Which main bearings?

[buickfever]

I have a stout 109 block, RJC girdle, will mostly see street use with some track time peppered in. With std. main bearings, I get about .002 clearance. I tried a set of .001 under for fun, and come out between .0008 and .001. Is this too tight for the street? Should I settle for the .002? I just can't take anything back to my machinist...I don't think I trust him anymore (which explains why I'm assembling myself).

 

[thadeal4real]

what are you measuring with?

 

[chadly]

what are you measuring with?

I’m assuming you’re hoping not for plastigage as a response? But what is the preferred way to measure? Mic the crank and then use a telescoping gage on the ID of bearing?

 

[thadeal4real]

well yes and even use a ball mic on the shells themselfs

plasti gauge is quick guide but not very accurate in 1/2 thous

 

[750H.P.V6]

If you have an honest .002" main clearance you are in the right ball park. You'll have adequate clearance and still maintain good oil pressure also.

Neal

 

[buickfever]

what are you measuring with?

Yea, I know you didn't want to hear plastigage, but it's better than just assuming everything is fine.

I also know .002 is a little on the high side, but I am running a high volume oil pump and ported front cover...I would think that helps make up for the larger gaps, right?

 

[WSLN 6]

I am running that clearance on the mains, hivol pump. With 5w30 synthetic I have 25psi hot oil pressure at idle.

 

[williambavila]

Yea, I know you didn't want to hear plastigage, but it's better than just assuming everything is fine.

I also know .002 is a little on the high side, but I am running a high volume oil pump and ported front cover...I would think that helps make up for the larger gaps, right?

most likely your going to have to much gap there.and a highvolume oil pump and ported front cover will not fix the problem. higher oil pressure is what causes bearing failure tighter clearences and lower pressure will keep the engine running longer.:biggrin:

 

[buickfever]

most likely your going to have to much gap there.and a highvolume oil pump and ported front cover will not fix the problem. higher oil pressure is what causes bearing failure tighter clearences and lower pressure will keep the engine running longer.:biggrin:

I can see how high ol pressure will cause leaks, but can you explain to me how higher pressure will cause bearing failure? I don't doubt you, I'm just curious.

 

[m233roller]

.002 is NOT to much clearance if you plan on running the engine hard and we all do. I found the bearings to look alot nicer at .002 than at 1.5. I don't have and don't even believe in hi volume covers ( and yes Iv'e used them way back when). I have a stock GM cover with the oiling mods done and have 22 to 24 Lbs. at HOT-HOT idle in gear and right at 60lbs. at 50- 60 miles an hour. Nail it and I have 70lbs. I'm running .002 on the mains and have been for 6 years (same motor with lots of miles and hard runs) I use 10-30 Vavoline VR1 and a cup of Lucas oil stabilizer.

 

[turbofabricator]

Install half of the -.001" bearing in the block side (this will move the crank lower in the block helping the timing chain) and then use the std. bearing in the bearing cap. I do this all the time to get the bearing clearance to .0018" my target clearance and then use a std volume oil pump. I don't like hi vol. pumps for most applications. Blueprint/port the cover and all the passages in the block. Use a good high flowing filtration system, too.

 

[williambavila]

I can see how high ol pressure will cause leaks, but can you explain to me how higher pressure will cause bearing failure? I don't doubt you, I'm just curious.

look at the cars we drive today and things such as big diesel trucks and stuff they are running like 50lbs at cruising speed and 20lbs or less at idle they run less clearance and lower oil pressure they car run upwords of a million miles.cars like toyota,vw,honda,inports all run very tight clearances to prolong engine life. now I am sure with .002 your car will be just fine but if you can tighten the clearances it would help a little.I am just throwing in my 2 cents.

 

[Chris Hogeland]

Bearing

Most Guys try to set these Engines up to tight in my take on it. On all my Engine I do for my Customers and my self I set them up at 2 to 2 1/2 and never have any problem. Always have 20 to 30 psi hot at idle and what ever I set it on at wide open throttle. But every thing has to be set up right with the Oil Pump and front cover and the Oil passages in the Block and have to have good Machine work.

 

[williambavila]

Most Guys try to set these Engines up to tight in my take on it. On all my Engine I do for my Customers and my self I set them up at 2 to 2 1/2 and never have any problem. Always have 20 to 30 psi hot at idle and what ever I set it on at wide open throttle. But every thing has to be set up right with the Oil Pump and front cover and the Oil passages in the Block and have to have good Machine work.

X2 + CLEAN CLEAN CLEAN= HAPPY MOTOR...:biggrin:

 

[buickfever]

Install half of the -.001" bearing in the block side (this will move the crank lower in the block helping the timing chain) and then use the std. bearing in the bearing cap. I do this all the time to get the bearing clearance to .0018" my target clearance and then use a std volume oil pump. I don't like hi vol. pumps for most applications. Blueprint/port the cover and all the passages in the block. Use a good high flowing filtration system, too.

Thanks to everyone for your input. Does the mix-match of std/.001 bearings really work without any ill effects? In theory, it should put me right in the
.0015-.0018 range, but if it causes premature wear, or something worse, I'll stick with the .002. BTW, I've had the HV pump on a stock cover and std main bearings for years with great results. But recently had crank polished and blueprinted front cover. I know polishing doesn't remove much material, but want to do the best I can with what I have. Again, thanks eveyone.

 

[williambavila]

Thanks to everyone for your input. Does the mix-match of std/.001 bearings really work without any ill effects? In theory, it should put me right in the
.0015-.0018 range, but if it causes premature wear, or something worse, I'll stick with the .002. BTW, I've had the HV pump on a stock cover and std main bearings for years with great results. But recently had crank polished and blueprinted front cover. I know polishing doesn't remove much material, but want to do the best I can with what I have. Again, thanks eveyone.

yeah man your motor will be fine your thinking right. the only problem is when you post stuff like this so many people have been tought so many different ways you may get 20 different answers but they all lead back to the same thing. and i have just purchased a motor with mix matched bearings in it and i will keep you posted on how it performs.

 

[buickfever]

OK, I'm gonna try the mixed set and see what happens. I'll post the results tonight or tomorrow night (depends on when I get some spare time) for anyone that might be interested.

 

[LOT]

from the factory

OK, I'm gonna try the mixed set and see what happens. I'll post the results tonight or tomorrow night (depends on when I get some spare time) for anyone that might be interested.

I have disassembled more than 1 unopened engine. From the factory I find mix sized bearings. If you're thinking the hole won't be round "It will be in just a little bit"
Good point on putting the .001 under in the block to tighten the chain, BUT most of the load is on the cap bearing as the crank is being pushed downward all the time.
And I mix bearing halfs all the time. I have some old V bearings that are .002 under.

 

[buickfever]

OK, used both sets together and came out exactly .0015 on #'s 1,2 and 4. Just a hair tighter on #3, but decided to stick with it since it's mostly a street car. Now on to the rods. Thanks for all your help, guys. Happy spooling!

 

[gnxtc2]

Most Guys try to set these Engines up to tight in my take on it. On all my Engine I do for my Customers and my self I set them up at 2 to 2 1/2 and never have any problem. Always have 20 to 30 psi hot at idle and what ever I set it on at wide open throttle. But every thing has to be set up right with the Oil Pump and front cover and the Oil passages in the Block and have to have good Machine work.

x2

Just be careful in running tight clearances. Don't get hung up on tight clearances to increase oil pressure. Focus more on oil delivery and flow. Running a tighter clearance increases bearing temps.

By running tight clearances, there is little room for error.....the oil has to be kept clean, be careful if jump on it to race someone.

Billy T.
gnxtc2@aol.com