piston opinions wanted

Discussion in ''Da Nailhead' started by cobravii, Dec 28, 2016.

  1. bhambulldog

    bhambulldog 1955 76-RoadmasterRiviera

    "Auto Tec will tell you you will have to go through myself to get these pistons that we spent over 1 1/2 yrs. working on."

    That's only fair.

    Have you made any 322 pistons?
     
  2. telriv

    telriv Well-Known Member

    Not as of yet but many have asked. The answer is YES!!!!
     
  3. Babeola

    Babeola Well-Known Member

    Actually, that compounds the problem. Power adders increase the temperature (even with inter-cooling) of a larger more volatile charge subject to greater cylinder pressure. You want a good quench in that situation along with anything else that will cool the charge (porting or increased intake dwell time). We have learned a few things with our supercharged Cobra over the last 13 years.

    Cheryl :)
     
  4. nekkidhillbilly

    nekkidhillbilly post whore

    ill keep you in mind then when I get to that point.
     
  5. nekkidhillbilly

    nekkidhillbilly post whore

    ok tom im getting to that point so basically putting p600b if I win the bid or another centri supercharger on the car. My engine is a stock 62 401. what exactly do I need? im going to have machine work done so 30 over isn't out of the question at all. it will be intercooled and tbi fed. im looking for that 500 hp number.
     
  6. 8ad-f85

    8ad-f85 Well-Known Member

    You could use a std 454 BBC forged piston and 6.535" rod with .062" over bore and grinding .050" from the crank.
    It would be much stronger and a lot less expensive for your boosted application.
    There are other combos that work, and obviously the machine shop would be doing valve notches and other minor mods if need be.
    If you were starting with a heavily ground crank or already bored block, you would be close to this anyways.
    If you weren't in a super rush, those pistons seem to pop up often here and there. I don't think many 454's get built with forged pistons at a std size these days, many were made and are out there.
     
  7. nekkidhillbilly

    nekkidhillbilly post whore

    not really going to save me that much they go for about 500 or more for the pistons alone.
     
  8. 8ad-f85

    8ad-f85 Well-Known Member

    I've bought the last 8 or 9 sets for $125-225. New rods are in the $125-175 range.
    I've used +.100" hypereutectic for the 425 bore.
    455 rods will work if piston guided, bushed, and some piston top trimming.
    I'll admit to being spoiled because I have the machines to do this though.
    Already stated, many of them were made and sitting on shelves, not likely to be used as a std bore build.
    Gotta do some snooping to find them I guess.
     
  9. nekkidhillbilly

    nekkidhillbilly post whore

    yeah I don't have those tools so a toms would be more ideal for me. plus some of this is greek to me.
     
  10. 8ad-f85

    8ad-f85 Well-Known Member

    The shop you use would do the exact same things to yours as a simple rebuild, with the addition to possibly cutting some more to the valve reliefs and very slight milling of the piston dome.
    They are off the shelf parts that are extremely close to fitting, requiring simply choosing a slightly different dimension to finish to...all done for less than the cost of the custom piston.
    The very slight dome you would use on a 454 piston for your low compression nailhead only needs slight massaging to clear the nailhead chamber.
    I do respect the convenience of a drop in part for the garage builder though.
     
  11. telriv

    telriv Well-Known Member

    I don't know this for a fact, but I don't believe the BBC piston your talking about has enough of a dome. Don't forget the "Nail" has a fairly large combustion chamber in the head. Approx. 120 (minimum) +CC's.
    I WOULDN'T bore a 401 .062" over WITHOUT sonic testing. Even IF it does measure OK (approx. .150") the rebuild won't last as long as it should because of the flexing at the bottom of the block. Here's where the Epxoy I add on EVERY rebuild comes into play.
    Don't forget the cast pistons you get will be .050"-.065" in the hole. Now you need to deck the block to gain back some compression & correct the Quench area. Then, if you use the composite head gaskets you will lose approx. .77-1 on compression. Now you need to cut the heads, but this will do NOTHING to improve the quench area. Now you run into the VERY real possibility the corners of the pistons will hit the heads. ALSO, most times the valve notches will have to be deepened making the piston WEAKER in this area. OR, spend the EXTRA $$$ for a set of OEM steel gaskets. None of this will make up for the shortcomings + you've added MUCH MORE to the machining costs. Now the CUSTOM designed pistons I sell will be close to what the EXTRA $$$$ it would cost for the EXTRA machining nec. to correct all these shortcomings.
    Price it out some of you machinists out there. AND, no discounts for your buddy's. Real world costs & $$$$. .040"-.065" removed from the deck. You CAN'T make this in one cut, it has to be multiple times!!! ALSO, your weakening the deck. Cutting the heads .020" .030", .040". AGAIN, you CAN'T make this in one cut. Now your weakening the head surface. Cutting the valve reliefs. Cutting the corners of the pistons so they DON'T make contact with the heads. The additional cost for OEM steel gaskets. How MANY times are you going to take it apart, measure, make changes, etc. & put it back together???? It ends up being VERY frustrating & time consuming. A machinists time & paying attention to details at his hourly rate will quickly add up, unless of course you can & have the ability to do it yourself which MANY don't have the luxury of doing.
    Just my thoughts on the subject.


    Tom T.
     
  12. nekkidhillbilly

    nekkidhillbilly post whore

    that was my thoughts tom. So basically I want low comp forged piston for this engine tom. what exactly am I looking for I know you sell these. I'm not a engine guru so some of the numbers are greek to me. my engine is pretty low mile so the rods and crank shouldn't need much more than a clean up. also its a stock cam engine should I switch to a more of a boost cam. do I need a full roller or will flat tappet work?
     
  13. 8ad-f85

    8ad-f85 Well-Known Member

    Add up 1.645" and 6.535" and see how close to zero deck you get.
    No more surfacing needed than any other rebuild.
    A 16cc dome is a smidge over 8:1, perfect for supercharging.
    The sides of the dome need minor milling to clear, as stated. (If mocking up an engine to solve that simple problem is too worrisome, then my suggestion is for a different level of engine assembler)
    Minor valve notches in a piston top that are quite thick already... easy.
    No different than when you used to buy semi-finished dome pistons.
    Roughly $100-120. Maybe costs are different in your area.
    The rod/piston combo is slightly lighter, requiring a bit of drilling on the crank, but then you might be balancing it anyways.
    (25 grams difference in bobweight is about 1%, so use your judgement)
    Definitely agree on the need to verify the bores' thickness and filling.
    I've done them using the 455 rod (with a bushing), saving some $$.

    I believe that any home builder skilled enough to use the head as the jig to cut valve notches or carefully set up a router jig to trim the domes could easily skip the machine shop for that.

    The post was asking about piston options and I do not know everyone's experience level, just offering what's been done before.
    Other than that, Tom's pistons are by far the best option for plug-and-play.
     
  14. nekkidhillbilly

    nekkidhillbilly post whore

    well Id rather have a plug in play option. so maybe tom you could pm me some what I need and pricing.
     

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