Racer Buzz

iTrader: (1)

My engine builder heated up a bare block LS block (only) in a oven today and found out that the main bearing block journals grew by .003" at just 220 degrees. What does that tell you about keeping the main bearing clearances tight on the setup! That's why Chevy says .0008" on the tight side is OK. But on a race motor set at .0008" on the mains you would need to first pre-heat the oil (and maybe the water) and then spin the dry sump pump to circulate the warm oil prior to starting the motor. A real pain. So I'm going for .0015" to .0017" cold main clearance.

racecar

Hey Buzz, That was a good experiment. It's great to see proof of the theory.
If the crank was in the oven, it would expand 50% of the block expansion. Block .003, crank .0015, So your clearance grows by .0015. Of course the block is aluminum, and the main caps are steel, so it may not be exactly 50%, but we are close. That's why the
.0015 on the mains works. That sounds tight, now we know why.

Louis

iTrader: (7)

Our Race motors need pre heating of water and pre heating of oil to 160* before it can be fired. Thats tight. But thats what it takes.

fossil

iTrader: (1)

We just replaced piston in a 2007 "LS7" with 9,000 miles, factory clearence at this time. Main bearings clearence .0019-.0020". Rod bearing clearence
.0020".

67SS509

iTrader: (25)

Reading these threads have helped me understand the slightly low oil pressure that I'm seeing with a 402 (LS2 block) I just recently built for someone else. Which oil pump do you race engine builders prefer? Can something capable of higher pressure be used to get the pressure up a little?

racecar

Just shim the oil pump bypass spring about .09-.100. That will help pressure.

fossil

iTrader: (1)

Can something capable of higher pressure be used to get the pressure up a little?[/QUOTE]

Im using the Melling high volume pump part #10296. Hot oil pressure at idle
around 60psi and pegged past 80psi on wot runs.

67SS509

iTrader: (25)

Im using the Melling high volume pump part #10296. Hot oil pressure at idle
around 60psi and pegged past 80psi on wot runs.[/QUOTE]

Are those numbers with the 10# higher spring or the stock spring?

JL ws-6

iTrader: (50)

You can always run a thicker oil with the looser clearances, this will help keep the pressure up and will provide a thicher layer of oil to take up the slack.

I don't know the exact clearances that my motor was built to, but I know it was a little on the loose side, and that's why I run a 20/50 oil. IT's worked out pretty well so far, I'll run it again for this year and at the end of the season, I'll tear it down, see how things look. I suspect that it will be in good shape. I've been changing the oil after every track trip wether I make 1 run or 10, and the oil always comes out very clean, never have ai seen any signs of anything bad going on, oil analysis also confirms that.

For a road race engine, I am not sure if the same type of setup would work, but I can't see running the engine a little on the loose side with a slightly thicker oil being a bad idea, the heavier oil shouldn't thin out as much, so the pressure should be maintained.

fossil

iTrader: (1)

That is with the 10lbs spring. My engine is also on the loose side for bearing clearances and I run 20-50 weight oil. So far no problems.

helicoil

iTrader: (104)

Interesting thread, I am assembling one right now and using a Federal Mogul 152M1 with an Eagle crankshaft. I have between .0024"-.0026" for oil clearance and a #3 thrust bearing that fits loose both on the radius and laterally.

The block is a Brand NEW LS2 and so is the crank. The block's housing bore measures dead on the small end of spec, 2.7590 and the Eagle's main journals are 2.5582"-2.5583" (small side). FM doesn't make a .002" undersize, does Clevite?

This is a street motor/occasional drag 12-15 times a year. LS2 402.

Have any of you had problems with the FM 152M sets and the number #3 thrust fitting loose? Tried the bearings in two different LS2's, same thing.

Weird thing is a 7298M (Aluminum replacement bearing) thrust bearing fits nice.

Sounds like I should be targeting .002" on the mains or a little lower, wondering if a Clevite MS2199H 1 would do any better. I have heard the Federal Mogul LS main bearings run a little looser on oil clearance. No explanation on the thrust bearing problem - manufacturing tafoo??? Anyone care to chime in from their experiences?

racer7088

Yes some of the flanged bearings are just like that as the "snap" or press has to be made into them differently as they are of course much stiffer. I have seen GM and FM and Clevite all like this at times.

helicoil

iTrader: (104)

Thanks for the input, it was just weird that I tried a std. 152M and a stock replacement 7298M thrust bearing, as well as the Clevite and they fit snug like most. The 152M 1's made me uneasy.....so you say not to worry with this fit???

To add to this thread I would like to mention that I confirmed the Clevite MS2199H1 mains gave me .0015"-.0017" oil clearance on the 1-2-4-5 mains and .0014" on the thrust. This is right about .001" tighter than the same size bearing 152M1 (.001" under) in Federal Mogul, so it is true that the Federal Mogul Performance bearings run looser than the Clevites, at least on the LS engines.

racer7088

Yes that does usually seem to be true for us. We were unable to even use the Clevites a while ago on LSx's and stopped because they were always so tight and sometimes ended up substantially tighter on the #3 than on the others.

JL ws-6

iTrader: (50)

This is all good info, I'll need this next fall when I have my motor apart

Erik, any reccommendations on the coated bearing front? When I tear the motor down at the end of this season, I'm gonna put some hardblock in the water jackets to try to stiffen the bottom end up some after I have Keltech go thru the block, I'm probably gonna have them do a clean up hone on it, as well as check the mains for alignment and all that. It will have 2 seasons on it by then, probably a good idea to have it redone I figure, plus having the mains line honed probably will help with the bearing fitment.. I am planning on ditching the low tension rings because of the cankcase pressure issues (no vacum pump) and putting coated bearings in the thing while it's apart.

racer7088

JL ws-6,

I like coated bearings but you have to still check all clearances as sometimes the coatings are not as consistent as we want them to be. We have some coated STD bearings that lose over a thousandth and then sometimes less than a thousandth clearance after coating. I try to run the clearance I want even with the coating so I don't tighten it way up with the coating. Anotherwords I start with a looser bearing like an X and then coat it so my clearances will work out the same.

JL ws-6

iTrader: (50)

I understand. I was just wondering what your thoughts are on the coated bearings, good, bad, worth it for a drag race engine or not, any specific ones that tend to hold up better then others, that type of thing.

racer7088

I think they are a good deal overall and a little extra insurance if your engine does lose oil pressure for a bit intermittently etc.

JL ws-6

iTrader: (50)

intermittent oil pressure loss... that doesn't sound like something I want to happen LOL.

racer7088

No one wants any kind of oil starvation but it happens every once ina while like under extreme braking and the pickup gets uncovered or wheelie or aerated oil after a lot of high rpm use etc. With a real dry sump you are pretty safe but with a wet sump all hell is breaking loose down there!