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Covalt - 85 D100
https://www.slantsix.org/forum/viewtopic.php?t=56667		 Page 21 of 21
Author:  Rick Covalt [ Sat Jan 18, 2025 8:47 am ]
Post subject:  Re: Covalt - 85 D100
When I had the "brain" issue and was trying to find out why I didn't have oil pressure, I actually swapped out the oil pump for one i had on the shelf. It was an early, aluminum, narrow rotor pump and had about 50# at WOT and 20-25# hot at idle. But I had the original pump that was mated to the cam in the truck; so yesterday I unbolted the RH motor mount and jacked the engine up a smidge. I removed the aluminum pump and installed the newer wider rotor pump that went with the camshaft. Fired everything up and took it for a ride. Allowed temp to get up to about 200 degrees so I know everything was hot. Checked my pressures and had about 52# at WOT. But my idle pressure was up at about 35#. I am guessing the wider rotor pushes a little more volume at idle than the aluminum pump did. Now to find that pesky rattle I hear every once in a while! :D :D
Author:  Charrlie_S [ Sat Jan 18, 2025 11:17 am ]
Post subject:  Re: Covalt - 85 D100
That is as it should be. Look at it this way. If the rotor is 10 % wider, then at any given rpm the pump will pump 10% more oil. So with the restriction of the oil system being the same, the pressure will increase at any given rpm. This will hold true until the pressure reaches the pump bypass valve setting, at which point the valve will open and bypass the excess oil volume to maintain the pressure at that number.
This is why changing the bypass spring will have no effect on the low rpm oil pressure, with a given pump. The pump does have enough volume and just cannot supply enough oil to the engine. It is also why in most cases a slant does not need a "high volume" oil pump.
Author:  Dart270 [ Sun Jan 19, 2025 8:22 am ]
Post subject:  Re: Covalt - 85 D100
Charlie explained it very nicely!
Lou
Author:  Rick Covalt [ Sat Feb 01, 2025 11:18 am ]
Post subject:  Re: Covalt - 85 D100
I finally pulled the engine apart that we removed from the truck after the Knoxville race. I think I found the problem. :D :D
Attachment:
piston.jpg
piston.jpg [ 422.51 KiB | Viewed 5025 times ]
Pretty sure that is why it had so much blow by. :D It also had a couple other top rings broken but still in place. This was a "quick" re-ring on an old engine I picked up for cheap. I cut the cylinder ridge and then did a quick hone and installed new rings and bearings.. I imagine the rings broke first then the piston went down hill from there. The engine had run 5 or 6 racing seasons in my Valiant, then was placed in the truck for the last 2 or 3 years. It made trips to London, Knoxville. Wilkesboro...etc, so it probably had 8-10000 road miles on it before this happened.

I already have a set of reconditioned rods with .030 over pistons on them. So I will probably just get the block cooked / cleaned and then bore it .030 over. Crank looks pretty good but will need a polish at least.
Author:  Greg Ondayko [ Sat Feb 01, 2025 2:34 pm ]
Post subject:  Re: Covalt - 85 D100
nice to find out what happened.

Looks like some of Charrile's Nitrous Passes pistons.

Maybe Ryan put the Hose sprayer on there when you were not looking?
Author:  Charrlie_S [ Sat Feb 01, 2025 4:40 pm ]
Post subject:  Re: Covalt - 85 D100
Quote:


Looks like some of Charrile's Nitrous Passes pistons.

:lol: :lol: :lol: :lol: :lol:
Author:  Rick Covalt [ Sat Feb 01, 2025 7:01 pm ]
Post subject:  Re: Covalt - 85 D100
Quote:
Maybe Ryan put the Hose sprayer on there when you were not looking?
I looked closely and could not find any hidden nitrous bottles! :D
Author:  Greg Ondayko [ Sun Feb 02, 2025 4:38 am ]
Post subject:  Re: Covalt - 85 D100
Quote:
Quote:
Maybe Ryan put the Hose sprayer on there when you were not looking?
I looked closely and could not find any hidden nitrous bottles! :D
That's good but you were busy that weekend not getting red lights, playing with GM LS Spark plugs and such!.. I bet he threw it in the creek before you came by, then said, "it's running badly."
:D :D :D
Author:  slantzilla [ Sun Feb 02, 2025 1:15 pm ]
Post subject:  Re: Covalt - 85 D100
At least it's not too horrible. :mrgreen:
Author:  Rick Covalt [ Sun Feb 02, 2025 4:39 pm ]
Post subject:  Re: Covalt - 85 D100
Quote:
At least it's not too horrible.
So a 3/4" wide ring land should be Ok? :D Just run 20W 50 oil.
Author:  Charrlie_S [ Sun Feb 02, 2025 5:00 pm ]
Post subject:  Re: Covalt - 85 D100
Quote:
Quote:
At least it's not too horrible.
So a 3/4" wide ring land should be Ok? :D Just run 20W 50 oil.
Straight 50 with 2 cans of STP added. :P
Author:  slantzilla [ Sun Feb 02, 2025 7:13 pm ]
Post subject:  Re: Covalt - 85 D100
As opposed to rods kicked out the side......
Author:  Rick Covalt [ Sun Feb 02, 2025 8:32 pm ]
Post subject:  Re: Covalt - 85 D100
Quote:
As opposed to rods kicked out the side......
Yeah! For sure. Really surprised it ran home 500 miles as well as it did. :D
Author:  Dart270 [ Mon Feb 03, 2025 6:47 am ]
Post subject:  Re: Covalt - 85 D100
Thanks for the detailed report, Rick. Best wishes getting it back together in better-than-ever running order.
Lou
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