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Rich Biebel · 03-18-2010, 08:06 PM

General rule of thumb has always been stay above .0025" on clearance especially on the mains. What has a lot to do with it is the quality of the parts and how much do they tend to deform also how big they are and how much "grunt" does this engine make. Rods that easily go out of round...blocks, cranks and caps that are less likely to stay round....harmonics that might play into it....and balancing....all add into it....

I built a 555 for a racer and it had the absolute best of parts. It was alcohol injected and was abused pretty good with all kinds of poor tune up issues and some pretty stout rpm.....after 3 season I took it apart for freshening and the bearings were like new.....uncoated Clevitte H's.... clearances all around .003 or a little under....Titan oil pump......So good parts can take it.......and this is an engine making 900hp....

Basically you have to learn about your stuff and what it can take and what it needs....your working on something fairly new.....I have no idea why you hurt some engines but you need to figure it out...

My first question is when the rod broke in your last engine, did it spin a bearing first? If it did that is what hapened first, so your failure was from a spun bearing. If it did what was the clearances when you put that one together...what were you using for oil, and oil pressure and engine rpm....

You need to look at the failures and make changes.....

Loose is good tight is not....coatings won't stop a failure if your parts are scuffing or you lose pressure....

03-18-2010, 08:06 PM	#7
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: Mixing bearings for clearance General rule of thumb has always been stay above .0025" on clearance especially on the mains. What has a lot to do with it is the quality of the parts and how much do they tend to deform also how big they are and how much "grunt" does this engine make. Rods that easily go out of round...blocks, cranks and caps that are less likely to stay round....harmonics that might play into it....and balancing....all add into it.... I built a 555 for a racer and it had the absolute best of parts. It was alcohol injected and was abused pretty good with all kinds of poor tune up issues and some pretty stout rpm.....after 3 season I took it apart for freshening and the bearings were like new.....uncoated Clevitte H's.... clearances all around .003 or a little under....Titan oil pump......So good parts can take it.......and this is an engine making 900hp.... Basically you have to learn about your stuff and what it can take and what it needs....your working on something fairly new.....I have no idea why you hurt some engines but you need to figure it out... My first question is when the rod broke in your last engine, did it spin a bearing first? If it did that is what hapened first, so your failure was from a spun bearing. If it did what was the clearances when you put that one together...what were you using for oil, and oil pressure and engine rpm.... You need to look at the failures and make changes..... Loose is good tight is not....coatings won't stop a failure if your parts are scuffing or you lose pressure.... __________________ Rich Biebel S/C 1479 Stock 147R Last edited by Rich Biebel; 03-18-2010 at 08:12 PM.