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Technical Lets build a small block Mopar

Discussion in 'The Hokey Ass Message Board' started by mcmopar, Nov 5, 2017.

  1. mopar362000
    Joined: Feb 14, 2008
    Posts: 88


    308 head is the one to use if u are going to use la engine.Magnum engine is the one to Evan at mopar madness can regrind the roller cam .Evan likes the eq heads they flow better than edlebrock heads but they are iron.I think he has a spec sheet on these engines.
  2. saltflats
    Joined: Aug 14, 2007
    Posts: 9,896

    from Missouri

    If I was building from the start I would get a rod and piston combination that would put the piston to the top of the deck not cut the heads down.
    Set your quench with the head gasket.;)
    squirrel likes this.
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 45,227


    On the older engines, yeah, the 360 stuff will bolt on a 318. But if you put a 360 intake on 318 heads, there will be a substantial port size mismatch, for example. It may or may not affect performance, there are a lot of variables.

    Of course, the right thing to do is build up a 318 Poly motor, to keep it trad :)
    Arominus and patmanta like this.
  4. 73RR
    Joined: Jan 29, 2007
    Posts: 6,285


    ...and the Poly head flows better than the LA...the down side is the expense of the CPM intake. Then toss a 4" arm in there and get-r-done. I sure like to spend OPM.:p

  5. squirrel
    Joined: Sep 23, 2004
    Posts: 45,227


    don't cost me nuthin
  6. BadgeZ28
    Joined: Oct 28, 2009
    Posts: 1,031

    from Oregon

    I got into learning about the LA motor family when I got a project car with a 360. Just a tip. You can adapt small block Chevy headers to a set of LA aftermarket flanges. The difference in spacing are not so much different that you can't move the pipes to fit. Opens up a whole lot of fitment applications.
  7. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,686


    I beat on a lot of 318 when I was a kid. The first thing I did was replaced the 2bbl with a 4bbl and installed dual exhaust. On the street, the differences in the ports won't make much difference in the seat of the pants. If it bothers you, its pretty easy to use a 360 intake gasket and hog out the end 1/4" of the ports in the 318 heads to match the gaskets. Even that 18 year old kid could do it back then. The small ports on 318 heads makes great throttle response, as long as you don't think you need to wind it up past 4,000 or 4500 rpm, then they fall flat, can't move enough air. A street car with very quick throttle response in a car geared for lower rpm shift points can cause great heart ache for high power, high rpm brute in a run shorter then a 1/4 mile.

    Most of those 318 sure upset a lot of guys. Nothing hurts more then getting your butt handed to you in a 4 block long street race then getting beat by a 318. I was sure to tell them all what they got beat by.

    I took one 318 too far, I installed the biggest hydraulic cam I could get for a small block Mopar. The 318 was in a 70 Road Runner. With headers, 318 heads (with springs to match the cam) match ported to the 340 intake, 780 Holley, a 4 speed, traction bars and a good rear gear, it was a monster up to 4,000 rpm. Power shift 2nd and beat most comers in the downtown street events of the time (1978-1981). At WOT it was great fun, almost scary. As a daily driver, it sucked. Cold blooded, temperamental, the cam had a lot of lope, which vibrated everything loose all the time, it was real scary to drive in the rain, bad gas mileage, heavy duty clutch was a pain at a traffic light, and only lasted about 1/2 a summer before it started slipping, hard on rear tires, an almost weekly broken parts changing events. AH the price we pay to go fast. The 318 ran hard enough that it broke the crank after 2 summers of abuse. 318s can be built to run, but the same money spent on a 360 will run harder. Gene
  8. mcmopar
    Joined: Nov 12, 2012
    Posts: 1,524

    from Strum, wi

    saltflats, that is what I was thinking, but then, kb pistons and shaved heads are a proven way to make good hp. Downside is now ya have a set of heads that can go on 1 motor. I really didn't want to mix abunch of different parts from different makes to get what I want.
    There is no plan to put a poly motor in and that wont change. In the last couple of days I have read a lot on this motor, and its a love hate relationship with people. The majority says get the piston up out of the hole, a better set of heads to breath, and a cam to match, and ya have a healthy combo.
    If I don't cut down the heads, and go they way of rods and pistons, can I just get (.100 just a number until I take it apart and check proper dimension) longer rods, or have pistons made with the wrist pin up .100? What do I need to be careful of or look at closer?
  9. squirrel
    Joined: Sep 23, 2004
    Posts: 45,227


    Looks like there are quite a few aftermarket pistons with the right compression height to get the deck height close to zero. That would be the way to go, rather than machining stuff a whole bunch or spending money on rods.

