22 replies to this topic

[DEXISWOLF]

Ive recently just bought and fitted a short 1380 engine kit i got from jonspeed, now i got it fitted and ran lovely apart from a problem with the oil pressure, it was 70-80 psi but dropped slightly to 55-60 when revved , and once warmed up it drops to 40-50 at idle and drops more and more as rpm increases the lowest i let it get was 20psi then let off the pedal and it shot back to 40-50 so i figured there must be a fault somewhere so i changed oil filter , pressure relief valve, tried ball and thimble type, changed filter housing and tried 3 different gauges! So in the end i took to engine out and stipped it down,
Every crank shell was like new still so i changed the pump and gasket just incase that was faulty and also the gaskets on the oil pickup, rebuilt it all and its still exactly the same, now im completely out of ideas because the engine does run and sound nice apart from the lack of pressure at higher rpms , one thing i seen on reading through other topics on mini mania someone had similar issues and it was down to a cracked web in the block so im hoping its not that

[nicklouse]

I would be trying a known oil pressure gauge just Incase you a have a fault with your current one.

If it does the same then strip and measure the journal sizes to check they are in spec.

[imack]

If the oil pressure's dropping as the revs increase I'd be looking for a blockage before the pump.
Is the gauze clear on the pick up pipe? Pick up pipe clear? Gallery between pick up pipe and pump clear? Oil pump gasket fitted the right way around?
A leak in the pick up pipe, gaskets between pipe and gearbox or block to gearbox or between pump and block (pump mounting bolts too long) may also cause problems but if a leak in the pick up side of things was present I'd expect to have difficulty building oil pressure in the first place.

[DEXISWOLF]

Ive tried 2 more gauges just incase and still the same readings, i think either way im pulling it out again but i would have thought there would be damage to the shells if the journals was out ?

[DEXISWOLF]

If the oil pressure's dropping as the revs increase I'd be looking for a blockage before the pump.
Is the gauze clear on the pick up pipe? Pick up pipe clear? Gallery between pick up pipe and pump clear? Oil pump gasket fitted the right way around?
A leak in the pick up pipe, gaskets between pipe and gearbox or block to gearbox or between pump and block (pump mounting bolts too long) may also cause problems but if a leak in the pick up side of things was present I'd expect to have difficulty building oil pressure in the first place.

Ive tried all the above, my forst port of call was the oil pump/gasket so i changed both, and checked the bolt lengths to make sure, ive even tried different brand oils and its still the same, the pickup pipe is clear and i changed the gaskets on that too twice just to make sure and the o ring box to block is definitely there i even changed that again to make sure aswell , nothing i have done has changed it slightly the readings have been the same every time

[DEXISWOLF]

The only thing i havent checked yet is the head, is there anything up there that can cause this as i presumed it would be more the bottom ends problem of sorts ?

[nicklouse]

Nope. The pressure is made in the block. Excess flow to the head would see a rocker cover full of oil but no loss in pressure.

[DEXISWOLF]

Thats ok then i thought that was the case but thought id ask just to make sure

[imack]

If you're pulling the engine again I'd definitely check that the oil pump gasket is correctly orientated.
If you fit the gasket to the pump first and then fit the pump and gasket to the block it's very easy to fit the gasket backwards which then blocks or partially blocks the feed to the pump.
I speak from experience, I now always fit the gasket to the block first when it's really easy to see if it's fitted correctly.

Wrong way

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Edited by imack, 22 September 2019 - 04:47 PM.

[DEXISWOLF]

I did fit it to the block first with the big and small holes lined up ? Its one thing with every pump ive fitted ive been so paranoid about that gasket so i have to check it about 60 times before i tighten them bolts up ?

[carbon]

The only time I have experienced oil pressure dropping with increased rpm was because of excessive clearance on the big-end bearings.

 

Was most noticeable when engine fully warmed up after a run.

[DEXISWOLF]

I hope not, i used the bearings that came in the kit, i wish i had measured them now but i assumed all that would have been done back at jonspeed

[cal844]

I hope not, i used the bearings that came in the kit, i wish i had measured them now but i assumed all that would have been done back at jonspeed

That's what a proper rebuild is, maybe it was an inexperienced user that measured your engine? I hope not! I'd be chasing Jonspeed for all it's worth and explaining the situation

[Rorf]

Check bearing clearances with plastigage or micrometers; what is the thrust bearing float clearance; have the cam shaft bearings being installed correctly and how is the clearance there. Are the oil gallery plugs in correctly - not leaking slightly. What oil are you using. There could be a problem with the pressure relief valve seat. What intake type are you using - there could be a restriction there. Hopefully you don't have blobs of silicon gasket sealer in the system. 

[gazza82]

I hope not, i used the bearings that came in the kit, i wish i had measured them now but i assumed all that would have been done back at jonspeed

 

You obviously didn't read this ..

 

http://www.theminifo...n-speed-racing/