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Author Topic:   another oil press question
Dustejr73
Member
posted February 20, 2004 05:48 PM
Sounds like its definitely not on the tight side,
prolly some worn cam bearings or alot of side slop between the rods or bearing clearances.
Me personally i like them(loose motors)they seem to live where tight ones won't make it,one of my best motors held 45 lbs oil pressure 'round the track and lasted for years.


77k
Member
posted February 21, 2004 11:15 AM
cam bearings or worn cam can cause that.


Ego Racing
Member
posted February 21, 2004 11:23 AM
The old rule of 10PSI per 1000 rpm is a safe mark but I know that with synthetic oils there are many teams going as low as 5PSI per 1000rpm, there are some that run lower, This came for some Nascar crewchiefs in an engine building conference in Daytona 2 or 3 years ago.


Dustejr73
Member
posted February 21, 2004 02:52 PM
The 50# wouldnt bother me on the track as much as the 5-10# at idle. Thats too low even for synthetic. I would guess you bearings are a little on the loose side or possibly you have a standard volume oil pump and it cant keep up with the loose bearings. On our motors I like to see 60-65 on the track and a minimum 25 after a race at idle.


dan ferry
Member
posted February 22, 2004 07:00 PM
here is my thoughts, i put a brand new engine together with all proper machine work and new rotating assembly. i run a high volume pump not high pressure/high volume. checked every single bearing clearance. my engine will do the same thing if you have idle set too low. you can watch the needle surge and light flicker with the lope of the cam.i never noticed the problem when the automatic trans was in because it needed to idle alot higher i switched to manual and changed carb at same time ended up setting idle below what i should have and after running awhile presto light tring to flicker and needless to say my the wind went right out of my sails.. after a little swearing and pouting i put idle back up above 1000 rpms and had plenty of psi.. motor is still brand new looking inside. good luck to all


dirtbuster
Member
posted February 22, 2004 08:01 PM
I wouldnt idle a race motor below 1000rpm. In fact i would say personally 1200 minimum and 1500 is better yet. That way you keep a good amount of oil being flung around inside to keep the cylinders and cam well lubed.


dan ferry
Member
posted February 22, 2004 08:32 PM
yep i dont know how it ended up that low was an oversight i guess or too many hands involved.


udecide66
Member
posted February 22, 2004 08:53 PM
We plug the bypasses on all our engines and they will fast idle(2200) 70-75 cold 65 on the track hot and will idle 30-35 hot after a race at 1500.
If your pump can push 20 psi through the filter cold and the oil is thick thenthe filter should not be more restrictive and cut your pressure down when the oil is hot and thinned out. Personally i think you should have more than 20psi cold even with a standard volume pump and worn out bearings. A fairly fresh motor with a standard pump and 10w30 oil will make 40+ cold at idle. Id bump your idle up to 1200 minimum, you might pick up a little psi, but I think it might be time look into the bottom end, might need bearings and/or a high volume pump to make up with for the excess clearances.


zeroracing
Member
posted February 23, 2004 12:58 PM
Smitty What pump pan combo are you running? You may be sucking all of the oil from the pan and it is not comming back to the pan fast enough.


Okie11m
Member
posted February 23, 2004 09:40 PM
Smitty what kind of oil filter do you run? We had this problem & it turned out to be a FRAM filter. It was collapsing under high flow & cutting the pressure. Even with the bypass plugged, if it wont go though the filter the pump will bypass.


racer2
Member
posted February 24, 2004 06:55 AM
i'll never use another fram. too many oil pressure problems with 50 wt


smitty1856
Member
posted February 24, 2004 08:11 AM
WE had a block that would sit and ilde fine all day long. But as soon as it went on the track and took about a lap at speed lose oil pressure and it would start pumping oil out of the valve cover breather. Turns out the block was cracked and leaking water into the cylinder and the rings never seated. On the track there was enough blowby to pressurize the crankcase and hold all the oil up in the vavle covers and not let any drainback. Changed out the block and it has been fine ever since.


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