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toolmanmike

toolmanmike

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I've got a 1985 318 out of a 5th Avenue. It is a roller cam motor with 302 casting heads. I was planning on putting together a magnum head motor with a XE262H Comp cam (262-270 dur. 492-501 lift with 1.6 Magnum
rockers) and a Air Gap intake. Here's my questions: I would like to bump the compression up by using the small cc heads but I believe the combustion chambers are similar size. The Magnum heads do flow better but compression should be about the same.(the pistons are flat tops with no valve reliefs and are about .048 below deck) The older 318's have a open chamber head and benefit by changing to the better heads which raise compression. I also don't know if I can use my flat tappet hydraulic cam in the roller cam block.
I was planning on just freshing it up without doing much machine work.
It will be a temporary moyor while I am rebuilding the stock HP 273 in my 66 Dart. Can I use the pieces I have and make a good running small block or should I Just scrap the idea? Thanks for any feedback! Mike
 
You can use the Hyd. cam in a roller block and the Magnum heads with a milling. No problem, but you'll need to re-measure pushrod length (Not hard) and get the proper pushrod ends, ball and cup up top.
Also mill the manifold face proper (Specs in the MoPar engines book or a search here) fit. Possible bolt hole enlongation on a heavy mill. Not a problem with a drill and hole size bit or dremel/die grinder.
I'm guessing the 273 is OE for that car? I'd go with a pocket ported 302 headed, roller 318 in a heart beat and lie to everyone. "Yea, I'm tellin ya , it's a 273, it rocks! I can't believe a little MoPar make this kind of power!"
 
toolmanmike,
The heads from magnums and the 302's are very different and so are the chambers and they very 6 cc's or more depending, with the 302 being the smallest, the 302's will be more efficient also, just due to port and valve size. Also the pushrods are oil thru and not like the old style ball and cup. Magnums bolt up for the intake is different also as they are straight up and down and the old style is 45*, lots of machining here to do right. Let alone getting it right with a dremel or die grinder and the lack of the bolt boss. Sorry Rumble for stepping on your toes a bit but this is what I have found. Also the rockers are 1.6 and not 1.5 as they claim, actually 1.5 is really 1.43-1.46 and the 1.6 is really 1.54-1.57 so take this into consideration even though they are advertised as such, they still give more.
Then why have a bigger engine and claim smaller ? I always get more compliments when the engine is what it really is and kick there butts. Most people can't get a engine to run and especially a Mopar! So when it does run give it the justice it deserves and have fun.
 
I have been collecting parts for a Magnum head motor for some time now. I have 2 sets of heads, lifters,pushrods, springs,retainers,keepers the
Air Gap and the cam. I knew I was getting the engine a long time ago but didn't know what it was inside until I took it apart. Knowing what I know now I would have stripped the Lean Burn stuff off, stuffed in a new cam bolted on a nice intake/carb and ran with it. I haven't been able to find any info about
these newer 318's. Everybody seems to write about the mid 60's-mid 70's 318's. toolmanmike
 
toolmanmike, The newer 318's are very similar to the old 318's other than the roller cams, and lifters, they do have shorter pushrods but this is pretty much the only differences everything else will swap.
 
You might have a clearance issue were the pushrod goes through the head. Magnum heads were ment to be used with roller lifters, they are taller than hydraulic flat tappets. It puts them at a different angle. Check to be sure.
 
I did something similar to what you are doing only I used a 68 318 bored 60 over = 328 ci. Short block was free, the dude giving it away didnt even know the motor had been bored - cha ching ! What a nice surprise when I tore the motor down!

I got a set of the 302 heads, ported them, put 160 188 valves in them and used the old 273 cast iron 4 bbl intake. Cam is an mp 450/455 lift 268/272 degree hydraulic. carb will be a 625 afb, shorty laysons headers, electronic ignition. I cc'd the heads and measured the piston deck height, with the thin mp gaskets it'll be right at 9:1 CR, which is fine for me. I figure this combo is worth somewhere between 300 and 350 hp. A conservative motor, but it should be able to run all day with no issues, which is what I am after. Haven't run it yet, motor is still waiting for me to get my s#$% together with the rest of the car. Oh well.
 
That sounds a lot like my combo. You'll have to keep me posted. Mike
 
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