Update on my broken cam
Thread Starter
Le Mans Master
Joined: Aug 2000
Posts: 6,362
Likes: 7
From: Brazos TX
Cruise-In IV Veteran
Cruise-In V Veteran
Update on my broken cam
Well I finally had the time to remove the engine so I could get the other half of the cam out. Here is what it looks like.
And here are close-ups of the break.
There is no evidence of a crack propagation/fatigue failure but I'm not sure how much information cast iron will give for such a condition. I will say that the cam bearings show evidence of overheating and the main bearings have cam bearing material embedded in them. So I will be changing all the bearings.
I'm debating if I should replace the rings while I'm at it. I'm happy to hear opinions on it. I will probably remove the pistons to change the bearings. The rings only have 15,000 miles on them so I don't know if I want to do that or not.
And here are close-ups of the break.
There is no evidence of a crack propagation/fatigue failure but I'm not sure how much information cast iron will give for such a condition. I will say that the cam bearings show evidence of overheating and the main bearings have cam bearing material embedded in them. So I will be changing all the bearings.
I'm debating if I should replace the rings while I'm at it. I'm happy to hear opinions on it. I will probably remove the pistons to change the bearings. The rings only have 15,000 miles on them so I don't know if I want to do that or not.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Check the ring end gap and that will tell you how much they are worn. If the gap is too big replace them.
Did your oil pump size to cause the shear break in the cam?
I would not have believed it till I saw this last year. I had a friend doing a small block and he called me up and told me that he couldn't fit the cam in. He didn't want to force it and tear up the cam bearings.
The Comp Cam was warped from one end to the other. He got it from local Summit racing and it could have been on a shelf with weight on it for a couple of years. They gave him a new one. But I got to thinking if you got one with less warp and managed to install it. It would just kill the cam bearings over time and maybe sieze up from bearing heat.
Cast cams are weak. If somebody ever dropped it it could have had a crack from day one and it took a hickup 15,000 miles later to break.
Did your oil pump size to cause the shear break in the cam?
I would not have believed it till I saw this last year. I had a friend doing a small block and he called me up and told me that he couldn't fit the cam in. He didn't want to force it and tear up the cam bearings.
The Comp Cam was warped from one end to the other. He got it from local Summit racing and it could have been on a shelf with weight on it for a couple of years. They gave him a new one. But I got to thinking if you got one with less warp and managed to install it. It would just kill the cam bearings over time and maybe sieze up from bearing heat.
Cast cams are weak. If somebody ever dropped it it could have had a crack from day one and it took a hickup 15,000 miles later to break.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Been there, done that. But mine was twice and the result of broken rods. Junked nearly everything. Block, heads, pan, and once even took a valve cover. When the tach needle goes all the way around to the "H" as in "TACH", crap happens. 
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
I missed the first post on this one. What brand of cam was it. I see comp cams above. That would suck big time. Could someone link up the original thread.
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
Holy crap!!! I am really starting to have second thoughts about my CCxtreme choice!
My cam did not slide into tthe block that easy. I am wandering if maybe it is warped. How would you tell?Did you have any valve to piston slap when that cam let go?
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
That's nice how it broke right in the middle: You can now use the cam in a 4-cylinder engine! Simply cut your block in half behind the first two cylinders, weld a flat plate onto the back to seal it off, re-install the cam and use a crank trigger ignition instead of a distributor. No problem! There's an easy fix to everything...
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Thread Starter
Le Mans Master
Joined: Aug 2000
Posts: 6,362
Likes: 7
From: Brazos TX
Cruise-In IV Veteran
Cruise-In V Veteran
Eddie, here is the link to my original post http://forums.corvetteforum.com/show...3&page=1&pp=20
BlackRat, at least three valves are bent and it looks like another one touched so I will replace all of those.
Yeah lars, I like that idea. Kind of like the Scat V-4 that is based on a small block chevy. I like easy fixes.
GDaina, I would expect to wipe lobes before snapping a cam. Besides, the springs where not very stout so I don't think that was the cause. All the lobes look really good as do the bottoms of the lifters. I'll be talking to Comp Cams soon and I'll let you guys know what they say.
BlackRat, at least three valves are bent and it looks like another one touched so I will replace all of those.
Yeah lars, I like that idea. Kind of like the Scat V-4 that is based on a small block chevy. I like easy fixes.
GDaina, I would expect to wipe lobes before snapping a cam. Besides, the springs where not very stout so I don't think that was the cause. All the lobes look really good as do the bottoms of the lifters. I'll be talking to Comp Cams soon and I'll let you guys know what they say.
