Why not to buy from a place that starts with SLOW.......

[Mitch Delmer]

So we finally found out whats wrong with the Stroker.  The crank we got from Slow boy racing was ground wrong... Some Dumbass Crank grinder took the time to grind 0.028" off the seal end of the crank.  This is also where the flywheel is a slight press fit to the crank to keep it centered.  Well being that much too small caused the flywheel to be mounted off center and out of balance, and when it went to 9500+ it shook so bad that it loosened all the bolts and that was the noise we heard.  So it could have been worse but now we are fighting with them to get a new crank and flywheel cause it's toast too.  No wonder they are called "Slow Boy Racing". Their machinist must be drunk all the time.  That part of the crank is never supposed to get touched.  I had my machinist come take a look to see the damage and he verified that it shouldn't have been ground.  I phoned and talked to Mark and he told me that if the seal didnt leak there wasn't a problem with the crank, because the six bolts hold the flywheel centered on the crank...WTF?  even on a brand new flywheel the holes are nowhere near the right size to be centered on the bolts...  the two press together and the dowel pin holds the flywheel in place, the bolts are just to hold it to the crank. So anyway thats the problem and now with any luck they will send a new crank and flywheel, but by his attitude yesterday on the phone I would't hold my breath. Im gonna try to get ahold of the owner today and see what he has to say.

here are pics

2.4 crank


2.0 crank


flywheel


flywheel again, didn't know the holes were supposed to be threaded....lol

[Mike Meron]

did you not install a dowle in the crank to center the flywheel?? everyone know this is a must it will shake loose without one.

[Mitch Delmer]

you can see the dowel in the crank in the pic, the 2.0 is the one without a dowel cause I had to take it to put in the 2.4 crank. That only center's the one side.  being 0.028" out the other side rocks up and down, or side to side whichever way you look at it.

[Ryan Lore]

9500rpm+ seems kinda high

I thought 7500-8000 was the limit for a stroker because of the rod ratio

Shouldn't your engine guy have caught an "out of balance" situation when you had the engine balanced before you ran it? Seems logical that if you plan to rev the bag off of a low revving engine you would have had the rotating assemly balanced

[Kimyee Lai]

It's a missed shift Ryan...

[Mitch Delmer]

yeah it did seem to shake a little bit but dont all strokers with no balance shafts? so yes maybe we should have noticed it sooner but it didnt make any noise till it overrevved from the missed shift.  Normally steve doesnt take his car over 6000.

[Ryan Lore]

I don't know anyone who warranties damage from  a "missed shift" or a "missed driveway"  :wink:

However I do understand what Mitch is trying to say.
Maybe pics with a caliper measurement of the inside back of the flywheel showing that it matches the 2.0 crank may help get his point accross.

I've seen Eddie's crank bolts back out so many times I think Lowell welded them in.

I don't think it was assembly error, I believe it  has to do with solid motor mounts, gorilla shifts, and high HP.

[KevinBuckham]

Just curious, but people are having isses with crank bolts backing off with high temp loctite?  (I believe it, I'm just getting paranoid looking at my non balance shaft 2.4 and my twin disc "flywheel".)

Any recommendations on methods to prevent this besides welding the bolts on?

[Mitch Delmer]

here are pics of the measurement of the flywheel



here is of the press fit, I can hold the flywheel and the crank wont fall with no bolts


I just dont think we would have had a problem if the flywheel fit the crank properly, and I used lots of red loctite but that didnt matter when the flywheel started moving.  

So let this be a lesson, I know it is to me, Check the fitment of the flywheel to the crank.  Dont trust anybody but yourself.  I even had the crank checked by my machinist before installation to verify bearing clearances, and he missed that measurement too.  Its supposed to never be an issue.  We may even add a dowell pin or two extra to ensure that this doesnt happen again.

[Martin Raska]

Well isn't the torque in the 100ft-lbs range?  I think red loctite is recommended as well, since you can take a torch to that area anyways when it has to come off.  Who torqued the bolts and how much?  And was there any compound on it.  That really sucks though.

[Mitch Delmer]

Mike Huml of Slowboy is giving us credit for a new crankshaft, since his are 60 days away and i know where three are, so thanks Mike.  I was the one who torqued the bolts and to 100ft/lbs as per spec but a 14 thou runnout (i measured it with a dial indicator) at high rpm was obviously too much to keep them tight.  Hopefully this time he will destroy his 12.9 with something alot faster, and by more that a second.  So on to the reassembly!!!