More oil system woes, with pix
We have been dyno testing a 598” Boss 9 hemi, and seeing some strange oil system behavior.
Engine data:
4.6” x 4.5”
Our Boss 9 Hemi heads…. (The set from our 2009 Engine Masters 511” entry), Ported
Unported 4500 Kaase intake
1150 dominator carb, by Dale Cubic @ CMF
13 to 1
282-288, .457” lobe, 112 CL Comp Cam
Wet sump pan with our pump
Best power, 1100 HP @ 6900, 875 Ft/Lbs at 5500
This engine is built for a friend to take to Maxton, NC , for the 1 mile speed runs
This has been a great engine, except for the oil system. It has a Moroso road course oil pan. The pickup is ¾ toward the rear, in a 4” x 4” trapdoor box. There is directional screen over most of the bottom. The pan is mostly flat, front to rear, with a trapdoor divider half way back. During a dyno pull, it loses oil pressure, 5 to 10 lbs or more. We tried jacking up the front of the engine to help more oil get to the rear. We tried thinner oil, Mobil 1 0-W50. We tried more oil. Started with 8, then 10, then 12. Then I really got pissed and threw in another 4 Qt, total of 16. Didn’t hurt the power much, but didn’t help the loss of oil pressure. It would start at 60 psi, and go down to 48. When we ran it from 4500 rpm to 7000, the oil gauge would nose dive at 6500 and over. 6200 to 7000 and it still fell at 6500, 4000 to 7000 and it still fell fast over 6500. The length of the dyno run didn’t seem to matter, it was when it reached 6500 rpm and over that the oil pressure went to hell.
The block is aluminum, which has lower head oil drains, so the heads don’t hold much oil in the valve spring area. The lifter lines are restricted. We took it off the dyno and pulled the pan. Bearings were OK.
Because we needed to know whether the problem was the pump or the short block, or the pan, we decided to change pans to my EngineMasters pan and pickup. It’s a 12” deep front sump with no baffles or screens or covers anywhere. Just a big, deep, open pan.
Well, we ran it today, and it was perfect. Even when the oil was hot. It started at 72 psi and would gain a pound or two at 7000. The pressure gauge was perfectly steady, where with the other pan it would bounce a little. We only had 7 qts of oil in the pan!
So, the oil pressure problem was obviously the oil pan. I think most people would have blamed the pump. I had my doubts about it. Now we have to figure out what’s happening in the customer’s pan and fix it. There is a square hole in the screen for the pickup to fit through when the pan is installed. I think maybe all the windage and pulses from the pistons above are disrupting the oil around the pickup.
Next week we’ll work on the pan, and I’ll post some pictures and dyno sheets here.... Kaase
We have been dyno testing a 598” Boss 9 hemi, and seeing some strange oil system behavior.
Engine data:
4.6” x 4.5”
Our Boss 9 Hemi heads…. (The set from our 2009 Engine Masters 511” entry), Ported
Unported 4500 Kaase intake
1150 dominator carb, by Dale Cubic @ CMF
13 to 1
282-288, .457” lobe, 112 CL Comp Cam
Wet sump pan with our pump
Best power, 1100 HP @ 6900, 875 Ft/Lbs at 5500
This engine is built for a friend to take to Maxton, NC , for the 1 mile speed runs
This has been a great engine, except for the oil system. It has a Moroso road course oil pan. The pickup is ¾ toward the rear, in a 4” x 4” trapdoor box. There is directional screen over most of the bottom. The pan is mostly flat, front to rear, with a trapdoor divider half way back. During a dyno pull, it loses oil pressure, 5 to 10 lbs or more. We tried jacking up the front of the engine to help more oil get to the rear. We tried thinner oil, Mobil 1 0-W50. We tried more oil. Started with 8, then 10, then 12. Then I really got pissed and threw in another 4 Qt, total of 16. Didn’t hurt the power much, but didn’t help the loss of oil pressure. It would start at 60 psi, and go down to 48. When we ran it from 4500 rpm to 7000, the oil gauge would nose dive at 6500 and over. 6200 to 7000 and it still fell at 6500, 4000 to 7000 and it still fell fast over 6500. The length of the dyno run didn’t seem to matter, it was when it reached 6500 rpm and over that the oil pressure went to hell.
The block is aluminum, which has lower head oil drains, so the heads don’t hold much oil in the valve spring area. The lifter lines are restricted. We took it off the dyno and pulled the pan. Bearings were OK.
Because we needed to know whether the problem was the pump or the short block, or the pan, we decided to change pans to my EngineMasters pan and pickup. It’s a 12” deep front sump with no baffles or screens or covers anywhere. Just a big, deep, open pan.
Well, we ran it today, and it was perfect. Even when the oil was hot. It started at 72 psi and would gain a pound or two at 7000. The pressure gauge was perfectly steady, where with the other pan it would bounce a little. We only had 7 qts of oil in the pan!
So, the oil pressure problem was obviously the oil pan. I think most people would have blamed the pump. I had my doubts about it. Now we have to figure out what’s happening in the customer’s pan and fix it. There is a square hole in the screen for the pickup to fit through when the pan is installed. I think maybe all the windage and pulses from the pistons above are disrupting the oil around the pickup.
Next week we’ll work on the pan, and I’ll post some pictures and dyno sheets here.... Kaase