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Thread: I need some old-school engine building expertise...

  1. #1
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    I need some old-school engine building expertise...

    I'm basically trying to get as much assistance as possible regarding the motor i'm putting together for my 1970 Subaru FF-1 project. I'm not getting much help in the main thread, so I'm going for the actual engine information section for this.

    Anyway, here is a short brief:

    Its an old EA Subaru motor, EA63 to be exact (1400, 1.4l, 1361cc).
    The original motor was an EA61.
    Pushrod, carburetor, 2-valve, no timing belt old-school 70's style motor.
    The shortblock is a NEW 1.4l dry-sleeve (as opposed to wet-sleeve which is what most 1.4l's are, finding a dry-sleeve 1400 is HARD to do).
    The cylinder heads are dual-port (front/rear port) 1400 heads, which I MUST use due to engine mount/crossmember location (cant use single-port heads).

    Now, for the serious information...

    I'm trying to use a VERY rare Weber manifold on the engine, as seen here:






    The big issue is the Weber manifold is 4mm shorter than the stock manifold!

    This is because that manifold is designed for a JDM-only "sport" motor (1300G) that had a shorter shortblock. That motor I can't find, and don't want to use anyway due to the fact it is a WET-SLEEVE motor (more headgasket failures, harder to maintain, HARD to rebuild). This manifold will let me use a very nice dual-barrel carb setup, and I spent a LOT of money on it so i'd like to use it

    Now the problem:

    As you can see in the picture, the manifold DOES bolt to the engine and line up perfectly with NO HEADGASKETS installed. I've done all the measurements and figured it is exactly 2mm each cylinder head that needs to be shorter.

    I've started talking to engine machine shops about this along with various old-school Subaru guys and i'm getting mixed information/opinions.

    My goal with this engine is NOT a pure-race engine, but a quality, reliable street driven engine.

    Known Options:
    Shaving the heads -
    In order to run the manifold, the easiest (and cheapest) option is to shave the head 2mm each side. This will increase the compression ratio of course, however i've been told anywhere from 10.0:1 to 15.0:1 (stock compression ratio is iether 8.5:1 or 9.0:1, depending on the year of the 1400, in this case i'm not sure but i'm guessing 9.0:1). I'm fine with something around 10.0:1 as long as the headgaskets will hold up and i'm fine running and tuning it to premium gas.

    Custom thin headgasket -
    I've done some homework into custom headgaskets that are thinner (the OEM and aftermarket headgaskets for this motor are 2mm thick) like Cometic and Copper gaskets. From what i've read, MLS (multi-layer steel) headgaskets are best, but Cometic won't make just one set of custom headgaskets.
    Copper gaskets i'm getting mixed messages about, with some saying they are a PITA and should only be used on pure-race engines, while others have no issues with them.
    Either way, i'd still have to shave whatever the thinkness the gaskets are from the cylinder head to fit the manifold.

    Pistons -
    I've been thinking that somehow modifying the piston (shaving?) to solve the compression ratio issue with shaving the cylinder heads. Custom pistons are expensive, so are modifying normal ones something that actually occurs?

    Other potential solutions -
    I've had people say to modify the intake manifold or put some kind of spacer on there. Thats more difficult that one would think because not only does air travel down the manifold but coolant as well...
    Any other ideas would be helpful.


    My only other solution is to run the stock manifold with a 32/36 weber carb which is what most other people run on old EA motors, which isn't that interesting of an option (plus i'd buy a new one of those with the adapter and such, which runs around $400 anyway. Shaving the heads and using the weber manifold with the carb I have with that will cost less than that!)

    Note: I have not calculated the cc of the compression chamber and have never done something like that before, but it has been mentioned to me.

    P.S. If you have any other general questions about what i'm doing, or need more photos of something specific, just say so...

  2. #2
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    BTW, here is the main thread for reference: viewtopic.php?t=3002

  3. #3
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    I would think cutting approx. .080 off each head would not be good. Generally, you would not cut more than .030 off a head before it's past the service limit and considered junk. I would imagine the water jackets start to get thin enough that cracking may be an issue and the thickness is not there to prevent the head from warping. Then there is the issue of valve train geometry. Custom length pushrods are a must. If that's not enough, there is piston to valve clearance to think about, especially if a performance cam is in the cards. It would seem on the surface making the manifold work, while possible (and expensive), will not lead to a "reliable" engine. I definately see your point in trying to run that manifold, but in all reality, a 32/36 will probably be more than enough carb for the amount of HP the motor will be putting out. I'm pretty sure you'd have to choke the IDA down to 32-34 mm chokes anyway for good street manners. The only solution I can think of off the top of my head to use that manifold may be to weld up the holes on the head and redril and tap new ones to match the manifold location and do some grinding on both the head and manifold to taper the ports to blend into each other. A custom gasket would be needed, but is easily made from gasket paper. The bigger issue is do you want to hack up the manifold?

    Mark

  4. #4
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    Piston-valve clearance is good, and custom length pushrods i'm told are not a huge deal.

    I'm not sure what you mean by watter jackets though, nothing much will be changing in terms of the coolant passages even shaving that much off the heads.

    The 32/26 would be fine yes, but this weber manifold is like the crown jewel of the project :P

    http://www.youtube.com/watch?v=HGoHp0pU_yw

    Maybe I should be looking more into modifying the block...

  5. #5
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    I can't help that much, but I do know that shaving a mm or 2 of the pistons have been done, and are still done by some.

    Usually when it comes to low budget turbo builds to lower compression alittle bit.

  6. #6
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    I did some "ghetto" cc measurements of the cylinder heads and some calculations for the compression ratio.

    The worst case scenario is about 11.5:1, with abou5 10.5:1 being average from the measurements I did.

    If it does get to be ~11.0:1 the machine shop said they can "dish" the pistons a little bit no problemo.

  7. #7
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    Uh... 2mm is nothing, you say it already bolts on? Sounds like all you need to do is take a die grinder or heck, a file to the weber manifold. Its called port matching.

    edit: or the heads if the weber manifold is more valuable. You should still have plenty of surface area left for the coolant jacket to seal.

  8. #8
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    Its 2mm each head, but the manifold isnt perfectly horizontal, its at a slight angle, which means even more would have to be shaved to match the ports, and that would also create bad flow into the head, plus the fact the coolant channel runs through there as well.



  9. #9
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    The manifold gasket also matches up perfectly to the Weber manifold, so getting the head and manifold matched up equates to the best possible solution.

    And yes, the manifold is easily 10x more valuable than the heads. Cost me 5x as much as that block too.

  10. #10
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    Well If you wanna spend the money on machining go ahead. Even if you don't match it, thats such a small gap you wouldn't notice a performance loss unless you were on the dyno fighting for every 1/10 hp. I've taken apart factory engines (not japanese haha) where the intakes ports are 1/16 to an 1/8th in misaligned due to poor casting or the gaskets were way off. In the end it just isn't a huge deal.

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