Ford Mustang Forums banner

Why do strokers eat thrust bearings?

18K views 41 replies 22 participants last post by  89llx 
#1 ·
This may be a dumb question,, but why is it that I seldom hear about 100,000+ mile 5.0 cranks eating up thrust bearings, but I see a lot of threads about 331's and 347's eating them up shortly after they get them running? Is it because of the aftermarket crank? Is it more common with a cast steel crank vs a forged steel crank or vice versa? I'd hate to build a new stroker and have it ruin the block and crank!
 
#12 · (Edited)
That reminds me of my Dad teaching me how to rebuild our first 302 30 years ago. It was time to torq the rods and we set the torq wrench to #15-#20lbs and when it clicked, the next words out of my dad's mouth were: "That can't be right-give me the ratchet" and he proceeded to tighten them to where he felt it was good and tight. Needless to say the first time the engine made it to about 4000, a rod pulled apart. It was a priceless moment when dad looked under the car and I asked: "Do you think we broke anything?" and his reply was; "I think so-there's a big dent in the oil pan". Looking back it was hilarious how we thought we were doing it right. My dad is still living if you'd like him to help assemble your new engine for you. ;)
 
#8 ·
properly setting and knowing the crank end play is helpful and not hard to do..

I can see over looking something like that in the "excitement" that is assembling a motor but you should always double tap... It can't hurt if you know what I mean LOL
 
#10 ·
Aftermarket cranks usually have tighter tolerances than OEM cast. I just finished up a Mitsubishi Evo (yeah yeah yeah) that had a Manley forged with some aluminum rods. Crank end play was a whopping .001". A large screwdriver and a dial caliper are your friend when assembling a motah.

Clutches that are set up incorrectly can also destroy a thrust bearing.
 
#11 ·
I do remember a guy saying that the thrust surface on his new stroker crank had a nasty coarse machined surface which he felt might lead to a failure, so he had it polished or something. I have always checked endplay etc. but never really payed particular attention to the surface on the crank itself.
 
#14 ·
Someone mentioned it earlier -- but clutch/transmission issues also often eat thrust bearings. Torque converter not seated all the way so when the tranny is cinched up it's pushing too hard on the back of the crank; similar when manual trannies are changed/swapped and there's a difference in input shaft length, etc.
 
#16 ·
Sorry for the bad luck. Any idea what caused it? It seems so weird that our old 5.0's go 200,000 miles regardless of clutch adjustment etc. but yet it seems like so many strokers eat em up real quick. It'd be nice if there was a clear cut reason that could totally eliminate the chance of it happening.
 
#18 · (Edited)
Without having your crank remachined, how do you set thrust? I know that the stroke itself has nothing to do with the thrust getting eatin. I have to assume it is because aftermarket stroker cranks are not consistently machined to the correct tollerances & surface finishs that OEM cranks are and if we don't catch it before we put it together, it's too late? I have a brother-in-law that works in a factory that makes powdered metal gears. He said if the aftermarket finds one of their gears are bad, they have to replace it, but if Ford finds a bad gear, they are required to replace every gear in that shipment. He said that Ford OEM standards are much higher than the aftermarket. I took a tour of B F Goodrich factory and every tire that is made is weighed and checked for balance, the best tires all go to the OEM car companies and we get the rest. That explains why you never see a large wheel weight on a new car , but when we go get new tires the weights are 3" long. OEM standards are pretty high quality for the most part.
 
#20 ·
I have an in depth video of how and why to set the thrust. Its not optional its mandatory and has nothing to do with machining your crank. It has to be done during assembly. Its not some trick of the week or speed secret. Not to mention its deadly simple. Its done at oem's and done by regular folks building there engines. If you didnt do it and your alright you got lucky is all.
 
#21 · (Edited)
I really need to get into your video series to learn all this stuff. Just like checking thrust, I have always checked it with a dial for front to back movement and they have always been within specs, but I never got into anything more than that as far as thrust goes. . I want to start watching the video series, but was kinda waiting until I got closer to being able to build something. Otherwise, at my age I'll forget everything I learned. I am really anxious to get started though. Sounds like tons of good info!! Plus if I can do the DIY set-up, that should really help in getting it right the first time!
 
#27 ·
On my fresh scat 408 setup, it ate up the thrust as well within 200 miles. And that's being paranoid of thrust issues. Proper clutch freeplay, I kick the car out of gear and not stand on the clutch at lights, etc. machine shop is supposed to be top notch, but the end verdict was apparent ####ty surface on the crank thrust face. Bunch of downtime, bunch or tear down of heads and various other parts for clean up, and a bunch more money to fix what should have been done the first time.
 
#28 ·
Try a factory Ford Service Manual. Best car investment you will make. It will instruct you to properly set and check the thrust bearing along with supplying the allowable spec. As an old guy you probably still remember how to read :)

PS people who properly set a thrust bearing and use the right clearance rarely if ever have a problem. When they do it is usually something screwed up in the drive line.
 
#29 ·
It sounds like checking the thrust surface of the crank is just as important as checking the clearance. It would be easy, even for a machine shop to assume that a brand new crank would be ready to use. I guess you can't take anything for granted, especially with aftermarket stuff.
 
#30 ·
One thing is most of the newer manual trans cars require you to push in the clutch to start the engine, when the oil is cold and has dripped off of the thrust bearing. I always start my car in neutral.

And I've ruined a thrust bearing when a cover bolt broke on my pressure plate and I had to push extra hard to shift into a gear.
 
#37 ·
Hi Guys, Quick Question now that I saw a disturbing reply in here that may be my problem. I had the Performance Shop down here in DE install my New T56 Mag Trans with Spec Clutch. I now have a vibration that I never had before. Is it possible, when they installed the new trans, it pushed the Crankshaft foward and is causing my issue? Is there anyway to properly check Thrust clearance between the T56 Input shaft and the Crankshaft?? Please help as If this is the case I don't want to damage my trans or Engine. Thanks so much.
 
#40 ·
Every time you push in the clutch the crank is pushed forward, do you feel it vibrate. You come off like an ####### with a question like that, nobody owes you an answer, you are not paying for any of this info, don't act like his answer didn't meet your expectations, you are not even the one with the vibration issue. My free suggestion would be the flywheel balance is the issue.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top