Hi everyone !

I'm lost !

here the story :

2002 Corvette C5 with LS1 engine of course.

Engine rebuilt by myself completely all bearing are new.
forged piston, FAST 102 intake, camshaft ....

New mellins oil pump, underdrive cranck pulley and new ARP bolt.

I install an autometer oil pressure sensor just before the oil filter, so I can read the oil pressure at the exit of the oil pump and compare to the stock oil pressure sensor.

When I start the engine, I didn't pay attention to the oil pressure but I haven't the "check gauge" warning light ....
I drive the car to make the new tune (with HP tuner). No problem.
After 400miles I push the car harder to tune the WOT, I do 3 10mph to 160mph without any problem.
Then I put the 3rdgear (automatic gearbox) go to 6000rpm the let the car goes down and I got the firt low oil pressure warning light.
I check, no oil leak at all, no smoke, spark are good so no oil in the cylinder, oil level stay the same, so no oil leak.

I check and change the O ring of the pick up tube.
I check the inside of the pump, look good
I check the oil line in the block, ok.
I change the oil, change the oil filter (3 time), same pb.
I change the stock oil pressure sensor

When everything is in place, I read 6/7PSI at the stock sensor and 18PSI at my autometer sensor ... so not enough pressure ! I guess the difference is because of the oil filter.

As soon as I remove (or just unscrew and push back of 0,1inch) the pulley I got 20 PSI from the stock sensor and 40 PSI at my autometer gauge.

I got the same result with the stock oil pump so it's not the pump. I even try with and without the timing chain cover (to check if it is not "touching" the pump because the meelins is 0,1inch wider thand the stock one ...)

I have modified the pulley itself by reducing the diameter of the "part" touching the end of the crakshaft (sorry cannot explain well, I not speaking english well .. I'm french .. nobodies perfect I know lol). So The pulley do not touch the pump.

I didn't try yet with the stock pulley ....

Have you an idea ? everything is good as soon as the pulley is not screw at maximum.

For information I have some mark on the crackshaft, and after a few start and stop for 5 sec, the cranckshaft is hot, the oil pump is VERY hot but the oil inside is cold .... (but as I said, I change the pump and I have the same problem).

 

Can you provide pictures of what said screw in pulley? And all of the things you mentioned?

 

If its the high low melling pump I have it too. I installed mine a few months ago and have no issues. Make sure the spacers are on correctly and not blocking anything. Even my stock sensor reads 40psi idle hot. Also make sure you oblong the hole on the pickup tube to compensate for the width of the spacers. It MUST sit 100% flush. I've done this twice on 2 different setups and never had an issue. pic should help. There might be other things going on but try this first. Even a slight pinch on the oring is bad...

 

thanks for your reply.

I'll make some pictures tomorrow.

Concerning the pump, the pickup tube and the pump fit correctly. Could you explain me what is the "spacers" ?

As I have the same pb with the stock pump, I think the pb is another thing.

 

If the "crankshaft is hot" and the "oil pump is VERY hot", but the oil is cold that ain't good. Friction(interference) causes heat which oil is supposed to prevent, but if the parts are getting hot before the oil has time to warm up you have metal to metal interference somewhere. It sounds like some parts which are adjacent to each other are not moving at the same speed or one is moving and the other is NOT. As far as the spacers are concerned they may be talking about the spacer that move the oil pump forward when a double row chain set is employed. Because of the design of the double chain and sprocket the pump sits forward by about 3mm so shims are used to take up this space. I like the idea of opening up the hole for the pickup bracket. This idea could also work on the flange that fixes the pickup tube into the oil pump where the "O" ring is located when installing a double row chain. Because of the spacers the tube must be forced forward by 3mm which it doesn't seem to want to do. Opening up the hole in the flange with a dremmel tool would help solve this problem. I'm going to make myself a note to remember to do this the next time I install a Rollmaster.

 

Hi eallanboggs.

You'r right about the fact of metal to metal interference. I'll check that.

Maybe it is the reason that I don't get enough pressure. So first pb "solve" ...

But why I got the same pb with the stock pump (which is not getting hot).

For info, I do not have a double row chain.

I'll post some picture later this day.

 

Here is two pictures.

first :

you can see the marks on the cranckshaft because of the rear of the oil pump (2nd picture). that's why the oil pump became hot before the oil.
On the first picture you'll also see the work I have done to the pulley to be sure it not touching the oil pump.
I'll check on the timing chain cover I think the oil pump touch it ....

Instead of these pump pb, I still have the same pb with the stock oil pump, which fit perfectly and do not touch the cover.

I'll try today with stock oil pump and stock pulley.

 

It does NOT appear that the crank pulley is fully home in the 1st picture unless that picture is for illustration purposes. There is a gap between the rear of the pulley hub and the front face of the of the timing chain/oil pump sprocket. When the pulley is finally assembled it should buck up to the sprocket. The pulley, crank and sprocket should all be married together and spin at the same speed. The crank pulley is an interference fit to the crankshaft. The force(torque) required to push the pulley home is nearly constant until the two faces meet each other. At that point the torque required to turn the crank pulley bolt goes to infinity.

