Had my '89 350 GMC serviced and mechanics told me I had a worn camshaft. Said it's a big job because of how the engine sits in my van - lots of parts they have to remove to get at it. They can't do it for a few weeks.
The thing is I was planning on driving it from Melbourne to Kangaroo Island next week for a ten day round trip. In the 15months I've owned the van I haven't noticed anything different with it and done lots of long trips - one recently to Alice Springs without problems. Mechanics told me engine has excellent compression - if that makes a difference.
Should I risk driving it, keeping in mind I will be on highways most of the time?
Worn camshaft, the only way these wear to the point the hard facing surface starts to break up, then it can become an issue.
Did he say the cam lobes were pitted?
Ask that, if he says yes, ask how big are the pits, if just small, then it shouldn't cause to much of a drama until you can get it sorted.
If no pitting, then its fine to use, but I would question how they calculated its worn?
I would guess he can see some heavy wear tracks in the lobe surface I suspect.
They say getting at the camshaft is the problem. It's a van and 80% of the engine sits under the cabin. To get at it they have to get in from the front. I know myself there is no room there, which means removing lots of bits and pieces. On a van it's a big job.
They believe that either the cam lobes are worn or maybe the bearings. They just serviced it and say the engine missing. I've never noticed anything different myself since I've owned it, but will have a listen to it more closely today.
I've got no reason to doubt them, as they just had a 70s chevy in that needed the whole engine replaced because of this same issue.
I've done thousands of miles myself in the van - mainly on long trips. I clocked the odometer in October (100,000) miles when I drove to Alice Springs. Odometer now reads 2474 miles.
Have he visually inspected the camshaft if is that hard to reach it in the first place? Is it a 4L, V6 or V8 engine?
If is it a OHC (Overhead Cam) engine it is just below the head covers, not hard to reach at all. I am not familiar with you van but it would typically involve removing the air intake, air filter, throttle body, head covers, sometimes the Alternator, Alt Stand etc are also in the way to reach it.
If it is a V engine you can double that (two head covers, etc). Large engines (specially V) fitted in vans have a ****load of items packed closed together. Maybe a day's work to pull stuff out until they reach the camshafts (I guess they are professionals).
Apart from an excessive clearance at the bearings (resulting in a oil pressure drop across the whole engine that would/could hurt your crankshaft mains and connecting rod bearings), and wiped cam or bearing problems could result in wobble at the valve train operation, flat spot during accel among a myriad of other problems.
If it is a good engine with good compression, I wouldn't push it through that kind of journey and would get it fixed properly before hammering it.
If you love the car, spend a few hundred with a rental car for that journey and get yours fixed. If you ruin your crank, pistons, etc while giving it a go your problem with get exponentially more $$$ to fix from the current point.
It's a 350 V8, it's not an overhead cam. I think the camshaft runs straight through the upper middle of the engine block. I can't even see the engine block when I open the hood. So full of other stuff. One good thing is that you can remove the spark plugs from inside the cabin.
To get at the camshaft they are going to have to remove the grille, radiator, air con and all the other bits sitting in front of the block and access it from the front. They say pulling out the engine is a whole other issue with vans - and I believe them. They wanted the van for a week and mentioned a figure of 3K. I've used these mechanics for 10 years and they do this sort of work on these types of cars all the time - they are always busy.
Yeah, I think you are right, not worth taking the risk, by driving it and potentially causing worse problems.
From a classic V8 block, removing the cam can be considered a task for a proper engine rebuild. You need to pull the whole engine out anyway.
So it is clear the mechanics didn't visually inspect it at least for this stage. Installing a new camshaft will require need bearings anyway, which are also a good deal to pull them from the case and to install the new ones. Normal mechanics normally don't touch that and outfarm it to engine rebuilders.
With the engine out, is probably worth changing the crank main bearings, con bearings, oil pump, rear main seal, timing chain/belt pull and clean thoroughly rockers, rocker shafts, pushrods etc.
Engine is not coming out - they are reluctant to do that right now.
When I look at how the engine sits in the van - 80% of it sits under the cabin - I get it.
Have a look in you tube videos what entails to pull a camshaft out a V8. Some come out very easy, some don't.
