92/95TransAm

i just got finished rebuilding my LT1. i broke it in got small problems figured out and took it for a drive. at idle (running temp) the oil pressure sits just under the first line on the oil pressure guage. is this low or about normal? it has 5-30 in it for break in oil. i will be switching to 10-30 tomorrow or tonight.

MachinistOne

You have some problem....you say you broke it in...its a roller cam, not necessary. Did you look at the oil pressure guage when you first got it running? Do you have specs on bearing clearances...who preped the block and installed oil plugs in it...

slowpoke96z28

do you have access to a real oil pressure guage? get one and chech the pressure. you should have about 6psi at 1000 rpm, 18 psi at 2000, and 24 psi at 3000

MachinistOne

Ummm...no

You should have minimum 20psi idle, 65psi WOT

slowpoke96z28

based on what?

1racerdude

Based on the principals of engines and what they should do.
Go with a streight 30 and see if it comes up on a manual guage. 25-30 idle and 40-45 at 4000 would be the minimum I would like to see on a fresh engine.

slowpoke96z28

what did you get for main bearing clearances when you measured? that will have an affect on it. as far as the pressures i posted, those came out of the Helms manual for a 1994 LT1, and seconded by a Chiltons manual. however, who ever manufactured your bearings(ie Clevite, Federal Mogul, etc.) would have the final say.

1racerdude

Well if any engine I built for a customer had 6psi@1000 I would tear it back down and find out what was wrong, because something IS wrong with that kind of oil pressure.

CamaroSS30thAnn

mine usually goes up to about 45-50 when wot , its been idling kinda low lately , its teh second time i lost pressure making a left hand turn in 3 month period,
im getting kinda worried, i guess im gonna have to change the pressure sensor if that dont work im most likely gonna have to drop teh pan to check teh pickup

slowpoke96z28

yeah, you should have about 20 psi at idle on a fresh or new engine, but you are allowed(per the manual), at a minimum what i stated above. thats just the way i interpreted what he was asking. main thing is get a mechanical oil pressure gauge and use it. don't rely on the dash gauge when you are concerned about the health of a brand new or rebuilt engine. and if you don't believe any of our specs, call the bearing manufacturer. the bearing is what the oil pressure is critical to, so the bearing manufacturer will be able to tell you what kind of pressure his bearings work well with. i don't build engines every day, so i'm not as experienced as these other dudes, but i have built a couple. for the record, i'd be concerned if it was less than 15 psi on a new engine. just me though.

92/95TransAm

the engine has been at about 10- 15 PSI idle according to the electric guage and at about 60 psi expressway speed. all of the bearing clearances are .003. the oil plugs were installed by the machine shop along with the crank polished but not turned. my bearings are federal mogul and all are stock size. i dont have access to a mechanical guage at this time but i will try to get ahold of one and see what it says.

BLinindoll

I will second the fact that 6 psi at idle is the spec on an LT1... new or old, it doesn't matter. I have looked into it long and hard. This was also confirmed by one of my professors. He said many engines these days are designed to run on a very low oil pressure. The LT1 is one of them. All engines are not build the same and are designed to run at different specs.

MachinistOne

The LTx is just a small block chevy....it does not have any special things that control oil pressure other than the oil pump displacement, pressure spring, bypass valve, bearing clearances, etc....it should be at 20 psi min at idle. Are you sure that the oil plug under the main cap was installed? I don't think that would effect overall pressure, as it only directs oil to the filter, but I have never tried to run a motor without it lol, its easy to miss if you havent done these motors a lot.

BLinindoll

Yeah, maybe cold, but not warm.

I can't find the PSI spec at idle at the very moment, but at 2000 rpm's the spec is 18PSI at operating temp. That information is directly from the ARRC site. At idle it will be around 6PSI (I've seen in another source, I just don't have access at the moment). The info on the ARRC site is usually exactly the same info as in the service manuals, which come directly from the manufacturers. If you don't believe me then look it up for yourself, but don't just base your answer on another engine, even if you THINK it should be the same or not, because obviously, it's not.

MachinistOne

You are looking at what the "min spec" number is......