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318 heads. Edelbrock vs Indy/imm

Performance Upgrades

  1. drewkins

    drewkins Well-Known Member

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    Looking to build my 318 to around 400hp. I was wondering if anyone had input on the Edelbrock vs Indy lax imm heads.

    Thanks
     
  2. Adam

    Adam Well-Known Member

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    I have used both; Lax heads are iron, Eddy’s are alum... both are great. Both have small combustion chambers for high compression. Aluminum dissipates a lot of heat and reduces compression about 1 point, from what I’ve read. If weight is not a big issue, and going high compression (10.5+) for the 400 hp, I would use the iron heads, but either is a good choice. A 318 will need to be up in rpms to get to that power level. 318s rev very well, so don’t skimp on good valve springs and cam choice will be vital
     
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  3. rumblefish360

    rumblefish360 Well-Known Member

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    HP to weight = speed.
    Like above, that’s good advice. If your hunting 1/4 times, aluminum.
     
  4. drewkins

    drewkins Well-Known Member

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    thanks for the comments. I think i will go with the iron heads. Not going to do much 1/4 mile and have been leaning towards the LAX
     
  5. PureGTS

    PureGTS Member

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    Bare in mind 340-360 intake runners will need more 318 engine RPM to work properly. IMO get/make a bigger engine. You don't put B1 heads on a 383 or even a 440 without planning on spinning it to 7500-8000+ RPM. Eddys are better suited for that level of CFM and RPM. Go 500 inch and it needs more head. 318? not so much. It's a common misconception that 360-340 heads work good on a 318 street car. The engine won't produce good power until the upper RPM's. Besides, only you know how many cubes are really in there. A 360/408 can be dressed up to look like a 273. Can you say, "Here Chebbie, Chebbie…"
     
  6. rumblefish360

    rumblefish360 Well-Known Member

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    Cough cough cough — Bullshit — cough cough cough


    Since a 340/360 head has the larger ports, it acts like a ported 318 head but with a lower velocity. Your better off selecting a good 318 head to port for a higher velocity which will equate to a snappier throttle response and a higher quality air and fuel charge.

    Here’s the deal with any engine, 318, 360 etc....

    When it comes to building an engine with performance in mind, once you re cam the engine the power starts and ends in a difference rpm range. For the sake of simplicity and this is really over doing it but it applies loosely...

    Cams have a operational rpm range to them. The grinder will list there ranges in the catalog. Generally speaking, it’s good basis to go by but it is highly flexible depending on the part used in the engine.

    So! Once you cam up your engine, it has a new rpm range which can go up or down from the catalog listings. Let’s say for example you choose a cam in the 2-6K rpm range. A stock head will lower it 500, a good head will perform as advertised and a really good head will add 500 rpm.

    Putting a 360 head on a small cam is not the best way to go. The ports are large and the velocity will be low. If you gave it a medium size cam more suited for the head, it would be operating as intended.

    Your lack of low rpm is a result of the size of the cam and not the head to a huge degree. This is where people give the bad rap to the 340/360 head on a 318.

    You could use a Edelbrock head on a 318 really well. The accompanying parts would be more suited to a higher rpm engine. It really isn‘t as bad as the above B1 heads in a 383.

    Between the above two heads and the build, what cam are you considering and how does the build go together?
    (Parts intended and well, the goal your seeking!)

    Ether head and a cam duration @.050 of approximately 230@050 is about what you would be looking at.
     
  7. moparleo

    moparleo Well-Known Member

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    To greatly simplify... It is the COMBINATION of bore, stroke, cam choice, intake manifold, cylinder heads ( which is the biggest choke point ) exhaust headers size, and then tire size, gear ratio to put the engine in it happy spot. Just putting different cylinder heads on any engine without doing something else will not really take advantage of the increased breathing POTENTIAL until you match the rest. once you get the propr cam,intake, carb, headers it will incrementally come alive. Remember that an internal combustion engine is just a glorified air pump. The smoother the pathway from the air intake to the exhaust port, the more flow potential that you will have.
     
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  8. PureGTS

    PureGTS Member

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    Odd, that sounds like what I said... and a B.S. (Barbra Streisand) wasn't really necessary.

    Exactly! Bigger motor (CID) needs bigger ports and more CFM to work right OR you have to generate more air flow (A.K.A. more RPM) to get results. The trade off with bigger ports and low CID is weak bottom end because the air loses velocity (slows down) trying to fill the runner volume. 318-360 performer manifold it what that manifold was made to do. 318 ports and runners for a 360 huge low end response, high velocity for a smog burner engine better bottom end torque, snappier throttle, etc.
    Again I come back to the small CID 383 using B1 heads comparison. Real life case in point. 500CID BBM 2.19 int Eddy RPM heads 6.86 1/8th mile. 451 same everything conv, trans, gear, etc. With one exception: went from 1.6 rockers to 1.5. Same everything, cam and all. 6.80 with less cubes. The heads were the limiting factor for the 500" motor. But the 451" had the better combination so it worked better.
     
  9. rumblefish360

    rumblefish360 Well-Known Member

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    Wow! Didn’t I just say that? Dang! ECHO! echo, echo....
     
  10. PureGTS

    PureGTS Member

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    Why be a jerk about this? It would seem we're in agreement but you seem to want to look for a fight. I don't get it. Are we here to help each other, share experience(s), and the like, better the other guys car so they don't embarrass the brand? Or is this site full of trolls that just want to pretend to be bigger, badder, more knowledgeable than the next guy? Come on, we are adults here and there may even be differences of opinion off and on, but when we're on the same page; What's the point?
     
  11. rumblefish360

    rumblefish360 Well-Known Member

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    You make something out of nothing.
    So, what is the point?
     
  12. Adam

    Adam Well-Known Member

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    Years ago, in the 80s, I went with a friend to Ed Pink’s engine shop in Los Angeles to drop off some Ford SOHC heads and manifolds. One single carb, and one dual carb intake. They offered him $5000 for the parts, which he declined.
    Anyway, I was blown away by the size of the intake runners; you could pour golf balls into the carb opening and they would easily roll out the runners. It looked like you could force a tennis ball through without too much effort.. these engines were rated at 611 hp (dual quad) but were plagued by tuning problems for the street. The huge runners let the air/fuel mixture move so slowly at idle that the gas would fall out of solution and back into a liquid causing rough running, on the street. I still remember the guy saying “Yeah, you either stalled, or burned out for 100 feet, no in between.”

    I think this is a good example of street vs strip engines, and there is a lesson somewhere in there about intake runners being too big, or too small.

    I never saw the completed SOHC engine, but it was going into a gold 68 Shelby fastback to replace the factory 427 or 428, (iirc). The owner told me he was driving about a hundred when the engine started to come apart, so he put his foot into it. The results were spectacular. I was paid just to remove the grenaded engine, but once I had it out I had to drop the oil pan,out of curiosity. The oil pan had several holes in it, and most of the camshaft was in the oil pan! No piece bigger than two lobes. The crank looked like it was made out of clay and some giant finger took a swipe at it... good times.

    427 tunnel port heads