As part of my effort to find a reason for low oil pressure in my pinto engine I have tonight dropped the sump and checked the main bearing clearances.
The method I have used is to insert a piece of feeler gauge behind the shell then to re-tighten the cap and see if the crank is nipped. I found that
with a 0.05mm feeler in the crank would still turn, the crank would only nip with either 0.08mm or 0.1mm.
Assuming I have used the correct method this looks well over the recommended max in the Haynes manual of 0.063mm. Have I done this right and if so is
this the likely cause of my low oil pressure when the engine is hot?
The engine was only re-built last year and I am sure I checked the clearances just after the rebuild and they were okay, which coupled to the fact
that the oil pressure was a lot better then also makes me think this is the problem.
Any help would be really appreciated.
I would have the crank measured at an engineering shop and then order a new set of shells to match.
Can't be the problem after that.
HTH
Mark
What do you call low pressure ?
When it is properly hot, down to about 15psi. 75psi when cold using 20/50.
is the low pressure when its hot on idle or hot with 2500/3000RPM
quote:
Originally posted by Orange Indy
When it is properly hot, down to about 15psi. 75psi when cold using 20/50.
Even under revs once the oil gets properly hot (unfortunately I cannot say what 'hot' is as I have not oil temp gauge) after the engine has been running for 30mins or so, the pressure drops off. Does not drop below 15psi though even on idle.
My engine had a full rebuild last year when hot at tick over it has 15 psi at driving speed about 3000 rpm it has about 50--60psi i dont see a
problem with this
Jacko
I had my Pinto built with 2x the normal clearance for maximum power and have a high pressure high capacity oil pump. Running fully synth oil.
When hot I get about 15psi at idle going up to about 50-60 at few 1000 revs. When cold it's off the gauge at 90psi.
So has anyone go any views on my clearances? Have I used the right method to check them and is the fact that they are this much over the recommended
gaps the probable cause of my low oil pressure when the oil is hot?
Cheers
James
Your main bearing clearance should be 0.05-0.064mm. Toward the higher end if possible for a high performance engine.
The only proper way to measure bearing clearances is with Plastigauge, as even measuring with a micrometer with the crank out will give you variable
results due to how the bearings are made and how they fit in the tunnels.
David
You can get Plastigauge from Burtons - fairly cheap, and comes with instructions. If you do what's required then you'll know exactly what the clearances are.
Thanks - will give that a go.