RS Motorsport :: Classic Speed Restored

As I have mentioned elsewhere, sometime after a previous event I started seeing around 60psi oil pressure rather than the 80+psi that I always had before. Have ot been able to find the cause yet although everybody decided previously that 60psi is nothing to worry about. Seeing as I have the engine out of the car I want to find the cause.

The dry sump pump has been pulled apart and has a big issue with one of the scavenge sections (the section taking from around #3 & #4 cylinders) but the pressure section only has light scoring - probably not enough to effect pressure.

I have removed the sump (as it leaks and I need to find where - could be via the gasket due to the poor scavenging causing the sump to overfill?) so am thinking of checking the bearings. The engine is NOT making any noise (not that I could hear over the destroyed gearbox bearing lol) but I have noticed that #4 rod cap has at least twice the sideways movement of the other 3. Might be a good starting point.

Is there a tolerance/measurement for the big end 'wobble'?

I assume there is not issue with removing the rod caps whilst the engine is assembled on a stand?

I cannot find details of what torque the engine builder used for the rod bolts. No loctite I assume? Ideas on torque?

Is it worth using plastigauge to measure the bearing clearances?


I am inexperienced in playing with engine internals so am treading carefully. I do not want to get the engine checked over by the builder if I can avoid it but maybe you would suggest I do that?

I don't know much about dry sumps either. Is their a pressure regulating valve in the system that could be playing up? If it cant scavenge properly will that drop pressure?
Was there any metal in the oil?
The rod bolts should have been assembled and torqued to manufacturer settings with the supplied lube(ARP bolts anyway)

This sideways movement, I assume its along the crankshaft journal ie north/south?

The sideways movement is just the rod sliding along the journal and is stopped only by the counter weights. Just seems that one journal is a fraction wider than the other 3 so I don't think there is an issue there.

The pump does have a pressure relief system but that was previously checked and OK.

Looking at the sump, there are marks on the windage tray where rod bolts on #3 and #2 have been hitting it. #3 has caused a 1mm deep gouge and that oil would have gone through the scavenge that has the wear so it appears I have found the cause of the pump issue.

So there is nothing to stop me taking off a cap to check the bearings then retorquing to spec? If I do this one at a time then no issues?

If the sump isn't scavenged properly there will be not enough going back to the tank and the pressure stage cavitate because it's sucking air but if you fill the tank enough it's not an issue
All your dramas are in the pressure stage and relief valve
Big end float is not something that effects pressure only temperature of the oil and too be honest you can't run enough clearance as I run at least 0.010" and Nascar guys run as high as 0.125" and guide the rod with the gudgeon boss, who assembled the engine and what bearing clearances did it get

Chris Milton Engines

· Main Clearance .0022” to .0025”

· B/E Clearance .0025”

Mains 90lbft
Rods 50lbft

Following on from Danny's comment about poor scavenging I decided to take a look at a sump issue that has been in teh back of my head since I bought it.

I have a dry sump that is a modified standard sump (bought from UK). It has a windage tray in it but that tray is a solid sheet of metal with no holes for oil to drain into the bottom. One side of the tray has a 6mm gap where the oil drains. I have always thought that this design would not be providing sufficient oil drainage and may well 1. cause scavenge inefficiency and 2. cause the crank to still sweep through alot of oil.

Having looked at many windage tray pics on the line my first thought was to cut some slots into the tray as shown has the pink lines below;

Sump2.jpg (127.09 KiB) Viewed 8676 times

I had thought about doing more but decided it may be unnecessary. What are your thought on this??? The original manufacturer must have had his reasons for not adding holes/slots originally but I cannot see a reason not to do it.

Also, he has brazed the tray in place. I do not have the tools to braze so I cannot see any reason why it cannot be spot welded back in after I remove it (need to find the source of the pan leak)??

BTW - the 2 silver diamond shapes inside the pan towards the top is where the rod bolts have scrapped the tray. This has removed up to 1mm of tray material and is no doubt the cause of the damage I have in one of my oil pump scavenge sections. Will need to be carefull there is no rubbing when it gets put back together.

Leave it alone as cutting holes in will defeat the purpose of stopping the windage

Glenn, can't find your emailaddress ... but if I had I could send you a photo of a Pace drysump pan. Regards, Leon.