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cb-743p rod bearings clearance

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Post  maverick172 November 3rd 2022, 6:47 am

anyone know a bearing that gives extra clearance. most my rost come in with .0019 to .0024 clearance would like to open them up a bit . i tried cb743hxn but they come out with over .0035 with these and even with half shell i still get .0030 plus there are not as wide as the cb-743p bearings . so i am not comfortable using them with only a half shell .?thanks

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Post  Scott Foxwell November 3rd 2022, 8:51 am

maverick172 wrote:anyone know a bearing that gives extra clearance. most my rost come in with .0019 to .0024 clearance would like to open them up a bit . i tried cb743hxn but they come out with over .0035 with these and even with half shell i still get .0030 plus there are not as wide as the cb-743p bearings . so i am not comfortable using them with only a half shell .?thanks
Sounds like you need a set of 743HN standard bearings. (The X is .001"oversize...gives more clearance) I'd be real happy with .0024. The HN bearings are narrowed which you'll probably want anyway.

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Post  maverick172 November 3rd 2022, 2:35 pm

Scott Foxwell wrote:
maverick172 wrote:anyone know a bearing that gives extra clearance. most my rost come in with .0019 to .0024 clearance would like to open them up a bit . i tried cb743hxn but they come out with over .0035 with these and even with half shell i still get .0030 plus there are not as wide as the cb-743p bearings . so i am not comfortable using them with only a half shell .?thanks
Sounds like you need a set of 743HN standard bearings. (The X is .001"oversize...gives more clearance) I'd be real happy with .0024. The HN bearings are narrowed which you'll probably want anyway.
yes i am shooting for 24thou but . we will see i ordered a set of cb743hn i noticed the cb743hxn are narrower than the cb-743p which is ok but i would not want to use one narrow and one not narrow shell together . so i might end up using one 743hxn and 1 743hn would you use the cb-743hxn on the top or bottom or does it matter if i end up useing these as a mixed matched set.
thanks

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Post  Scott Foxwell November 3rd 2022, 6:04 pm

maverick172 wrote:
Scott Foxwell wrote:
maverick172 wrote:anyone know a bearing that gives extra clearance. most my rost come in with .0019 to .0024 clearance would like to open them up a bit . i tried cb743hxn but they come out with over .0035 with these and even with half shell i still get .0030 plus there are not as wide as the cb-743p bearings . so i am not comfortable using them with only a half shell .?thanks
Sounds like you need a set of 743HN standard bearings. (The X is .001"oversize...gives more clearance) I'd be real happy with .0024. The HN bearings are narrowed which you'll probably want anyway.
yes i am shooting for 24thou but . we will see i ordered a set of cb743hn i noticed the cb743hxn are narrower than the cb-743p which is ok but i would not want to use one narrow and one not narrow shell together . so i might end up using one 743hxn and 1 743hn would you use the cb-743hxn on the top or bottom or does it matter if i end up useing these as a mixed matched set.
thanks
I wouldn't mix and match the P's and the H's, I agree. You said the HXN's gave you .0035 so the standard HN's should be .001 smaller and give you .0025. No need to mix those but to answer your question, IMO it won't make any difference. Vertical clearance is what's critical and that's what the crank will see. The bearings are not round...they have more clearance at the parting line. The P's have more eccentricity than the H's but IMO the difference in eccentricity between an X and a standard bearing is negligible.
The N's are narrowed to allow clearance for an aftermarket (or performance) crank's larger corner radius. The older H bearings (H for high performance) used to be chamfered to clear the radius but they just went to a narrower bearing instead. Lot easier and cheaper to manufacture. The P's may give you a problem there if you were to use them so the HN's are probably a better choice anyway.

