Inside Diameter Knurling

n2omike · Dec 9, 2018

Hey Guys! I have an old 1966 Mustang that is a street/strip car. Recently, the pilot bearing popped out of the rear of the crank, and did a little damage. When I went to install a new one, it was too loose, and would slide in most of the way by HAND. It's a 6003 sealed bearing. 35mm OD, and the crankshaft is a steel 1970 Boss 302 unit. Not sure of the alloy they used back then. I don't want to have to pull and completely disassemble the engine.

Can I knurl the recess in the crank where the Pilot Bearing fits? I think it was already loose to start with, and may have been why it came loose. I did find this tool... I just don't have the machining experience to know if it will do what I need.

I don't care if the fix is semi-permanent. My initial plan is to knurl it the best I can, rough up the OD of the bearing, and use whatever semi-permanent epoxy I can find to lock it in place. A new engine will be going in down the road, but I want to get a couple more years out of this one.

I appreciate your thoughts and expertise!

Eagle Rock K1-229 Hand Knurling Tool for Internal Bores - K1-229- - Penn Tool Co., Inc

imageRendering__62912__59841.1418128386.1280.1280.jpg

Seaman · Dec 10, 2018

I'd scrap the roller bearing and push a bushing in there. Most Ford cranks of that era had bushings, not bearings. Nothing fancy, just apiece of bronze with the correct OD and ID for the tranny. The crank has some heat treat, so it may be very difficult to knurl.

Good luck.

Dave

gbent · Dec 10, 2018

Locktite is a much better friend than knurling.

L Vanice · Dec 10, 2018

gbent said:
Locktite is a much better friend than knurling.

True, and cheaper than that fancy tool. But, if you go looking, look for "Loctite." You have to clean the oil off the surfaces you want to bond. I usually use lacquer thinner or acetone. There are a number of different grades of Loctite, some stronger than others.

Larry

Gordon Heaton · Dec 10, 2018

I suggest LocTite 'Stud & Bearing Mount'. It is not the same as threadlockers and it comes in thick & thin formulas depending on how loose the bearing fit is. I believe you can fill gaps up to .015" with the thick one.

Illinoyance · Dec 10, 2018

Seaman said:
I'd scrap the roller bearing and push a bushing in there. Most Ford cranks of that era had bushings, not bearings. Nothing fancy, just apiece of bronze with the correct OD and ID for the tranny. The crank has some heat treat, so it may be very difficult to knurl.

Good luck.

Dave

Bronze is a great idea. Oilite or equivalent is best.

n2omike · Dec 14, 2018

Thanks Guys...

Thing is, I'm using a sintered iron clutch disk (racing), and the dust from it kills bushings in no time... so the only option is the sealed bearing. It's commonly used in small block Fords.

Problem is, the mounting area is loose. I can push the bearing in most of the way by hand. The bearing is in a pretty severe environment, and I need a way to tighten it up. I was going to try and knurl it, then possibly epoxy it in place.

Will the above tool do anything with the factory steel crank? I don't need a huge amount. I just need to tighten it up. Is there a recommendation for an epoxy? If it's permanent, I don't really care. The crank is already 0.030"/0.040", and I can use heat to remove it down the road if it comes to that, anyway. I saw someone mentioned a stud compound... I've also thought about the green sleeve retainer, or even JB Weld!

Thanks Guys!

Mike

guest · Dec 14, 2018

n2omike said:
Will the above tool do anything with the factory steel crank? I don't need a huge amount. I just need to tighten it up. Is there a recommendation for an epoxy?

I think you'll get a little out of that tool. It's going to take some pressure though. The journals are probably nitrided if it's a factory Boss 302 crank, but 4340 is common for forged cranks and they don't harden the crap out of them because they will break. So the ID on that end is probably not all that hard- mid 40's or so.

JB Weld ought to do the rest of the job if you don't want to use loctite.

Erich · Dec 14, 2018

Loctite 609 (I think) is made to hold bearings in place. Just put some on the bearing and push it into the crank. Let is setup for a day or two and you are golden.

Tony Quiring · Dec 14, 2018

Visit a rebuilder where they may have junk cranks and buy one or examine it.

Practice in it to perfect your fix.

They make epoxy for hvac work that is very strong and high heat.

There could be a metric bearing or possibly use a 0.001 feeler gage stock as a shim and hammer it in.

There are many ways to address this, get a junk crank to play with to determine what option works.

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Lakeside53 · Dec 14, 2018

I'd use loctite 620. Gap filling and way better than just "epoxy"

MattiJ · Dec 15, 2018

Third and n-th vote for loctite. 620 or 638 if it is really loose.

IMO only use for knurling is in this case if the bore is so sloppy that the bearing wont center properly.

EmGo · Dec 15, 2018

Tony Quiring said:
Visit a rebuilder where they may have junk cranks and buy one or examine it.

If you know of a junkyard with Boss 302 cranks lying around, can you tell me where it is ?

Tony Quiring · Dec 15, 2018

Crank size is what you are after.

