Rob 's 73

I had this posted in the LQ4 pump thread but though I might be able to get some recommendations from engine builders if I created a new thread. Thanks in advance.

Doe the Melling flow more oil than the LQ4?

Reason I am asking is that I recently put a 416 in my car with the supplied GM High volume low pressure spring pump. Cold idle oil pressure with 20/50 oil is right at 50. 200 degree idle is 31-32 and cruise is 40psi. It will go up to 50 or so at higher rpm. This weekend at the track (road course) I shifted at 4500-5000 because my oil pressure under load at 260 degree oil temps was 35 psi. The pressure would not go up with the RPMs. I only did one session because I was worried that I would be ventilating the block. If I let off the throttle the pressure would build about 3 psi at the same RPM

Main Brg Clear
1 - .0029
2 - .0027
3 - .0028
4 - .0028
5 - .0027

Rod bearing are all .0026

These are the measurements supplied by the builder. When I asked them about minimum pressure they sent me a new high volume pump saying that they may have shipped me the wrong one. They didn't but it got me off the phone I guess.

I am running a oil cooler and accusump.

Do I even need more oil pressure? I am going to switch to synthetic oil. Hopefully it won't break down as much with the heat.

Thanks for the help.

Rob 's 73

I spoke with the builder today and he is saying my choice of lifters is most likely the culprit. I am running the Crane Billet lifters. He said that aftermarket lifters are slightly undersized and recommended that I change to OEM LS or Caddy Racing Lifters. He said that Jessel recently started making an OEM sized lifter. Is this where my oil pressure is going? I certainly don't want to ditch my $575 lifters if my oil pressure isn't going to increase.

FWIW, he also said that the GM High Volume pump flows 30 % more than the OEM ls6 while the Melling High Volume flows 18% more than the OEM ls6.

Comments please.

Tony Mamo @ AFR

iTrader: (13)

I have built a handful of engines with those lifters (a preference of mine actually) and never experienced anything of the sort. Your pressure is too low even cold in my opinion with that thick an oil. I personally build my engines tighter than that on the clearances but you will get mixed opinion. But, even at those clearances I would expect more pressure with 20/50 non synthetic. I think synthetic may even worsen the problem but thats a bridge you will have to cross and give it a try. Hot cruising at 40 psi is also low....should be in the 50+ range and go higher with RPM. Think about how your stock engine behaved....it shouldnt be much different honestly.

If I were you I would invest in a tool to cut open your oil filter....if your bearings start going away from excessive pounding you can catch it early by seeing the dreaded copper metallic particles in the pleats of the filter. Best to catch it early so as not to damage the engine further needing a deeper undersize crank when the smoke clears to clean it up.

Im not trying to be doom and gloom but being a little proactive here isnt a bad idea considering the money and time invested and the fact oil pressure seems clearly to be an issue here. While you might not need 10 psi per every thousand RPM's with modern synthetic, the reality is with proper clearance and oil viscosity thats usually how it works out anyway.

-Tony

racer7088

I agree with Tony. Cut the filter open just to be sure you aren't having problems that could get worse fast.

JOHNBOY66

Is anybody else bothered by the 260* oil temps?

I would try to get the oil temps down closer to 200*. I bet that would help alot. I have no problems with the listed bearing clearences.

Rob 's 73

Tony, Erik

Thanks for the input. I will cut the filter I had on for the one track session tonight and post the results. I am not sure if I had the filter on long enough.

This is frustrating as he!!.

JohnBoy

260 is normal for the track. Track guys run it up to 300 without coolers. 260-280 with.

Rob 's 73

Update!

I opened the filter and there was some gold flake on the filter media and in the bottom of the filter canister. It wasn't a lot but I had less than 100 miles on the filter and one half a$$ed track session. My plan is to pull the short block and take it back to the builder to make it right. I can't live with the feeling that I'm going to blow it up everytime I get on the throttle.

Thanks for the feedback.

Tony Mamo @ AFR

iTrader: (13)

Its really good to catch that kind of thing early....(if there is a silver lining in the fact your car will be down again)

Good for you Rob

Let us know how the new shortblock works out.

-Tony

Rob 's 73

I'll get the motor out tomorrow. I am becoming an expert in wrenching on a C5. I know every size bolt and pretty soon all the tq requirements.

I drove my wife's LS3 corvette (stock) this morning and it idles hot at 35 (650 rpm) cruise at 1500 rpm is 45. It will quickly climb to 60 by 5000 rpm.

Tony Mamo @ AFR

iTrader: (13)

Dont forget it has much thinner synthetic oil in it as well....the fact you had a fair amount less with 20-50 was the big clue something may have been astray in your lower end.

Good luck getting everything resolved

-Tony

ChucksZ06

iTrader: (9)

Your main bearing clearances are too big. That might not be your entire problem but it is maybe worth 20 psi. should not go over .0025. Aluminum blocks expand when heated.
Many builders build main clearances for iron blocks.

Rob 's 73

The motor is out and the short block is in the box it came in. I will be taking it back within the next week or so. It sounds like the builder will work with me. Even doing the work yourself there are still some expenses with gaskets and fluids.

What main clearances do I need ask them to shoot for? .0020-0025?

What about the rod bearings? Are they okay?

ChucksZ06

iTrader: (9)

Yes on the .002 to .0025. In my experience that is a good range with being close to the .002 ok. Rods at .025 are ok...same as sbc cause it is steel on both ends. I think that the main clearance is the real critical one as far as oil pressure is concerned. Problem with all the oil running out the sides of the mains is that is does not get to the rods with sufficient pressure to keep things lubricated. In my opinion the higher flow pumps are a band aid for clearance problems in the engine (not always).

shoemike

iTrader: (25)

Are you using a mechanical or the stock gauge?
Once my car warms up the stock gauge sits just under 40psi and never moves,
my mech gauge under the hood tells a different story.

I have the looses built LS1 in history with countless WOT runs and road race sessions
and it's close to 50,000 miles.

Rob 's 73

I'm using the built-in oil pressure gauge. I don't have any reason to question it's accuracy. When the motor was cool the oil pressure would easily get to 70+.

If they get the main clearances down to .002 to .0025, should I continue to run the high flow pump with the low pressure spring?