Thanks Thanks:  0
Likes Likes:  0
Page 3 of 3 FirstFirst 123
Results 21 to 26 of 26

Thread: my afterthought

  1. #21
    Team Member
    Join Date
    Mar 2005
    Posts
    559
    Post Thanks / Like

    Default the "cold stick" problem

    Tim:

    Your comment about letting the engine get to operating temp before "stabbing it" is well taken, and I remember a problem I had with a "D" (40 CUI) Konig in the early 70's. At the time the only piston alternative to the Konig piston by Mahle, were cast pistons made by Stan Leavendusky Sr. Stan of course had much experience casting pistons for the Quincy Flatheads of the time, and for quite some time right up to the end of their competitiveness against the Konig, was the supplier of pistons to Quincy in both replacement and OEM categories.

    I had purchased a D Konig that was in bad shape insofar as the bores were concerned, and asked Stan to bore and fit a set of pistons to it. Long story short, I kept sticking one or more pistons as soon as I would open the throttle of the motor after starting and running a lap or so at part throttle, as I was always a believer in taking it easy for a little bit until everything had had a chance to warm up some.

    This happened about 4 or 5 times with these pistons, and finally, as I could not afford a couple of pistons everytime I ran the engine, I sent it to Harry ZAK who had started to work on my engines, first with his pipes and cut rotary valve disks. Harry looked at the way the pistons were sticking, just barely a small smear right by the exhaust port and just above and a half inch or so below the ring, and only enough to kill the motor, and then the motor would be free by the time the boat coasted to a stop.

    Long story short, he called it a "COLD STICK" and said it was happening because the aluminum used in the piston did not have the same coefficient of expansion as the Konig/Mahle pistons. He (Harry) fitted new pistons (4 Mahle's) and I never had the problem again. Not to say that Stans pistons were bad, but just not the right mix of aluminum evidently for that engine. We also tried various clearances and were not able to stop it from sticking by that method either.

    Harry later made some small thermostat housings from billet aluminum and used OMC thermostats for various racers that ran both Konig and Yamato engines, and that seemed to help the sticking problem and also the motor ran much better from the word go, as it would usually take several laps in a race for one to really come on, leading him to believe that the motor was not fully at operating temp until it had been run hard for several laps. In the PRO category, since we only ran 4 laps, and usually took it easy for engine longevity while milling for the start, the engines never really got warmed up till run hard for a lap or so.

    The one bad problem with the thermostat housing was that that is was just another place for water stoppages to occur due to picking up trash while running with the force-feed water type pickup, and you really needed a "telltale" so as to be sure you were getting plenty of water while running.

  2. #22
    Team Member
    Join Date
    Nov 2008
    Location
    Horseshoe Bend, ID
    Posts
    657
    Post Thanks / Like

    Default

    Woof! Your frustration with the Leavendusky pistons must have been maddening (I've have been there). It's difficult to race knowing the engine is brittle: You've always got the fear of an impending teardown and repair bill in the back of your mind. It's good you found Zak to solve the problem and put you in a position to focus on racing.

    Knowledge of eutectic properties, mechanical engineering, and well instrumented dyno testing are needed to establish a durable engine. This is best done by an OEM or large aftermarket company, it's way too much for the typical racer. We can't afford the time or $$$ to develop durable parts, and the cost of failure is high.

    Regarding piston/bore fit, it never ceases to amaze me how many people mis-direct a machinist. Example: When a piston comes marked +.030", this means it is designed for a bore .030" over standard: Clearences are always machined into the piston. Several times in my career, customers insisted the clearance should be added to the overbore! Once I complied to find the engine would not support sufficient compression to run! From then on, if the client didn't agree with correct fitment, they were sent away to inflict the damage somewhere else.

    Tim
    Last edited by Tim Kurcz; 10-24-2012 at 03:14 AM. Reason: grammar

  3. #23
    Team Member
    Join Date
    Sep 2008
    Location
    Singapore/Melbourne/Italy
    Posts
    780
    Post Thanks / Like

    Default

    Hi Tim
    Can you do that with forged pistons as well?

  4. #24
    Team Member
    Join Date
    Nov 2008
    Location
    Horseshoe Bend, ID
    Posts
    657
    Post Thanks / Like

    Default Piston talk

    Quote Originally Posted by Powerabout View Post
    Hi Tim
    Can you do that with forged pistons as well?
    Please restate the question more fully - I don't understand what you're asking.

    Tim

  5. #25
    Team Member
    Join Date
    Sep 2008
    Location
    Singapore/Melbourne/Italy
    Posts
    780
    Post Thanks / Like

    Default

    Quote Originally Posted by Tim Kurcz View Post
    Please restate the question more fully - I don't understand what you're asking.

    Tim
    Do you run the forged pistons in std + 030 bores?
    OMC never had forged pistons so hence where was all the testing done re piston to bore clearance?
    thanks

  6. #26
    Team Member
    Join Date
    Nov 2008
    Location
    Horseshoe Bend, ID
    Posts
    657
    Post Thanks / Like

    Default Wiseco aftermarket sizes

    Quote Originally Posted by Powerabout View Post
    Do you run the forged pistons in std + 030 bores?
    OMC never had forged pistons so hence where was all the testing done re piston to bore clearance?
    thanks
    You betcha. I've installed Wiseco forged pistons in standard, +.020", +.030", and +.040" bores. Wiseco provides the product and dyno testing. See http://www.wiseco.com/AboutUs.aspx

    3115PS $100.00 3.000in STD Cylinders: 3
    Notes: Loop Charge

    3115P2 $100.00 3.020in .020in Cylinders: 3
    Notes: Loop Charge

    3115P3 $100.00 3.030in .030in Cylinders: 3
    Notes: Loop Charge

    3115P4 $100.00 3.040in .040in Cylinders: 3
    Notes: Loop Charge

    Except for running without oil, cooling water, or too lean, they run just fine. There are some that say tin plated OEM cast pistons are faster, but I've no AB testing to prove this one way or another.

    Please remember that all factory and aftermarket piston testing is done in service engines. The mods built in my shop see much more taxing duty. No manufacturer guarantees pistons in racing applications. I can tell you that both cast and forged will burn down if too much spark, too lean, too low octane, etc.

    You know the saying: Too lean, too long, too bad!

    Tim

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •