Chevy, rotating in reverse after a spinout

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
rdkonkel
Member
Member
Posts: 103
Joined: Sun Mar 17, 2013 11:23 am
Location:

Chevy, rotating in reverse after a spinout

Post by rdkonkel »

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?
ProPower engines
Guru
Guru
Posts: 8686
Joined: Sun Jan 21, 2007 1:16 pm
Location: Victoria BC Canada

Re: Chevy, rotating in reverse after a spinout

Post by ProPower engines »

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.
Real Race Cars Don't Have Doors
User avatar
speedtalk
Site Admin
Site Admin
Posts: 986
Joined: Mon Apr 21, 2003 2:43 pm
Location:

Re: Chevy, rotating in reverse after a spinout

Post by speedtalk »

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.
In Memory of Don Terrill
SpeedTalk Owner/Admin
redliner
Expert
Expert
Posts: 777
Joined: Sun Feb 26, 2012 4:07 pm
Location:

Re: Chevy, rotating in reverse after a spinout

Post by redliner »

speedtalk wrote: Tue Aug 07, 2018 3:17 am 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.
why
Circlotron
Guru
Guru
Posts: 1141
Joined: Tue Feb 05, 2013 6:56 am
Location: Melbourne, Australia

Re: Chevy, rotating in reverse after a spinout

Post by Circlotron »

redliner wrote: Tue Aug 07, 2018 5:13 am
speedtalk wrote: Tue Aug 07, 2018 3:17 am 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.
why
Reverse rotating engine sucking air and powdered rubber into forward facing exhausts.
Truckedup
Guru
Guru
Posts: 2728
Joined: Mon Jan 21, 2013 2:41 pm
Location: Finger Lakes

Re: Chevy, rotating in reverse after a spinout

Post by Truckedup »

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...
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
Newold1
Guru
Guru
Posts: 1963
Joined: Fri Apr 08, 2016 9:50 am
Location:

Re: Chevy, rotating in reverse after a spinout

Post by Newold1 »

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?
The Older I Get, The Dumber I Get :wink:
Roundybout
Pro
Pro
Posts: 396
Joined: Tue Dec 29, 2015 8:09 pm
Location: TN

Re: Chevy, rotating in reverse after a spinout

Post by Roundybout »

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.
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: Chevy, rotating in reverse after a spinout

Post by CGT »

It could definitely unprime the oil pump etc.
PackardV8
Guru
Guru
Posts: 7619
Joined: Sun Jul 30, 2006 2:03 pm
Location: Spokane, WA

Re: Chevy, rotating in reverse after a spinout

Post by PackardV8 »

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.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
pamotorman
Guru
Guru
Posts: 2802
Joined: Thu Mar 06, 2014 11:55 pm
Location:

Re: Chevy, rotating in reverse after a spinout

Post by pamotorman »

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.
user-23911

Re: Chevy, rotating in reverse after a spinout

Post by user-23911 »

Every time I've spun out, the engine has stalled.
redliner
Expert
Expert
Posts: 777
Joined: Sun Feb 26, 2012 4:07 pm
Location:

Re: Chevy, rotating in reverse after a spinout

Post by redliner »

Circlotron wrote: Tue Aug 07, 2018 8:04 am
redliner wrote: Tue Aug 07, 2018 5:13 am
speedtalk wrote: Tue Aug 07, 2018 3:17 am 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.
why
Reverse rotating engine sucking air and powdered rubber into forward facing exhausts.
Thanks!
peejay
Guru
Guru
Posts: 1946
Joined: Tue Aug 10, 2010 9:16 pm
Location:

Re: Chevy, rotating in reverse after a spinout

Post by peejay »

Circlotron wrote: Tue Aug 07, 2018 8:04 am
redliner wrote: Tue Aug 07, 2018 5:13 am
speedtalk wrote: Tue Aug 07, 2018 3:17 am 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.
why
Reverse rotating engine sucking air and powdered rubber into forward facing exhausts.
Not too many people put air filters on their exhaust pipes!
Kevin Johnson
HotPass
HotPass
Posts: 9365
Joined: Tue Nov 22, 2005 5:41 am
Location:

Re: Chevy, rotating in reverse after a spinout

Post by Kevin Johnson »

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.
Driving Force Online: BREAKING NEWS—Ohio Governor Signs SEMA-Supported Vehicle Freedom Bill Into Law!
Post Reply