I have a job coming up where I need a D8 dozer with a ripper. In working through the decision to rent or buy I have noticed that some of the ads refer to spacer plate engines. Would some one educate me as to what this means?
-
Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!
D8H spacer plate engine?
- Thread starter f311fr1
- Start date
kshansen
Senior Member
- Joined
- Mar 11, 2012
- Messages
- 11,157
- Location
- Central New York, USA
- Occupation
- Retired Mechanic in Stone Quarry
Cmarks answer is probably all you need to know but if you have some time to waste here are my additions
If you are familiar with any "wet sleeve" engines the sleeve has a thick flange at the top, maybe 3/8 thick. On older Cats and most other engine with wet sleeves the top of the block is bored out a few thousands of an inch less that the thickness of the liner flange. Then the head gasket holds down on the top of the liner when head bolts are tightened.
Now if you have a spacer plate engine the top of the block is flat, not counter bored, instead a plate of steel slightly thinner than the flange on the liner is used with all the holes for the head bolts, water and oil passages and the liners is installed between the top of the block and the head gasket.
The basic theory would be that when the counter bores are cut into the top of the block that causes what would be called a stress riser, Google that one, and makes cracks likely.
Cat is the only one that I have seen use this design but I'm sure someone else has. There are other versions of this design but I'll leave those some one else.
Basic point is a "spacer plate engine" "should" be a better one all things being equal. But when are all things equal?
If you are familiar with any "wet sleeve" engines the sleeve has a thick flange at the top, maybe 3/8 thick. On older Cats and most other engine with wet sleeves the top of the block is bored out a few thousands of an inch less that the thickness of the liner flange. Then the head gasket holds down on the top of the liner when head bolts are tightened.
Now if you have a spacer plate engine the top of the block is flat, not counter bored, instead a plate of steel slightly thinner than the flange on the liner is used with all the holes for the head bolts, water and oil passages and the liners is installed between the top of the block and the head gasket.
The basic theory would be that when the counter bores are cut into the top of the block that causes what would be called a stress riser, Google that one, and makes cracks likely.
Cat is the only one that I have seen use this design but I'm sure someone else has. There are other versions of this design but I'll leave those some one else.
Basic point is a "spacer plate engine" "should" be a better one all things being equal. But when are all things equal?
Last edited:
A D-8 with a 342 is something to stay away from.
Bob
John C.
Senior Member
Early D8K engines were counterbored. It's just basically the D8H engine with a little more horsepower. The counterbored engines could be a pain to rebuild because all the counterbores were supposed to be the same so the liner heights would be close or the same. If they weren't in spec you could put shims in a low counterbore to maybe get a liner up enough to be in spec with the liners next to it. As Mr. kshansen says the counterbores can crack in the corners causing compression gas to leak into the cooling system. The other issue was they seemed to allow the liners to vibrate a little more than the spacer plate engine which was evidenced by the liner pitting I've seen in every counterbored D342 engine I've pulled down.
The spacer plate engines did away with the counterbores and the cracking counterbore problem. The liners will still dance a bit and mark up the top of the block but you can just have the top machined flat and get a little thicker plate instead of worrying about cutting counterbores, doing shims or putting in Z sleeves. It did bring up other issues with trying to get that spacer plate to seal.
The big issue with the "K" engines was the placement of the muffler under the hood. Overheating became a big issue until the exhaust system was modified by putting the muffler on top of the hood. If what you are looking at has the muffler under the hood, run away.
The last thing is that I concur with Mr. Bluox. Your questions about the D8 indicate you might be a little light on experience to be using these machines in any production application. They are very old machines now, have acquired many hours of wear and tear and need someone with a lot of experience to operate, maintain and repair them in a way that will allow you make money on their operation.
The spacer plate engines did away with the counterbores and the cracking counterbore problem. The liners will still dance a bit and mark up the top of the block but you can just have the top machined flat and get a little thicker plate instead of worrying about cutting counterbores, doing shims or putting in Z sleeves. It did bring up other issues with trying to get that spacer plate to seal.
