Another oil pressure thread

[Rawze]

In the case of oil some mysterious internal lower-than-normal oil pressure issues after an inframe or bearing replacements ( or if there is mysterious vibration issues ), THEY ALSO NEED TO PLASTIGAUGHE THE ROD/MAIN BEARINGS like i mentioned above! - ESPECIALLY IF THEY NO LONGER HAVE THE ORIGINAL BEARINGS TO COMPARE PART#'S TO!

I did mention this in previous post [here] above so I will elaborate...

Some ISX engines came from the factory with an over-sized connecting rod and/or main bearings. This is COMPLETELY UNPREDICTABLE and was done as the engine went down the assembly line at the factory. It could have even come from factory with DIFFERENT SIZES mid-engine!. -- If the clearances on the crank were in excess, they would switch to to a larger size connecting rod (or main) bearing, over-sizing them. This is why the bearings were not supplied in the overhaul kit (in the past any ways), as some ISX can randomly have been machined to have thicker than normal crank or rod bearings. This cannot be looked up and has to be checked only as the old ones are removed by comparing part#'s and using calipers on the old ones in the places they are not worn out. It has actually been seen in the past where they will change sizes of crank or rod bearings even from one cylinder to the next, mid engine. I remember gearhead even telling me a few years back that he got an engine to inframe once that required 2 different size bearings in it mid engine.


The engine may or may not vibrate, but usually always loose some oil pressure at idle once the oil is at temperature. - If it requires over-sized bearings, it will also not last very long, then eventually break the crank or spin a bearing. -- NEVER GUESS AT WHAT YOU GOT!-- MAKE SURE SOMEONE GOES BACK AND CHECKS THIS PROPERLY!.


part#'s are...

4089405 - Standard size connecting rod bearing kit.
4090016 - 0.010" (0.25mm) over-sized connecting rod bearing kit.
4090017 - 0.020" (0.5 mm) over-sized connecting rod bearing kit.

-- This is all assuming these bearings are "Thicker"?, for an undersized crank?. -- I have never measured, nor needed a set of them myself.

This is also true of the main bearings. There are a few sizes of of main bearings for the ISX. ON RARE OCCASION they would install the over-sized bearings from the factory. Again, why the main bearings are not supplied in the overhaul kit. Again, this could even happen mid engine.

3800298 - standard size main bearing.
4089845 - 0.010" (0.25mm) over-sized main bearings.
4089846 - 0.020" (0.5 mm) over-sized main bearings.

-- Again: This is all assuming these bearings are "Thicker"?, for an undersized crank?. -- I have never measured, nor needed a set of them myself.


-- I mentioned plastigauging the crank on my rebuild series in this video at 7:13 ...
https://youtu.be/X_HLvJfA20o

The clearance you are looking for is between 0.002" and 0.005" on the crank and/or the rod bearings. Obviously if you come up with +0.012" (greater than 0.005" per side), or perhaps even +0.022 (greater than 0.010" per side)" you need the over-size bearings. This would DEFINITELY MAKE ONE HAVE LOW OIL PRESSURE!. -- EVERY SINGLE ONE should be checked, as it could very well be that only one or 2 may have the different size bearings in them. The ISX, although not very common, has been known to come from directly factory where they re-machined a crank or bore to use the next size up bearing as needed to get the engine right.


Another reason why the OEM under-trained gaggle of "slap-it-together and get on to the next victim mentality" morons are NOT TO BE TRUSTED!.

AS TIME GOES ON, there are fewer and fewer mechanics that are properly trained on these ISX engines... it is getting pretty bad these days and only getting worse all the time. Everyone blames these engines for their problems but most always, it is some under-trained idiot that is too much in a hurry to give a damn anymore... leading to problems like this, and costing someone a fortune.