Cam lobe going flat?
Thread Starter
Safety Car
Joined: Apr 2001
Posts: 4,795
Likes: 1
From: Regina Saskatchewan, Canada.
Re: Cam lobe going flat? (SprintCarDriver)
The engine had all kinds of power until the day it came apart but it seemed to fall off during the end. I think most of the power loss came from the rings but that one lobe doesn't have the same shape as the others. There is a couple more just like it too. This cam saw alot of valve float, I think that's where it came from.
[Modified by Stingy74, 10:08 PM 11/18/2001]
[Modified by Stingy74, 10:08 PM 11/18/2001]
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Cam lobe going flat? (Stingy74)
Usually when a cam lobe wears flat, it gets almost round very quickly. Only the outer surface on cams is "flame hardened" and once that wears off the cam is soft and wears flat (or almost) in a few miles. To check the wear, put the cam between centers or on "V" blocks and set up a dial indicator to measrure the lobe lift by rotating the cam. Multiply this figure by 1.5(rocker ratio) and compare the reading to the valve lift specs. of the cam. To get a good reading you need a marble surface plate and a GOOD dial indicator. :chevy
Drifting
Joined: Aug 2000
Posts: 1,758
Likes: 4
From: Medford, Or
Re: Cam lobe going flat? (Stingy74)
It looks like your #7 intake lobe is going flat. How many miles do you on your cam and how did the lifters look? When I pick up my current Vette from the auction about two years ago the original engine had a bad lifter noise. I bought the Vette cheap. When I got the Vette home I remove the valve cover and found the #7 exhaust lifter was making all the noise. I push down on the lifter and the lifter noise went away. Bad Cam! The cam only had 98,000 miles on it and had around 9 bad lobs with a few dished lifters. The factory must not have broken in the cam property.
Dan
Dan
Tech Contributor
Joined: Aug 1999
Posts: 14,376
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From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Cam lobe going flat? (silvervetteman)
silver is right: When a lobe starts to go, it becomes completely round very quickly. It will also completely trash and mushroom/concave the bottom side(s) of the lifter(s). I have had 2 Vettes round off cams so far. In both cases, the lobe went round almost immediately, and in both cases I had to remove the lifters by tapping them down through the lifter bores.
The right way to check the cam is as silver states. You can get a rough indication of a problem by simply taking a dial indicator to the major diameter of the lobes and comparing measurements from one lobe to the next (accounting for intake and exhaust lobes on a dual pattern cam).
The right way to check the cam is as silver states. You can get a rough indication of a problem by simply taking a dial indicator to the major diameter of the lobes and comparing measurements from one lobe to the next (accounting for intake and exhaust lobes on a dual pattern cam).
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5th Gear
Joined: Nov 2001
Posts: 5
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From: Whittingham Lancashire
Re: Cam lobe going flat? (Stingy74)
Bought a '80 305 ci California vette last year and the backfiring through the carb on full throttle was bad. Stripped the motor and 3 lobes (intake 6 and intake and exhaust 8) were round as could be with no lift. The motor was running on 6 almost. No easy way, new cam,lifters,timing chain and gears did the trick. :rolleyes:
