Missing main cap bolt.

[truracer20]

The caps have to go in the position they were machined in. If I were you I would pull the crank out. Then try each cap in each position checking for the best fit at the mating joint. Measure the bore of each with the cap torqued in place using the bore size of the known correct mains for reference. When you get them where you think they belong the re-install the crank with new bearings and check the rotation after each cap is torqued. If when all are torqued the crank spins free then you may have gotten lucky and the engine might live. But often the caps are so close to the same that it isn't possible to tell where they go. Good luck.

 

[pontiacgp]

The caps have to go in the position they were machined in. If I were you I would pull the crank out. Then try each cap in each position checking for the best fit at the mating joint. Measure the bore of each with the cap torqued in place using the bore size of the known correct mains for reference. When you get them where you think they belong the re-install the crank with new bearings and check the rotation after each cap is torqued. If when all are torqued the crank spins free then you may have gotten lucky and the engine might live. But often the caps are so close to the same that it isn't possible to tell where they go. Good luck.

I tried that once on a friend's SBC with the piston rod caps. He never marked them and had them all in a box. Got the proper clearances and rotating torque and the engine lasted about 15 minutes before it threw a rod.....

 

[truracer20]

Since you are on a tight budget I seriously suggest getting the mains line bored. It will be cheaper in the long run than destroying the engine. It very likely will spin bearings if the caps aren't put back in their correct position. The same goes for the rod caps, they have to go back on the rod they were machined with otherwise they will need resized.

 

[MrSony]

The rod caps are fine, I put each one back on the same rod in the same orientation they came off of on. Wish I at least had a damn sharpie handy with me on teardown day. Gonna try my damnest on reassembly day to match the correct main caps to the crank journals. It's my first engine, so it's a learning experience I guess.

 

[G_Body_Enthusiast]

get a punch or an awl and mark them NOW. Even dimples are better than nothing to tell which cap goes where. This isn't like rocker arms where you can change their position and get away with it. It will mean the difference between a running engine and a car you won't be able to drive.

It only costs a little bit to have a shop align hone your mains. Spend a little now or a lot more later. It might be around 150 bucks but at least then you will know for sure where the caps go after that. Be thrifty, not cheap.

 

[565bbchevy]

I used a little Harbor Freight rotary tool to scribe the main caps on the SBC I am building since they were not numbered,
I also scribe my last name on any parts that go to the machine shop to make sure I actually get my parts back, for $10 you can't beat it.
http://www.harborfreight.com/rotary-tool-kit-80-pc-69451.html

 

[MrSony]

Would I be able to install each main cap with the bearings and the crank, torque it, and see which one has the least amount of rolling resistance and match them from that?

 

[Rktpwrd]

Would I be able to install each main cap with the bearings and the crank, torque it, and see which one has the least amount of rolling resistance and match them from that?

No.
You will destroy the engine if you do that. That's what everybody's been trying to tell you.
Your machinist will do that and find the best fit, but from there it will still have to be line-bored to ensure the main journals and caps are straight and inline with each other.
You're talking about very close, fine tolerances here, if it's off even a thou or two, you will wipe out the crank, main bearings and you will have wasted your time.
Don't try to skimp here. Spend the smart money and do it right.
Some of us have been down roads like this (me included) and are speaking from experience.

 

[MrSony]

How would it destroy the engine? The bare block is on a stand. What I'm saying is with the bare block upside down on the stand, couldn't I just first bolt the caps to the block, get a good reading of what journal the caps match up with the closest, then take them off, put the old bearings and crank in, lube the crap out if it, then put one cap on at a time and see which one of those three has the least amount of resistance in a given spot? Rotating the crank by hand.

 

[drogg1]

How would it destroy the engine? The bare block is on a stand. What I'm saying is with the bare block upside down on the stand, couldn't I just first bolt the caps to the block, get a good reading of what journal the caps match up with the closest, then take them off, put the old bearings and crank in, lube the crap out if it, then put one cap on at a time and see which one of those three has the least amount of resistance in a given spot? Rotating the crank by hand.

Doing it that way will likely give you a better chance of getting them in the right spot.

However, as has been said, it is common practice to not do that as it is still likely that will result in bearing failure when the engine is started.