Hi guys,

I've never been around these much but just recently bought a '86 D100
With a 225. Everything on the truck is factory. I bought it for cheap after selling my car needing some cash before I head to Parris Island in a few months for boot camp. When I first bought the truck I drove it home about 40 miles and it was running like a champ except for the intake/exhaust gasket leaking. However, once the truck had been running for a half hour or so at roughly 50 mph (No tach so Im assuming mid range rpm there) it began to knock steadily. Once I got it home and I noticed the oil seemed a little gritty on the dipstick, the truck had sat for nearly a year. I bought a can of "Motor Flush" is it just me or does that stuff smell just like kerosene??. Anyways, poured it in and let it idle for about 5 mins then drained and changed oil and filter. I put in 4 quarts of 30 weight and a bottle of Lucas with a Carquest filter. Seemed to be running a little smoother lol. When the truck first cranks for about 1.5 seconds it will knock with the oil light on, then light goes off and knock goes away until you've been running down the road about 15 mins. It seems like the longer you keep driving the louder the knock gets, maybe it has to do with the oil being hot? My real question is does this sound like a bad oil pump from sitting or a clogged screen/pickup? Or does it sound like a main (not sure if these even have thrust bearings) bearing?

Any thoughts on the matter from someone who has experience with these engines would be greatly appreciated.

I guess noone wants to break the bad news to me that I'm going to have to rebuild this thing and get the cylinders bored and possibly the crank turned. Thats what I'm assuming its going to need.

Install an oil pressure gauge and get oil pressure reading hot and cold at idle, then report back what they are. This could be piston slap, or something hitting the dipstick, or a loose flexplate, or a number of other non-catastrophic problems.

Try installing a 205 degree thermostat and running 5W-30 oil.

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Casually looking for a Clifford hyperpak intake for cheap.

Well, holdjyer horses, don't assume yet.

Those engine flush compounds can be really dangerous to an engine's health when just dumped in like that. A more careful procedure is necessary if you want to try to clean out the engine without disassembling it. However, in your case it sounds like some disassembly will be needed. The first thing to do is to service the oil pressure relief valve to make sure it's doing its job, as described in these two threads: thread 1, thread 2. If that doesn't clear up the problem, then the next step is to drop the oil pan and clean the oil pickup screen and pipe.

The thrust bearing is integral to the #3 main bearing, BTW.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

So the pressure relief valve was stuck. I bought a new oil pump and put it on. I was too scared to use the old one after what I found out. Had to take to loose a motor mount and use a bar to get the old one in and new one out(lol). Gotta grab a new oil filter in the morning before I can start it back up. Hopefully there has not been any serious damage. I reckon we will see if this fixes it. Thank you for the information SlantSixDan. If I have any other issues I'll know who to go to. Thanks again.

Eh. Fixed part of the problem. Gonna have to buy and put on a harmonic balancer.

Just to check, what brand of new oil pump did you get for the motor and more importantly does it have a factory (the old) oil pump gear on it.

Many reproduction Slant 6 oil pumps today have poor quality oil pump gears that are softer then what is preferred. In the worst case scenario the oil pump gear will shred, causing oil system failure (oil pressure drops to zero) and possibly damaging the cam. Yet when preventive measures are taken to limit cam movement, remove resistance from the oil system and limit over all oil pressure these softer gears are less likely to fail.

All the same, it's a subject to be informed in when rebuilding Slant 6 motors.

For more information go to: http://www.slantsix.org/articles/oil-pu ... report.htm

Allen

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So the truck slung a rod. Kinda brought me to tears. Getting another engine put in. I dont have the time or the stuff I would need to do it and actually be finished before I went to boot camp. Lesson learned.