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Post  dfree383 November 3rd 2022, 6:14 pm

What’s the application?
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Post  supervel45 November 3rd 2022, 6:35 pm

maverick172 wrote:anyone know a bearing that gives extra clearance. most my rost come in with .0019 to .0024 clearance would like to open them up a bit . i tried cb743hxn but they come out with over .0035 with these and even with half shell i still get .0030 plus there are not as wide as the cb-743p bearings . so i am not comfortable using them with only a half shell .?thanks


Maybe switch a tight rod to a loose journal and see what happens. With that much variance, ".0019 to .0024" seems like a rod could be undersized, if the crank journals are all the same. Just a thought.

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Post  maverick172 November 3rd 2022, 10:23 pm

supervel45 wrote:
maverick172 wrote:anyone know a bearing that gives extra clearance. most my rost come in with .0019 to .0024 clearance would like to open them up a bit . i tried cb743hxn but they come out with over .0035 with these and even with half shell i still get .0030 plus there are not as wide as the cb-743p bearings . so i am not comfortable using them with only a half shell .?thanks


Maybe switch a tight rod to a loose journal and see what happens. With that much variance, ".0019 to .0024" seems like a rod could be undersized, if the crank journals are all the same. Just a thought.
ya my guess it is in the rods the variance to be honest , cause i tried differant shells in the same rods and did not change much may a .0001 up or down but not enough to get my exact clearance i want . i think i will try the narrow ones and see how it goes.
would be better off going more clearance say using half a x shell and a standard shell and maybe settle for the .0026 to .0031 area ? and be happy with it rather than leaving them on the tight side?

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Post  maverick172 November 3rd 2022, 10:24 pm

dfree383 wrote:What’s the application?
street strip but car will be buzzing at times in the 6400rpm or 6500

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Post  maverick172 November 3rd 2022, 10:26 pm

Scott Foxwell wrote:
maverick172 wrote:
Scott Foxwell wrote:
maverick172 wrote:anyone know a bearing that gives extra clearance. most my rost come in with .0019 to .0024 clearance would like to open them up a bit . i tried cb743hxn but they come out with over .0035 with these and even with half shell i still get .0030 plus there are not as wide as the cb-743p bearings . so i am not comfortable using them with only a half shell .?thanks
Sounds like you need a set of 743HN standard bearings. (The X is .001"oversize...gives more clearance) I'd be real happy with .0024. The HN bearings are narrowed which you'll probably want anyway.
yes i am shooting for 24thou but . we will see i ordered a set of cb743hn i noticed the cb743hxn are narrower than the cb-743p which is ok but i would not want to use one narrow and one not narrow shell together . so i might end up using one 743hxn and 1 743hn would you use the cb-743hxn on the top or bottom or does it matter if i end up useing these as a mixed matched set.
thanks
I wouldn't mix and match the P's and the H's, I agree. You said the HXN's gave you .0035 so the standard HN's should be .001 smaller and give you .0025. No need to mix those but to answer your question, IMO it won't make any difference. Vertical clearance is what's critical and that's what the crank will see. The bearings are not round...they have more clearance at the parting line. The P's have more eccentricity than the H's but IMO the difference in eccentricity between an X and a standard bearing is negligible.
The N's are narrowed to allow clearance for an aftermarket (or performance) crank's larger corner radius. The older H bearings (H for high performance) used to be chamfered to clear the radius but they just went to a narrower bearing instead. Lot easier and cheaper to manufacture. The P's may give you a problem there if you were to use them so the HN's are probably a better choice anyway.

yes i am going the hn route on these i think it is the better solution . the p's were fine for radius clearance as the rod has a shoulder built in that sets the bearing in from radius about 3/32 of a inch or so .

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Post  supervel45 November 3rd 2022, 11:05 pm

If it was me I would want to see a good micrometer on the crank and the rods checked for size/roundness, I believe.

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Post  maverick172 November 4th 2022, 10:30 am

supervel45 wrote:If it was me I would want to see a good micrometer on the crank and the rods checked for size/roundness, I believe.
crank is all within .0002 i checked it .

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