I'm sure this has been asked many times but i don't have much money to spend and i would like to bring up the compression on my 72 318 with stock pistons, I have 360 heads from aerohead racing and was thinking about the magnum heads, would this be a better way to go.
better head selection
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1wild&crazyguy
Banned
You have to cc the 360 heads and see where they are at, you'll probably be able to mill them down to 60cc which is smaller than the advertised 318's 62 which is more like 65ishc cc's.
That will pick it up a tid bit.
Other wise your talking about buying mag heads and throwing money at them for a rebuild and then still having to mill them as well cause they around 64ish cc's on average.
There are a few who run the magnum heads here that can maybe clue in to how big the chambers are, well at least the ones who actually cc'd their mag's.
That will pick it up a tid bit.
Other wise your talking about buying mag heads and throwing money at them for a rebuild and then still having to mill them as well cause they around 64ish cc's on average.
There are a few who run the magnum heads here that can maybe clue in to how big the chambers are, well at least the ones who actually cc'd their mag's.
fishy68
Tyr Fryr's Inc.
The magnum head swap is a good upgrade from what I've read but it isn't as simple as that. They use a totally different valve train so you'd have to buy everything. I haven't had any to cc but I've read their in the 62 cc range. Like Wild one said you can mill yours down. Just remember to mill down the intake side .0095" for every .010" you mill the chamber side to keep the intake aligned. And when you done the end gaskets probably wont be able to be used cause of all the milling. Just use silicone there.
needsaresto
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o.K,with a stock magnum head cc of 64,piston down the hole .060.and a .028 thick head gasket compression comes out to 9.1:1. Right where it needs to be for a nice daily driver without changing the pistons or milling heads. Swap in KB 167 for more compression.
The port sizes are bigger than a stock 318 as are the valves. You will not find a better stock small block exhaust port,period. The head chamber has double quench for a fast burn,so it is designed for todays fuel.A magnum motor needs less total timing than an LA to make the same power.
The magnum head oils through the pushrods. You will need AMC type .904 lifters that have an oiling hole,which come with just about all the aftermarket cams anyway.You will need hollow pushrods. Magnum rocker gear.Magnum head bolts. Either a magnum style intake,one that is drilled for both LA and Magnum or drill the Magnums to accept both styles.
Dont worry about the block oiling holes for the LA head.The magnums will cap them off effectively.
I would use an Edelbrock airgap.
I thnik the magnum will outperform a 360 head on a 318 by virtue of better bottom and midrange torque.
The port sizes are bigger than a stock 318 as are the valves. You will not find a better stock small block exhaust port,period. The head chamber has double quench for a fast burn,so it is designed for todays fuel.A magnum motor needs less total timing than an LA to make the same power.
The magnum head oils through the pushrods. You will need AMC type .904 lifters that have an oiling hole,which come with just about all the aftermarket cams anyway.You will need hollow pushrods. Magnum rocker gear.Magnum head bolts. Either a magnum style intake,one that is drilled for both LA and Magnum or drill the Magnums to accept both styles.
Dont worry about the block oiling holes for the LA head.The magnums will cap them off effectively.
I would use an Edelbrock airgap.
I thnik the magnum will outperform a 360 head on a 318 by virtue of better bottom and midrange torque.
would it be worth milling the 360 heads to 60cc if i can along with milling the intake, i already have a rpm airgap intake set up for the la head. i just wanted to get decent compression at least 9 to 1, put new bearings and rings and swap in a larger cam. what would be the best economical way to do this, just a reliable cruiser with enough power to have fun with.
fishy68
Tyr Fryr's Inc.
I believe it will work fine. In spite of what alot of guys say I have personally seen the 360 heads that weren't even milled alot work fine on an otherwise stock 318. An example goes back about 25 yrs. ago when I didn't know the chambers were larger on the 360 heads and I helped a buddy install a set on his 74 Dodge 1/2 ton 318 powered pickup. It ran great with them even in spite of the low compression. Yes there are better heads out there but you can always say that about most any engine combination. If you already have them you might as well use them. The Air-gap intake is a great choice. Don't go too big on the cam as the small cubes and low-ish compression won't allow good torque. A Lunati 60402 or comp XE262 should do you good. You also need good flowing exhaust. Headers are a big plus for power even if they are a pain to work around.
turbodart68
Well-Known Member
I milled my X heads .040 on my 360 and the compresion went up from 9.9:1 to 11.11:1. A 318 will be less because the stroke is less. Go here to figure out your compression ratio.
http://www.csgnetwork.com/compcalc.html
The answers you get out of this program are only as good as the numbers you input. With that being said, if you use consistent numbers and only play with the cc of the chamber then you can at least gauge what the improvement would be. Also there are thin sheetmetal shim type gaskets out there that can improve your ratio. My heads started at 72cc and are now 64cc IIRC. You can expect a 5-10 percent increase in power with a full point of compression depending at what level the compression is at. I have had no problem with these heads sealing and I even use a 150 shot of nitrous and make 496 hp at the rear tire. Remember to have your intake cut as well.
