Stock medium journal small block Chevy cranks measure 2.450" on the mains. You're saying that you are measuring around 2.430". That would tell me that the crank has been turned 0.020" undersize and that you need 0.020" undersize bearings. If it's tightening up like you say, I would think you're trying to use 0.030" undersize bearings on a 0.020" undersize crank. I'd be surprised the crank would drop into the 0.030" bearings at all, but that's what I'm taking away from your post. Maybe the bearings are for another application, a different motor altogether. Anything is possible in this present climate of "don't care, just show me the money" attitude of workers. Does anybody else see it differently?

 

tech inspector1 thank you for your input, its always respected and appreciated. so i should look into the correct bearings. i figured it was something to do with the bearings but just wanted to make sure i was'nt missing something obvious. the bearing i have came with the block when i purchased it.... probably shouldn't trust em i guess. thanks

 

The undersize should be marked on the back of the bearing shell. What do they say??

Where are you measuring bearing thickness in the bearing itself?? Don't measure at the ends, they will be thinner there. Bearings are made eccentric on the inside, thinner at the parting line, so that they don't pull in at the parting line under power and turn into a oil wiper and burn up. Measure in the middle of the bearing.

 

If the bearings are correct, did you mix up the main caps?

 

It may seem stupid, but did you put a good amount of lube on the crank and bearings before you installed it? If not then your problem is as simple as that. Hopefully you didn't make this mistake though, it would scare me.

 

If the bearings are correct, did you mix up the main caps?

EEEEEEEAAAAAKKKKK
I didn't even think of that.

 

mix up the main caps.. dont scare me guys lol i did not mix them up since its been in my possession. thats not to say the man i bought this from didnt though. this was a motor that sat for a year fresh from the machine shop and never finish. when i picked it up it had the crank, rods and pistions asembled. it would not turn then either. i didnt think much of it as i was planning on taking it apart so i could check it all out anyway. i'm hoping my bearings are just to big. but if not and the caps are mixed up where does that put me? i did measure them all and they did come very close to each other within .0015. iv worked in machine shops for 13 yrs so i know my way around machin tools just have never done anything like this so if you tell me to do something i'll do it lol

thanks guys always love getting on this forum.

 

Measuring the block mains doesn't mean they're aligned, maybe a straight edge along the caps would give you an idea. Doesn't sound like you're too far along with the build, if everything else checks out, I'd align bore it. The caps didn't get number stamped or center punched I assume?

Is is an OEM crank? If not, maybe the edges are wide beveled, needing narrow bearings? Just a thought.

 

im actually ready to put this whole motor together. i have a ton of performance parts and $ wrapped up in this. the block is fresh(0miles) since the machine shop and after i read you post yesterday i went back out and looked and there is #'s stamped on the caps. very hard to see but they are there. 1,2,&3 from back of block to front of block. but theirs no stamps on the block itself so i dont know if they are n the right position. does anyone know how thick the bearings should measure? i didnt see any # on them to see what they are supposed to be.

 

there is #'s stamped on the caps. very hard to see but they are there. 1,2,&3 from back of block to front of block. but theirs no stamps on the block itself so i dont know if they are n the right position.

Main caps are numbered 1 through 5, starting at the front (timing chain) end of the block. They should also have cast in arrows to orientate them; arrows point to the front of the engine.

does anyone know how thick the bearings should measure? i didnt see any # on them to see what they are supposed to be.

FWIW, Clevite STD H bearings measure .0955". You should measure them w/a ball micrometer to get an accurate measurement w/o damaging the shell. Measure the central portion of the shell; the ends at the 'parting lines' are thinner. Other bearing types will also measure differently- this is one reason measuring the shell thickness can be troublesome.

But- nothing on the bearings- even when viewed w/a magnifier?

To "properly" measure the oil clearances, install the bearing shells in the block and the caps. Torque to specs, then measure the ID. Compare that measurement to the OD of the crank main journals. The same procedure is used for the rods.

Don't try to use plastigage. If the bearings are too small, clamping the crank into them will ruin the bearings- if they're not already. A brief rundown is HERE.

 

there was no stamping on the #1 & #5. i assume the machine shop figured it was pretty self explanatory. i was thinking maybe i'll swap #1 & #3 and see what that does. arrows are pointing the correct direction. i'm really hoping its jsut the wrong thickness bearings. i'm gonig to play with it some more when i get home tonight.

 

there was no stamping on the #1 & #5. i assume the machine shop figured it was pretty self explanatory. i was thinking maybe i'll swap #1 & #3 and see what that does. arrows are pointing the correct direction. i'm really hoping its jsut the wrong thickness bearings. i'm gonig to play with it some more when i get home tonight.

You said earlier this is a 4-bolt block. If so, you can't swap #1 cap for #3 cap. The only caps that can get munged are the three, center (4-bolt) caps.

Just remember, front to back, #1 through #5. Center 4-bolt caps #2- #3- #4. Arrows to front.

 

You said earlier this is a 4-bolt block. If so, you can't swap #1 cap for #3 cap. The only caps that can get munged are the three, center (4-bolt) caps.

