missed a shift

no water · 08-03-2006, 10:05 PM

How much for a top end rebuild on average? (machine heads, replace the valves that are bent)

Steve@Rennsport · 08-03-2006, 10:20 PM

Labor rates vary greatly but expect to pay somewhere around $5K for a top end that includes all parts, machine work, and labor.

no water · 08-03-2006, 10:38 PM

thank you. That was the exact amount he quoted me.

MBAtarga · 08-04-2006, 08:04 AM

Are you near John Walker?

no water · 08-04-2006, 03:48 PM

yes i am. i had him do work in the past

cstreit · cstreit's Garage

Sounds about right... However keep in mind that in some cases a bent valve can crack the boss or ding up a valve seat so there are some variables that can drive the price up once the engine is disassembled.

You say "Missed shift". A missed shift should not require a top-end as the rev-limiter would protect the engine. A miss-shift (ie shifting into the wrong lower gear) would, however, do some damage. (BTDT).

If that is the case, you over-revved your engine and your rod-bolts are suspect because they may have stretched, particularly if they are factory OEM. I would never leave the stock rod-bolts in after an overrev....

no water · 08-05-2006, 02:20 PM

The motor had a full rebuild about 40k ago. Do you think the rod bolts are still suspect? And yes i overreved the motor due to a wrong shift.

Ken911 · 08-05-2006, 02:45 PM

depends on what rod bolts were used during the rebuild if they were arp bolts ore raceware you are probably ok, stock bolts will stretch, then the nuts will come loose then BOOM.

cstreit · cstreit's Garage

Even with ARP it will also depend on what RPM you hit. Stock pistons are relatively heavy. For example I just did the same missed shift (4-3 instead of 5) but because I have lightweight J&E pistons it did not exceed the yield strength of my rod bolts, so they will not stretch and loosen. However the Mahle's that were in there before, would have been over the limit...

So yes, they are definitely suspect.

In my case I knew exactly what RPM I hit because of the data aquisition, and exactly what my rod ends, pistons, etc.. weighed and worked with ARP to calculate the force applied to the bolts and was able to see that I was well below their yield strength.

If you can't do that, then for the cost of replacement, it is WELL ADVISED to replace them. "Maybe they're okay"... But are you willing to risk your entire engine grenading on a "who knows?"

Jeff Alton · 08-05-2006, 07:19 PM

It will cost you an hour extra labour and some $ for a new set of bolts. Cheap insurance as you can't really test them....

Cheers

cstreit · cstreit's Garage

Truth that. You can do them without splitting the case, though it is a pain....

jacko241 · 08-13-2006, 09:43 AM

Only an hour extra labor to R&R cylinders and pistons and replace the rod bolts? That doesn't sound like enough.

hcoles · 08-16-2006, 09:08 AM

this reminds me... what are the system out there one can buy that help protect against going into the wrong gear at to high a speed...I think I've seen two such but don't remember where

911pcars · 08-16-2006, 09:46 AM

I'm biased, but here's one device I recommend to help prevent bent valves:

Cheaper than replacing a valve spring lock (that must be removed to extricate the bent valve(s) from the cylinder head that also must be removed). And that assumes the pistons and rod bolts are okay.

Sherwood
www.seinesystems.com

snowman · 08-17-2006, 07:27 PM

If you bent a valve, you need to tear down the case and replace the rod bolts. Also check the pistons very carfully for cracks and dents. Cost is rod bolts, labor for case split and inspection. My guess is $1k more if no damage is found.

But if you run it and have a bad rod bolt, your going to lose the entire engine at worst, and have to pay for crank repair at best.

BReyes · BReyes's Garage

Yesterday discussed with Frank, in Largo,the causes of the miss shift (for example why a customer of his happened to mis-shift- costing him full R&R- was because of driver.

7 valves bent. While you are there mods included head studs... but since yours is fresh, doing what these guys state above is comprehensive solution.

p.s. I also stated to Frank a wevo, but he noted that it is closer. I have to ask do you have upgraded shifter components?

Best Regards,

cstreit · cstreit's Garage

I do now, however no system will prevent gross driver error which I've been guilty of a few times... SO I built my race engine to withstand all but the worst.... Two mis-shifts to 8500 RPM but my engine is safe.