Tried this in a subforum, but I think the halls are empty there. No area specific for Cummins in other vehicles so here goes (mods spank me if you have to, better yet, how about a area for the 8.3L 12V and the smaller 4BT's):

Have a few questions if someone can help specifically for the 8.3L 6CTA so starting a new thread here:

The 5.9's have had a few issues over the years. I know my father had his issues with each of his 3 Dodge trucks over 20 years, every one was modified to some extent. And he bought this RV so my mom and him could travel even after he couldn't drive. Had to be a Cummins, he wouldn't even look at anything else. Now I'm keeping it on the road and doing the stuff he would've if he was still around. So...

Does the 6CTA 8.3L have weaker head gaskets, comparable or even stronger than the 5.9 does? Has there ever been issues with the dowel pin or other problems I should be aware of?

With the Cummins 6CTA 8.3L circa 1994 in a 30K lb RV what is considered safe when messing with the P7100 pump timing? 14, 15, 18? How far can one go before you see "issues"?

I'm attempting to get a feel for what would be a conservative bump and what is considered running too aggressive. It can be a fine line sometimes. After all, this is for a retired, widowed, great grandmother's coach (my mother) and I need to keep her rv running reliably so she can terrorize our Nations' highways one ricer at a time... The straight pipe at least keeps them off her back left corner and merging towards the hammer lane has become a lot easier now.

Installed Isspro Gauges last week for a field trial from them. Warning lights at conservative settings for Pyro, Boost and even Back Pressure on the Exhaust Brake. Going to mess with timing this weekend if it all works out and see our friends 750hp+ twin turbo 6.7L he's building.

Thanks!

 

granny's gonna be rollin coal is she? that's the best news i heard all day. i dont have expertise on the 8.3 so i cant give you any information i don't know to be true but as far as the lack of forum for those and 4bt's i can see an argument in both directions however i still think they should exist. they are more rare and not too many with them but there is no clear place to post when you do have them. Good decision on the guages. Always good to see more people caring about how there engine is feeling and not just pouring smoke glad to have ya here

 

sounds like something id call a diesel tech shop about and ask and a fuel plate gauges etc. is where i would stop but hopefully somebody will come along and give u all the goodnews u want to hear. the afc housing tweaks are always good but idk about a 40k lb rv

 

I've talked to a few people but it's hard finding a experienced knowledgable person on the 8.3's. They came in 250 and 300 in my year of a Coach. Cummins themselves hinted I may be able to re-rate as high as 325 but referred me to a "distributor" as their systems at the help line didn't cover the older stuff anymore.

Anyway they are very capable of making BIG numbers in HP and longevity. I've been seeing the early 8.3 on a few boat sites with ratings as high as 475hp. All before the electronics of the late 90's. Of course their cooling systems were a little bigger.. Ocean sized.

I just kind of wanna know more before we get into any serious numbers and to make sure we don't miss something obvious. One person said it may even be other internals in the different ratings between 250 and 300 so my questions naturally stem from that.

We'll likely hook a trailer up this weekend, stick a 4x4 Cummins on it, and start advancing the timing this weekend to 14.5 or 15. I think it's around 12 now. Take it out and pull some hills with the load behind it. Not necessarily for more HP (thats just a benefit) but for better fuel mileage. Even 2 mpg will make a huge difference when filling a 105 gallon tank considering it doesn't cost anything to re-time at this stage.

 

Dodge Truck and Cummins Turbo Diesel Forum - Diesel Bombers

Recreation Vehicles (RV's) - Diesel Bombers

Try posting it in these 2 areas as well... the more hits, the better eh?

 

Ive played with a couple of those in rear engine buses. I cant help you on the timing but I did find out these things from personal experience.

1. A very mildly turned up pump will quickly get the egt's to around 1600f+ with very little smoke.
2.^^That leads to your ex. manifold turning white and cracking.
3. The same pump setup above will also result in a blown hg's and stretched head bolts.
4.The compressor wheel in the turbos in ours are only 57mm, a 62 or 64 would cool it better.
5.Once you get the tuning right the transmission then wants attention of its own.

You will probably have better results because you RV is more than likely not worn out,but that has been my experience with tinkering with the 8.3 in a bus/rv setup

 

I have heard the 8.3 is a cleaner engine than a 5.9 of the same year. Basically, don't expect it to smoke much if at all. And we have waited until we have gauges to do any power mods. The previous owner had already done a plate, and last week we just did the muffler delete, 3K gov spring kit (to help the drivability/trans shift better) and Isspro gauges. Just pulling small hills so far all I've seen is 800-900 max on the Pyro and maybe 20-22 on boost. So Timing is where we're going next. I doubt we'll ever do a bigger turbo or injectors, so it's strictly what we can get from moving the plate and messing with timing. We really are just going for good mileage now because we know the power will come with that. By deleting the muffler that should lower our egt's. So does the timing to a lesser extent from what I understand. I hope I'm grasping the concept as it applies to a diesel correctly. All my practical experience has been pretty much in street rods (v8 chevys) and very minor exposure to my late fathers' Dodge 5.9's.

White93, what specifically did you do to your "mildly turned up pump"? What explains your EGT's climbing so high? I'm assuming it was also a Bosch 7100?

 

Good input! Good to see someone who has tinkered with these motors before..




Driver- have you posted in those 2 areas I guided you to?

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Also check these links out

Banks Power Pak for Cummins ISC 8.3L

Cat 3208 vs. Cummins 8.3 Turbo - Topic Barthmobile.com

8.3L cummins power suggestions - Dodge Cummins Diesel Forum

Post a new thread on your 8.3l here (there's already a few 8.3l cummins threads...)
General Diesel Discussion - Dodge Cummins Diesel Forum

 

I've posted in some of the other areas..

We're not adding more fuel yet, just getting what's already in place working at it's best. Feeling that a couple of degrees of timing will give us better fuel burn (should be safe as long as we keep it below 14). We're only making 22 PSi on boost but will keep an eye on that as we mess with timing. I don't want to go over 30 there. I think my Isspro gauge is set to give me a warning if it exceeds 33. Saving any fuel plate shifts until the hot summer and we can really see what it does if we even feel we need to do it. The power should help midrange torque and allow us to pull rolling hills without the coach hunting between 5th & 6th (thus mileage should improve). At least thats what we hope it'll do.

 

Went to Timing @14.25°, just a few more degrees. Cummins said 12 was stock over the phone, engine data plate said 11. We stayed conservative but a few people said 15-16 if I really wanted to hot rod it. I don't, just looking for better mileage, don't need to worry about the head gasket. Boost didn't move and neither did egts so we'll wait until spring and some higher temps, maybe bump the plate a little to get boost into the mid to upper 20's. Banks' Stinger system runs 28psi as does TSTs so I don't see any issue there.

Don't worry much about the trans as the Allison MD 3060 is in other coaches and trucks that are 15K heavier and putting out 350+ hp.

Next needs a water pump.. just starting to weep a little...