timing gear pin killed another good engine!

Two weeks ago during first round of eleminations cam pin broke on the lunati cam, dropped an exhaust valve and bent several others. Most of the piston, rings and cylinder wall came out the header! This was the 557 in my t-bird. I first thought of what was once said about cam journals being too tight, not the case. The cam spun very freely in the coated durbonds, and had no visible wear or scaring of the cam bearings. The snout of the cam was ground down for correct clearence, bolt was a grade 8 torqued to spec with a sbc balancer washer behind it. I knew better then to use a cam with only one pin and a 3/8 bolt but the ultra wise guy at Lunati assured me that he never had one break. Bullshit, he must have been thinking of some pos sbc with an rv cam. I called lunati to see if they could drill out the bolt hole to 7/16 and drill out the broken pin and drill for the extra pin he said they could not. Then he told me to call bullet. Now that is service. I didn't ask for a freeby because I knew better than to use that cam but I was in a hurry to race as usual. I will be putting the smaller cam motion stick in this engine that I am putting back together.

I bought a cam from Lem ...it came double drilled with a big ol bolt in it...drilled the timing chain gear too.

Had a local machine shop do the last one and cam gear at same time cost me $30.

Got me nervous now. Comp cam single pin.

Wouldn't take much to pull it out to have it fixed...Might be worth it.

I had that happen once also. Luckily I was idling but I still bent 8 intake valves. I found that my ARP bolt was few threads too long so when I torqued it I wasn't getting a good reading. My new cam I ordered from Lem. He sent my cam gear to comp and had them double pin it and tap it for 7/16" fine thread.

I thought about pulling mine out over the winter several times. It was alot more painful pouring a piston and a cylinder out the header!

Try this shop. In the Owensboro, KY area.

www.jetboatbob.com

I made a jig and do my own.

512Fairlane wrote:I had that happen once also. Luckily I was idling but I still bent 8 intake valves. I found that my ARP bolt was few threads too long so when I torqued it I wasn't getting a good reading. My new cam I ordered from Lem. He sent my cam gear to comp and had them double pin it and tap it for 7/16" fine thread.

Most I have seen break were idling. Kind of like running over a speed bump in a parking lot at low speed it moves the suspension more.

512Fairlane wrote:I had that happen once also. Luckily I was idling but I still bent 8 intake valves. I found that my ARP bolt was few threads too long so when I torqued it I wasn't getting a good reading. My new cam I ordered from Lem. He sent my cam gear to comp and had them double pin it and tap it for 7/16" fine thread.

Relative to 'too long' bolts....I had the same luck with a high dollar ARP crank bolt/washer kit....a little too long for the bolt lenght. Luckly I caught it during the install. Just because it came from ARP don't make it correct.

I try to always add "7/16" bolt please" to all of my solid roller cam orders from CompCams. Cam grinders buy the cores from a few different suppliers and a lot of the cores have a 3/8" thread. I've never had Comp charge extra for the 7/16" request but, one will have to call out and pay for the dual pin option.

Another thing is....if you are doing an engine with a new cam and adding a D. Bee belt drive kit...request that the cam company dual drill and leave the 2nd pin out and install the 4340 pin that is provided with the kit.

If the 2 pin holes in cam and timing set is same size how u now which way to install them?

bigjohn2007 wrote:If the 2 pin holes in cam and timing set is same size how u now which way to install them?

When correct....both valves should be closed at TDC at # 1 cyl.

I've seen a guy engrave a note as which was the orginal pin.

rmcomprandy wrote:When I order a roller cam, I request a 7/16" threaded snout however, some still get to me with thread for a 3/8x16 bolt. When I get those, I drill and tap them for a half inch thread so even more bolt holding torque can be used.

One 3/8" bolt just won't apply enough holding strength for high spring pressure, even with a double pin.

That's a fact..................

So with my new motor having a solid roller cam in it. I should check thus before I run it. It is a lunatic cam.

bronco wrote:So with my new motor having a solid roller cam in it. I should check thus before I run it. It is a lunatic cam.

Yes, I have seen them run and not break but, I have seen a bunch break also. As for me it's not worth the gamble..............

What do you use to hold the cam from turning while tightening the bolt? I just stuffed a rag between the chain and gear, but it didn't seem like it was the professional way to do it.

Put something throw hole in the gear and wedge it against the block so it want turn.

I use a wrench to keep the crank from turning with one hand and tighten the cam bolt with the other hand.

IDT-572 wrote:

bronco wrote:So with my new motor having a solid roller cam in it. I should check thus before I run it. It is a lunatic cam.

Yes, I have seen them run and not break but, I have seen a bunch break also. As for me it's not worth the gamble..............

Definitely not worth the gamble. Mine didn't let go right away I had several runs on it. Grade 8 7/16"-20 bolt torqued to 70 ft. lbs. is much better than 3/8"-16 torqued to only 45 lbs. imo. An engine is only as good as its weakest link. You can tear up a lot of sh#t when that happens.

wow, didnt know this was happening. I should have my roller cam for my 420 SBF that bullit is going to grind me double pinned and 7/16 bolt added to that to ya think?

stanggt wrote:wow, didnt know this was happening. I should have my roller cam for my 420 SBF that bullit is going to grind me double pinned and 7/16 bolt added to that to ya think?

It wouldn't hurt!

Has anyone had one to break both pins ?