Piston ID

Frankvintagefullflowcom
Frankvintagefullflowcom Senior Contributor
edited December 2013 in HUDSON
I've got a 308 here that was somebody's hot rod engine at some point in it's life and the pistons have an unfamiliar factory marking on the top. It says "1/4 LC" and there are no other markings. It's at .100 over so they're obviously aftermarket performance parts but I just wondered if anyone knew who made them. I could tear it down and look for other clues but it's just not in the cards right now. Too many other projects under way. My calculator says it's at 324.65 inches as is. Cool.
Frank

Comments

  • SuperDave
    SuperDave Senior Contributor
    L/C for Low Compression? LOL
    Just curious.. have you measured the stoke?
  • Frankvintagefullflowcom
    Frankvintagefullflowcom Senior Contributor
    Holy Stroker, Batman! I had thought about measuring the stroke but since it was low priority, I just didn't bother and figured it was stock......not so. It is in fact 5 inches, yielding......click, click.......click,..click, 360 + cu. in. Interesting. It appears to be in nice shape, virtually no ridge and no ratchety-clank noises from the crankcase but something is 'way off when it comes to cam timing. Not worth a lengthy explanation here but suffice to say that it's very wrong. The intake valve shouldn't be open on the piston up-stroke.......and yes, I do know which way an engine turns.
    It must not have been fast 'cause the water pump and tappet chamber covers are chromed.
    This will be interesting...........
    Frank
  • hoggyrubber
    hoggyrubber Expert Adviser
    sounds like a fun find. wonder if the timing chain slipped?
  • GrimGreaser
    GrimGreaser Senior Contributor
    Ah, poked AND stroked... Why can't I find stuff like that. :)
  • Frankvintagefullflowcom
    Frankvintagefullflowcom Senior Contributor
    Well, there's got to be something wrong with it........I'm not that lucky.
    There hasn't been recent work done on it and it appears to have some miles behind it. The chain isn't slapping the inside of the cover so it doesn't make sense. I'll eventually find out but I just can't take time for it now. Nice relief work, too. Odd that valve lift looks like stock. I'll check it later....it's not important right now.
    Assuming all else is OK, I'm wondering where in the heck will I find rings for a 3.9125 bore? A question for a later time.
    F
  • hoggyrubber
    hoggyrubber Expert Adviser
    thought I heard egge machine would make custom size rings.
  • Frankvintagefullflowcom
    Frankvintagefullflowcom Senior Contributor
    Could be.....maybe Ross or one of the other performance piston outfits. I'll worry about that when/if I get there.
    I did take a quick check on valve lift and see that it's about .370 (intake) so it's not a stock cam @ .344 Hardly radical but somewhat greater. I'm still baffled by the odd cam timing, though. It's not just a little off......it's 'wayyyyyyyy off, and there's just no slack in the chain that I can detect. Weird.
    F
  • bob ward
    bob ward Senior Contributor
    Frank, inlet valves on the stepdown 6 close 91.9° after bottom centre according to the manual. Or do you mean they are closing way past that point?
  • SuperDave
    SuperDave Senior Contributor
    I bought a great 53 SuperWasp because a local mechanical shop installed the timing chain wrong after a major overhaul. Thank goodness that is all they did wrong. Drove the dickens out of it for years. looked like they tried to align the timing marks towards each other.. Can't get away with dumb mistakes like that on an OHV engine!
  • Frankvintagefullflowcom
    Frankvintagefullflowcom Senior Contributor
    Bob,
    Logical question but I'm quite aware of typical cam timing and do have info regarding the specifics of the Hudson engines. That said, the intake valve comes to a full close ~ when the piston is just reaching TDC. Hmmmmm. I don't think I can rely on that much inertia of incoming gasses. Maybe it had a two stage supercharger at 200 psi or so. Not likely.

    True, if there is one advantage of the "side valve" design, it's that we don't have to worry about piston/valve collisions. I'm having some bumper stickers made that say "Hudsons are Clearance Engines". Think anyone will get it?

    I had considered the prospect that someone had installed the chain incorrectly but this thing has evidence that it has been run for some time as it is. It wouldn't even run as-is. The only reasonable assumption is that it jumped.... or the crank key sheared and is jammed enough for me to turn it now without slippage. That's my guess. Time will tell. It's buried in the dark, less accessible depths of the shop so it may be a while.

    Whoever did the work did an impressive job on the relieving.
    No surprise, it has 1/2" studs. I got it w/o head so I don't know what was used. My quick calcs indicate a near 10:1 with a 262 head and around 8.5 w/7.2:1 308 head. Judging by the appearance of the combustion chambers, it was a happy engine the last time it ran.
    Frank
  • Frankvintagefullflowcom
    Frankvintagefullflowcom Senior Contributor
    I see from a quick review of posts regarding Hudson cam specs that I likely have a '55 -'56 Mechanical cam @ .372 lift. in this engine.
    F
This discussion has been closed.

Categories

In this Discussion