Need replacement for Workhorse 8.1 L engine

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Yeah, given the nature of the failure I wouldn't expect an oil analysis to show anything. The damage to the cam lobe is really minor in the grand scheme of things, and who knows whether that damage was done "just now" or during a prior oil change. The piston damage would have gone out the exhaust, no evidence there. The valve retainer was found, so nothing in the oil.

Timing should be 100% computer controlled - you couldn't change it if you wanted to. Well, not without a programmer. :)
 
driftless shifter said:
The initial timing on the distributor may very well be off, being as the cam has been replaced.

Bill
They had the cam sensor off to replace the camshaft. Sooooo if they didn't set the timing and just put the sensor back where they thought it was, the initial timing could very well be off. If it is advanced too much using regular fuel the ecm will keep pulling timing until no knocks are received. Don't know for sure if a 8.1 has a distributor, don't think it does.
 
You can't move the sensor - it only goes in one spot. :) The only way the ignition timing can be off is it the trigger wheel is off, which is not quite but almost impossible. :)

http://farm8.staticflickr.com/7436/9037617632_b613327bf0_c.jpg

The L18 has no distributor, it's not even based enough on a previous engine to have a spot to put one. :)
 
thesameguy said:
You can't move the sensor - it only goes in one spot. :) The only way the ignition timing can be off is it the trigger wheel is off, which is not quite but almost impossible. :)

http://farm8.staticflickr.com/7436/9037617632_b613327bf0_c.jpg

The L18 has no distributor, it's not even based enough on a previous engine to have a spot to put one. :)
You're right, don't look adjustable. I've never worked on a 8.1. There has to be a way to set the initial timing on them though.

Just looked it up, says the timing is non adjustable. Makes me want to put the scan tool on mine to see how much timing it has running down the road.
 
The crank sensor picks up engine speed and TDC from the trigger wheel on the crank. Based on those two items it computes timing on the fly. The only way to change timing is to reprogram the computer, which is actually pretty trivial to do. :) You can definitely watch the computer's magic with a scan tool to see what it's doing. Pretty amazing how fast it makes changes!
 
I've been told that a knock sensor can pick up an exhaust pipe rattle or other extraneous rattle in the driveline including a belt driven component, and think it needs to back off the timing.

Bill
 
Well the shop couldn't duplicate my "stumbling" and reduced gas mileage problems, so they didn't do anything.  The stumbling primarily occurs on hills, and there aren't any in Florida.  Note that there were no codes during my 1,027 mile test drive when I noticed the stumbling.  I'm about to do a 1,300+ mile trip through Pennsylvania and New York States where there are lots of hills to test the engine repair out.  The shop I used doesn't have the GM Tech II tester, which could quickly check all of the sensors in this Chevy engine. 

So I guess that is the end of this saga, although if I find out anything more, I'll update this forum.

Thanks to everyone for all of your valuable information.  I certainly learned a lot!
 
Did you say you had some sort of OBDII scan tool? I'd keep that plugged in, maybe you can see something on your drive. Or, pick up one of the cheap ELM327 Bluetooth dongles and an iPhone/Android app that's capable of datalogging. Something like that you may be able to find patterns for timing/a:f/temp etc. that gives you a direction. Given that you've had major engine work done, you shouldn't have to live with anything less than a fully performing engine.
 
I have an update on the stuttering problems.  On the 1,300+ mile trip home I got sever backfiring under heavy loads.  When I checked the engine, the repair shop had replaced the wires without replacing the plug heat shields, which I knew were there before the engine work.  I asked the owner why they had replaced the plugs and wires when they only had 282 miles on them.  He said they had trouble removing them and they got damaged in the process.  I now know that there is a proper technique to removing the shields and wires without damaging them, and apparently the shop didn?t know how to do this.  I also know that the heat shields were in place when I brought the RV in for the work as I remember seeing a squashed shield and wire on the floor but didn?t know what it was at the time.  He claims they bought the wires from Workhorse.

So I?m going to replace the wires (and maybe the plugs?), but don?t know with what.  I should probably switch to one of the posts discussing the burnt wire issue for that, although I?m not sure which post to use.  The choice of wires seems to be between the Taylor Extreme Service Series (which Taylor says not to use the heat shields with, and says the wires protect up to 1,500 F), the Accel Extreme 9000 Ceramic custom fit wires (they say the ceramic boots withstand up to 2000F, but the wires only 600 F), but don?t have a listing for the Workhorwe 8.1L engine and don?t mention the heat shields), and the UltraPower Magnum workhorse/GM8.1L wires that do require the GM Heat shields. I have thought about installing an engine ventilation kit, but I know the engine easily ran 10,000 miles since I bought it (used), including a trip from Florida to Arizona and back to the east coast without problems.

I?ll let you know what I decide and if I switch to another post.
 
Based on personal experience, I would highly recommend against the Accel wires and recommend for the Taylor wires. Accel products are *really* hit or miss in terms of quality control, and I suspect it's because they're a private label operation and not a manufacturing operation. Taylor makes their own wire and assembles their own finished products and it seems to result in tighter QC. I have never purchased Accel products, but I've worked on enough cars with faulty PO-installed ones to know to stay away. Taylor is my go-to where I don't want to spend the money on something like Magnecor wires. Right now, my 454ci P30, 5.7l Suburban, and 3.4l Fiero all run Taylor wires and they fit/install/work flawlessly.

That said, *actual* backfiring should not happen on a fuel injected engine. That would be a very serious and highly unlikely problem to occur. Maybe something else?
 
Well the "backfiring" was through the exhaust of course since there is no carburetor.  Other posts with this type of issue were resolved by installing good wires and sometimes a ventilation kit.

Do you have any experience with the metal heat shields that GM uses on this 8.1L engine?  At this point I don't have the shields, but I've read that Taylor says to not use them.  I haven't called them to confirm that.

What about good spark plugs?  I read something about iridium plugs.
 
I would take it back to the shop that removed them and make them replace them. They did wrong but didn't care enough to do the job rite. The shop owner and I would be having it out.
 
morefun said:
Well the "backfiring" was through the exhaust of course since there is no carburetor.  Other posts with this type of issue were resolved by installing good wires and sometimes a ventilation kit.

Do you have any experience with the metal heat shields that GM uses on this 8.1L engine?  At this point I don't have the shields, but I've read that Taylor says to not use them.  I haven't called them to confirm that.

What about good spark plugs?  I read something about iridium plugs.
....  Lean miss back fires under load? By all means fix your plug problem the a/c delco plugs are platinum and the heat shields need to be on.  Better check fuel pressure? Injector pulse width and fuel trims and O2 sensors, need a good scan tool. I shop rockauto.com OE and after market good price.
 
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