    But I don't build engines like most magazine articles tell us to....I'm a cheapskate.
    Mike Miller likes this.
  10. 73RR
    Joined: Jan 29, 2007
    Posts: 6,285


    Two thoughts...Being 'down in the hole' is only a problem if you are trying to maximize output. For a street package this is not always needed but most often wanted. Yes, any custom piston maker will put the pin where you want it but those pistons will cost ya $800 or more. Valve clearance always has to be checked.
    Get yourself a copy of the Mopar Engines Manual, #9 is a good one, and follow the engine build package that is outlined. Although many of the part numbers listed are NS1 there will be replacements. MaMopar says that the 318, with 9:1 c/r, is capable of 11 sec ¼ mile in a bracket race car. Not too bad in my book.
    When I look at modifying a MoPar engine beyond what they recommend I have to remind myself that even in the old days their R&D budget was probably similar to the GDP of some small countries......:cool:

  11. I'm not 100% sure, but i think retrofitting a mechanical fuel pump can be done on a magnum motor. You would have to replace the timing cover, water pump and accessory drive plus add a fuel pump eccentric to the front of the timing set. If would bet the crate magnum 360 from Mopar is set up this way. Put a set of Enginequest heads on and use that six pack!
    Personally, the connecting stock connecting rods should be more then good enough for your build. I have stock rods in my 360 and and have spun it to 7000 rpm's on the street and drag strip regularly since 1999.
    Dont get me wrong, there is nothing wrong with the 318, but why not gain 42 cubic inches and a roller cam with the good core you already have?
  12. F.O.G
    Joined: Oct 31, 2006
    Posts: 259

    from Pacific,Mo

    Chrysler did put a four barrel on the 318 from the factory, and it was a quadrajet, in
    the eighties. They were in New Yorkers mostly, smog motors for sure.
  13. desertdroog
    Joined: Nov 16, 2001
    Posts: 976


    Some reading for you (360 recipes):

    I plan on going with a 5.9 Magnum (which is a roller top end 360 with some minor differences from the LA) with the EQ "Iron Ram" heads, drilled for the LA intake, tossing the factory Fuel Injection and brain and changing over to a carb to keep it simple for my 41 Plymouth build. Just picked up a good running complete 5.9 for $300 locally. You can find these engines with the crosshatching still visible on the bores, usually. It isn't the most HAMB friendly engine, however it will be under a hood in a custom, so who cares?

    Need Louvers? has a built 360 in his 47 Plymouth Club Coupe in front of a TKO stick, and was rowdy when it was up and running. has a wealth of info on all sorts of builds and swaps for further tech reading. is where I got my idea to do a modern version with some ideas on how to disguise it a bit from looking too high tech.
  14. Budget36
    Joined: Nov 29, 2014
    Posts: 3,221


    What are his options for stroking the 318?
    I ask for two reasons,one he has a 318, and the other, I do as well,mine however was rebuilt .030, rods resized, heads rebuilt,etc...but has been wrapped up for 10+ years or so.

    Are there stroker cranks for another 20-30-40 cubes? Or is the jump to the 4 inch 390+cu the only thing out there?

    Not really a hijack...mcmopar HAS a 318:)
  15. Arominus
    Joined: Feb 2, 2011
    Posts: 379


    Throw a 4" stroker crank kit in your 318 with aluminum heads/intake, a cam and you will be very very happy, seriously. 350-400hp is easy on that combo, more is likely. I don’t think I would build a small block any other way at this point. You run a fairly mild cam and still get good power, so as long as it’s built right and the carb is dialed (use an O2 sensor to tune!) it will be reliable. If you want other opinions, ask this question in the moparts forums in addition to here. Those guys are on top of the built small block game.

    Here is another good reference for you as well. This is a stealth build using a 360 block made to look stock.

    PS if you wanted to keep it trad, the 4" stroker cranks work in the A series block, an aluminum intake and headers are available for it. This would still be a more expensive build, but killer.
    Last edited: Nov 15, 2017

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