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  1. #1
    Geezer's Avatar
    Geezer is offline Chief Engineer
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    Intake Manifold SBC

    Just decided to do a minor engine clean-up which now has my Inlet Manifold etc. all over the garage.

    A couple of questions:

    My rebuild manual and the Manifold gasket set talks about 'Restricted Port Gasket' or 'Heat-Rise Passage' (if they are one and the same). This, presumably, is the centre port in the heads. The gasket set has 4 stainless clips, 2 of which clip onto each gasket leaving a smaller hole than the port size once fitted. That's fine but the old gaskets did not have those fitted. So, what are they Are they necessary Why wouldn't the original gaskets have had them fitted

    My rebuild manual says that Silicon only is the preferred method on the front and rear valley rails although a thin smear of sealer should be used if using the rubber fittings. Any comments

    Finally, the Gasket Set has 4 rubber valley seals, 2 with the rubber prong inserts and 2 with overlaps to keep them in place. Is one type better than the other or is it just stay with a silicon bead

    Thanks guys

    Pete
    Pete


    BAE SBC 350 (with a Carb...)/ TKO500 / 3.54PL -
    Less of a mess now but still plenty to do...
    Number of polishes - 1/2 and a bit...
    SOLD...SOLD...

    If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.

  2. #2
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    Pictures are mighty useful things ya know

    I recon using all my years of experience (thats 0 then), they are just a simple form of reducer to suit a certain type of manifold size and exhaust size. If you can get away without using them then you will be better off without any restrictions in your exhaust passage (pun intended)... It will allow a little more power similar to porting an engine.

    To see if your existing manifold will fit without the clip on stainless parts, line the gasket sets in reverse to how they fit on the cyl head ports, it should match up with your manifold as per your old setup... Otherwise you will need them in place for compatibility.

    I would wait for other people to correct me if I am wrong though (highly likely)

  3. #3
    Miket's Avatar
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    Quote Originally Posted by wood85 View Post
    Pictures are mighty useful things ya know

    I recon using all my years of experience (thats 0 then), they are just a simple form of reducer to suit a certain type of manifold size and exhaust size. If you can get away without using them then you will be better off without any restrictions in your exhaust passage (pun intended)... It will allow a little more power similar to porting an engine.

    To see if your existing manifold will fit without the clip on stainless parts, line the gasket sets in reverse to how they fit on the cyl head ports, it should match up with your manifold as per your old setup... Otherwise you will need them in place for compatibility.

    I would wait for other people to correct me if I am wrong though (highly likely)
    Inlet Manifold
    Mike
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    Well, I'm fortunate to have a chemical engineering background, one of the things I enjoy most is turning beer, wine, Scotch and margaritas into urine.

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  4. #4
    Geezer's Avatar
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    Quote Originally Posted by Miket View Post
    Inlet Manifold
    Quite right Mike...

    Further info - I have Iron heads and an Edelbrock Inlet Mainifold. I guess if no info is coming forward I could just fit the new gaskets as per the old.
    The manifold had been put on with just sealant on the valley rails but I did wonder if the rubber seals (with a dash of sealant) were a better or worse option

    Pete
    Pete


    BAE SBC 350 (with a Carb...)/ TKO500 / 3.54PL -
    Less of a mess now but still plenty to do...
    Number of polishes - 1/2 and a bit...
    SOLD...SOLD...

    If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.

  5. #5
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    ..........Edelbrock recommend using silicone only on their web site, but using the rubber gasket is a matter of choice. As for having 4 gaskets, if the same as Big Blocks, you will find one of each type is longer. Tall deck blocks need a different length gasket.

    As for the exhaust gas cross over restrictor, this just gives you some control over the amount of exhaust gas carb heating. If you have a street motor, then no restriction should be necessary, but personally I would fit some restriction but not blank this off. Just a tip from a Drag race buddy. Lots of heat in our engine bays.
    Ian DAX 454 Chevy
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    Geezer's Avatar
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    Quote Originally Posted by slogger View Post
    ..........Edelbrock recommend using silicone only on their web site, but using the rubber gasket is a matter of choice. As for having 4 gaskets, if the same as Big Blocks, you will find one of each type is longer. Tall deck blocks need a different length gasket.

