Cummins air compressor


For you lovers of the Class 8's and bigger.

Golden Jubilee
Golden Jubilee

Posts: 3525

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Mon Feb 15, 2016 8:37 pm

Re: Cummins air compressor

Well, the experiment is coming to an end. I am leaking coolant between the heads. I pulled it down to find the counter-bores are shot. Since this block already has 2 salvage sleeves in it, and has had the counterbores bored oversize already, the only hope for this block is to have it bored for lower press-fit liners. In short, and out of chassie overhaul.
I decided to throw the one head back on and drive it until I can prep another engine, and until the weather warms enough to swing the engine outside. I have 4 855 engines but they all need work. I am thinking of building a 350hp NT88 for this truck. The one I have was so worn that it leak oil from every gasket, but should be buildable without machining (I hope). The other option is to put the "core" engine I bought for my other Cabover, in this one. I wait to make the choice until I have pulled the heads on the NT88 and can look at the counterbores.
All in all not a productive week.

Golden Jubilee
Golden Jubilee

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Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Mon Feb 15, 2016 10:53 pm

Re: Cummins air compressor

OK, I finally got it. four, 855 engines. Can you imagine the size of that pile of castiron Do the Holset compressors still have to be timed to the engine?
I would rather have tools I do not need than to need tools I do not have

Golden Jubilee
Golden Jubilee

Posts: 3525

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Tue Feb 16, 2016 8:46 am

Re: Cummins air compressor

Not like they did when they were all part of the accessory drive. The are supposed to be set at the 10 o clock position to cancel out as much vibration and gear noise as possible, but will function just fine "out of time".
In the old days, and now with the accessory drive. if you put them in wrong, the engine will run fine, but the timeing marks will be off making a tune up a big job, have to reset the accessory drive to be able to set the valves and injectors.

Golden Jubilee
Golden Jubilee

Posts: 3525

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sat Feb 20, 2016 7:49 pm

Re: Cummins air compressor

I got it back together and got a surprise, while there is some seepage from the loose counterbores, it looks like the lions share of the leak was from the connection between the head and upper waterrail. It took several attempts to seal, but now the coolant leak is much reduced.

Rookie
Rookie

Posts: 23

Joined: Mon Dec 03, 2012 10:44 pm

Post Sat Feb 20, 2016 11:35 pm

Re: Cummins air compressor

Hello:
Cornbinder just pore a can of black pepper in the cooling system and go on down the road. Black pepper is the best stop leak that I have ever found,I ran it in my KW big cam 400 more than 500,000 , I would have to add more pepper every 2 or 3 months when the water filter removed the pepper.
The pepper will not plug up the heater core or hurt the water pump seal.
With out the pepper in it the water would squrt out between the heads when I would start the engine,and continue until the engine wormed up.
I ended up pulling the engine out and having the counter bores bored out and new counter bore sleves installed. I ran it another 350,000 before I retired. without any water leeks.
Back in the late 70 and early 80s it seemed like water leaks around

the counter bores was stander equipment the 855 engine. Don Graves

Golden Jubilee
Golden Jubilee

Posts: 3525

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sun Feb 21, 2016 8:59 am

Re: Cummins air compressor

I know a guy who tried pepper and plugged the aftercooler core! I think I've got it to the point where it will last until I can swap in another block. Then I will have this one bored for lower press-fit liners which is supposed to cure the problem once and for all. If all it does is weep I can live with that.

Freshly Restored
Freshly Restored

Posts: 203

Joined: Fri Dec 14, 2012 10:49 pm

Location: Eastern Kentucky

Post Sun Feb 21, 2016 4:17 pm

Re: Cummins air compressor

Glad you got it to where you can manage it. Now maybe you can get some time to devote to the 9670. Dan

Golden Jubilee
Golden Jubilee

Posts: 3525

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sun Feb 21, 2016 6:29 pm

Re: Cummins air compressor

actually, they are both 9670's! '83 and '89! Just started the teardown of the replacement engine.It is so much easyer "out of chassie" than when it is in the truck. Less then 1/2 a day and I had it almost stripped. The last out of chassie I did was about 15 years ago on a KTA Cummins 600.

Golden Jubilee
Golden Jubilee

Posts: 3525

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sun Feb 28, 2016 10:16 am

Re: Cummins air compressor

Well the leak is still there as big as ever.
I pulled the CPL 840 (spare engine) down and found it had one cracked piston and one liner that was scoured. I have it just about down and can order a rebuild kit for it. It looks like this will be the 1st time it has been done. Liners fit looks good. Now I just have a whole bunch of cleaning to do before the parts come.
Since it leaked so bad, it is getting all new gaskets and seals, and boy, are there a lot of them! I hope to get the block and pan steam-cleaned somewhere in town, then pull the cam followers and paint the block.
Since this engine sat for over 10 years, there is a lot of rust that needs to be cleaned off and stuff re-painted.
This block can be built "low flow" only on the cooling system. This means a radiator change as well as re-plumbing most of the hoses. I have radiators and hose is easy to move.
I'm doing all this in between runs with the cabover with leaky liners. Right now freight is slow and cheap so better to get this done now and hope for better days to come. It is against my nature to spend money when I'm not making money, but am trying to force myself to do it this time around.

Golden Jubilee
Golden Jubilee

Posts: 3525

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Mon Mar 14, 2016 9:21 pm

Re: Cummins air compressor

Got the short block built. The new (replacement) pistons are 1/2 a point lower on compression 16.5:1 vs 17. I guess Cummins decided they were asking too much @17:1. Add to that the "kit" didn't come with a complete selection of cam-follower gaskets, so I ended up knocking the timing back a notch. Both should help it last longer. Now If I could get the heads back from the machine shop, I could get it installed. The shop said it needed a few guide, which is understandable, considering it has over 1 mil on it.
If the heads don't get here soon, I'm going to have to swing the short block in and finish the build in situ.
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