 

Yes, it is just to illustrated. When I screw to end, to pulley touch the cranckshaft as you said.

But I think that it require more and more force to push the pulley home... no ?

 

Maybe it's been covered already, but did you make sure the pump was centered on the crank? Looks to me that the drive gear on the crank is touching the pump housing?

 

is it a stock crank?
with hemi stuff, we had to chamfer the crank gear using a certain aftermarket crank (K1 i think..) otherwise it would cause the crank gear to bind against the oil pump and promptly destroy the pump.

just thinking outside the box here... trying to familiarize my self with LSx stuff cause im fixing to sell my hemi

 

Yes the crank is stock.

Yes, the oil pump housing (thanks for the word) is touching it. I though the pump was centered but it shouldn't ... how could it happen with the 4 bolts ...?

Last new, I didn't see it before ! When I put the sotck pulley to try (but I cannot because of the time ) I see some mark on the timing chain cover ...

looks like the pulley touch the cover !

SO pulley touch the cover, cover is pushed on the oil pump, oil pump "moving", touching the crankshaft and loosing pressure ... ? What do you think ?

 

The force required to push the pulley fully home should increase only slightly as the pulley moves closer and closer to the home postion, but once the pulley bucks up against the sprocket the torque instantly goes through the roof. Maybe the pump is NOT concentric with the crankshaft. If this is a concern you can use 0.002" feeler gauges. You need at least 2, but 3 or 4 would be even better if you use this method to obtain concentricity. Depending on the number of feeler gauges you have will determine which clock positions you place the feeler gauges at. This would help to avoid excessive interference at one location and little to no contact at a point 180 degrees away. GM has a special tool just for this one job. Probably Kent-Moore or OTC. Some Kent-Moore tools are reasonable priced, but others are ridiculous.

 

There is some play in the four bolt holes on the oil pump, so yes, the pump is not necassarily centered even with all four bolts in.
I usually install two bolts and use the feeler gauge method to center the housing and then torque down the two remaining bolts with loctite. I back the first two bolt out again and torque them down with loctite as well.

You must either make sure to use the feeler gauge all the way through the pump (not just against the gear) or dissasseble the front cover of the pump so you can easier get to the rear of the pump housing and measure with the feeler gauge. (This is the best way)

 

As Roar mentioned even with the bolts installed some pump movement is still possible. That's why GM has a special tool to make sure the pump is concentric with the crank. You don't need the special tool. You can use the methods Roar detailed for you. As far as the crank pulley pushing the timing cover backwards into the pump that's highly unlikely. The timing cover is cast aluminum. Cast aluminum is not very flexible. Castings in general don't like to be flexed or bent very much without disasterous results. If the crank pulley was bending the timing cover backwards into the pump there would be one hell of a racket when you started the engine as the pulley would literally eat a hole the aluminum cover where the two items were rubbing against each other since steel(pulley) will eat up aluminum. You would instantly realize there was a problem and shut the engine OFF.

 

Thanks.

I'll mount everything up today with all you advice and test again.

 

Hi everybody.

So, I set up everything as you advice me to do. Oil pump, cover and pulley ...

Still not work !

So I think the problem is not coming from here ....

Just a new point of view ...

I got 20 PSI just before the oil filter and half less after ... I though that the oil filter retain some pressure .... BUT, If I got 20 PSI in a big gallery (before the oil filter) I should have MORE after because the gallery is smaller ....

In that case, if I get 20 PSI, I should have 30 or 40 PSI ... so it will be perfect !

I do some research on this forum, I read about some oil pressure relief valve which, when the oil pressure is to high, let the oil get back directly in the snug (oil pan).

I call an US chevrolet dealer, he told me there is not kind of valve in the LS1. Only the valve in the pump (not my pb because I already changed the pump) and the oil filter bypass valve which only by pass the oil filter.

- There is one more ? but where ?
- the oil filter bypass valve also do a pressure relief valve
- I read mistake and my problem is another thing ...

PS : This story of the oil pressure relief valve is interresting because, I lost pressure on a big acceleration ... so this valve could be stuck in open position .... and don't allow the oil pression to be what it should be.

 

Do you think it can be the bearing clearance (at the cranckshaft or the camshaft) ? But I heard no weird noise ... so I guess it's ok ....

the pressure goes up very well when I push the throttle, just it's starting too low.

 

You were misinformed by the Chevy dealer. The pressure relief is part of the oil pump. Examine the old pump you removed and you will find it. It is on the side of the pump. You will find a set screw. If you remove it the set screw you will find a piston and spring which do the relief function. Some people add a shim to increase or install a lower rate spring to decrease pressure.

 

Right, I saw it and I had already check. I install the red spring (given by mellings and rated to 70PSI ....)

So ... I think I'll unmount the oil pan to check the rods bearing clearance ..