Cummins ISC 350 24 valve...?

[RJThurston]

New to site and Motorhomes. Looking at buying a used 2000 39 ft coach. The dealer says it's a 24 valve 8.3, 350 hp cummins. I have heard of a 24 valve 5.9 but not a 24 valve version of the 8.3. I'm thinking because it's an older engine that an internet search did not produce anything specific. If anyone has any specific information (torque specs, reliability, fuel mileage, know problems, etc) it would be greatly appreciated.

Thank You.

[wolfe10]

RJ,

Welcome to the FMCA Forum.

Yes, the ISC as opposed to just the C engine does have 24 valves.

I have Cummins literature going back to 9/98 showing the 24 valve configuration.

[RJThurston]

Thanks for the prompt reply, that's good to know and that the salesman had it right, I've talked to many sales people that didn't know a Cummins from a Cat. Makes me more comfortable dealing with him.

I'm thinking the 24 valve should be a stronger and more efficient engine than the 12 valve version of the 8.3.

Any suggestions on a web site that might give specification of the 24 valve engine....???

[wolfe10]

On the Diesel RV Club (an FMCA Chapter) Technical Website:

http://forum.dieselrvclub.org/index.php/topic,7170.0.html

[jg053047]

Hi and welcome to the club.

I also have this engine in a 2000 model American Eagle and it has been a fine operating machine. I have though adjusted the valve lash after 36,000 miles and that made a big difference in the overall noise level from the upper end. I found they were out of adjustment in excess of 4 to 5 thousandth on most of the intake and exhaust valves.

My mileage on average is 8.2 mpg at 1500 rpm loaded pulling a Smart car.

I would recommend this maintenance to the overall performance for the future.

Good luck with your new adventure and travels.
Jim G

[RJThurston]

Thank you, that's what I was looking for, great information.

[obedb]

IMHO. More valves are there to help the engine builders conform to increasingly onerous EPA regulations. That may be in part why a legendary manufacturer (Caterpillar) chose to leave that part of their business. The more parts added to an engine valve train increases the complexity and possible failure. I don't think adding more moving parts to an engine helps it to be more robust. Just a guess on my part.

[wolfe10]

And, I would suggest that better breathing, whether gas or diesel is better for BOTH power and emissions.

[obedb]

But is it more robust?

[huffypuff]

Valve adjustment not needed until 150,000 miles as per Cummins. See maintenance link below.

http://www.cummins-sp.com/support/rv_maintenance_operation-isc.htm

[dickandlois]

Valve adjustment not needed until 150,000 miles as per Cummins. See maintenance link below.

http://www.cummins-sp.com/support/rv_maintenance_operation-isc.htm

That might be there recommended point, but I decided to have my valves adjusted at around 70,000 miles and it made a very noticeable difference.

Rich.

[jg053047]

I agree with Rich. My engine was getting noisy at the top end at idle and after adjusting the valves the noise is gone and it seems have improved the overall performance.

The hardest thing to do whole performing this task was not being able to access the plug to rotate the crankshaft. I had to remove the starter and rotate the flywheel with a pry bar to open the proper valve sequence during the procedure. To do again I would probably have had it done by a good shop.

Jim G

[RJThurston]

Yes your correct, the 8.3 will not last as long as the N-14 or the Detroit 60 series, those are larger engines that typically go in class 8 truck made for pull 80 K down the road almost continually, although you can find them is some of the newer larger coaches. But the 8.3 is a strong, and long lasting engine if used as intended. What I like about this particular coach is that it a 2000, and is free of all the emissions add-on that contribute to the complexity of the engine management system.

Having life long friend that's a certified Cummins mechanic, he knows first hand that the valve lash can make a big difference in how a Cummins performs, even when done earlier than recommended by Cummins. In fact at his shop, they adjust the valves a little different than what's recommended, which also adds a little to the performance characteristics.

[wolfe10]

But is it more robust? Will it live as long as the N-14 Cummins or the Detroit Series 60? The more things that go up and down depending on an oil pump?

The reality is that virtually all diesel engines used in RV's in the last couple of decades will far outlast the rest of the coach.

Can you kill one-- sure, but doubt you will ever wear one out.

[jleamont]

Well said Brett!

I have seen many diesels killed, not worn out, some by design defects, most from lack of proper maintenance or someone tinkering with HP and torque.

Valve adjustment is good preventative maintenance, as soon as I have the ambition I’m going through mine, I already bought the barring tool. Trying to find the ambition.....still haven’t found it.

[obedb]

I believe I read that earlier models had some problems. Guess that I am just a Detroit and Cat lover, but if I ever get to trade up, a Cummins will be in my future.

[wildebill308]

But is it more robust? Will it live as long as the N-14 Cummins or the Detroit Series 60? The more things that go up and down depending on an oil pump?

I have not heard of any problems with a 24 valve engine because it had anything to do with design. I do think they run better. How robust do you need? No one is having problems.

"I believe I read that 1998 to 2002 models had the most problems, but I would not swear to it." You need to have something to back that up as all you have posted is hearsay.

Bill

[huffypuff]

If the valve train gets a little noisy by all means get them adjusted. Otherwise you may find you are throwing your money at just a couple of thousands off. I can understand improve performance after adjusting noisy valve train as the valves are not opening enough. I stick with a good maintenance which includes changing oil and filter at least once a year regardless of not driving the 15,000 miles. Maybe that will keep the wear down in the valve train but I won't know just yet as I only have 43,500 miles on mine.

[obedb]

I can see that I am on the wrong side of this discussion. I apologize.

[wolfe10]

ObedB,

Not sure there are "sides" here.

But, I do agree that there are so many "if you read it on the Internet it must be true" statements floating around, that some substantiation is really a good idea.

Much better to have FACTS rather than OPINIONS, particularly of 2nd or 3rd hand ones.

[jleamont]

The only negative I had heard with the Cummins was exhaust manifolds cracking on the ISC and the CAPS fuel injection pumps failing prematurally around 300,000 miles, and I forget what year that was introduced and replaced with the common rail design, all I know is my 2002/2001 engine has it, and it didnt scare me away. I got that from our Cummins rep at work. I figured at 300,000 miles the unit would be long past due for replacement.

Obedb, no sides here note the "F" in FMCA, its all good..Family/Friends as far as I am concerned.

But....you mean if its on the internet it might not be true?

[obedb]

I was just plain wrong! Heard some things in my part of PA (mostly Cat people here). Read some things on the net possibly by people with axes to grind, and although it happened many years ago, had a lot of trouble with a brand new big cam 400 Cummins in my first purchased Peterbilt. Left a foul taste, but I need to move on.

Hey I am used to being wrong. My DW tells me all of the time.

Thanks for the kind words.

[huffypuff]

ObedB if we made comments and the DW don't hear us are we still wrong. Yes according to my DW we are. If you ever meet my DW I know nothing about this.

[kaypsmith]

IMHO, the better the air intake, and the faster the exhaust, the better the performance. If the valve cover is off for valve adjustment, takes very little extra time to adjust 24 than 12. I still love my old 6V92 Detroit with only 6 valves, but I have

owned all three over the years, with very good service out of all. Maintenance is the life of any, and no abuse to the engine, as Brett said the engine will outlive most motorhomes.

[wolfe10]

Yup, nothing like the sound of a Detroit 2 stroke at higher RPM's.