Thread: mixed up main caps

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I bought a used 4 bolt main block, where i bought it from didn´t mark the main caps, is there any way i can find out which cap goes where? i don´t really feel like orderin new bearings with a larger O.D. and Line Boring and all that and the block is almost new.
Thanks for any help

Originally Posted by DennyW

Well, first what motor ? chevy, ford, jeep, .

Most of the main caps have the number cast right in them stock.

YUP !!!! Thats what I was thinkin,but didn't want to open my mouth till I looked at a block @ the house shop tonight.....and they usually have an arrow cast in wich indicates front...

get you some plasti gauge, take your time and keep everything clean and go at it. if the clearances are right then it should be ok, for the st. anyway.

you can look for hone/ machine marks in the main bore and they are like a thumb print and if you can not see this the caps allmost all the time are never right on center of bore to center of the main caps so if you put the cap on the wrong place then you can feel the bore with your finger the cap will hang in or out where the cap bolts to the block . and when you think you have them right. check with a bore gauge if the caps are not for this engine then it is time for cap fitting and aline bore i have done this many times for new caps on a old block

Beg, borrow or steal an inside micrometer and check the bores yourself, or find a machinist to do it for you. Don't just fake it, it won't work.

They have numbers, 1-5 and arrows which should face forward. If the block hasn't been line bored, this is the way they will fit. If it has been line bored, the order and orientation may have changed.

Originally Posted by 76GMC1500

They have numbers, 1-5 and arrows which should face forward. If the block hasn't been line bored, this is the way they will fit. If it has been line bored, the order and orientation may have changed.

no this should never happen. if this has been done then look for a new shop if one cap has been lost or damage then that cap should have been re stamp and line bore/ hone .not all the caps are stamp with numbers like small blocks when the engine was new .

Thanks a lot everybody, very helpful, it is a 350 small block, what i did was just try each cap on each bore and then felt with the fingernail if the cap was aligned with the bore, there is one cap where i can feel a little bit of a edge, but i have seen more blocks with the cap hangin out or in just a little bit.
Thanks

Originally Posted by nolimits10

Thanks a lot everybody, very helpful, it is a 350 small block, what i did was just try each cap on each bore and then felt with the fingernail if the cap was aligned with the bore, there is one cap where i can feel a little bit of a edge, but i have seen more blocks with the cap hangin out or in just a little bit.
Thanks

now that you think you're close, take a piece of "plasti gauge" and check it. won't take but a min. and cost very little. i would, could save you a lot of work. if you don't know how to use it , just do a search on plasti gauge on the webb.

Originally Posted by nolimits10

Thanks a lot everybody, very helpful, it is a 350 small block, what i did was just try each cap on each bore and then felt with the fingernail if the cap was aligned with the bore, there is one cap where i can feel a little bit of a edge, but i have seen more blocks with the cap hangin out or in just a little bit.
Thanks

I would also add this.
Don't use a stamp set for any rod's or cap's you will distort the rod's for sure.
Buy an etching tool instead.

Use NEW connecting rod bolts for the final assembly. Consider the torque and centrifugal forces working together at 4000 + rpm.