# Main caps and rods torqued engine will not turn



## Gunnar Couture (May 1, 2020)

I am putting together a 400 not for sure what year it’s around the 74-76 and when I put the bearings into the rods and caps and torque everything(stepped the torque up for 15-30-45 on rods) after the final torque it wouldn’t turn. I don’t want a boat anchor sitting on my engine stand please help


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## Jetzster (Jan 18, 2020)

Did you use Plastigauge to check tolerances under the bearing caps after torqueing?
Do them each one at a time , pull cap back off , check the crushed thread Next to the included chart to see what your bearings clearances are doing for starters


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## Gunnar Couture (May 1, 2020)

I got the engine from a builder (would’ve cost around 1200-1500 for him to do it) and said that it just needed Standard bearings. But he said the caps got mixed up could that have something to do with it.


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## Jetzster (Jan 18, 2020)

I would think so, need to backtrack ,
Do one at a time, looking for any like numbers , machines grooves, or arrows/dots on rods and caps, the dots/arrows used to face towards front of engine, feel for “Lips" first between rod and cap inside each assy with no bearing inserted. Also verify the oil holes are open in each bearing ,check the mains caps they should also be numbered, use plastigage everywhere regardless, then torque mains , rotate crank, adding only one rod at a time till you find which one is binding, suddenly way harder to turn...
May or may not have to remove rings first to make cranking easier to find the one that’s wrong


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## Gunnar Couture (May 1, 2020)

We looked for numbers numbers when we throes to put it together the first time on the rods and caps couldn’t find anything I’m thinking this engine was a problem for the guy.
I am not joking it was just given to me the car is what I paid for when I bought it


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## Jetzster (Jan 18, 2020)

If its like that , something he dumped on you, may be smartest to just bite the bullet ,and take it to another shop for a complete check out & an estimate to at least finish up the short block assy, then some sort of short block warranty will be guaranteed , also have them check both the heads whilst their at it.You can put heads on then knowing all is well below..
May be a lot more hidden issues, its way too much work to have to redo it over again, now is the time to know...
If it was me , I’d ‘Spare no expense’ at this point, I learned that the hard way once


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## PontiacJim (Dec 29, 2012)

The connecting rods/caps do not typically have any numbers on them to match them up. The machinist should have used new rod bolts, then sized each rod/cap as a unit, and then kept together. If they were removed and thrown in a box as a group, you may have trouble on your hands, so I would have all the rods verified for roundness and size.

The main caps are numbered, so that should not be an issue.

Look at the rod bearings. Some will have a flat edge while the opposite side is beveled. The beveled side of the bearing is designed to match the radius/fillet found on the crank pin - look at it and you should see this. Since 2 rods fit one crank pin, the flat side of the bearing will be on the inside of each rod - ie where they would be touching. The beveled side of the bearing will be facing away/outside on the rod.  IF you put the flat side against the radius found in the crank, it will bind up. Your connecting rod will also have a radius/fillet that determines how the rods are positioned on the crank. 




As noted, checking the bearing clearance with plastigauge is a must. Not all bearings may have the same tolerances. You can sometimes juggle the bearings around to get your desired clearances to match closer this way. Same with the crank.

Do the crank first. Plastigauge with bearings dry. If good, remove the crank and install the rear main seal in the block. Put the rear main seal into the main cap. Then put some oil on the bearing saddles in the block and a little on the rear main seals. Drop the crank in. Put oil on the main cap bearings and tighten. EXCEPT for the thrust bearing cap. Push the crank to the rear so you seat the thrust bearing flat with the thrust bearing surface on the crank and tighten, but not torque. You can check your thrust clearance (forward/backward movement of the crank) and make sure it is in tolerances -You don't want it too tight or loose. Once that checks out, then go about torquing the main caps. Once done, you should be able to spin the crank by hand fairly easy. 




If the bock is a mid 1975 and up 400, look at the casting number found on the block at the rear. If you see 500557, you have the weaker block. The main saddles are thinner and the block is not recommended for a big HP build. Enclosed a pic of the block and you can see where the main saddles under the main caps are "sunken" in and not flat. Pontiac did this to save weight/money as HO levels were fairly low. The good blocks are the Trans-Am 400 blocks and will have XX in the lifter galley and casting number 481988.


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