While you have the heads apart it might be a good tight to grind away at them. You can do a little shaping in the bowl area in about an hour and pick up some impressive results. Its free, with the exception of a few bucks for the cutters from summit racing, and it will add to the overall package. I have done this before and have been surprised at that the change in characteristics of the motor. It went from okay to a tire spinning monster! Good luck and I think you'll like the results.
http://www.csgnetwork.com/compcalc.html
The answers you get out of this program are only as good as the numbers you input. With that being said, if you use consistent numbers and only play with the cc of the chamber then you can at least gauge what the improvement would be. Also there are thin sheetmetal shim type gaskets out there that can improve your ratio. My heads started at 72cc and are now 64cc IIRC. You can expect a 5-10 percent increase in power with a full point of compression depending at what level the compression is at. I have had no problem with these heads sealing and I even use a 150 shot of nitrous and make 496 hp at the rear tire. Remember to have your intake cut as well.
While you have the heads apart it might be a good tight to grind away at them. You can do a little shaping in the bowl area in about an hour and pick up some impressive results. Its free, with the exception of a few bucks for the cutters from summit racing, and it will add to the overall package. I have done this before and have been surprised at that the change in characteristics of the motor. It went from okay to a tire spinning monster! Good luck and I think you'll like the results.
turbodart68
Well-Known Member
It looks like its just under a point. 8.38 to 9.11.
needsaresto
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Is it worth it? Depends on your local machinist and what they charge to mill the heads I guess.
My Magnums rebuilt and with all the rocker gear are $300.I would think your machinist can do what you need for less than this.Check around.
1wild&crazyguy
Banned
What's included in the rebuild?
port volume/velocity wise the mag is a closer match for the 318, but once it's rev'd the benefits reaped from that fade, you could even argue they then come up short.
But if you could get the mag thang going for $300 then all you would need is a new intake, pushrods, lifters, rockers [cool thing is they are 1.6, bummer is thet are pedestal stlye..]
I would think the average guy will spend around $1000 to get it together with only a 3 angle VJ and, a mill and some seals, thats finding good cores at the yard and then buying the push rods,lifters, intake and such.
port volume/velocity wise the mag is a closer match for the 318, but once it's rev'd the benefits reaped from that fade, you could even argue they then come up short.
But if you could get the mag thang going for $300 then all you would need is a new intake, pushrods, lifters, rockers [cool thing is they are 1.6, bummer is thet are pedestal stlye..]
I would think the average guy will spend around $1000 to get it together with only a 3 angle VJ and, a mill and some seals, thats finding good cores at the yard and then buying the push rods,lifters, intake and such.
needsaresto
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I also have a porting template kit for magnums. Should help it breath to 5500 or 6000.If you want a good street head this is the way to go. A 360 head will leave the mag behind over 6000 rpm due to it's large port volume but you also lose a lot of bottom end snap with those big ports on a 318. They just cant use all the volume a 360 head provides and the air moves sluggishly in daily driving.
I had a factory 318 4bbl cop car which comes with 360 heads from the factory. It was a dog until about 3500 rpm. Raising the compression will help this somewhat,but wont change the fact that the port volume is too much.A looser tc will help this.
Something that hasnt been discussed here is 302 heads. Smaller in port size than the mag,it needs major port work to compete with it.But it ends up being a better match for a 318 if you are willing to spend the cash. It is a bolt on deal though.
And you dont need any rocker gear with my heads.They come with all of it,rockers etc.In fact ,for $350 you could have the ready to run heads,stock magnum valve covers and the porting template kit.You would need to buy the head bolts($50),pushrods ($80?)and then your intake.Im not going to count in the lifters as you will likely get them with a new cam.I would drill them for an LA style intake,cuz then the selection opens right up.You could easily use a crosswind or a summit intake. Better yet,you could get one here cheap.
There is also a member here that has mp hi performance valve springs for magnums,if you need more lift/rpm.
One final word on the magnum head design. Seems lots of folks here think they are a chevy style head and have weak rocker gear. Truth is that chrysler enginees based thier design on the old AMC head. And there a literally millions of chev motors on the road/track to argue the point of chevs reliability when it comes to rocker gear.Im not a chev guy by any means but the facts do speak for themselves.
An advantage to the magnum is that they CAN use a chev style roller rocker.This makes aftermarket rocker selection endless and cheap.
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