How much to mill intake??

Discussion in 'Street/strip 400/430/455' started by ranger, Mar 13, 2018.

  1. ranger

    ranger Well-Known Member

    Hi folks,

    I am running Bulldog heads w/ a SP-1 intake.

    I believe my heads have been milled .010, and the block supposedly was decked/squared. Still, one bank of pistons sits .025" in the hole while the other side sits .015." Not sure if the machinest made an error or not. I guess it's theoretically possible that 4 rods have (coincidentally on that one side) stretched more than the other bank--by .010"

    Would like to run T/A composite gaskets and their gasket of 062" thickness seems a good choice for durability. Still, that is quite thicker than the steel-shim factory gasket, so about how much should I mill the sides of the intake??

    The ends of the intake are not an issue, as the gap is already too big because of the Bulldog head design. I am thinking I should mill the intake around .030" to .040"

    Thanks, in advance!

    Best,

    Ranger
    Aiken, SC
     
  2. 8ad-f85

    8ad-f85 Well-Known Member

    Save your money and raise the top of the port to match.
    (I make money when doing those things and would rather not waste their budget like that)
     
  3. ranger

    ranger Well-Known Member

    Thanks for the input but not sure I follow you. I would think that I have to LOWER the intake port to match the head, no? I might have as much as .030" combined shaved from the block and heads.

    I used the .062" composite gasket and intake fit was poor. Bolts cut into bolt holes in aluminum intake.

    Thanks in advance for your input.

    Best,

    Ranger
    Aiken, SC
     
  4. 8ad-f85

    8ad-f85 Well-Known Member

    I typically enlarge the holes a tiny bit and raise the port to meet the intake's exit...if it sits lower due to the condition you describe.
    There are different thickness gaskets, which is what most prefer.
    There's also the issue that many aftermarket heads don't measure exactly the same across the pair.
    (Not saying that it's an issue in this case)
    I don't think it ever hurts the airflow to raise the head's opening and many intakes have slight direction mismatch issues to the point that it's a first thought over milling.
    That and any engine I'm working with already is being ported sooo...while you're down there :D
     
  5. BuickV8$Mike

    BuickV8$Mike SD Buick Fan

    We are struggling, orctainly I am with the bit about raising the top of the port to match. Thicker intake manifold gaskets?
     
  6. 8ad-f85

    8ad-f85 Well-Known Member

    I'm assuming here that when the block and heads are milled, the intake port gets lower compared to the intake.
    If your intake manifold port roof is lower than the head (opposite condition) then you would need thicker gaskets to raise it up...or use a die grinder if using a thicker gasket makes the holes mismatch worse.
    Still not milling to correct.
     
    Last edited: Mar 13, 2018
  7. Jim Weise

    Jim Weise GOT AIR?

    No way to tell for sure with that head, other than a mockup.

    Set the intake on it, and see how the bolt holes line up.

    JW
     
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  8. 8ad-f85

    8ad-f85 Well-Known Member

    I guess I'm wondering, Are you milling the intake? or,
    Is a shop milling it and waiting for your instructions?
    Either case has the same solution.

    For the deck issue, I'd be finding a way to measure things.
    It's foolish not to take things apart to figure it out.
    If the shop goofed up the block, they should honor whatever the commitment was.
    There's an uncommon reason for the difference in height...but it's not likely in this case.
    When you see random short pistons in a short block, it's quite possible to have a short rod by virtue of it being bent.
    It's tough to even see it once installed with the piston, with the skirts so far down in the way.
    I've seen engines with several bent ones installed, fresh from a machine shop after honing.
    It's also possible that the shop matched your rods bank to bank. They aren't always consistent.
    Same goes for pistons. They might have been dealing with broken or mismatched sets.
     
  9. Jim Weise

    Jim Weise GOT AIR?

    What most likely happened with the piston deal is they did not square the block.. it's not uncommon for one side to be considerably taller than the other.
     
    ranger likes this.
  10. BrianTrick

    BrianTrick Brian Trick

    I think they decked it,but did not square it. As Jim said,it’s not uncommon to have one deck higher than the other. If you take the same amount off each side,you still have one higher.
    Mock the intake up and see where the ports are in relation to the head ports. I understand what 8ad-f85 is explaining. If you mill your intake,or mill it too much,it could position the intake ports lower than desired.
    If everything is milled as you say,taking .005” off each side should do it. If you have the higher side of the block decked again,it may require more.
     
  11. Bens99gtp

    Bens99gtp Well-Known Member

    Remember once you cut an intake like this it's very hard to get it to work correctly on another application later on too
     
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  12. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I would just use the thinner TA gaskets. They come in .032 and .015. I have used the .015 before, sealed up just fine.
     
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  13. ranger

    ranger Well-Known Member

    Well, I actually always thought it was just the opposite--that the intake port would now be higher on the head, thus requiring the use of milling the sides of the intake (or thinner gaskets) to get it to sit back down.

    Best,

    Ranger
    Aiken, SC
     
  14. ranger

    ranger Well-Known Member

    Yes, Jim--no doubt it was decked but not squared. Pretty sure they told me they squared it, but they could have been off by .010"

    Thanks.

    Best,

    Ranger
    Aiken, SC
     
  15. ranger

    ranger Well-Known Member

    Larry, thanks, and good to hear. I had thought they I shouldn't dare go thinner than their .062" gasket but I will just use either one of those thinner ones instead of milling the intake

    Best,

    Ranger
    Aiken,, SC
     
  16. ranger

    ranger Well-Known Member

    Thanks, Jim. Gonna do just that.

    Best,

    Ranger
    Aiken, SC
     
  17. 8ad-f85

    8ad-f85 Well-Known Member

    I think we both are applying the term 'intake port' vaguely.
    I had trouble getting the edit function to work again...
    I stuffed too much info into the post.
    If the head gets closer to the crankshaft, it's 'intake port' drops down lower compared to the unmoved 'intake manifold'.
    I prefer keeping the intake as close to a blueprint condition as possible so that it can be used on other engines when you decide to upgrade later.

    Don't guess, get in there and measure stuff.
    I could have mentioned the most likely causes, but went the other way because it's the elusive ones that really goof with people. You're going to look for the common ones anyways.

    Once you have the situation assessed, then explore what to do.
    No need to worry about all the fixes until you know what's going on.
     
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  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    There are .032 gaskets on my current engine. I have used the .015 gaskets with no problems. Easier than milling for sure.
     
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  19. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    With a 464 in my own Skylark I ended up using one TA .015 on one side and one .030 on the other side for perfect alignment. I can't recall if it was the block deck or the heads causing the issue. I do recall it was a couple weeks before Bowling Green so I wasn't starting over. It worked great and needless to say I don't use that machine shop anymore.

    Larry
     
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