The shop im having my 4 bolt main conversion done asked me if I wanted my clearance and i quote "tight" or "loose". What would be the benefit of each with a forged eagle crank?

 

I belive its oil film that will be affected most.

Loose means you'll be using a thicker oil (20W50 say) and expect to run HIGH oil temps. You may also consider a high-volume oil pump in this situation.

Tight means you're at stock levels and can use more traditional oil system.

At least that's what I've been told

 

Depending on what your machinest defination of tight & loose is.
Loose is better than tight to a POINT.My defination is the LOW or HIGH side of factory clearance or accepted racing clearances. Anything below .002 IS tight,.002-.0025 is average and .0025-.003+ is loose.The looser your clearance the more "cushion" of oil you have between the crank and brg's if you have enough oil pump to supply the oil needed for loose clearance (HV).Same goes for the rod and all other brg's.Unless you are planing to turn it above 7000 on an extended basis(road racing) or spraying a butt load of NOS or a 30PSI blower there is no need to go with more than ..0028-.003 on the mains and .0025-.0027 on the rod's or maybe a tad tighter and have to run a power and money robbing oil pump on a good street build.It is also hard on the brgs on cold starts with big clearances.Your oil could remain the same.Some of my race engines run 0-10W with .0028 main clearance.But these are not street engines."O" put .004 in the cam brgs.


My nickle's worth

 

Those numbers seem very loose to me.
I believe the stock tolerance for the LT1 mains on some of them is
.0008 to .0015

 

Better recheck your figures.

 

it would really suck trying to acheive those tolerances!!!

jeremy

 

Do you think it would have driveabelity issues after the first 100 miles with those clearances?

Like locked up-can't start.

 

I'm running .0028" mains and for my street/strip motor it's a little too loose. Stock oil pump (w HP spring) can barely keep up (even with 15W-50). I'd be way better off with less clearance, lighter oil, and stable oil pressure.

Where can I get .001 under main bearings?


Steve

 

What is your hot idle pressure?My engine's with .0025-28 with 0-10W have 25lbs after a pass,at idle-HOT.Are you checking with a mech guage. Your problem is not brg clearance its to small of an oil pump.The "spring"gives you pressure and you need volume to go along with it.When you have more space to fill up you need more oil to that space..001 under brgs will be to tight IMO for a built engine.You could adjust the clearance with the caps,but that is best left to someone who has done it.You could cost yourself a line bore job.
If you put in a larger pump instead of fooling with the brgs you will be OK.

 

Yes, I agree that is the other way to go. I was worried about sucking my stock oil pan dry with a HV pump. I now have a Canton pan (not yet installed) which could take care of that problem. I wasn't going to go a full .001". I planned to use only one side of a .001" under set to tighten up things by .0005". I have not checked Pressure w/ a mechanical gauge, so I suppose there could be some error in my system also. My Pressure was about 20 at Idle hot but I could not get over about 35 or 40 hot at 6500 RPM. During launch the pressure would drop down below 30 and never recovered very well the whole way up through the RPM range. Even w/ heavy Mobil I 15W 50 , oil pressure isn't stellar, Maybe 45 or so at 6500. I feel I'm living dangerously at that. My thought was to tighten things up a tad so I could run a stock volume oil pump, use thinner Mobil 1 and maybe free up a couple of ponies.

 

Don't worry about sucking the pan dry,it ain't going to happen unless you have got 1/2 the drainback holes blocked off.
IMO your brg clearances don't need fooling with,you NEED an oil pump.One with the 3/4" pick up.Several Companies make them.
I just got through with a mild build with a DynaGear stock pump with 3/4" pickup,stock pan.With 10/30 it had 20-25psi at idle and 40-45 at highway speed in 4th,that is plenty for a driver.You don't need 100PSI out the back door on a street engine.30PSI average is enough to make it live a long life as long as it has the volume and you can beat the hell out of it.You need the clearance for the oil cushion on the brgs.
Have you opened up your filter and checked for metal?If there is no metal you are good to go.
When you put the Canton on get the 3/4" pickup from them and a Melling HV pump and use the drive shaft with the metal "clip" on the pump end.And forget the extra work and expense to make them to tight.If you don't have quality brg's they will beat out causing a drop in pressure also.Like I said you have to have an oil pump to supply oil to the clearance's ,to fill up the gap so to speak. The stock pan has a habit of letting the oil "climb"the back of the pan when launching and away from the pickup.(not good)

 

My car is 90% strip 10% street. Running King Accular(sp) main and rod bearings. I have the Canton pan and Canton pick up but it sure doesn't look like the PU tube is 3/4". I've checked the oil filter and everything looks hunky dory so far.

Thanks for your opinions


Steve

 

The King brg's are good brgs,but if you have the soft setup I wouldn't run them on the street much--I know people will disagree--They make some that are like the Clevite "H" series for the street (don't offhand remember the numbers).IMO all you need to do is put a pan,pickup and oil pump on the beast and go have fun.
When you have the pan off,I would check the brgs for S&G.If they look good, torque them up and call it good.
LT-1's have 2 size pickups 1-5/8 & 1-3/4,Well all Chevys do.I would get the 1-3/4 one from Canton that fit's your pan and set it 1/2" from the floor of the pan using clay to check.