I'm getting ready to open my stroker back up soon, to make some changes to it in order to increase power, efficiency and reliability. I'll be bumping up the compression, going to a custom cam, and upgrading to 4 bolt splayed caps. It is in the car and runs fine now, just makes less power than it should (382 RWHP/RWTQ). I've been considering several upgrades while it is apart, like a stiffer oil pump spring, crank scraper or canton pan, etc... My crank and rods are 4340 and all spec out perfectly fine. Right now I'm running Clevite P std. bearings with up to 60psi of oil pressure, usually 45-50 while cruising. Has anyone noticed any significant difference in reliability or oil pressure by going to a .001" undersize bearing or an H-series bearing? This is a street/strip motor.

 

The role for undersize bearings is to adjust clearance. Typically to compensate for a crank that has been turned or is out of spec. The very small oversizes (001 and 002) are used when the desired clearnace is not obtained with a stock journal crank. What are you trying to accomplish? That will determine the correct clearance and the size bearing you need. There is no generic advantage to undersize bearings, the issue is proper clearance.

Rich

 

"H" series are a better brg. Ya don't want over 2.7-3 on the mains and 2.5-2.7 on the rods. Your oil pressure is very good and if ya loosen it up ya gonna have to get a bigger pump to maintain.The pan is a good idea and a pickup to match the pan.
The HP isn't from your brgs it's heads,cam and intake system,all of it from the air cleaner to the piston.
Ya will only see minor gains with the oil pressure thing.

 

The idea is for me to increase reliability, mostly through additional oil pressure. Even though I'm not worried about the oil pressure at all, I would feel most comfortable with about another 10psi or so. The intent is to close up the clearances sligntly, not open them up.

 

I think you have a mistaken idea about the relationship of clearances, oil pressure, and engine longevity. Low oil pressure, assuming everything else is working right, is a sign of wear or excessive clearance from the git go and thus portends problems. Simply raising the pressure by installing a larger pump (for example) or using a thicker oil does nothing about the underlying problem. By running excessively tight clearance, you will increase friction and heat and increase the chance of spinning a bearing or of excessive wear. Stick to standard clearance and think of the oil pressure reading as a diagnostic test, not a tuning aid.

Rich

 

Noooooo what I meant was I wanted to raise the oil pressure so I could make sure the engine stays lubricated over 6000 rpm... my engine so far only has 8k miles on it and doesn't have any wear or oil pressure problems. I was just wondering if anyone has had any success using a set of these, but not to cure oil pressure problems. Just looking at all my options. I figured I would loose a slight amount on the crank when I get it polished (when I tear it back apart) so this was part of the reason for considering these.

 

Just go with a bigger pump,pickup and pan. That will take care of it and remember the clearances I posted.Pressure isn't the answer in a SBC but volume is.Much over 65lbs while hot running will lead to brg failure due to the oil cutting a grove all the way around the brg right where the oil hole is.Ya also need enough volume to keep the front of the motor oiled.
Which would ya rather have 2 gallons at 40psi or 2 qt's at 80psi?

 

I pretty much agree with this post, which is unusual for me! Maybe I should have been a lawyer? Just to clarify though, most motors don't need an HV pump. But if you are using a good pan and pickup setup, it won't hurt other than costing a few hp. Keep in mind, they run those Cup engines at about 50-60psi at 9,000rpm and they last for hours at those kind of revs.

The way to get higher pressure at high rpm, IF that is what you want to do, is to install a high pressure spring in the bypass. The bypass is why the pressure does not keep rising with revs. Improper clearances will not accomplish anything and will lead to problems. Imagine a motor that is beat, all the clearances as loose as Paris Hilton. It generates very low oil pressure, just as I couldn't generate much pressure for Paris. If you installed a humongous pump, you might see great oil pressure, but the motor would still be shot. It's like when people have low oil pressure and they use a thick oil. It reassures them to see a "normal" OP reading, but it does nothing to help the motor as the reason for the low pressure is still present.

Larry: what clearances do you use? Do you like them (motors) loose or tight?

Rich

 

LOL

 

Larry: what clearances do you use? Do you like them (motors) loose or tight?

Rich[/QUOTE]


"H" series are a better brg. Ya don't want over 2.7-3 on the mains and 2.5-2.7 on the rods.
I usually try to stay on the low side of these number's in a small block.

 

NO, Rich. Lawyers are part of the problem, physicians are part of the solution.

My computer filtered out some of the highlighted stuff, but I got your drift and I agree. So who is this P**** H*****?

 

Just a five star hotel in France Jon.

You aint missing much... don't drink the water.

-Mindgame

 

That water thing is in Mexico. Wine in France is OK.

Been there done that and got Montezuma's revenge and didn't drink the water. Doc said what kind of water did I think the Cokes were made of and what kind of water did I think they fed the cow's that provided the steak's.