The big issue with the "K" engines was the placement of the muffler under the hood. Overheating became a big issue until the exhaust system was modified by putting the muffler on top of the hood. If what you are looking at has the muffler under the hood, run away.
The last thing is that I concur with Mr. Bluox. Your questions about the D8 indicate you might be a little light on experience to be using these machines in any production application. They are very old machines now, have acquired many hours of wear and tear and need someone with a lot of experience to operate, maintain and repair them in a way that will allow you make money on their operation.
kshansen
Senior Member
- Joined
- Mar 11, 2012
- Messages
- 11,157
- Location
- Central New York, USA
- Occupation
- Retired Mechanic in Stone Quarry
In my opinion, and it is worth every penny you pay for it, I would say no. I would be more interested on how well the machine was taken care of than if it did or did not have a spacer plate engine. It is a newer and in many ways an improved design.
Guess a lot depends on what your project is and how many hours you expect to be using this machine. Sometimes I think one is better off hiring somebody with a machine to do the job. It not only saves any cost of a machine failing at the wrong time and hopefully you get someone who knows how to run the machine and therefore get a better job done in less time.
But if you are looking for a machine to just play around on and don't care how long the project takes go for it but have your eyes open wide as any machine of that size can cost big dollars to have even simple repairs made.
Might be better off buying a smaller machine like a D6 even if it takes a few extra passes to move the same pile of rock. Yes I'm sure you might find a D6 to actually cost more than the D8 but if you plan on selling it after the project is done that may cancel itself out. And a D6 is a lot cheaper to get moved I'm thinking!
DMiller
Senior Member
Older Cats and Cummins ended up with upper counter bore cracking where they would seep coolant unstoppably as well developing liner shifting which accelerated the degradation of the blocks. Have installed counter bore sleeves in the past but generally when an engine needed these the next overhaul they may or may not be trashed. I liked the spacer plate engines, did not see as much upper deck erosion from head shifting, if the spacer developed the erosion could be replaced.
do you particularly want a D8H over a K model . As you are wanting the dozer for ripping you may want to consider more than the motor . I know of two H's that had broken the rear housing ripping . One had been traded in to the Caterpillar reps to be sold on that failed after just a few meters of ripping , Cat stood by the machine and repaired it , another locally bought by a farming family to pulled its self to bits . On the other hand I know of no "K" pulling a stunt like it , not saying they don't , just have never heard of it .
Junkyard
Senior Member
Somewhere on here there's been a thread (or part of one) comparing the H's and K's not to mention later model machines on ability to rip ground but NOT themselves.
We have a very experienced operator. We need the machine for 3-4 months for one for sure job. @ 18-25K per month rental we just might be able to buy a D8 or D9, pay for it on this job and use it on other larger jobs in the future.
Job value has enough in it to purchase a good D8K or a Komatsu D155 , expecting a D8H to rip for 3 months is pushing luck just too far .
Nige
Senior Member
I'm sure you do but how much hard rock ripping experience does he have..? I'm assuming that the plan is not to just drop the hook in the ground and stir things around a bit but to actually do some serious ripping of large quantities of good competent rock. I've come across lots of very experienced tractor operators who didn't have a clue about how to rip correctly. Round our way in the times when 8H/8K plus D9G/D9H were king if a customer needed a large amount of rock ripped there were a couple of specialist contractors you'd hire to come in and do it with their tractors rather than f**K your own tractors up. They cost top dollar to rent but their operators were the best in the business and so were their machines.
A D8H or D8K at this point in time is a dinosaur however well it has supposedly been maintained over the last 40-ish years. If you look at prices of used equipment could you get a D8L or D8N for a similar price..? The 8L would be somewhat larger than an H/K, the 8N more like for like. However the 8N would also be newer which might jack the purchase price up.