Just remember, front to back, #1 through #5. Center 4-bolt caps #2- #3- #4. Arrows to front.

no, further up in the thread i mentioned that they only stamped the three middle caps(1 through 3) so i thought about swaping positions of 1 which would normally be #4 and 3 which would normally be #2. this is a 4bolt main. i guess this is part of the headache when buying someone elses unfinished work

 

i guess this is part of the headache when buying someone elses unfinished work

I feel ya! I traded for a pristine, standard bore 400 SBC, only to find the rear main cap (that had been in a box w/the rods), was for a 350-sized journal. Now I have a great 400 block w/no rear main cap... BUMMER!

 

why cant we just be rich and buy it all brand new lol oh well i'll get it figured out. i'm just bummed cuz iv bought so much stuff and the car is ready and the only thing holding me up is getting this motor together

 

ok went through the bearings. i actually have two sets. they are cleavitte one set says std. the other set says .010 I'm assuming the std stands for standard. they were mix matched so i pulled them all out. but if there is standard and .010 over ..... i don't know now I'm just confused. and then the rod bearing said .030 over. guys am i missing something or is this a lot easier then I'm making it out to be?

recap on mains and crank, journal id's are 2.641, crank main od's are 2.430

recap on rods, od on crank for rods is 2.059 and id of rods are 2.013

can someone please help me understand this and what i need to buy from this point?

thank you so much for any imput, you guys are always much appreciated.

 

2.059? 2.10 is STD never seen a SBC rod journal turned down more than .030

The mains appear to be .020 under if your measurement is correct.

What do the bearings have stamped on the back side?

 

ok went through the bearings....r
ecap on mains and crank, journal id's are 2.641, crank main od's are 2.430

recap on rods, od on crank for rods is 2.059 and id of rods are 2.013

QUOTE]

Did you measure the i.d.'s with the caps torqued? To torque the rods, place the big end in a vise so you don't twist it.

If the three 4-bolt caps are stamped, trust the stamp, front to rear, 1, 2, 3, and arrows pointing to the front as said earlier.

 

so is it id minus od devided by 2 +/- .002-.003 tol. to figure out what size bearing i need? what i'm gathering so far is my crank is turned .020 under but i'm still lost on my rods. im pretty sure i measured everything right.

and 66nova yes i torqued them to measure. thank you

 

I'm assuming the std stands for standard

Let's hope it does.

 

so is it id minus od devided by 2 +/- .002-.003 tol. to figure out what size bearing i need? what i'm gathering so far is my crank is turned .020 under but i'm still lost on my rods. im pretty sure i measured everything right.

No, just the whole difference between i.d. and o.d., take a look at this article, it's easy reading:


http://www.carcraft.com/techarticles/ccrp_0805_high_performance_engines_bearing_clearance/index.html

You can also mix bearing halves if needed to get you closer to optimal clearance.

 

ok went through the bearings. i actually have two sets. they are cleavitte one set says std. the other set says .010 I'm assuming the std stands for standard. they were mix matched so i pulled them all out. but if there is standard and .010 over ..... i don't know now I'm just confused. and then the rod bearing said .030 over. guys am i missing something or is this a lot easier then I'm making it out to be?

recap on mains and crank, journal id's are 2.641, crank main od's are 2.430

recap on rods, od on crank for rods is 2.059 and id of rods are 2.013

can someone please help me understand this and what i need to buy from this point?

thank you so much for any imput, you guys are always much appreciated.

If these crank measurements are correct, the crank is .020" under on the mains and .040" under on the rods.

I can't come up with anything that matches that rod id figure, a large journal rod will have an id of 2.225"(rod itself, no bearing in it), your 2.013" figure is too small even for a small journal rod(which is 2.125").

Some things don't jibe...so what tools are you using to measure with??

 

Are you measuring the i.d.'s with bearings in them?

 

If these crank measurements are correct, the crank is .020" under on the mains and .040" under on the rods.

I can't come up with anything that matches that rod id figure, a large journal rod will have an id of 2.225"(rod itself, no bearing in it), your 2.013" figure is too small even for a small journal rod(which is 2.125").

Some things don't jibe...so what tools are you using to measure with??

I'm gonna be so ticked if i have to buy a new crank. i have a machinist tool box from when i was working on the floor. now i sit behind a computer. but anyway i have mic's, calipers, etc. I'm hoping maybe i read/wrote down the wrong # for the rod id, and yes i did check it without the bearings in it. I'll check again tonight when i get home.

i will never buy an unfinished project again. this is exactly what i didnt want to happen. i'm just glad i decided to pull it apart to check it all out before i put it together and in my camaro.

 

ok guys after ericnova72 scared the crap out of me for telling me it dont jive i went out and remearured. got totally different #'s. my caliper broke so i had to fix it. remeasured again and the mains were all the same but the rods were different. so hear goes.

rod id is 2.225
rod od 2.070

so does this put me in a better position? so my block is .020 over how do i figure out what my rods are. the bearings i have are std, 0.010 & .030. needless to say i'm going to go buy a new set of bearings so i KNOW what i have.

and 68NovaSS thank you for the link i read that article very informative and easy to read, thank you

brian