Getav8

I just had a entire new motor put together from the rods to the oil pump.

When it is first started it has good oil pressure at idle (just above 40) and will climb above 60 during accelleration. After the car warms up it falls to 20 pounds or just bellow that and will barely get over forty pounds even on hard accelleration. I put the first 500 break in miles on the motor with what i was told was a break in oil.? I was then told to run a dino oil for the first 1000 miles after that before switching to a synthetic. I now have castrol 5w-20w in it. (not sure what the starter oil was) I had the same problem with both so far. As soon as I get to the 1000 miles I plan to switch to mobile 1 15w-50.

When I asked the builder why pressure was low he told me the engine was built that way, that the tollerances were not as tight as a stock motor so it would have more of a coating of oil between parts in the motor. (i cant remember the technical words he used to descride this) He said that this motor was made to be beat on.

This does not sound right to me but, I am looking for some educated opinions on this. The builder is a very reputable place and hasnt steered me wrong yet but something doesnt sound right to me on this.
Thanks,
Getav8

wrencher

iTrader: (2)

Did he say it was excessively clearanced? I wouldnt want it have loose bearing tolerances IMO. I wouldn't run 5w20 either....

LS1Maniac

You only need 5 psi for every 1,000 rpms, 20 psi at idle is more than enough unless you're idling at over 4,000 rpms.

It's not anything to really worry about. You're running a much thinner oil on a non-stock engine, the psi is going to be lower, especially once the oil warms up. You'll be fine.

yak

iTrader: (15)

my car is mostly stock and I only have about 25psi at idle. Is that bad?

Getav8

No, he said it was originally built to handle a 200-250 shot of spray. He is suppose to give me the build sheets with all the tolerances by part.

Getav8

When mine was stock it would idle at 40 psi

Getav8

I hope so i wouldnt want to have premature failure on anything due to lack of oil flow.

yak

iTrader: (15)

mine used to sit at 40, but I noticed in the warmer weather it dropped to about 20. I think my oil pump may be going. any ideas?

Camaroholic

iTrader: (1)

Depending on your main and rod clearance, yes, that can affect oil pressure. I had to re-line-hone my 1000 mile block when I switched it from a 346 to a 383, the mains were that far out of whack. If your builder didn't set up the mains tight, I could see it. Without the line hone, I was looking at .0035" clearance on the mains with +1 bearings. We decked the caps and line honed it and got .0020 (you want to set it up tight, because the aluminum blocks expand quite a bit when hot).

So check your build sheet for the main bearing clearance, and that *may* answer your question as to why it's a little low. Now what can you do about it? Probably not much. Run a slightly thicker oil. Is it bad? Doesn't really sound like it.

Getav8

How many miles do you have? Mine is a 98 also it had 133,000 hard miles on it. I notice over the last year that the pressure was starting to drop it went from around 40 at idle to about 30. Three weeks ago on a top end run it bent 4 push rods and broke another. Hence the reason I have a new motor.

Getav8

I will get them to send me the build sheets. He showed them to me but they still needed to be put together in the computer to give me a print out.

Inspector12

iTrader: (29)

Look that low oil presure at Idle is fine if it was set up that way. It's not going to hurt a think and unless he told you to run that 15w50 I would stick with a 10w30 or 10w40. That thicker oil can work against you on cold start up and even when you are getting on it. People are just used to judgeing how good there engine is by it's oil presure whitch has nothing to do with it so don't be afraid just use a good synthetic when you are done breaking it in how every you want.

Getav8

Thanks.

Inspector12

iTrader: (29)

No problem. I have had lengthy conversations about this when I was talking with Kurt over at W2W about seting up my clearances on the motor I was building for myself etc... Have fun.
Jeff