Boosted One

iTrader: (6)

It's a 347 with Mahle pistons and eagle H beams.The engine builder said he ended up with .003 on the mains and .0025 on the rods. Do you guys think the mains are going to be too loose? What kind of oil pressure should I expect? He told me to run 10w30.

His reasoning he didn't go tighter was that clevite didn't make a H series thats .001 oversized. I didn't look into it yet but I know Federal Mougle does. You guys think it's worth it to add the other bearings to tighten up the clearance now, or should I put the motor in and give it a try?

Thanks
Frank

Bo White

iTrader: (59)

Those clearances will be fine if they were measured accurately.

strokedls1

iTrader: (1)

Same clearance as me and my buddys motor and both have run great and have good oil pressure. Don't sweat it and put that puppy together.

sb427f-car

Remember, alum. will expand TWICE as much as iron, so if you're thinking iron clearances, double them (give or take)

Boosted One

iTrader: (6)

sb427f that's what I was worried about. I guess I'm going to give it a try and see what happens. Seems like there are some people running loose clearances without problems.

Frank

L-EATER

iTrader: (2)

I have done this twice now and both times the results were low oil pressure. The 5.3 in my work truck has .003 on the mains and I have to run 15w50 and a can of STP just to get the hot pressure to non scary levels. It hot idles about 10psi and runs about 40psi at freeway speeds. This is a motor that had 40psi at idle and 80psi before the crank swap. Nothing else was changed, the heads have never even been off.

I would tighten it up now while it is easy to do. At the very least I would shim the pump.

GrannySShifting

iTrader: (10)

I know a few local machine shops in Maryland that "attempted" to put together LS1 and seem like they consistantly run stuff too loose and oil pressure is in the pits. i tend to just not mess with local guys anymore. yeah if something goes wrong they are right around the corner, but Ive had places STATES away stand behind their stuff and one person locally that will.

Who do you have doing your stuff?

Jason99T/A

iTrader: (21)

.0030" is too loose on the mains when using the aluminum block in a street driven applications. For a car that sees alot of street time, I would set the mains at .0015-.0018". When running clearances this tight, the oil should be up to temp. before hard driving/racing. This should be done on any motor, but very important when running tight bearing clearances.

.0025" is fine on the rods.

Jason

BLUEBALLS ZZ

iTrader: (2)

what he said.^ .003 will give you low oil pressure in most cases, done a few LS1's. LS1 's aren't like the old 350's!!! people at these machine shop's think they can run them at the same FU%@ clearance's and get away with it

Boosted One

iTrader: (6)

Alderman Machine in New Caslte, DE.

I guess I'm gonna talk to them Mon. and figure out what I shold do. This really sucks, I bet I'm going to have to buy all new main bolts again. I don't think I want to put it in there only to find out my oil pressure sucks. Guess I should have left well enough alone and flycut my stock pistons and put the thing back together, It ran perfect before.

Frank

Steve - Race Eng

iTrader: (1)

Jason has it right on main bearing clearances for the aluminum blocks. I would tighten the rods up to .002" for a street engine. The rods will run ok at .0025" but you will be throwing more oil up on the cylinder walls increasing consumption.

You guys need to be careful with some of the crank kits being sold. In most cases the included bearings end up giving you .003" on the mains. I align hone the block to the low limit and install one under bearings with these cranks. You end up with just under .002" clearance which works with the correct weight oil.

Steve

Cody Brooks

iTrader: (2)

less than .002 on mains on any engine old school small block or gen 3. the tighter clearances are needed on street engine for oil pressure and longer engine life. Lunati did a test on mains and came up with .0015-.002 being ideal for street engines. the reason most machine shops set clearances at .003 is because they save themselves some time and effort to do it that way, by no means optimal.

sb427f-car

This is why I read here. Not that I'm @ this point yet but hopefully in a year.

GrannySShifting

iTrader: (10)

Sometimes your right leave well enough alone is better then getting bad advice/service product in many many cases. On the mains if they are stock, you will be throwing them all away. I cant justify buying stock mains for that reason yes they are half the price, but if it ever comes apart again for checking anything etc etc, youve just now spent what ARP stuff would cost

your in the area, if you need anything let me know

SAM98WS6

I agree... take the mains down to .002"

Boosted One

iTrader: (6)

I talked to the machine shop today and he agrees, I'm going to take it back up there and he's going to put in .001+ bearings. Only thing that sucks is that I have to buy new bolts again. oh well at least it will be right.

Thanks for the advise guys
Frank

ROGERSPERF.

With new cnc type machines you now run tighter clearance.I built Busch Grand National engines and we would run the rods at .0018 and the mains at .0025 45 lbs of oil pressure and straight 30w at 8500rpms.The reason for wider clearance in the older days was the machines doing the machining were not that accurate as todays are.If it is for the street keep with factory clearance the engineers at GM spent millons to figure out what oil flow is needed and pressure for clearance in the engine.






mike rogers

Boosted One

iTrader: (6)

Does anyone know what the factory clearances are?

ROGERSPERF.

I beleave i have them give me a min to find them

ROGERSPERF.

rods are .0009 to .0025 production
rods .0009 to .003 service limit

crank .0008 to .0021 production
crank .0008 to .0025 service limit



Do you need any other ones?




Mike Rogers