Hi there - I am new to this forum, but have enjoyed reading many helpful posts as I try to get my wood chipper running well enough to make some chips. We raise beef cattle and I am hoping to use this chipper when clearing field edges.

The chipper is powered by a slant 6 which seems to date from the early 1980's. It has an industrial version of the Holley 1904 carburetor which has some modifications owing to the fact that the motor either idles or runs flat out - so there is no vacuum advance for instance, and no fuel pump in the carb.

I got it last fall and it seemed to run well, then it started to run hot. I replaced the thermostat, radiator hoses, radiator cap. It seemed better, but still did not run well - I cannot get it to idle below 1500 and while it runs ok at full throttle, it tends to die after 20 minutes.

Over the winter I rebuilt the carburetor, primarily because the throttle shaft was rattling around - I rebushed it and the choke, as it was pretty bad too. Otherwise it seemed ok - not too crudded up.

The carb rebuild did not help much.

From my reading here, I thought I would adjust the valves next, but the valves do not appear to be adjustable. At least, there is nothing to adjust with a wrench. I will try to post a photo.

When I pulled the valve cover off I found evidence of water in the oil - which explains why the coolant was low. I have changed the oil and added 2 quarts of coolant.

When poking around I came across the heat riser - not something I knew about before. I am now wondering if my overheating issues were due to the heat riser valve being in the wrong position. The shaft spins freely, stop to stop. There is evidence of a spring, but it is not complete.

I must admit I am now over my head. I am not sure what to do about the valves. I am not sure what I might have damaged running hot. I am not sure where the coolant is getting into the oil.

I look forward to any input you all may have!

Thank you

Bart

Welcome to the site!

In 1981 Chrysler FINALLY switched the slant six to hydrauc lifters with a non-adjustable valvetrain. It sounds like you have a hydraulic lifter engine, so no valve lash adjustment is necessary.

Water in the oil is not good. Have you done a compression check? You might have a blown head gasket.

The fact you can't get it to ie below 1500 combined with the overheating suggests over-advanced base timing. Verify your base timing and verify that the outer ring of the vibration damper hasn't slipped and caused the timing mark to be inaccurate.

Post pictures of your chipper! We love pictures of slants, especially in seldom seen apications.

Absolutely! More pics! Mine came from a forklift-style aircraft tug, but now is residing in a D-100. I have read where the industrial slants have different guts, but have never torn mine down to look. I know the carbs were different (mine was propane) and the distributors may have been different; mine wasn't. I think you might have timing issues, like Reed said, and possibly head gasket leakage. Pics are always welcome here.

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If it was easy, everybody would be doing it.

Thank you both - the idea that he valves do not need to be adjusted is very reassuring!

I will try to check the timing and compression tomorrow. What should the timing be? I seem to recall people being happy with 105 psi or higher for compression.

Here are some pictures -







It is a bit torn apart just now.
When it ran well, it did a fantastic job of chipping wood!

Thank you,

Bart

Interesting! Is there any chance you can post the numbers stamped on the pad direct above the coil? That looks like a head for a hydraulic lifter slant six, but it looks like it also isn't the original head. It is possible somebody swapped a post 81 cylinder head and rocker arm assembly onto a pre-81 mechanical lifter engine. Giving us the number stamped on the pad above the coil will let us decode exactly when your engine was built and determine if it has hydraulic lifters or not.

Also, check if the pushrods are hollow with a hole on each end. Hydraulic lifter engines used the pushrods to feed the oil to the lifters.

I see your distributor has a vacuum advance pod. If you run the engine at wide open throttle when chipping you should connect a vacuum hose from the vacuum advance pod to a source of manifold vacuum. This will give you more timing advance and more power huge chipping.

Base timing should be in the neighborhood of 8-12 degrees BTDC. Be sure to verify that the outer ring on the vibration damper has not slipped causing the timing mark to be incorrect.

105 PSI is getting pretty low compression for a passenger car, but for a wood chipper it sounds fine.

Is it missing a fan shroud? That appears to be an awfully big gap between rad and fan.

It appears you have the filter on the suction side of the pump. I'd put it on the pressure side.

Yellow slants sure are purdy.

