Chevy, rotating in reverse after a spinout
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Chevy, rotating in reverse after a spinout
Had a motor blow this week after the second place car hit us and spun car, did a 180, then rolled backwards for 100 ft or so with a direct drive transmission. Car did fire up, then blew a lap later.
Question is: did the motor spinning in the opposite direction have everything and/or nothing to do with the engine blowing?
Lost a rod, piston hit the head/valves, broke cam, etc. block appears to be salvageable...
With some discussion we figured a direct drive transmission would reverse the oil pump after an altercation that sent the car rolling backwards. Any experience with this?
Question is: did the motor spinning in the opposite direction have everything and/or nothing to do with the engine blowing?
Lost a rod, piston hit the head/valves, broke cam, etc. block appears to be salvageable...
With some discussion we figured a direct drive transmission would reverse the oil pump after an altercation that sent the car rolling backwards. Any experience with this?
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Re: Chevy, rotating in reverse after a spinout
Unless it hydrauliced when it got turned around then I doubt it.
We run direct drive in sprint cars and get turned once in a while and 7 times out of 10 the engine will turn backwards.
Now if the PTV clearance was really tight I can see bending some valves but not break a rod. It may have been on the way out when the spin happened or during that race anyway it just went unnoticed when the oil filter was checked during the following weeks maintenance for the next weeks event.
We run direct drive in sprint cars and get turned once in a while and 7 times out of 10 the engine will turn backwards.
Now if the PTV clearance was really tight I can see bending some valves but not break a rod. It may have been on the way out when the spin happened or during that race anyway it just went unnoticed when the oil filter was checked during the following weeks maintenance for the next weeks event.
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Re: Chevy, rotating in reverse after a spinout
I would not have believed it had I not seen it for myself — Car spun out and went backwards with clutch engaged. Luckily for the engine the car was damaged and not restarted. When I pulled the heads off, the chambers were packed with rubber.
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Re: Chevy, rotating in reverse after a spinout
Reverse rotating engine sucking air and powdered rubber into forward facing exhausts.
Re: Chevy, rotating in reverse after a spinout
All the sprint cars have dry sumps? It's said that a wet sump engine can be oil starved during a spin...The driver restarts and a lap later the engine bearings fail...
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Re: Chevy, rotating in reverse after a spinout
I am wondering if the huge jerk on the rods when reversing direction at high rpms just pulled a rod rod or cap to a point where a rod bolt and bearing failed? We know that rods in a high powered engine are under big loads at high rpms the loads and when the loads and force is almost instantly reversed the rods might start doing some weird motions?
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Re: Chevy, rotating in reverse after a spinout
I remember watching a NASCAR race and someone spun and blew up a lap later. Benny Parsons then went on to explain why his engine blew up a lap later. In this case it kicked the dry sump belt off and the driver didn't realize until too late. He also mentioned the cam and tappets they were using do not like to be spun backwards. They can chatter because the ramps are all off and such. The valvetrain going in the wrong direction at 7500RPM is apparently not good. Wet sump of course will suck air. He went on for a good few minutes with some really cool info. I miss that guy.
Re: Chevy, rotating in reverse after a spinout
We know that rods in a high powered engine are under big loads at high rpms the loads and when the loads and force is almost instantly reversed the rods might start doing some weird motions?
OTOH, one could make the case that compared to the time for load reversal at 9,500, which the rods are expected to handle, the load reversal during a spin-out happens in slow motion.
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Re: Chevy, rotating in reverse after a spinout
I built my wet sump dirt circle track engines with road race pans because when these guys spin out they just gas it to spin the car around and it may not be to the left.
Re: Chevy, rotating in reverse after a spinout
Thanks!Circlotron wrote: ↑Tue Aug 07, 2018 8:04 amReverse rotating engine sucking air and powdered rubber into forward facing exhausts.
Re: Chevy, rotating in reverse after a spinout
Not too many people put air filters on their exhaust pipes!Circlotron wrote: ↑Tue Aug 07, 2018 8:04 amReverse rotating engine sucking air and powdered rubber into forward facing exhausts.
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Re: Chevy, rotating in reverse after a spinout
Ford Twin Cam will bend the bronze cam chain tensioner body. I talked to people that lost engines that way when spinning on the track. You are explicitly cautioned not to rotate the engine backwards during assembly.
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