main bearing clearance - what is too much - street use

for context when this engine was last together it held 30 psi oil pressure at 1000 rpm. and was on the 100psi relief at 4000rpm. (hot)
that was with main clearances in the .0028-.0030 range. these were king extra clearance bearings.

so i wanted to put fresh bearings in since a little dirt ran through no 2 and you cant buy only one.

bought a set of federal 3/4 groove extra clearance and 1, 2, 4, 5 are all .0029-.0030. No 3 though is .0040. put the king back in and its .0028.
so this bearing is just loose.

this is a stick car so having extra oil on my thrust surface isnt a bad thing, but .0040 seems really loose. if they were not different brands and material i would mix the halves.

i have extra volume and pressure to give on oil, but would .0040 be too much (with the others 0.0030)? i can put the king back in, but i would like it a few tenths looser than the .0028 that it is, especially since its No3.

my 3-4" micrometer has to be replaced and so i have another one coming, until then i dont know the exact measurement of that main bore. it was within spec, but i think it was on the tight side. so a third option is if there is room on the bore to open it up a few tenths and run the king thrust bearing.

just curious on .004 for a thrust bearing. street use car,
i shift at times at 6800-7000 limiter. and this engine gets heat soaked hence the clearances.

thanks all
chris

ChrisH wrote:for context when this engine was last together it held 30 psi oil pressure at 1000 rpm. and was on the 100psi relief at 4000rpm. (hot)
that was with main clearances in the .0028-.0030 range. these were king extra clearance bearings.

so i wanted to put fresh bearings in since a little dirt ran through no 2 and you cant buy only one.

bought a set of federal 3/4 groove extra clearance and 1, 2, 4, 5 are all .0029-.0030. No 3 though is .0040. put the king back in and its .0028.
so this bearing is just loose.

this is a stick car so having extra oil on my thrust surface isnt a bad thing, but .0040 seems really loose. if they were not different brands and material i would mix the halves.

i have extra volume and pressure to give on oil, but would .0040 be too much (with the others 0.0030)? i can put the king back in, but i would like it a few tenths looser than the .0028 that it is, especially since its No3.

my 3-4" micrometer has to be replaced and so i have another one coming, until then i dont know the exact measurement of that main bore. it was within spec, but i think it was on the tight side. so a third option is if there is room on the bore to open it up a few tenths and run the king thrust bearing.

just curious on .004 for a thrust bearing. street use car,
i shift at times at 6800-7000 limiter. and this engine gets heat soaked hence the clearances.

thanks all
chris

They way the main bearings made the thrust should have more clearance than the other 4. This assumes all other things are equal. I'll have to look into it but I think it should be more like .0004" bigger. If your going to have a big one....that's where you want it.

4 tenths bigger sure seems better. i was figuring on .0030 1, 2, 4, 5, and .0035 on 3 in a perfect world.

the deal here was i figured i would try the 3/4 groove. and federal is the only one putting that out.

i guess i could just buy a set of standard size federals. see if no 3 measures about .001 less. if so i can mix those halves with my current set and get right about the .0035 i want. probably the smart answer.


this is all going back in that block that had radial crack in the bore. both bores are sleeved and everything seems well so i m trying to get it back in the car and running to let me focus on the A headed engine you helped me spec out.

thanks Lem.

ChrisH wrote:4 tenths bigger sure seems better. i was figuring on .0030 1, 2, 4, 5, and .0035 on 3 in a perfect world.

the deal here was i figured i would try the 3/4 groove. and federal is the only one putting that out.

i guess i could just buy a set of standard size federals. see if no 3 measures about .001 less. if so i can mix those halves with my current set and get right about the .0035 i want. probably the smart answer.


this is all going back in that block that had radial crack in the bore. both bores are sleeved and everything seems well so i m trying to get it back in the car and running to let me focus on the A headed engine you helped me spec out.

thanks Lem.

You using 134M bearings?

yes these were the 134M 1x (extra clearance)

If you're tinkering with 134M and 134M1X main bearings and want to reduce the #3 main from 0.0040" down to 0.0035", then I have a loose 134M  #3 upper that will plug directly into the #3 main cap and bring the overall main clearance to 0.0035", and this shell will make for 360-degree oiling on the thrust while having 270-degree oiling on the other four mains.  Cool setup, problem solved, $24 delivered, call if interested.

ill give you a call tomorrow Paul. that definitely solves my issue.

thank you

chris

The latest 460 I built (really a 502) has .oo45 on the thrust and .0035 on the other main bearings along with half groove bearings .I have great oil pressure 80 cold 65 hot .My good oil pressure is from one of Paul Kanes oil pumps he set it up with a couple of shims did his magic to it and so far all is good .I believe your clearances are fine so just run it .Every engine I build the thrust is always .0005 or more larger it helps oiling the thrust surfaces .