so happy with it or what you have to do to it inorder to make it work half way decent.

I've been saying this for the last 10 years on BB forums. It allways comes up. It's allways the same. And it is a bummer when the builder/knowledge seeker beileves the majority of the think they know vs. "What you know!"

I also have to be hnest and say I seen some wacky stuff go on and surprise me. At this point, I call them liers cause there word on what it is dosen't equate to what it does.
 
Thank You,
You know where I'm comming from, I've built most all small block Mopars and have a very good knowledge of what works and what doesn't, it really discourages me when I can see where there going and they can't see the tree's for the forest. Keep in mind that I've also done BB Dodges too. And Rumble I know your daughter liked the pics.

With mikel's help we should have the new site up by friday next week. Sorry for the shameless plug.
 
I hear ya on that bobby. I'm not the sharpest tool in the shed I certainly don't know it all, but sometimes, I wonder.

LOL, shameless plug aaaaaway!!!!!!!!
 
Bobby, Looking forward to seeing your site. Will you have a board for tech questions ?
 
I really haven't talked to mikel about it, but there will be a tech page. Between work and trying to get the info for mikel it keeps me very busy.
 
Marland,
You know me, I try to answer all question that are asked reguardless of the number of them. If you have that many then call me and we'll get it done faster. Hehehehehe
 
Hey Bobby, have you seen this around ? It's been around for awhile. Shows the importance of the correct head.

I had the pleasure of talking with this fella for a while. Nice guy, stand up and helpful.

http://www.geocities.com/alwest_83/318

If your itchy for the meat and potatos of it all, scroll down to the right and read "DYNO TESTED 318"

Also note the power lose between heads. It's not as much as I stated above, but then again, this is a mello build and less of a compresion drop or what could be actuallly.
I was thinking of a slightly stronger build when I made that statemnet above.
 
Yep kind of re-enforces what I've been saying about the heads. But the use of the larger valves hurts the velocity on the intake side, now on the exh. side the larger valve helps tq.. If he checked the flow with the smaller valve and the larger valve and did the calculations he would have found that the smaller valves would have moved more air sooner with the head in ported form. With the smaller valve moving more air the tq. and the hp will come up. The difference that I found is about 40 hp more with the heads modified the same on a 318 engine. Keep in mind that a 302 casting head is only 118-120 cc's from the factory and that is why the factory used a 1.78 intake valve and not a 1.88 valve. The 1.88 valve needs to be in a head with 140 cc's or more and without major welding and rework the 302 head will never get this large. And on the flow bench there's not a 5 cfm difference at peak. And with the larger valve the low lift flows are less than the 1.78 and when using a cam thats .500 lift or just over the low lift flows are very important. On one of our cars we had the 360 heads with the 1.88 intake valves and it ran a best of 7.48 in the 1/8, and then we switched the heads to the 302's with the smaller intake valve and the larger exh. valves, and the car ran 7.31 in the 1/8 so with actual track testing this is where I get my info from. If you noticed that he never attemped to try the smaller valves in his artical, he just went straight to the 1.88 valves.
 
Can you weld up a set of heads? IE; the pushrod holes and open the port up larger for more aggressive engines?
 
Rumble,
What we do is make plugs for the pushrod holes and weld the plug in and then move the port over, but this hurts the port flow as some of the port velocity comes from the pushrod pinch area. This helps to direct the flow to certain areas and allows for better mixing of the fuel and air, basically it makes the air turbulent which keeps the fuel suspended. I've done this for another guy from another board and the heads would have to be used on a 408 engine or larger to make power.

Actually I made him a set of T/A heads out of a set of 915's. The ports ended up at 187 cc's and when he put them on his 365 engine he lost most all the bottom end Tq. because the port was too large and the air speed or velocity was too slow. They did flow very well at .400 and above but he only ran a cam that was .500 lift so in his case the heads were way too large and the engine slowed 2-3 tenths in the 1/8, and I told him the heads were too large but he wanted them anyway. His engine ran faster with a set of heads that were only 158 cc's and the pushrod pinch still in the head.
 
Just good to know that it can be done.
 
I tried the swap on another car. You're doing well in the sense that there is a port mismatch between the 340 intake and 318 heads. The 360 head will take care of that. I chased around trying to find 340/360 A-body exhaust manifolds. It was tough then, worse now.

When I rebuilt the engine I used the older piston which Mopar rated at 9.2:1. I used a Purple Shaft .444 lift as I recall. With a 625 cfm AFB on top and 3.23:1 rear, I was disappointed with the low end, but it pulled great on top. I felt that it tapered off around 5500 rpm.

I used the same pistons, carb, and rear end on the Demon. I have a little more cam (.455) and 302 heads. Car is livlier off the line and in normal driving. Still seems to go flat around 5500. Oh yeah, it gets better fuel mileage.

Unfortunately for this discussion, I have never been to a drag strip. Therefore, I have no timing slips. There have been a few street events, but these are not subject for discussion.
 
OK,
I agree that your engine won't perform at the same level, but you state that your engine is stock? correct? Or slightly over? But then your not a racer and this has count, so your performance isn't going to be there. Until you have a racers mind and set thinking even for the street the performance isn't going to be there.

There's never been a street car thet will run with a race car, now which do you want?
 
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