    As for the exhaust gas cross over restrictor, this just gives you some control over the amount of exhaust gas carb heating. If you have a street motor, then no restriction should be necessary, but personally I would fit some restriction but not blank this off. Just a tip from a Drag race buddy. Lots of heat in our engine bays.
    Yep, the restrictor plates bring it down to a hole the size of your little finger. As it feeds hot air through the Inlet manifold, I guess restricting it somewhat would allow a slightly cooler/denser charge but still help prevent Carb icing...? Can't see why you would need to warm the manifold otherwise bearing in mind there are water jackets at both ends.... unless it is to balance up the heat at both ends...

    Confused
    Pete


    BAE SBC 350 (with a Carb...)/ TKO500 / 3.54PL -
    Less of a mess now but still plenty to do...
    Number of polishes - 1/2 and a bit...
    SOLD...SOLD...

    If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.

  7. #7
    chevy country is offline Tyre Kicker
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    manifold

    Quote Originally Posted by Geezer View Post
    Quite right Mike...

    Further info - I have Iron heads and an Edelbrock Inlet Mainifold. I guess if no info is coming forward I could just fit the new gaskets as per the old.
    The manifold had been put on with just sealant on the valley rails but I did wonder if the rubber seals (with a dash of sealant) were a better or worse option

    Pete
    something I picked up on a bit ago, the restrictors are for stock engines with cast manifolds. The very early ones had a thermostatic flap in one side to direct exhaust gases under the inlet to warm the manifold when starting from cold, the restrictors with the gasket set are to aid that, it goes in one side only usually but sometimes both. With headers you get virtually no warming effect so no need to use restrictors.
    As for the rubber seals, if your block has three holes in the end rails use the rubbers with the prongs, if no holes use the ones with the flaps.Dont use sealer on the rubbers, only in the corners.
    Hope this helps.
    Mike

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    slogger's Avatar
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    ...........The water jacket takes time to heat up, but this exhaust gas heating is almost instantaneous and heats the intake runners to help cold running.
    Ian DAX 454 Chevy
    It's not shabby!............. Just has a highly developed patina! My Gallery Take a look.

  9. #9
    Geezer's Avatar
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    Quote Originally Posted by chevy country View Post
    something I picked up on a bit ago, the restrictors are for stock engines with cast manifolds. The very early ones had a thermostatic flap in one side to direct exhaust gases under the inlet to warm the manifold when starting from cold, the restrictors with the gasket set are to aid that, it goes in one side only usually but sometimes both. With headers you get virtually no warming effect so no need to use restrictors.
    As for the rubber seals, if your block has three holes in the end rails use the rubbers with the prongs, if no holes use the ones with the flaps.Dont use sealer on the rubbers, only in the corners.
    Hope this helps.
    Mike
    Thanks for that, Mike.
    In that case, shouldn't there be a hole left uncovered by the headers? If that is or is not the case, surely it would be best to fit the restrictors regardless?...
    Pete
    Pete


    BAE SBC 350 (with a Carb...)/ TKO500 / 3.54PL -
    Less of a mess now but still plenty to do...
    Number of polishes - 1/2 and a bit...
    SOLD...SOLD...

    If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.

  10. #10
    Geezer's Avatar
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    Quote Originally Posted by Geezer View Post
    Thanks for that, Mike.
    In that case, shouldn't there be a hole left uncovered by the headers? If that is or is not the case, surely it would be best to fit the restrictors regardless?...
    Pete
    Further update to the bo//ocks that I just posted.
    I just went to have a look at the heads and, through my beer goggles, you can see the exhaust valves on the 2 middle cylinders on each side. So, with the crossway through the inlet manifold there is some sort of balancing occuring - not the I would want too much exhaust gas passing through the bottom of my alloy Inlet Manifold
    Obviously the path of least resistance will be out through the headers but I am leaning towards fitting the restrictor assembly as I can see why I would need open ports.
    Obviously further investigation is required - perhaps an engine builder will get hold of the thread ...eventually

    Pete
    Pete


    BAE SBC 350 (with a Carb...)/ TKO500 / 3.54PL -
    Less of a mess now but still plenty to do...
    Number of polishes - 1/2 and a bit...
    SOLD...SOLD...

    If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.

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