I didn't think of this. Some people pull them out of the passenger door, it's recommended doing it from the front - but there is little room. I can understand why my mechanics don't want to pull my engine out to change the camshaft.
If it's the original engine it will have a roller cam not a flat tappet like the 70s chev. It will be very noise if the roller lifters are worn. Squealing chirping etc, it won't just be missing a bit when idling. I think you're mechanics are getting it mixed up, get a second opinion.
edit* your van should have a roller cam and not a flat tappet due to the age of van, the symptoms will be slightly different if they are worn. But it's not possible to tell based on the available info.
Yeah, that's interesting. I think chevy changed to roller cams in 1987.
Reading through some forums, it seems worn flat tappet cams are common in chevs now, because of the different oils that were used since the late 80's and the symptoms for a worn cam are similar to what I've got, missing at certain revs, slight popping at the exhaust/inlet etc. Although, I can't say I've ever noticed it.
I also think my van lacks power - but it's always been like that and I know it's geared for towing, so I don't know for sure.
I think I'll just trust my mechanics instincts. Seems like worn cam can only be diagnosed by pulling it out. To pull it out they have to remove the frontend of the van. If the cam's good, then it's another problem and they are halfway towards pulling the engine out. If the cam is bad then they replace it. Kind of makes sense to me.
fair enough, if that's what you planning to do, in answer to your original question, no I wouldn't drive around in it till its fixed. if a cam lobe is wiped out then tiny bits of metal will be wearing out your bearing and bores and everything else inside your engine.
Select to expand quoteadolf said..
I think I'll just trust my mechanics instincts. Seems like worn cam can only be diagnosed by pulling it out. To pull it out they have to remove the frontend of the van. If the cam's good, then it's another problem and they are halfway towards pulling the engine out. If the cam is bad then they replace it. Kind of makes sense to me.
What needs consideration with jobs like these is the $ invested to just replace camshaft, bearings and followers, while everything else remains as it was. I would be investigating the cost of having a long crate motor fitted.
I did suggest that - replacing the engine. They said they'd prefer to look at the cam shaft first. Compression was all good. They told me they drove around in it with the cover off the engine in the cabin. I reckon during the service they hit some sort of issue trying to tune it, and drawing from their experience with these engines suspected worn lobes. I guess I'll soon find out.
How will they hold the lifters in place (preventing them dropping inside the engine) without removing rocker shafts to release spring pressure from pushrods, and also remove the intake manifold to be able to hold the lifter ends from the top?
They will have to still pull out a lot of engine items to pull the camshaft out via the front of the vehicle.
Once I replaced all main bearings, con bearings, main real seal without removing the engine. Also replaced all welsh plugs in a FE352. It was a dog of a job to do with leaving the engine in place and this was in a passenger car with plenty of room above, below and not so much on the sides.
Don't know, I just know I better start looking to earn some more cash to pay for it.
Select to expand quoteactiomax said...
You could always ask oliver for a loan 
Phpmechanic could cough up some dosh
Select to expand quoteRex said..actiomax said...
You could always ask oliver for a loan
Phpmechanic could cough up some dosh
Careful - I do have the unique power to double thumb anybody on Seabreeze.
Select to expand quoteadolf said..
I did suggest that - replacing the engine. They said they'd prefer to look at the cam shaft first. Compression was all good. They told me they drove around in it with the cover off the engine in the cabin. I reckon during the service they hit some sort of issue trying to tune it, and drawing from their experience with these engines suspected worn lobes. I guess I'll soon find out.
Mate, I would compare the labour costs of replacing just the cam versus replacing the entire engine. Sometimes these incremental repairs can be more expensive than throwing in a reconditioned engine (not just a known working one).
At one stage a Chev 350 crate motor used to be easy to get, although I don't know how cheap.
There's a lot of cheap and simple problems which can make an engine run a bit rough at various rpm's , specially if it's got all that pollution control stuff on it,.. charcoal canisters,. exhaust gas recycle system, etc.
I wonder what makes them so sure it's a worn camshaft?
