Accidental 8,000rpm+ over-rev
06-08-2019, 08:25 AM
#1
Racer
Thread Starter
Accidental 8,000rpm+ over-rev
(1988 4+3 w/3.45:1, SBE with HCI/blower/n2o)
Last night while playing in Mexico I did something I've never done before...
I pulled a money shift from WOT 3rd gear @6400rpm (~95mph) back to 2nd gear and saw the tach flash past 8,000rpm while the rear tires broke loose.
Not sure how I did it, I've been power shifting this car for 3 years and I have NEVER landed the wrong gear. I guess accidents happen?
As soon as I let the clutch out and realized my mistake I upshifted to 4th+OD. I heard a loud ticking, but I had no choice but to limp it home.
I found that I had spit a lash cap from cylinder 2 intake valve. Pushrod is straight, HR lifter is not collapsed, roller rocker is tight. I reinstalled the lash cap and ran the valves. The car fired up and ran smooth as butter.
Now, my question(s):
What are the chances the rod bolts are still OK with a 8-9k spin?
The cam is a 228/228@.050" .570/.570" lift advanced +4°, did the lifters survive?
With the given cam specs, and the fact that I floated the valves. Did the valves kiss pistons?
I appreciate any constructive input. I'm just trying to figure out if I should trust any of the life left in this motor...
Last night while playing in Mexico I did something I've never done before...
I pulled a money shift from WOT 3rd gear @6400rpm (~95mph) back to 2nd gear and saw the tach flash past 8,000rpm while the rear tires broke loose.
Not sure how I did it, I've been power shifting this car for 3 years and I have NEVER landed the wrong gear. I guess accidents happen?
As soon as I let the clutch out and realized my mistake I upshifted to 4th+OD. I heard a loud ticking, but I had no choice but to limp it home.
I found that I had spit a lash cap from cylinder 2 intake valve. Pushrod is straight, HR lifter is not collapsed, roller rocker is tight. I reinstalled the lash cap and ran the valves. The car fired up and ran smooth as butter.
Now, my question(s):
What are the chances the rod bolts are still OK with a 8-9k spin?
The cam is a 228/228@.050" .570/.570" lift advanced +4°, did the lifters survive?
With the given cam specs, and the fact that I floated the valves. Did the valves kiss pistons?
I appreciate any constructive input. I'm just trying to figure out if I should trust any of the life left in this motor...
06-08-2019, 08:45 AM
#2
Race Director
Did this once on my 93, triple digits , went for 5th and got 3rd
put clutch back in. Thankfully didnt wreck (ive seen a c4 spin while racing when that driver got 1st vs 3rd).
No harm. Everyone told me how my car was now just a time bomb waiting to ‘give up the ghost’. Now the same bottom end has like 540 whp and 60000 miles later.
i think you are golden and wont have any problem
put clutch back in. Thankfully didnt wreck (ive seen a c4 spin while racing when that driver got 1st vs 3rd).
No harm. Everyone told me how my car was now just a time bomb waiting to ‘give up the ghost’. Now the same bottom end has like 540 whp and 60000 miles later.
i think you are golden and wont have any problem
Last edited by dizwiz24; 06-08-2019 at 03:32 PM.
06-08-2019, 08:55 AM
#3
Racer
Thread Starter
Did this once on my 93, triple digits , with for 5th and got 3rd
put clutch back in. Thankfully didnt wreck (ive seen a c4 spin while racing when that driver got 1st vs 3rd).
No harm. Everyone told me how my car was now just a time bomb waiting to ‘give up the ghost’. Now the same bottom end has like 540 whp and 60000 miles later.
i think you are golden and wont have any problem
put clutch back in. Thankfully didnt wreck (ive seen a c4 spin while racing when that driver got 1st vs 3rd).
No harm. Everyone told me how my car was now just a time bomb waiting to ‘give up the ghost’. Now the same bottom end has like 540 whp and 60000 miles later.
i think you are golden and wont have any problem
I'm going to take it for a spin today and see if the power is back. I noticed no smoke or noises after I re-installed the lash cap and ran the valves, so I think you might be right.
Now, what about the procharger? I'm running max impeller speed at 6500rpm, I oversped that by a large margin last night. The the P1sc-1 survive?
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dizwiz24 (06-08-2019)
06-08-2019, 11:56 AM
#5
Le Mans Master
Member Since: Oct 2002
Location: Las Vegas - Just stop perpetuating myths please.
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Valve springs are the most vulnerable. Once they go into valve "float" they become weakened and provide less closing pressure - maybe even progressively worse. But you can R&R the valve springs with the motor in the car so not such a big deal and you can continue to drive it and maybe not even notice any different while driving posted speed limits.
And the tach flashing to 8,000 rpm sounds more like tach needle swung to far due to lack of dampening rather than the motor "flashing" to 8,000 rpm.
