Cummins 4BT-6BT Dowel Pin Repair

[JimmieD]

I'll post a few pics of my method to repair the 'Killer Dowel Pin' on Cummins timing gear case.

[JimmieD]

Pic showing dowel pin location was too large so please see following attachments.

[JimmieD]

Third attempt at pictures. If it works the first shows the locking tab I fabricated and the second shows it locked in place in timing gear case.

[MoparNorm]

According to Gordon, your pictures should not link like that, so remove them immediately! ha!ha!
HEY, you have thumbs....= )
MN

[JimmieD]

Had lots of trouble posting pics and it turned out it wasn't me! this website's software was glitching and giving me a real hassle. I tried to post pictures straight up in the thread replies but couldn't figure that one out from the available options displayed. Maybe someday? Maybe not.

Oh, and those aren't my thumbs. I gave a wino 5$ to hold the screwdriver for the picture. Had to click quick to catch him between delerium tremens as no juice 'til the pictures were done and he was paid... :~ (

[rcts]

I don't understand what's wrong with the pin?

Guys, can you expain what was happening, have some members lost engines or gears due to this problem.

Thanks.

Reg

[JimmieD]

I posted this in response to the earlier thread regarding Cummins conversions. I should have posted more text here!

The 'Killer Dowel Pin' is an alignment dowel used during manufacturing of Cummins 4BT & 6BT for correct positioning of timing gear case. Unfortuantely the pin is just a wee bit small for the bore of the hole it is pressed into. As you can see by the location of dowel pin it will fall directly into timing gears if it slips out. Hasn't happened 'here' as such, but there's pics of catastrophic damage on other forums!

This repair is very easy once the timing belt and case cover are removed. There's a kit available for $50 to fix the problem but being the kind of guy I am I found another way that's cheaper: FREE! Not just that, but the kit features a flat retainer tab and on some Cummins like my 4BT, that tab won't work because of unequal surfaces inside gear case. Therefore I present to you the NEW AND IMPROVED DOWEL PIN REPAIR brought to you by JimmieD hisself, plus a contribution by a kindly but shaky wino.

All bolts in the timing gear case including the one which retains the NEW AND IMPROVED DOWEL PIN REPAIR DOWEL PIN RETAINER shown should be removed, thread bore and bolts cleaned, and have thread locker such as Loctite or Permatex PX27100 applied. Several of these can come loose and could possibly fall in timing gears during operation. Not a prety sight I'm told. The bolt shown had about 2-3 ftlbs torque on it, and one of the others was less than finger tight on my engine!

Due to Research and Development costs, rigorous Field Testing Procedures and the escalating price of Mad Dog 20-20 the JimmieD NEW AND IMPROVED DOWEL PIN REPAIR KITS are priced at $481.52 plus $198.41 shipping, with average installation charges at our State of the Art [that's the wino's name in case you were wondering] Shop running $3,571.62. For $4,000 even, me and Art will even include an oil and filter change and wash the windshield if your vehicle has one....

Hurry in today for this once in a lifetime discount pricing!

[rcts]

Thanks JimmieD, I will check this out on mine when I have the engine out of the 92

Scary stuff,

Reg

[Cheyenne Dave]

Hey Jimmie...

The alignment dowel actually came out in my engines case. Due to the rotation of the engine and timing gears, the pin got wedged between one of the gears and the case itself, thus breaking out the wall of the case itself. No damage to the gears at all.

My repair consisted of repairing the breach in the case and discarding the dowel. 80K later, no leaks, no problems of any kind.

[Gordon Maney]

I think I have read that this is a problem only in certain model years. Is that true?

Jimmie, the new deal where the forum is supposed to resize automatically may not be without bugs. If you do one at 125k or below it should work without flaw. Try that....

[Gordon Maney]

The alignment dowel actually came out in my engines case. Due to the rotation of the engine and timing gears, the pin got wedged between one of the gears and the case itself, thus breaking out the wall of the case itself. No damage to the gears at all.

My repair consisted of repairing the breach in the case and discarding the dowel. 80K later, no leaks, no problems of any kind.

So, to verify, you are running with no dowel at all, is that correct?

[...welcome back; long time no read.

[JimmieD]

Apparently the dowel pin serves no direct function except alignment at assembly as far as I know. Problem is there's no way to grab hold of it unless it's already worked its way out somewhat. Magnet won't necessarily do it.

There's another new post on another forum by a guy who just trashed his engine when it fell into timing gears. It's also imperative to remove, thoroughly clean and Loctite all gear case mounting bolts. One of mine was less than finger tight, another had maybe a few inch/lbs on it! Rhymes with KABLOOEY!

[Cheyenne Dave]

In reply to Gordon

There is more than one alignment dowel aligning the timing case to the block, I believe there is a total of 3. They are there to provide precise alignment of the case to the front of the block during initial assembly. The remaining dowels and the mounting bolts seem to hold everything in place just fine. I have talked to the head truck mechanic at the local dealer here and he has seen this problem several times. Each time the results were the same.

Due to the rotation of the engine, this particular dowel will fall into the gears in such a way that it will be spat out rather than get sucked in. In my case, it was forced between one gear and the wall of the case, right under the water pump pulley, and cracked it. There was no damage to the gears, and given the clearance between the case cover and the gears, I don't see how the dowel could have gone anywhere else. However, I suppose anything is possible.

Sorry for my lengthy absence...still suffering computer problems.

[JimmieD]

Welcome back and hoping you win the battle against the blasted electronic gremlins!

Hate to disagree but I've read posts from guys and have seen the incredible damage that can occur from that dowel pin falling between the crank gear and cam gear. Evidently it can fall and fit between gears under the wrong circumstances. Far as I know it is just the one that is able to fall out, as that's the only one I've ever heard mentioned. Maybe the others are behind gear faces or something?

I did find that one of my case attachment bolts wasn't even finger tight, and 2 oil pump bolts were maybe held by a couple of pounds torque if that. From the looks of things it appears some of the case bolts can fall into gears and I've read posts saying they have. Therefore I cleaned and applied Permatex Thread Locker to all I could get to. Better safe than sorry?

Lastly, it seems that on some trucks the dowel pin is a tight fit while on others it's barely retained in the block. Don't know on mine, and it looked okay, but I tabbed it anyway.