Wy do Hemi's kick the Rods ???

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by SMOKIN JOE, Aug 13, 2017 at 5:51 AM.

  1. SMOKIN JOE

    SMOKIN JOE Member

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    Looks like almost every used Hemi I see for sale has had windows, I even know personally of a team w/ all top of the line parts and keep up w/maintenance and even they have thrown the rods. WHY ?, Is it RPM ?, Too many runs on the rods ? How many is to many ? 20-30-40. 1/8 mile and 1/4 ?. Does one Rod manufacturer get more runs than another ?. If you keep RPM less than 9800 will it make any differance if you spin it to say 10'200. ?. I would like to here from the guys that have been there/Done that and listen to what you have learned or what you would have done differant ? I have run the 481x wedge w/a Screw,Roots, and even Turbo spinning them as high as 9800, Changed my GRP rods every 20 to 30 runs,and even 40 w/upgraded bolts and Rod material. All 1/8 mile and never kicked the rods. So wy do Hemi's seem to throw the rods more so than any other engine ? Thank You . Joe sr.
     
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  2. Mike Canter

    Mike Canter Top Dragster

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    Because of the tuner!
     
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  3. jay70cuda

    jay70cuda Member

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    Most guys own a Chevy motor first. Then when you run out of power and see almost every fast guy at the track with a Hemi , you make the switch. And your first mistake is thinking you can tune a Hemi like a Chevy. Boom! Out go the rods!! Or you see how old And primitive the oiling system is and you think to your self I can make that better or like my Chevy and cause yourself lots of grief.
    The tuning window of a Chevy is big. A Hemi is tight and narrow. And adding compression makes any small problems you were having much larger. Sometimes buying a proven piece or paying a high dollar tuner the first couple times makes it all worth it. I've blown up 3 hemis. Most of the times were my fault. Each one was no less than $9000
     
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  4. overkill69

    overkill69 Member

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    Quite a bit of wisdom there. I ran a detuned chevy and could run decent numbers with a fat low rpm tuneup. The BAE seems like its weak unless you get aggressive with it.
     
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  5. Mike Canter

    Mike Canter Top Dragster

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    Not sure I would ever say a hemi is weak unless you get aggressive. Look at our motor it is not what I call aggressive, in fact, it has a real safe tuneup in it and we go real fast for a roots car with no lockup. We never smash bearings or kick out rods.
     
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  6. Ron C

    Ron C Jr. Dragster

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    This is the correct answer, like it or not.
     
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  7. Nitro Madness

    Nitro Madness Super Comp

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    I am NOT an expert tuner.....but have had better luck with nitro and a short stroke (3.75) than I had with alky and a 4.500 stroke...so i think the short arm is your friend...
    We are running mostly 1/8 mile @ 4.00 give or take a tenth...1/4 mile are 6.00's...so not pushing it as hard as most TAD and TAFC guys...
    Started with all new stuff and very disciplined maintenance program...so far 134 runs since the beginning of 2013 with no major engine damage...maybe a couple of pistons each year due to a stuck ring...our max RPM is usually 8300...
    Thanks Troy Martin for the advice and coaching!!
     
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    Last edited: Aug 14, 2017 at 8:17 PM
  8. Mike Canter

    Mike Canter Top Dragster

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    Let me add to being the tuner that it is also your maintence program.
     
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  9. SMOKIN JOE

    SMOKIN JOE Member

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    How many runs do you put on your rods ? And What brand ?
     
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  10. Mike Canter

    Mike Canter Top Dragster

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    Use R&R rods with upgraded bolts. 18 runs
     
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  11. jay70cuda

    jay70cuda Member

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    That rnr rod looks really impressive. With everything being larger. I thought for sure it would go 30 runs??
     
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  12. sean70ss

    sean70ss Member

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    p/x 8-10 runs mgp rods but have never kicked a rod tuner is main key
     
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  13. lugnut

    lugnut Member

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    Been a few years back now but we ran all the IHRA races, every qualifying shot possible and usually went some rounds... In 3-1/2 years we did not break a single rod. One thing we stayed on top of was maintenance and was fortunate enough not to have to push parts beyond their run limits. I never saw Manzos car dumping connecting rods every race??? It takes a complete package - the drivers right foot, tune up, good parts, and 110% maitenance every lap.
     
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  14. jay70cuda

    jay70cuda Member

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    Rod bearings are key. They tell a good story on tune up. I'm a firm believer of killer oil pump. Titan, Rcd are a must. Oil psi isn't as important as oil volume.
     
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  15. Nitro Madness

    Nitro Madness Super Comp

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    On the oil pump - I talked with System One when building my car...decided on wet sump this time because we hafta dump the oil every run...they recommended their 1.800" length gear pump for a Nostalgia Fuel application...they make bigger pumps - 2.100 and 2.300" but Richard said the larger pump would be too much volume and could starve the bearings...he mentioned that there is a BUNCH of oil traveling through the engine at high RPM...one quart in each valve cover....several in the valley...one in the filter...one in the lines to and from the filter....one in the engine oil passages...some oil suspended and in the block returns...etc...

    We use 15 quarts...I did have bearing troubles years ago with a KB Olds - using only 10 or 12 quarts and was running out of oil during the run...
     
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  16. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Reasons kick the rods:
    Tune up (detonation)
    Too many runs for a hard tune up
    Too many runs for high rpm/stroke
    Oiling problems
    Something left loose
    Under stretched (may have hit the torque value, but bolt did not stretch to spec)
    Rod journal out of round


    In my experience I have seen just as many rods kicked from running out of oil in the shutdown, primarily in the 1/4 mile. We got a couple of motors with Foster's TAFC several years ago from the oil filter element being clogged. Looked clean (it was cleaned every run), but we suspect shop rag lint after several years of usage, finally clogged it up. Was running out of oil in shutdown. If you are low on oil in the tank or pan and the chutes hit, most likely the oil is going to run away from the pick up and you could potentially suck air.

    Even when I was running a twin scavenge oil pump, until we baffled the tank, it would still dip way off on oil pressure when I hit the chutes.

    Statistically speaking there are more hemi's out there. They make power at a higher rpm than a BBC or 481x. Also many of them start life new in a class like Top Alcohol or Pro Mod where the limits get pushed.
     
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  17. turbo69camaro

    turbo69camaro Member

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    I am working on an NHRA turbo pro mod team this year Brad 8 hemi We got 40 runs on a set of GRP rods this is a 10,000 rpm 1/4 mile deal One thing that i have learned is 1 run on new rods drop pan re torque and check them after every 4 runs they keep tightening up a little bit until 20 runs or so
     
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