Any damage to the bottom end is spilled milk now. And if you don't here any knocks or oil burning or loss of oil pressure you can still drive and race the car as before - but that doesn't mean something won't show up later. But you really have nothing to loose for now so don't let it bother you. Or you could be sourcing a replacement motor to rebuild using a rebuildable core. Hey that's really kind'a fun IMHO and I have 4 blocks getting ready for their turn in the machine shop - 3 of them are 400sbc.
Hope this helps ya.
And the tach flashing to 8,000 rpm sounds more like tach needle swung to far due to lack of dampening rather than the motor "flashing" to 8,000 rpm.
Any damage to the bottom end is spilled milk now. And if you don't here any knocks or oil burning or loss of oil pressure you can still drive and race the car as before - but that doesn't mean something won't show up later. But you really have nothing to loose for now so don't let it bother you. Or you could be sourcing a replacement motor to rebuild using a rebuildable core. Hey that's really kind'a fun IMHO and I have 4 blocks getting ready for their turn in the machine shop - 3 of them are 400sbc.
Hope this helps ya.
Last edited by cardo0; 06-08-2019 at 11:58 AM.
06-08-2019, 12:34 PM
#6
Le Mans Master
I wouldn't worry about it if everything is working correctly now. If you did any serious rod bolt damage you'd hear it and see it (in oil pressure.) Maybe drain the oil and check for shavings... that's just me though.
06-08-2019, 01:38 PM
#7
Race Director
What lash cap? To be cautious, I would replace the springs and check pushrods, and rockers carefully. I'm on the strip almost every week.
06-08-2019, 02:57 PM
#8
Le Mans Master
I did the same thing to a 1964 tri power GTO back in 1966. I was learning to powershift at wot. rear wheels bounced and squealed a bit but thats all that happened. If no noise, drive on brother.
Last edited by ghoastrider1; 06-09-2019 at 02:11 PM.
06-08-2019, 09:58 PM
#13
Melting Slicks
If the engine is built to run 8000 rpm it will be fine, i used to have a car with a 351 nascar engine it did 8,500 rpm and loved to rev.
The only problem is the valve collets, the wear is really severe with those large valves.
Had to replace the collets every couple of months on a weekend car, apart from that the bore wear is severe be it critical piston speed or to much fuel splashing the bores.
great for races but not for the street, should be fine to hit high rpm every so often.
The only problem is the valve collets, the wear is really severe with those large valves.
Had to replace the collets every couple of months on a weekend car, apart from that the bore wear is severe be it critical piston speed or to much fuel splashing the bores.
great for races but not for the street, should be fine to hit high rpm every so often.
06-09-2019, 09:07 AM
#14
Racer
Thread Starter
Valve springs are the most vulnerable. Once they go into valve "float" they become weakened and provide less closing pressure - maybe even progressively worse. But you can R&R the valve springs with the motor in the car so not such a big deal and you can continue to drive it and maybe not even notice any different while driving posted speed limits.
And the tach flashing to 8,000 rpm sounds more like tach needle swung to far due to lack of dampening rather than the motor "flashing" to 8,000 rpm.
Any damage to the bottom end is spilled milk now. And if you don't here any knocks or oil burning or loss of oil pressure you can still drive and race the car as before - but that doesn't mean something won't show up later. But you really have nothing to loose for now so don't let it bother you. Or you could be sourcing a replacement motor to rebuild using a rebuildable core. Hey that's really kind'a fun IMHO and I have 4 blocks getting ready for their turn in the machine shop - 3 of them are 400sbc.
Hope this helps ya.
And the tach flashing to 8,000 rpm sounds more like tach needle swung to far due to lack of dampening rather than the motor "flashing" to 8,000 rpm.
Any damage to the bottom end is spilled milk now. And if you don't here any knocks or oil burning or loss of oil pressure you can still drive and race the car as before - but that doesn't mean something won't show up later. But you really have nothing to loose for now so don't let it bother you. Or you could be sourcing a replacement motor to rebuild using a rebuildable core. Hey that's really kind'a fun IMHO and I have 4 blocks getting ready for their turn in the machine shop - 3 of them are 400sbc.
Hope this helps ya.
Agreed on the spilled milk, I took it for a spin yesterday and all seems well.
06-09-2019, 09:09 AM
#15
Racer
Thread Starter
06-09-2019, 10:29 AM
#16
Tech Contributor
What App did you use to capture the video/overlay speed? Looks cool
Last edited by Pwnage1337; 06-09-2019 at 10:29 AM.
06-09-2019, 11:30 AM
#18
Racer
Thread Starter
I am running a simple gopro hero5 with the overlays built in. It makes for some very simple, quick to edit videos
06-09-2019, 11:36 AM
#20
Race Director
Disagree with the people that problems will show up later.
Thats like saying piston rings will wear out if you drive it too much.
you either broke it or you didnt. And it sounds like you didnt.
Thats like saying piston rings will wear out if you drive it too much.
you either broke it or you didnt. And it sounds like you didnt.