I assume they mean worn camshaft lobes rather than a worn camshaft gear. But then I wonder how they would know the lobes were worn? It's not as if you can look in and see them.
A worn cam gear can clag out without any warning if it is that, but then the question is, how would they know that?
The timing difference between a worn cam gear and a new one is miniscule and makes no difference to the running of the engine,.. until it doesn't.
If the valves are not an interference fit I would just run it until it stops,. if it ever does.
If they are an interference fit that might be risky depending on how sure they are of their diagnosis.
I ran a car with badly worn cam lobes for years without any problems, after I fitted solid lifters in place of the original hydraulic lifters. Never any problems even though it eventually flogged the top off every lobe on the camshaft, intakes and exhausts.
My mechanics do these cars all the time and yes, they suspect warn lobes. I'm thinking they did the service and couldn't tune it right. They investigated other possibilities and are obviously hearing something I don't - they know how these engines should sound.
From my limited research, I reckon they and you are right. 350 engines are virtually bomb proof, but the flat tappet cams are a weak point. When the cam lobes wear, all you may notice, before other problems arise, is a lack of power, fuel economy, maybe some popping through exhaust or intake at some rev/m etc. I don't think a compression test picks up worn lobes. This leads them to think the engine is good - for now. The only way they will know for sure it's the cam is to pull it out and inspect it - that's the cost.
It's making sense to me. I feel the van lacks power - it always has. But it's a beast and weighs a ton, it is a retro apartment on wheels. It will cruise really well at 100km/h but would struggle to get to 120km/h. It's geared for towing, but I just get the feeling it should have some more grunt - but I don't know.
When they get to the cam and it's not the issue, they are more than halfway towards getting the whole thing out. Text book says that's a 22hour job, then 22 at least to put it all back - it's going to be expensive.
Part of me says drive it into the ground then get the whole thing rebuilt, the other half says go with what they are saying and maybe I'll save a couple of thousand.
If the engine is a solid lifter type then surely the mechanics would have tried to adjust tappet gaps and noticed that they've run out of adjustment. And by running out of adjustment then the lobe of the cam is worn down and has reduced the valve lift and also changed the valve timing. Valve lift would explain the lack of power. If the engine is solid lifter then you could just keep on adjusting........but each of those cylinders will be getting effectively smaller and smaller and you'll be putting more and more fuel into the motor to get some sort of power.
My 2 bobs worth is 1; take all the aircon/radiator crap off the front slide the ****er{camshaft}out.........throw the ****er{camshaft} as far as you can.
2: replace the cam with a proper camshaft{lpg?} then
3:replace and regas the aircon{nice!}
4:replace with a better radiator{nice!}
5: do LPG conversion.{nice!}
6: live a happy and productive life.
Select to expand quotelog man said..
5: do LPG conversion.{nice!}
Even better - do a dedicated LPG conversion if it suits your travelling plans [availability of lpg refuelling servo's]
A few of my mates run dedicated gas - much better than dual fuel.
No compromises due to needing it to run on 2 types of fuel,
More space for lpg tanks if you remove the petrol tank.
Have a lpg suitable camshaft, valve seats [and valves?] installed if needed, as well as the better radiator and trans cooler.
And the big bonus - no emission controls to worry about with a dedicated LPG vehicle [that I know of]
stephen
sorry to but in but if the cam shaft is worn you will not have good compression as the worn lobe wont open the valve to allow air in or out depending which lobe is worn old chevs had lots of issues with valves and lobes when somg laws came out you can check lobe wear with a dial indicator and measure lift this is done by removing valve covers . you also will here a loud tick. some chevs have adjustiable rockers that will need adustment. if i had a chev with good commpresion and no noise in the valve gear i would go looking for a air leak. you can inspect a 350 cam shaft through the valley by removing the manifold this is a 2 hour job if its worn it has to come off any way camshaft is take out through the front,advice would be to get the heads off and serviced if camshaft is replaced not much more work. 3000 quoted to do the job is ridiculous.its a four hour job on a old monaro and chev parts are cheep even allowing for in a gmc 12 hours would be plenty did this guy just pull this figure out of thin air,seems like a normal price because custome rcan always get 3 grand on credit
