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Broken dowel pin in timing gear

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MarkJ
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airford1
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Broken dowel pin in timing gear  Empty Broken dowel pin in timing gear

Post  airford1 January 26th 2020, 3:43 pm

Decide to freshen up my engine and the cam/timing gear had a broken dowel pin. Single pin broke in 3 pieces with one piece still recessed in the cam. Can anyone tell me why this happens? I guess I will have to drill in out of the cam to save that.
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Post  pmrphil January 26th 2020, 5:52 pm

3/8 bolt or 7/16? I would think not quite enough clamp load, or the bolt got loose. I've done a few with double pins.

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Post  airford1 January 26th 2020, 6:38 pm

Phil do you do engine at your shop?
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Post  MarkJ January 26th 2020, 6:43 pm

I wish I had your luck. That was the first thing that got me when switching from small block in 88. My single pin broke at the top of low gear. It took out every valve and push rod, fortunately the cam and lifters were good. Since then I always double pin them, suggest you do the same. Mark J
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Post  pmrphil January 26th 2020, 6:45 pm

Yes sir. The 3/8-16 cam bolt doesn't (I believe) provide enough clamping force for an aggressive roller. The 7/16-20 is a good option, but double pinning will prevent breakage.

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Post  airford1 January 26th 2020, 7:57 pm

MarkJ wrote:I wish I had your luck. That was the first thing that got me when switching from small block in 88. My single pin broke at the top of low gear. It took out every valve and push rod, fortunately the cam and lifters were good. Since then I always double pin them, suggest you do the same. Mark J
Dont know how lucky I am. I thought I was ready to go racing and noticed the water was low in the radiator with nothing in the overflow. Bingo the oil had a discoloration and was high. Water in the oil and it's not a head gasket. I may be lucky if I only have to polish the crank , new bearings and re ring. I think the water came from the intake gasket being crushed with RTV compound letting it deform the felpro slip all over.
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Post  MarkJ January 26th 2020, 8:45 pm

In an effort to make you feel better, at least you were not wheels in the air pulling second gear at just the moment you ran over your oil filter. Kicked a rod thru the svo block, putting 15 quarts of valvoline on the track. I shut the track down for a while. I am sitting in the trailer pondering getting a junk yard engine just so I can race when one of the track guys brings me my rod bolt with the threads from the trick of the week aluminum billet rod still in it. Should have stayed with howard rods and I would still be running that combo. Moral of the story, let someone else try out tge trick of the week. Mark J
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Post  rmcomprandy January 27th 2020, 12:38 am

pmrphil wrote:Yes sir. The 3/8-16 cam bolt doesn't (I believe) provide enough clamping force for an aggressive roller. The 7/16-20 is a good option, but double pinning will prevent breakage.

Even double pins will shear if the bolt torque is not enough and valve spring pressure is high.
Personally, I will only use roller cams having 7/16-20 threads and then use a rod bolt that torques to 90 foot pounds for retention. Be sure to use a thick, hardened washer, like an ARP 200-8717, too; (a one piece FE eccentric works well, also).

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Post  Gregaust January 27th 2020, 3:17 am

[quote="airford1"]
MarkJ wrote: I think the water came from the intake gasket being crushed with RTV compound letting it deform the felpro slip all over.

Those junk Felpro gaskets Sad . I went to Victor Reinz Intake gaskets many years ago now and haven't touched since ..

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Post  Dave De January 30th 2020, 10:49 pm

rmcomprandy wrote:
pmrphil wrote:Yes sir. The 3/8-16 cam bolt doesn't (I believe) provide enough clamping force for an aggressive roller. The 7/16-20 is a good option, but double pinning will prevent breakage.

Even double pins will shear if the bolt torque is not enough and valve spring pressure is high.
Personally, I will only use roller cams having 7/16-20 threads and then use a rod bolt that torques to 90 foot pounds for retention. Be sure to use a thick, hardened washer, like an ARP 200-8717, too; (a one piece FE eccentric works well, also).

This is same as the SBC crankshaft end bolt and washer. I feel better with a little loctite on the threads.
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Post  The Mad Porter February 1st 2020, 4:39 pm

I second Randy M's comment.

We did a Boss 345 deal not too long ago with an XM HR grind, double pinned and no FP eccentric. A two piece fuel pump eccentric didn't help.

Without a 1 piece eccentric the flimsy ARP washer included in the 1001 bolt kit was deflecting and would not apply the necessary clamping pressure to keep the cam gear from moving ever so slightly.

In this particular case a thick larger diameter washer from a SBF finishing kit and the ARP bolt solved the problem with or with out an eccentric.

The heavy washer from an FE finishing kit works well for the SR and HR cams that require the 7/16" NF bolt.

That ARP washer is SO from our local supplier EPWI

Good info Randy. Thanxx.



SJ
used 2b RHP


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