Crank doesn't rotate freely after main caps torqued
 

I am in the process of building the bottom end of my 1.6L. So far all that's been done is the oil squirters have been installed and main bearings, main caps and crank installed and torqued. Everything has been cleaned and checked over as well as covered in engine assembly lube. Once the main caps are torqued to spec the crank does not want to turn and takes a very large amount of torque to get it to move at all.

So far we have used plastigage to check all of the clearances and they are within spec. I also just got the block and crankshaft back from the machine shop where they checked the line bore and polished the crank.

I am using ARP main studs and ACL race bearings.

Any ideas on what could be causing it to not turn freely?

Are you positive you don't have oversize bearings?

I would try using stock bolts torqued to stock spec to see if it then rotates freely. If it does, then the bore is being distorted from the extra clamping load being applied to the caps from the ARP mains.

On my engine, I had the mains line honed with my ARP mains torqued up to whatever value I used. The crank rotates very freely when torqued.

+1 to what pat said. Main bore needs to be honed with the studs in.

Patsmx5: I didn't even think of that! I won't be able to work on it until this weekend but I'll definitely give it a shot. I guess I might be making another trip back to the machine shop.Thanks!

also make sure you haven't mixed up the main caps

Definitely check this. I had the same issue on my 1.6, ended up being two that were swapped unintentionally. Idk if all have this but the 1.8 vvt I recently built actually had numbers on the caps so it made it much easier to check when reinstalling.

If I don't have the original main caps from the block I am using is my only option to use billet main caps? That's what it's looking like based on my research. I was hoping the machine shop would be able to do something with the ones I have to make them work but if it is sacrificing reliability and/or the integrity of my engine, especially with the increase of power, I would rather use billet.

Anyone know of any billet caps for a 1.6?

They should be able to line bore a set of OEM caps. Which they would have to do with billet mains anyways.

Over the weekend I tried swapping out the ARP main studs with the stock main bolts and it is still binding on something. I torque them down in stages, 20-30-40 ft-lbs of torque and it was pretty difficult to turn starting at 20. I guess I'll have to drop everything back off at the machine shop and see what they can do. hopefully I won't have to order new bearings.

Do you know a ballpark of what a shop will charge for line boring on average? They line honed it the first time I took it in which I thought would address this issue but it appears something is off.

My shop gets $150 for line honing alone.

I can't imagine a 1.6 block being worth it (you mentioned not having the original OEM caps!). Not saying it can't be done but having worked on original OEM engine lines once the main caps/block is line bored the caps stay with the block (and in order 1-4) throughout the process. The main caps are only removed to assemble the crank and they go right back on in the same spot.

1.8L billet main caps are $565 and I'm not even sure if anyone makes 1.6L anymore.

Might be cheaper to either source another 1.6L block (complete) or make the move to the 1.8L world.

Is the crankshaft straight? Has it been rechecked?

OP, you say in post #1 "I also just got the block and crankshaft back from the machine shop where they checked the line bore and polished the crank."

How did they check the line bore?

Then, in post #8 you say "I was hoping the machine shop would be able to do something with the ones I have to make them work" which implies you gave them main caps off another block.

Did your shop give you actual main diameters and straightness specs or just diameters?

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​​​​At this point it wouldn't be worth it switching to a 1.8 as I already have a 1.6 turbo kit and supertech pistons. The reason I'm building the 1.6 is because one of the transmission mounting points on my original (well most recent engine, the original owner threw a rod and I swapped a new engine in) broke off. I was already boosted when this happened so I have the turbo kit. When I ordered my new block I wasn't aware how important it was to keep the main caps with the block and I got one that didn't come with them.

This is my first engine build and while I have done a lot of research I'm still new to the process and am learning the specifics to ask. I'm not sure specifically how they checked the line bore but they did say it was line honed, to my knowledge they didn't give me any specs, but they might have written them on the tag that was on the block (which is now 2 hours away so not too easy to check haha). Yes I did give them main caps off a different block. See my reply to another user for explanation on that.

Caps are the problem, you can't mix and match those. To fix it, the machine shop needs to skim the caps, and then line-bore the mains to get all the circles in the caps concentric. You should have told the shop those were the wrong caps, and then they should have done this to fix it.

Update: Just stopped by the machine shop and they do not have to ability to line bore so I'm currently in the search for one that can.

Sometimes you've got to learn the hard way I guess.

any update on this ? I believe it is neccesary to line bore when you using arp main studs ? and I guess ARP main studs is the only safe way to 8500rpm redline right ? :winner:

The only way to combine proper clearances and "crank won't turn when torqued down" is to mix up the main caps or use the wrong main caps, ARP studs won't cause it.