Engine gaskets and reseal. Upgrades possible

Discussion in 'Street/strip 400/430/455' started by 70 GMuscle, Dec 13, 2018.

  1. 70 GMuscle

    70 GMuscle Plan B

    pulling my 464. Need to reseal pan and timing cover.
    73 engine. Bowl ported small valve.
    Comp 278 cam. Performer n quadrapower qjet. Full msd. Dougs 1 7/8” headers.
    Piston i think .050 in hole for 9.3/1 compression.
    Will inspect bottom n chain.
    Will cometic .027 head gasket help over fel pro head gaskets?
    What will TA aluminum heads do as I have low compression w speed pro 10/1 pistons deep in hole. My bowl job is top notch from noted head guy at JA racing engines.
    Other wise stock w just a min mill.
    So where r my best bangs for buck.
    Car has gone 12.30@109. Best 1.69 60ft.
    342 gears 275/60 mt radials
    T400 self destructing w a 2500 stall.
    Which is being replaced when engine is out.
    Chris
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I don't think you are anywhere near 9.3:1. A 1973 engine was rated at 8.5:1, and they were closer to 8.2:1. Chambers were like 72cc and piston dish was about 35cc, Cometic gaskets won't get you much at all. Your best bet is to change the pistons. You have lots of choices for custom pistons with better compression distance to get you closer if not at 0 deck with custom dishes to get your SCR exactly where you want it.
     
  3. 70 GMuscle

    70 GMuscle Plan B

    I have the 10/1 pistons
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Have you cc'd everything?
     
  5. 70 GMuscle

    70 GMuscle Plan B

    Yes
    JA did.
    He said 9.3 to 1.
     
  6. 70 GMuscle

    70 GMuscle Plan B

    Pull engine saturday
    Its laying on motor mounts.
     
  7. 70 GMuscle

    70 GMuscle Plan B

    Pulling it down to short block probably.
    Thays why I asked about cometics.
    It has 4000 miles on it.
     
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    .027 vs .040 head gasket thickness will get you another .3 approximately, so 9.6:1
     
  9. Schurkey

    Schurkey Silver Level contributor

    Mill the decks, weld and offset-grind the crank, longer rods, or taller pistons.

    There's several different ways to get proper squish/quench. More stroke gives you more cubes, all of these should increase the compression.
     
    Donuts & Peelouts likes this.
  10. 70 GMuscle

    70 GMuscle Plan B

    I here ya shurkey
    I have a 71 virgin crank as my 73 was cut.
    It was perfect but a machinist I brought it too had it cut as he said polish is no good, ughh.
    One reason I left him. Plus he talked too much.
    Wayyyy too much.......
    Rods are rebuilt w arp bolts.
    Pistons new .040 over speed pro 10/1’s.
    How will that work w stroking crank.
    I dont know that math.
    I will get better idea of what I have when I pull engine tomorrow n strip down.
    Was planning on a reseal.....
    But......
     
  11. hugger

    hugger Well-Known Member

    You would be better off to put what you have back together and start with a new block. In the end modification to what you have will cost you a running engine you could sell, to help fund the new build or just simplify avoid frustrating down time while the new one comes together.

    With what we have avaliable now there is no way I would build a performance oriented 455 with out the Molnar rods and a modern piston. It simply makes everything else som much easier, camshaft selection becomes much easier for one.
     
    john.schaefer77 likes this.
  12. 70 GMuscle

    70 GMuscle Plan B

    Sounds good in theory.
    Car runs well for what it is.
    Will inspect and decide its future.
    I have spare 73 virgin engine.
    I have other cars to keep me happy/busy if I have to tear thru this.
    I appreciate all the ideas.
     
  13. Schurkey

    Schurkey Silver Level contributor

    Typical head gaskets are around .040 thick when compressed (give or take a few thousandths.)
    .040 is a good squish/quench distance. If the piston tops end up level with the deck, the gasket "is" the squish distance.
    Your pistons are .050 in the hole. You want to move the piston top UP .050, or the deck DOWN .050, or some combination.
    Getting the deck down is easy: strip the block, machine the decks square to the crank, and down .050. Or find thinner head gaskets, and take less off the block.

    Getting the piston up is harder/more expensive.
    .050 longer rods
    .050 taller pistons
    Some combination of slightly longer rods, slightly taller pistons and some deck machining

    Or as said, you could add 0.100 stroke to the crank. This moves the piston .050 up at the top of the stroke, and .050 down at the bottom of the stroke. You gain cubic inches, you gain compression. You'll lose piston-to-crank counterweight clearance which may or may not be important.

    Gaining 0.100 stroke can't be done with undersize BBB bearings. If there's a way to cut the crank and use bearings from another engine family, I don't know about it--but it MIGHT be possible. More likely, you'd need someone skilled in welding cast iron to lay a few beads on the top of the rod journals to build them up before re-grinding back to round--and increasing the stroke. Not cheap, and iron welding is not for the faint-of-heart.

    Or buy a custom crank that's already set up for some additional stroke.

    Any way you look at this, you're going to be spending money. Are you sure you want to dick with this? Having detonation problems? Need a lot of ignition advance for best power? .050 in the hole + .040 head gasket = .090 quench/squish distance. The way I understand it, that would be towards the high end of the "danger zone" for detonation. Maybe you've got so much clearance that the combustion chamber is acting like there is no quench, it's an "open" chamber. That can make for lazy, slow combustion needing extra ignition advance, but it may not detonate.
     
    Last edited: Dec 14, 2018
  14. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Easiest way is to buy pistons with the correct Compression Distance to begin with. Milling that much off an already light weight block can't be good for strength anyway, and milling costs a lot more to take that much off. With the affordability of custom pistons today, it makes no sense to use the commonly available BBB pistons as they will end up below deck by that amount. You can also offset grind the crank and use better rods to get 470 and 482 cubic inches out of the BBB with a 4.350" bore.
     
  15. 70 GMuscle

    70 GMuscle Plan B

    Pulled heads today and found pistons .032 in hole.
    Give or take a thou.
    Has fel pro 1125 gaskets.
    Everything looks good.
    Did find a booboo by felpro when they printed gaskets.
    Put Oring on bottom of gasket in wrong spot. No leaks tho.
    Top of gasket is correct for center bottom water jacket.
     
  16. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    What are your goals? 12.30s aren't bad. I'd leave the short block alone and add TA stage 1 heads. That'll put you in the 11s with ease.
     

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