Cam upgrade: bottom end risk?
Thread Starter
Heel & Toe
Joined: Mar 2003
Posts: 19
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From: Belmont CA
Cam upgrade: bottom end risk?
Hi everyone,
At 146,000 miles, the original Optispark on my 1992 coupe finally gave up the ghost. I'm planning to replace it with a Dynaspark and was hoping to update the timing cover and put in the GM extreme duty timing chain while I'm at it. As long as I'm doing all this, a new cam and upgraded valvetrain seems like a good idea (in fact, a new cam is necessary for the longer dowel pin for the 1995 front cover upgrade).
Unfortunately, while speaking with tuners about their cam and valvetrain packages, one of them (with a good reputation on these forums) strongly cautioned against upgrading the cam on a 146k mile bottom end -- I was practically guaranteed to spin a bearing. I was told this is a problem endemic to the LT-1: spun bearings on cam upgrades.
I don't find any mention of this here on the forums, but I certainly don't want to sink the time and the money into this project only to have to pull it all back apart in a day or a week or a month.
Is this a legitimate concern? I road race the car, so it does see high-rpm duty, but I'm not an especially abusive driver (still original clutch). Would you be reluctant to upgrade the cam if this were your car?
Thanks!
Matt
At 146,000 miles, the original Optispark on my 1992 coupe finally gave up the ghost. I'm planning to replace it with a Dynaspark and was hoping to update the timing cover and put in the GM extreme duty timing chain while I'm at it. As long as I'm doing all this, a new cam and upgraded valvetrain seems like a good idea (in fact, a new cam is necessary for the longer dowel pin for the 1995 front cover upgrade).
Unfortunately, while speaking with tuners about their cam and valvetrain packages, one of them (with a good reputation on these forums) strongly cautioned against upgrading the cam on a 146k mile bottom end -- I was practically guaranteed to spin a bearing. I was told this is a problem endemic to the LT-1: spun bearings on cam upgrades.
I don't find any mention of this here on the forums, but I certainly don't want to sink the time and the money into this project only to have to pull it all back apart in a day or a week or a month.
Is this a legitimate concern? I road race the car, so it does see high-rpm duty, but I'm not an especially abusive driver (still original clutch). Would you be reluctant to upgrade the cam if this were your car?
Thanks!
Matt
Race Director
Joined: Nov 2000
Posts: 17,103
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From: stop the fun suckers
Re: Cam upgrade: bottom end risk? (Matt Dusek)
When I took my motor apart at 140k miles the main bearing looked BRAND NEW. Very little wear.. nothing into the babbit at all. The same could be said for my rod bearings. However, The cam bearings had heavy wear and were a cause for concern. I wouldn't slide another cam into those bearings.. however, I would have had no fear about the mains.. I probably have pictures I can post.. I'll look see..
Team Owner
Joined: Sep 2003
Posts: 25,295
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From: I'm the walkin dude I can see all of the world...
St. Jude Donor '03
Re: Cam upgrade: bottom end risk? (Matt Dusek)
This is the exact same thing I am considering now. I also have a 92 with 143K. I am considering the Hotcam and 1.6 rr's. Right now the car is running better than ever. I will guarentee the car is still performing like a 30K motor. Dyno proven results are coming soon!
Interesting about the cam bearings... Anything that could be done about that?
[Modified by VictorRussell'92, 11:34 AM 6/25/2004]
Interesting about the cam bearings... Anything that could be done about that?
[Modified by VictorRussell'92, 11:34 AM 6/25/2004]
Safety Car
Joined: Sep 2002
Posts: 4,030
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From: Maryland
Re: Cam upgrade: bottom end risk? (Matt Dusek)
Matt,
I want to suggest to you that you could put on a Meziere Heavy Duty Waterpump and another HD timing chain (not the GMPP) for the same price as the mechanical pump and the GM Extreme duty kit. Talk to Nathan Plenoms here. I sort of wish i had.
I did just what you are suggesting, except my car had 74k on it and I was not cautioned about the cam bearings. I replaced the opti and waterpump out of convenience while on the cam/head job.
I want to suggest to you that you could put on a Meziere Heavy Duty Waterpump and another HD timing chain (not the GMPP) for the same price as the mechanical pump and the GM Extreme duty kit. Talk to Nathan Plenoms here. I sort of wish i had.
I did just what you are suggesting, except my car had 74k on it and I was not cautioned about the cam bearings. I replaced the opti and waterpump out of convenience while on the cam/head job.
Race Director
Joined: May 2001
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Re: Cam upgrade: bottom end risk? (Matt Dusek)
There have been issues with spun bearings after installing a cam in an LT1. I've never seen it personally but apparently it's pretty common. I believe that if your motor is healthy to begin with you'll be fine.
Team Owner
Joined: Sep 2003
Posts: 25,295
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From: I'm the walkin dude I can see all of the world...
St. Jude Donor '03
Re: Cam upgrade: bottom end risk? (Nathan Plemons)
There have been issues with spun bearings after installing a cam in an LT1. I've never seen it personally but apparently it's pretty common. I believe that if your motor is healthy to begin with you'll be fine.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: Cam upgrade: bottom end risk? (Matt Dusek)
I suppose either too much cylinder pressure or too high in RPM could cause a spun bearing.
So long as you don't spin your engine above red line with the new cam you should be fine. The increase in cylinder pressure shouldn't be enough to cause that problem alone.
So long as you don't spin your engine above red line with the new cam you should be fine. The increase in cylinder pressure shouldn't be enough to cause that problem alone.
Le Mans Master
Joined: Jul 2000
Posts: 5,012
Likes: 5
From: OKC OK
Re: Cam upgrade: bottom end risk? (Matt Dusek)
Is this a legitimate concern?
I'm in the process of changing cams again (yes, I'm
) and I'm a little worried about the cam bearings.
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Drifting
Joined: Jun 2001
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From: Lake Ozark MO
Re: Cam upgrade: bottom end risk? (Matt Dusek)
Ahh, the infamous "spun bearing after cam change".
You'll see this posted relentlessly on http://www.camaroz28.com
I'll bet my cookies that it's mostly based on poor assembly practices and the inevitable rpm increase that follows a cam change. Couple this with higher mileage engines and you have a consistent recipe for failure. There is also the percentage of "bound to fail regardless" engines that GM's slop house is likely to produce.
Perform your cam change with a good eye towards detail and you'll be fine. Although at your mileage I'd yank the engine and do the whole re-ring/re-bearing job. My LT1 looked positively new at 105,000 miles during tear down but I gave it new wear surfaces anyway.
You'll see this posted relentlessly on http://www.camaroz28.com
I'll bet my cookies that it's mostly based on poor assembly practices and the inevitable rpm increase that follows a cam change. Couple this with higher mileage engines and you have a consistent recipe for failure. There is also the percentage of "bound to fail regardless" engines that GM's slop house is likely to produce.
Perform your cam change with a good eye towards detail and you'll be fine. Although at your mileage I'd yank the engine and do the whole re-ring/re-bearing job. My LT1 looked positively new at 105,000 miles during tear down but I gave it new wear surfaces anyway.
Race Director
Joined: Nov 2000
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From: stop the fun suckers
Re: Cam upgrade: bottom end risk? (VictorRussell'92)
Nathan is there any way to check the cam bearings, short of a full engine teardown and rebuild?
