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Bad Camshaft


dirty dan's Avatar
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04-20-04, 05:14 AM   #1  
Bad Camshaft

'89 R1500, 5.7 TBI, 700R4 (Yeah, I'm still fighting with it!)

Starting to suspect bad camshaft on this engine. What would be symptoms of worn lifters or camshaft? Is there any way to verify without dial indicators or pulling the camshaft?

 
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04-20-04, 08:13 AM   #2  
the best way is...

...with a dial indicator on the pushrod. you can also use a vacuum guage, but it's not as accurate. with the vac guage connected to manifold pressure source, try blocking the idle air passage off to get the idle speed as low as possible. under 500 would be good...then watch your vac guage, if you have a bad lobe/lifter, you'll see the guage needle flick everytime that valve is actuated.

 
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04-20-04, 02:48 PM   #3  
I would think you'd reflect that in the compression also if it's bad enough.

 
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04-21-04, 04:56 AM   #4  
Thanks for the advice, I'm going to start on it this evening. I'll post back and let you know what I found.

 
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04-21-04, 12:57 PM   #5  
Another maybe...
What symptoms would I have if the 5.7 engine had a camshaft from a 5.0???

 
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04-21-04, 03:12 PM   #6  
Dan could you start again at square one.State the vehicle(r1500?)and the problem you are having plus the repairs/tests you have done so far.I went back through some of the posts and got tired of trying to match things up to the current post.That will give us all a clean slate and fresh outlook.Thanks.

 
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04-22-04, 04:58 AM   #7  
lack of power...

...due to difference in lift.

305 CID
intake lift...(.2484)
exhaust.....(.2667)

350 CID
intake lift...(.2600)
exhaust.....(.2733)


you can measure this with a dial indicator or remove the cam and measure the base circle , then the lobe, then subtract base from lobe and this will give you lift

 
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04-22-04, 07:06 AM   #8  
OK, but remember you asked! '89 R1500, 5.7 TBI
This is the burb that has no top end power when base timing is set correctly. If I advance the base timing, I get better (not great) highway power but the idle really sucks. If I put it in open loop while timing is advanced, the idles smooths out a bit.
This was an AZ Series II Engine (I know, first mistake), I put in a Crane R/V camshaft when installing the engine. Engine ran poorly from start, then we realized that the timing cover (including marks) were wrong. The O timing mark was straight up 12 o'clock (had to look behind the water pump) rather than @ 2 o'clock. The AZ builder had put what I assume was 305 timing cover on the block. (rechecked the block ID and it is a 5.7). AZ payed for this fix. The engine ran fine until the weather warmed up (Running a Cool T-Stat in South Louisiana). Then the engine began coding (knock sensor) when it would go into closed loop, and power would go to zilch. Put a scan tool (flight recorder) on it, and scan was not showing a knock when the ECM would code. Brought it to a local shop and they played with it for a while. Finally got GM involved and found out that the ECM would try to self test the EST when moderate acceleration, temp > 203F, and closed loop. This test advances the ignition timing until it creates a knock, then pulls back. GM determined that with the R/V camshaft, the EST advance could not create a knock where expected so it would let go of the ignition timing thus putting it back down to base @ 0 deg.
I told the shop to put the AZ furnished camshaft back into the engine. ( I should have had a chip programmed instead, 20/20 hindsight) I returned the Crane cam back to the parts store. Basically, the engine has not run correctly since. It can be tweaked to run better, but the power's not even close to my '91 5.7 Burb. I think Desi or Davo was correct earlier when saying the playing with the ECM devices are masking the real problem. Several shops have looked at this engine, all have given up. I'm at the point where it's a personal thing now.
I'm thinking now, that maybe since the wrong timing cover was installed, the wrong camshaft went along with it. I ran a vacuum check yesterday afternoon (connected to EGR port) with the timing set to spec, idling around 550, I'm getting @ 16 to 17" with a very fast back and forth movement on my needle. Additionally, every 2 seconds or so, I'll get a dip down to 15" with the same 1" quick variation. The engine sounds like it's missing during the dip to 15".
I ordered a dial indicator from Grainger this morning and will read off of my push rods this weekend.
Any Thoughts?

 
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04-22-04, 02:59 PM   #9  
I don't know if I said this before but I bought a 350 target engine from GM and had no power.I knocked myself out trying to figure it out.I decided to pull the timing cover off again(I took it off to make sure the marks were right the first time).This time I removed the gears and compared them to a set from an engine that ran properly.I found that the cam gear was marked 1 tooth off at the factory.A new cam gear fixed the problem.Just some food for thought.

 
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04-22-04, 03:11 PM   #10  
Posted By: dirty dan I ran a vacuum check yesterday afternoon (connected to EGR port) with the timing set to spec, idling around 550, I'm getting @ 16 to 17" with a very fast back and forth movement on my needle. Additionally, every 2 seconds or so, I'll get a dip down to 15" with the same 1" quick variation. The engine sounds like it's missing during the dip to 15".
That's not a good sign

 
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04-22-04, 06:09 PM   #11  
Compression Checked This Afternoon

Cylinder Read
1 148

2 140

3 148

4 140

5 148

6 139

7 145

8 145

Plugs were as clean as a whistle. My manual doesn't say what to expect for compression except that < 100 psi is bad and that all should be within 70% of high read. I bought my dial indicator/mag base today. I'll try to read tomorrow PM or Saturday and post results.
That's the first I've heard of your experience Davo. What brand gears did you replace it with??? I'm gonna replace the chain and gears when I get in that far. Factory manual says I have to pull the motor mount cross bolts and raise the engine to pull camshaft. Doesn't look like it to me. Any experience with this???

 
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04-24-04, 07:04 AM   #12  
Davo,
What problems did you have when your timing mark was off?

 
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04-24-04, 02:11 PM   #13  
Lack of power and a poor(floating) idle,it kinda bites that it took me a while to figure it out.Who would expect that though?

 
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04-24-04, 09:44 PM   #14  
Yanked the camshaft out today, haven't measured it yet. Looks pretty bad to me. It has some wear on the cam lobes up to 1/4 way across the flat. Broke a crank gear tooth so I will surely have to get the set to replace. Davo, what brand did you buy to replace your DELCO gear?

 
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04-25-04, 05:09 AM   #15  
I don't remember but it was a name brand the parts house had.I think it was Cloyes though.

 
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