The bracket attached to the top of the head, between the valve cover and instance, is that the same as the engine lifting bracket that they used at the factory?

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'66 Dodge Dart

That Holley 1904 carburetor (original application is '74 225 in forklift/industrial/agricultural applications) sounds and looks well and truly long past worn out—this family of Holley carbs has a reputation of reaching the "end of the road" from which no amount of fiddling or rebuilding will bring them back. I think you should plan on a new carb. But first you've got to fix what certainly sounds like a blown head gasket or cracked head.

The manifold heat control ("heat riser") valve may or may not be stuck, but it is not causing your problems.

I don't see an indication that this isn't the original head (Reed, what are you seeing?). If the engine was running great, it is not very likely that you've got a mismatched head/block situation.

What are the numbers cast on the side of the block underneath the manifolds? Is there an ID tag or plate anywhere on the engine?

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Too many people who were born on third base actually believe they've hit a triple.

I was looking at the second picture. Everything looks original industrial yellow except the head. I thought the head looked darker- like it is black, the color of the passenger vehicle 83+ slants. However, looking closer at the third picture, I see that there is yellow paint on the radiator side of the head. The engine could very well be all original and I was being too clever by half. I think the yellow paint on the head is a very god indicator that the motor still has the original head on it and is a hydraulic lifter motor.

Definitely sounds like it is time to check for a dead head gasket or cracked head and to search for a new carb.

I agree dan on the head. It looks like mine and I know mine is a stock head. But the fan dosenet look stock. I have the same radiator and distance from the radiotor to the fan with no shroud. But i have the mopar five finger fan and no clutch for it. Mine cools just fine. I would check the heat rizer like dan said. Mine would vibrate closed and over heat the motor when I had the stock intake and exhaust. I think the spring was bad. Im not sure but that red plug on your carb looks like a ported vaccume hook up.

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~Nic

Thank you all!

I was not able to find any marking on the head itself. However, it clearly was once painted yellow, and then silver. Under the yellow is a grey/black primer, and all the paint is flaking off.

When I had it running with the valve cover off, plenty of oil/water goo was coming up and out - I could imagine it was coming through the pushrods, but I am not sure how to check that they are hollow without taking the lifter assembly off - which I am not quite ready to do.

I did find some castings/stamps/labels on the block itself, as the pictures show. I presume this means the block is from 1984. The stamped number I presume is the serial number of the block and is very hard to read. There appear to be 2 lines, the upper one being obscured by paint. I could scrape it off if it would be interesting.

There is an enclosure which goes over the entire engine and provides at least some level of fan shroud.

I have wondered about the vacuum advance. The distributor definitely has a port for it, as does the carburetor. I have left it alone, both plugged, but I have wondered if that made the most sense. It would be easy to connect them. Is the carb a good source of vacuum in this case? Is there a better one?

As for replacing the carb - do you have any recommendations? I saw recently that there are new drop in replacements for the 1904s, but I don't know that I have heard much positive about new carburetors.

I am going to go check the compression and timing. I will report back.

Thanks again,

Bart

OK - the technique, hopefully correct:

* All spark plugs removed
* Choke plate open - i.e. air can pass through the carb unobstructed.
* Throttle open

I have a compression gauge with a release button, so I could thread it in the plug hole, use the starter to turn the engine over, and read the highest value. I gave each cylinder a 6 count - in all cases that was enough to build the pressure to its max, and hold it there.

The lowest sustained reading was 125 psi. The highest was 135. I think all the cylinders exhibited the same behavior, the pressure first being about 100psi, then about 115, and finally holding at 125-135. I think this means my head is sound, doesn't it? Or at least, the head on this engine. Sadly, I think that means the water is getting in somewhere else.

Although right now I am wondering - the carb was off all winter. I stuffed a rag in the hole, but it was out more or less uncovered all winter. And today I noticed a small drip of coolant at the top water line on the engine. Maybe it just sat for a while?

I will now attempt to determine the timing - first verifying TDC.

Bart

Don't know if this is any help, but here are a couple photos of other industrial governed carburetors. The one on the left is a Zenith off a John Deere, the one on the right is a Carter off a Massey Ferguson.



Another view,




CJ

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