The V8 Owners Forum -

hi guys, I have posted here before about a drop in oil pressure on my 3.5 RV8, but it just dawned on me..... I'm running an oil cooler through a sandwich plate at the oil filter, if the lines were too small a bore, this would reduce oil pressure in the block would it not??
Basicaly I'm running coolers from an RX7 and they run a 10-12mm bore to feed them, could this be my problem, or would it not affect the pressures?

Cheers
Jono

Hi
yes you are right it will reduce oil pressure, but 10 to 12mm bore lines are not too small (well 10mm are a on the lower end). It would help a lot to radius all the holes in the sandwich plate, and anywhere else in the oil system you can get to.
best regards
Mike

Hi Jono,

I have an engine oil cooler on my 4.6, with a sandwich plate before the oil filter, and my engine hasn't seen a drop in oil pressure. My cooler is designed for the Rover V8, so that may well be part of the reason.

Has your oil pressure drop only happened since you fitted the oil cooler?

Ron.

Oil cooler was fitted when I dropped the engine in, so can't realy say..... but I will have to check a few things in the next week or so (Rockers and try removing the oil cooler and resurface the pump housing when I do the service) as I need to get her ready for next seasons skids prety soon!!

Jono

10-12mm bore lines are bit bigger than fitted to my factory built MGB V8 with the 3500 engine. So I doubt that this will cause a drop in oil pressure.
Think about this for a moment. Where is the oil pressure gauge connected?

Before or after the cooler?

If its before the cooler and the cooler lines were too small you would expect to see an increase in oil pressure wouldnt you?

If its after the cooler and the lines were too small you may see a drop in pressure.

Does this engine have a dissy driven oil pump or crank driven pump?

Dizzy driven pump on her (SD1 engine) and the presure gauge is in the housing above the oil filter where the stock oil presure gauge would sit, so not sure if that is before or after the cooler???
I think the problem could be the rockers as they were purchased off ebay 2nd hand, but need to pull the covers off to check. The other thing is my rad is a tad too small and the water temps are around the 95-100c so this could be thinning the oil as a result and dropping the oil pressure?

Jono FD3 wrote:Dizzy driven pump on her (SD1 engine) and the presure gauge is in the housing above the oil filter where the stock oil presure gauge would sit, so not sure if that is before or after the cooler???
I think the problem could be the rockers as they were purchased off ebay 2nd hand, but need to pull the covers off to check. The other thing is my rad is a tad too small and the water temps are around the 95-100c so this could be thinning the oil as a result and dropping the oil pressure?

Hi Jono,
From what you have described the pressure gauge is after the cooler.
A clogged cooler could be causing the problem or collapsed/kinked pipes to the cooler.
BUT.
There are so many points on the RV8 that affect the oil pressure.
Are you using a 20/50 oil or a thinner type?
Worn rockers/shaft are a common cause of pressure loss.
A worn oil pump is another,
Worn camshaft bearings is another.
Obviously worn crankshaft bearings is another.
A sticking pressure relief valve in the oil pump is another possibility.
An air leak on the sump pickup pipe or front cover gasket also.

Regards Denis

Cheers for the info matey
Shall be having a look through those bits
Engine has had a refresh, replaced the rings, bearings and gaskets with new..... The engine was a fairly high miler mind, so could be the pump, would it be the gear set thats worn, or the lower housing plate below the gears, also where abouts is the relief valve?
The oil cooler pipes are all fresh rubber lines (hydrolic pipes) so shouldn't be any kinking with them and oil is the Comma Sonic 20w/50 so again, the correct oil for the engine

Jono FD3 wrote:Cheers for the info matey
Shall be having a look through those bits
Engine has had a refresh, replaced the rings, bearings and gaskets with new..... The engine was a fairly high miler mind, so could be the pump, would it be the gear set thats worn, or the lower housing plate below the gears, also where abouts is the relief valve?
The oil cooler pipes are all fresh rubber lines (hydrolic pipes) so shouldn't be any kinking with them and oil is the Comma Sonic 20w/50 so again, the correct oil for the engine

The relief valve is in the oil pump cover behind the largest hexagon plug.
Don't know much about the Sonic 20/50 but I have vague recollections of hearing that others had problems with it.

mmmmm, What oil would you guys use then?
Reason I ask is most of the recomended oils on the forum have been discontinued which was why I went for the sonic

Jono

I use Valvoline VR1 20/50 as it has an additive suitable for flat tappet engines.
Regards Denis

Sweet, cheers matey, I've just seen the Valvoline VR1 on an ebay search!
Think I shall give that a try for next season and keep the sonic as a top up if it needs any!

Don't overlook that the location of the pressure sensor is quite important. For some reason TVR put their serp sensor in the oil cooler take off tapping immediately on the pump exit ~ hence seeing the maximum measurable pressure in the engine? Difference between the sensor & switch locations can be over 5psi from what I've measured (even without oil cooler etc.)

spend wrote:Don't overlook that the location of the pressure sensor is quite important. For some reason TVR put their serp sensor in the oil cooler take off tapping immediately on the pump exit ~ hence seeing the maximum measurable pressure in the engine? Difference between the sensor & switch locations can be over 5psi from what I've measured (even without oil cooler etc.)

Yes, the TVR serp engine (Chimera) read point measures the pump output pressure and can be confusing as the gauge reading increases as the filter becomes clogged with use. Putting new oil and filter in gives a lower gauge reading which misleads a bit but the engine is actually getting more oil.
Not applicable in this non serp situation though.

Regards Denis

Hi Denis,

I use the Comma Sonic 20/50 so be interested in what you have heard and is it backed up by anything factual. It seems to have good levels of additives based on the spec

Regards
Reg