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Thread: How many passes you get on your motor ?

  1. #1
    Senior Member DYNO OPERATOR
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    How many passes you get on your motor ?

    I was wondering how many passes on a mild motor on gas or alcohol do you get before you go thru the motor.
    I know it depends on the motor and what parts you use but in general what's your opinion.
    My SBC motors I think are mild compared to some.

    I get about 150 to 180 passes before I tear them down.
    So far the motors look good. Just wondering if you guys think I could get more passes or am I lucky. I've been doing this for many many years.
    Like right now I've got 110 passes on my 67 Camaro and I'm gunna try to get another year out of it before I tear it down. I do routine maintenance and inspections everytime the car comes back from an event.

    Just looking for your opinions.

  2. #2
    Administrator RACING JUNKIE bjuice's Avatar
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    Vince in my opinion i would think you could get a little more run time out of your motors...

    maybe change some valve springs at 150/180 passes..keep the pressure knocked off them in the off season.

    perform a compression check on each cylinder..if it still reads good...then run it...this is my take..
    i assume when you re-freshen one your motors your only replacing bearings,rings,valve springs....

    and of course as long as your car is still running the numbers before you tear it down..

    i have seen mild conventional head motors run over 300 passes with only a valve spring change...

    this is only an opinion tho..

    Brian
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  3. #3
    Senior Member RACING JUNKIE
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    I go one season without freshing it up, of course I check up on things pretty good. Spring pressure and valve lash is a every couple weekend thing. One season for me is normally anywhere from 200-300 passes, I've done this on my SBC and BBC's and only had one issue (comp roller lifter break)
    I see a lot of people going well over 300-400 passes without anything but springs also, even see some take the intake off stick lifters in it and just keep racing them.
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
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  4. #4
    Senior Member EXPERT BUILDER
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    I run my motors 500 passes before tear down.I don't replace valve springs untill I rebuild engine.SBC,355 in a 3100 lb camaro,mild flat tappet,alky carb,13-1 mid 10.50 car.

  5. #5
    Senior Member DYNO OPERATOR
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    My opinion and what I did when I was racing my own.
    AS long as it is making good power, has good oil pressure, and good leak down keep running it. Why fix what isn't broken.
    If you don't have a good leak down guage buy the single guage leak down testor for Moroso ot the one I use from SnapOn Tools. IT is more repeatable in my opinion no matter were your air pressure is. Those that use two gueages have to be fed with the same air pressure or they are not as repeatable.

    I liked to do lots of between rounds checks, like checking valve lash, checking carbs to be sure everything was working right, and checking under car for loose bolts or anything I could find wrong. My engines lasted several years, so I guess that means several hundred passes. Finding the little things going bad before they do damage goes a very long way.

    Check valve springs all the time with an on the head pressure testor. If one gets 20 to 30 lbs weaker than all the rest get it out of there.

    I highly recommend and also sell the best oil filtration system availaible, from Pure-Power. www.gopurepower.com This makes for quick and easy oil and filter inspection between rounds and it is easy to clean. Costs lots more but you buy it one time only.

    I have customers that run their engines for years and others with high horsepower that bring them back at the end of the season for freshening.

    Some of how long you can run it will depend on your engine builder but a whole lot of it will depend on you and how much you stay on top of preventive maintenance.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  6. #6
    Senior Member EXPERT BUILDER
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    I usually run about 300 passes a year. If something breaks I fix it but usually goes fine. I haven't changed valvesprings until it forms a miss or slows down for no apparent reason.

  7. #7
    Senior Member RACING JUNKIE
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    I'm a big fan of the take apart oil filters, you can usually spot something wrong before it happens. I start out with 250 lbs seat pressure on the valve springs and check often, when they drop below 225/230 i change them out. We just pulled down a 434" junk blk, with 200 passes on it, pistons looked brand new leakdown was less than 3% with zgaps, but we did change out the bearings and freshened up the heads. The motor had slowed down about 5 hundreds. We broke 2 rocker studs, during those 200 passes, dragster ran a best of 4.88 and would always run 4.90s hilborn stacks injected alcohol.

    JMO

    Zip.

  8. #8
    Senior Member RACING JUNKIE
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    Here's a scenario for you, I ran a 73 nova footbrake car for about 7 years. When I bought the car it had a 11 to 1 hydralic flat tappet 396bbc motor.
    I knew the guy real well who originaly owed the car and he had been street racing the car at an area here in memphis we call rivergate.
    He loved nitrous and probaby had sprayed the car everytime he ran it, which was every weekend and thursday night after test and tune at MMP When I bought the car from him he removed his famed nos kit which I think wasa 250 shot. I ran it like that for about 4 years and later put a 150 shot myself, anyway the point is this motor lasted over 14 years and was not pampered in anyway I routinely wound it up, I performed only routine maintenace never changed a valve spring or a lifter nothing just oil filter and plugs etc.
    It had a bone stock bottom end, cast crank and stock rods.
    It finally slung a rod out the side of the block one night at the track, I had a 454 waiting in the wings cause I knew it was getting close. Nobody could believe that motor had been in this car that long and who knows if I had went into the motor and FRESHENED it up, it could have still been alive today.
    I actually wanted the thing to go though so I could put my 468 in it and go faster, I was leaning on it pretty hard the last few years so I guess you can say it was my fault. I killed it, I admit it but hey it was fun while it lasted.

    >< Cp
    ***IN GOD WE TRUST***

  9. #9
    Senior Member DYNO OPERATOR
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    I want to thank all you guys for the help. You just never know if your doing the right things until you ask and get more opinions. I pretty well do the things you guys have mentioned on maintenance and while the motor is sitting all winter. So far the motor has not slowed down at all. Springs are good and valve lash hasen't moved. The only thing I haven't done is a compression test which I will do this winter.

    When I do a tear down I usually boil the block, check and hone the cylinders, bore if need be, replace freeze plugs, cam bearings, crank and rod bearings, check and polish crank, new oil pump, check rods, weld the oil pick up tube, check deck height and head surface, do a valve job, check seats, guides etc, replace springs and check rockers and roller lifters, replace timing belt or timing chain and of course all new gaskets. When it goes together I check and recheck all clearances, end play etc.

    Maybe with more checks and maintenance I can get more than 150 to 180 passes out the motors.

  10. #10

    passes on motor

    I would say I go around 300 passes a year. Usually freshen after 2 seasons. It doesnt hurt to do it every year, just insurance, but I have seen many rebuild and break a crank or something a week or two out. We just tore into a 540 that was ran for 2 seasons with 750+ passes and it still had the hone marks in the cylinders. Still ran the same et as it did when we put it in. Back springs off during the winter, check valves every 2 weeks, and I change oil every 2 weeks which is probably not necessary, but its a habit.

  11. Racing Junk


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