Replace piston or pistons?
#1
Posted 02-21-2011 04:10 PM
Brimtek Motorsports
Team Four Racing
#2
Posted 02-21-2011 11:51 PM
#3
Posted 02-22-2011 10:16 AM
dave
Dave Wheeler
Advanced Autosports, the nations most complete Spec Miata shop
Author, Spec Miata Constructors Guide, version 1 and 2.0
Building Championship winning cars since 1995
4 time Central Division Spec Miata Champion car builder 2012-2013-2014-2017
Back to Back June Sprints Spec Miata 1-2 finishes 2016 and 2017
5 time June Sprints winner in Mazda's
6 Time Northern Conference Champion Car Builder
2014 SCCA Majors National point Champion car builder
2014 SCCA Runoffs winner, T4 (Bender)
2014 Central Division Champion, ITS (Wheeler)
2013 Thunderhill 25 hour winning crew chief
2007 June Sprints winner, (GT1, Mohrhauser)
Over 200 race wins and counting.
www.advanced-autosports.com
dave@advanced-autosports.com
608-313-1230
#4
Posted 02-22-2011 06:08 PM
We have all missed shifts, but very rarely will it result in a bent valve. As mentioned above, these motors are pretty strong. I would look very closely at what really happened.
The exhaust valve broke just below the keeper. It must have bent the valve stem just a little because the valve will not fall out of the head. I had Mike Rossini look at the head while at the track and he said he had seen similar failures on a missed shift.
So back to the original question: IF the number one piston is the only lower end damage, is it OK to just replace one piston. How close are OEM pistons in weight?
Brimtek Motorsports
Team Four Racing
#5
Posted 02-22-2011 06:25 PM
I am not sure you can get an answer here that you can take to the bank, You might talk to a motor rebuild shop and get an opinion of an expert.
Drawing from my current experiment with rebuilding my transmission, there is something to be said for taking a few extra precautions with a race equipment. we push this stuff to its limits, if there was any question while you are this far into it I would just do it and be done. But, and expert may have enough confidence to tell you, what you can safely get away with.
Frank
TnT Racing
SCCA Ohio Valley Region
#6
Posted 02-22-2011 06:35 PM
I am not sure you can get an answer here that you can take to the bank, You might talk to a motor rebuild shop and get an opinion of an expert.
Yep, without actually seeing even the best builders won't be able to give a full evaluation. That's a good benefit of having an engine program with a reputable builder. I don't mind doing my own junkyard/shade tree builds but when I get to the point where I make a bigger investment, I'll job the whole thing out.
#7
Posted 02-22-2011 07:22 PM
I got 2nd instead of 4th, data showed 8510 rpm! I raced that motor for a full season after that with no issues, it just got tired.
I'm with Davew, something else happened...
Steven Holloway
Artist formerly known as Chief Whipping Boy for Lone Star Region
#8
Posted 02-22-2011 08:38 PM
The exhaust valve broke just below the keeper. It must have bent the valve stem just a little because the valve will not fall out of the head. I had Mike Rossini look at the head while at the track and he said he had seen similar failures on a missed shift.
So back to the original question: IF the number one piston is the only lower end damage, is it OK to just replace one piston. How close are OEM pistons in weight?
Pretty close. I've been told not to worry about matching the weight by someone who knows volumes more than me.
I've experienced a bent valve following the dreaded Ooops that's not 4th! shift. I know people also who did the same thing and registered crazy high RPMs on their logger with no ill effects. Was it the botched shift or something else? Who knows for sure. The damage is already done so fixing it is the critical thing now.
I would check it out thoroughly. Nothing more annoying than fixing what you can see is wrong, only to lose several thousand dollars in parts the next outing from what you didn't see. It ruins the weekend and doesn't help the race budget. Once you have the engine out and the head off, tearing down the bottom end really isn't that hard or time consuming.
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users