Back in the day we worked at automotive machine shop and cranks by the many.

Use Google to locate rebuilder.

In Fresno there is still one left...the one we worked at.

It had 40 folks then but all that remains now are the building with machines with the owner.

Lots of old stock still there.

Places like this could have crank for same size engine...boss 302 may have different material but dimensions likely same as others.

Do NOT ask for "Boss 302" crank as that means $$$, instead ask by the forging number or indicator of the crank as that is how they identify it.

Imagine 200 crankshaft standing on end in rows...

That is how they are handled and the forging marks on the crank combined with the "look" is how they determine what it is.

Never called them by engine size...

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David Utidjian · Dec 18, 2018

You could try a thing called a 'tolerance ring'. When I used to work on cars they were a fairly common and inexpensive way to "repair" an oversize bearing housing. I even used them with good effect on rear axle bearings. You can find 'tolerance rings' by googling for them or: USA Tolerance Rings - Home has lots of useful info. Obviously you will need a tolerance ring that will fit your bearing OD to the crankshaft pilot bearing hole ID. From your description the hole is now a bit tapered. It will almost certainly also be out of round and may not align properly with the crankshaft center-line anymore.

Other trick we used was 'peening' the bore of the housing. Basically using a sharp skinny center punch and making an even pattern of dings inside the part that will house the bearing. This accomplishes the same thing as knurling with results depending on how carefully it is done.

All that said... none of this will address the issue of why the bearing failed to begin with. Dust and dirt from the sintered iron clutch? Transmission input shaft bent or out of round? Imbalanced clutch/flywheel assy? Worn input shaft splines? Misaligned transmission to engine mounting? Since you mention that you want to get a couple more years out of the engine before tearing it down or replacing it it sounds like you are not actually racing the car all that often. Perhaps you should go back to using a standard clutch setup and enjoy about a decade of trouble free cruising. There is a reason why race engines are swapped in and out and rebuilt every race or four.

-DU-

n2omike · Dec 18, 2018

Thanks for all of the replies, guys. I appreciate it! I had already ordered the tool, and am still waiting for it to come in. Hopefully, I'll get it soon, and give it a try. I'll let you know how it goes. It comes with medium, straight knurls. I was thinking about getting some of the diamond shaped ones that were more pointy if these don't knurl enough.

The engine is still in the car. The pilot bearing coming out caused the input shaft of the trans to move laterally and break the bearing retainer. The bearing itself was still good. It just popped out of place. The bearing had been in place for years prior. Use of the car is 'horsepower therapy' on the street (thrashing and burnouts) as well as around 3 trips per year to the track. Car is a 1966 mustang. Pump gas 306, stock toploader 4-speed, 4.33 gear. Race gas and nitrous at the track. Best 60 ft was a 1.39 with a 6.29 @ 109 1/8 and 9.88 @ 136 1/4. I had just installed some lighter Wilwood brakes all the way around, and the transmission broke on the very next pass, after a 1.339 60 ft. lol (perfect conditions... cold weather and a sticky track in the late fall)

Anyway, there's some info on the car. I'll post a picture of the rear of the crank. It got beat up pretty good. I had staked the bearing, but it didn't seem to be enough. Thanks again!

WHHJR · Dec 19, 2018

The knurl will NOT survive without a Locktite bearing retaining compound. It may help center the hole in the crank, but that is all.

2¢

iwananew10K · Dec 19, 2018

IMO the knurl will just make a bigger problem.
Might as well just pepper the hell out of it with a punch and beat the bearing in.

As already said, loctite.

dlaw · Dec 19, 2018

I have never worked on a crank however I have fixed 25 or so 20000rpm $750.00 muffin fans with wallowed out aluminum housings with red Loctite. The bad fit was so bad that the bearing would just fall out of the housings. Clean everything up, use loctite PRIMER on both the bearing & the housing & reassemble. I waited 24 hours before balancing & starting the fan. I only had to scrap 1 fan.
Good luck

n2omike · Dec 20, 2018

dlaw said:
I have never worked on a crank however I have fixed 25 or so 20000rpm $750.00 muffin fans with wallowed out aluminum housings with red Loctite. The bad fit was so bad that the bearing would just fall out of the housings. Clean everything up, use loctite PRIMER on both the bearing & the housing & reassemble. I waited 24 hours before balancing & starting the fan. I only had to scrap 1 fan.
Good luck

Wow, Loctite PRIMER, eh? Never knew it existed! ....So, I Googled 'Loctite Primer' and they have all sorts of different kinds. I believe the most popular style of Loctite recommended has been the 620 Sleeve Retainer. If I go with a fresh tube of this, what type of primer should I use? All I've done in the past, is clean it really well with Brake Cleaner or Lacquer Thinner.

I believe I did use some Green Loctite last time, as you can see the remnants in the photo. Looks like it all stuck to the crank, and not the bearing. Will likely rough up the outer bearing surface a bit before installation this time.

Thanks Again!

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