what would ideal rod and main bearing clearance be and how would i go about changing bearing clearance without machining the crank? im putting in a new crank and connecting rods along with new bearings into my truck and want to make sure all my clearances are right

 

Clearances vary depending on application and engine.

 

If the crank hasn't been turned then you can buy bearings to adjust it up tighter. You need a good bore gage that reads in .0001 to do it though. I wouldn't trust plastigage when adjusting bearing clearance.

 

this is your 545 kit?you can go up and down .001 on the rods and mains by different size bearings.can mix and match a .001 over and a std 1/2s to get the ideal clearance.check EACH rod.the big ends out of the box will vary a little from manufacturing tolerance and the bearings themselves will vary a little even tho they are marked the "same" size.mine i always shoot for the looser side .0027-.003 on the rods..0025-.003 on the mains.
if this is your 545 i think you said it was going to be on the lower rpm side in a street truck i would shoot for a little tighter ,maybe .002 -.0025.

of course this may not be your 545 but the numbers should translate to something else too.

 

Without background info trying to answer this is shooting in the dark...

 

if we keep shooting we're bound to hit something

 

yep bronco521 its for my 545 mainly, but was also wondering about my 347 stroker project for my 75 maverick- its a little higher rpm by nature but not so much that i need much of a stall converter- im figuring a 2000 rpm stall for my 347, and i finally ordered my hydraulic roller retrofit cam for my 545- i decided to build it the way i originally wanted to and do the whole blue thunder headed dual quad propane hydraulic roller block- but i decided on the big hr cam- 228 intake duration @.050- but being a 545 and 13.2-1 static compression i figure i could get by with a 2000 rpm stall on that too if not a little lower, and still have a pretty decent idle just looking for basic guidelines for bearing clearances. i still dont plan on revving either engine all that high, probably 5500 rpm max and that only short bursts. once i get a 1978 courier and a 1968 galaxie my collection will be complete

 

if i could only tell ya how many times i've heard "once i get a 78 courier my collection will be complete" ,not-so-many,really.

for the 545 i'd shoot for clearances on the tighter side on both.the 347 i'd at least go for a little looser on the rods in case you ever want to buzz it.too tight is bad and waaaay loose is bad.

 

oh yeah,a 228 @ .050 cam is tiny for a 545 cube engine.

 

well, i figure a courier would have the 1.8 or 2.3l, and they only weigh about 2700 lbs, so i could probably get 30+ mpg out of one- and running propane itll run forever- perfect for a daily driver but of course id be rebuilding it too so id need bearing clearances for that as well... so thats why i put the bearing clearance question in the general forum instead of the engine specific forum multiple engine builds spanning the whole range from really big to really little

 

Well, you could go with the specs the manufacturer decided to use... heh.

I think I'm a little too shade tree, what with all the oil dripping under engines for it seemed like weeks. I used plastigage. I was happy. I am not a machinist.

I tend toward closer clearances because I figure I won't load the engine so hard it will overheat the oil, and then sieze or spin the inserts, and it makes it less noisy. Some want more clearance to get more oil flow to cool the bearings.
So the real answer depends on how you plan to run the engine, but the mfg generally knows what they are doing.
tom

 

when i raced we would polish the crank so to give us .001 extra clearence on both the rods and mains. meaning we would under size the crank from say std. or .010 under to minus 001. or to .011 under std. this allows the oil to flow easier though the motor and allows a heaver oil grade to be used. if you go plus as i have seen a few state the crank will not be able to flow oil around and seize up very quickly.
raceing motors are some thing unlike a street motor in how they are built and set up.oil wise it's always more never less for any clearence.
as to doing a self polish/clearence job it can be done and i always have done my own. you will need corcuas polishing cloth in the long narrow rolls, tear a strip of about 12 inches in half. rap it around the crank so it over laps where you will pull on both ends. spray it all down with some thing like wd40 to lube the cloth. and work it back and forth over the jurnall. while pulling on the ends .with in a few mins recheck with a micrometer for size in 3 spots of the jurnall you are working on. when it's .001 and flat under the size your working with go on and do the rest. when done take a lot of time with some thing like spary cans of brake cleaner to remove all the dust from the crank. then rewash it with soap and water. then air to blow it all out and dry it off.
usally in about 1 hour i have my std. sized crank done to .001 under and ready for raceing. i assemble my short block. checking every bearing with plastic gage to be sure.

yes you can set one up by micro checking with a bore gauge set and a std out side micro but i'm old school and known to refreshen a motor at the track in less then perfect conditions and still run great. useing plastic guage.

piston rings are another as we would file fit them to just a little more the the factory end gap settings so a fresh motor could be run sooner. or run a little looser right of to full rpm plus.