Crankshaft Timing Gear Slop

tom1394racing · 01-09-2005, 06:55 AM

During the crankshaft inspection process for my 3.0L rebuild, I notiiced what I consider to be significant play in the crankshaft timing gear.

I am able to rotate the timing gear on the shaft so that the outer edge of the teeth moves tangentially by about 0.125". It's almost as if the key or the key slot somehow got damaged.

Is this normal? I would think that this would really screw up the cam timing and make the engine run poorly however the PO did not report any problems other than some "noise" somewhere in the valve train. The rest of the crank is spotless and all the bearing journals are within spec. The teeth on the timing gear also look fine.

My plan was to have the machine shop deal with the gear removal if it was required. I am now thinking that maybe I should remove both the distibutor drive gear and the timing gear to investigate the problem before I send the crank and other parts to the machine shop.

Any suggestions??

john walker's workshop · 01-09-2005, 09:19 AM

unfortunately, the snout of the crank is worn badly. i had one welded up and reground recently, and there are a few 2.7 cranks upstairs with the same problem. they also make noise when the engine is running.

tom1394racing · 01-09-2005, 04:10 PM

John Walker...Thanks for your reply.

Can I get the gear bearing surface re-welded and re-machined or do I need to look for another crankshaft?

What would cause this? Is it a common problem?

Wayne 962 · Wayne 962's Garage

Not sure what the cause is, but it's definitely not normal. These gears should be super-tight on the shaft...

-Wayne

john walker's workshop · 01-09-2005, 04:33 PM

common, as in one out of a hundred or something like that. i sent the last 3.0 crank to northwest machine in portland to get the snout welded up and reground to stock. the keyway needs a bit of hand finishing after the weld job, so the key will fit nicely, but the shop did that. cost was about $200, compared to the $1000 average price for a used 3.0 crank. find a shop that does crank repair related to welding. the rest of the crank is not affected, so the journals can remain standard. they should check it for being straight after the job is done. hard to say what causes it. maybe a less that optimal interference fit when the gear was installed. the gear is heated to expand it, then slipped over the end where it cools and contracts.

tom1394racing · 01-09-2005, 06:23 PM

John

Sounds like I should send the entire crank with gear attached to someplace like Ollies to have it repaired and checked. I was going to send the crank out anyway to have it magnifluxed and polished.

john walker's workshop · 01-09-2005, 08:02 PM

well, that particular crank was sent to ollie's first, and the $175 estimate over the phone was ballooned up more than double after it got there, with no actual final cost quote. same job, nothing extra from what i asked for over the phone. the guy said that nobody would have quoted it at that price. i beg to differ. this was after it was there about 2 weeks without even looking at it, when they promised approx a week turnaround on the phone. pissed me off, because i had the engine waiting to assemble. i just had them send it back, and took it elsewhere.

Wayne 962 · Wayne 962's Garage

Sounds like you should just send it to the place that John recommended!

-Wayne

tom1394racing · 01-10-2005, 01:27 AM

Can Northwest Machine do all of my other machining work as well? I'll need the standard engine machine work described in Wayne's book in addition to the crank repair.

I'll also be speaking with the shop that I purchased the engine from. Paid $4500 for the engine and they told me it was making a slight valve related noise but was running fine. Thay are a very reputable shop and they are currently doing the body and fabrication work on my RSR Clone. I think I should get some type of compensation (like the cost of the crank repair) from them.

john walker's workshop · 01-10-2005, 06:56 AM

i would ask them to provide another crank, and perhaps help you out on the parts costs. you paid a lot for an engine that was basically a core. the guy at northwest machine is fully versed in 911 machining. his name is dick elverud, and he is very well known among the northwest guys. 503 648 6742 nwmach@easystreet.com.
wayne's favorite place is competition engineering, as noted in his book.

tom1394racing · 01-10-2005, 03:56 PM

I took the crank back to Auto Associates today. They pulled the the timing gear and confirmed that the crank snout needed welding just as John Walker described. They also don't ever recall seeing anything like it. Just my luck.

They are sending it out for welding & re-machining. The rest of the crank is spotless and should be re-usable.