Main caps

[Rich G.]

Working on a 73 340 and to my surprise when I took the oil pan off the 2 and 3 main caps and bolts are missing!!!! There was a windage tray there so those are the bolts that were missing. If anyone has them or knows where to get them let me know. 😩

[Cuda Cody]

   That's not good.  Not having the original main caps can be a bit of a challenge.  If you find a set of main caps they'll need to be machined to match.

[pyro273]

As Cody said, not a good situation and if you can find new aftermarket ones, then that is the direction to go.  Used main caps are a crap shoot when it come to line boring as there may not be enough material there to make it work.  Regardless, the block needs to line bored so, depending on how much money you want to put into the engine, it may be cheaper to find another, complete 340.

[Rich G.]

I know it has to be line bored. Trying to keep the original engine. Who the hell throws out main caps! Doesn't surprise me with everything else that was screwed up on this car.

[jimynick]

340's and 318's share the same crank size, so I wonder why caps off a 318 couldn't work, unless they're not as beefy? 

[Brads70]

If your stuck this place might be able to help?
https://pro-gram.com/

[Bpret]

So what do you need? 2 caps and bolts. do you need windage tray also. I went through the same thing I had a numbers matching block with no caps. It took two sets before I found a match. The machine shop can tell if they will work or not. I still had it line bored. So I have some caps bolts probably a windage tray if needed. I live in ct so not to far.

[73440]

If your stuck this place might be able to help?
https://pro-gram.com/

Looks like they have them for 340 , https://pro-gram.com/product/m340c2/

Made in Barberon Ohio. They do look nice !
Got a bumper sticker from a bar I used to drink in in Barberton Ohio. Dang it now gotta find that bumper sticker.

[Rich G.]

Thanks for the info. I'm going to contact them and see if I get lucky

[RUNCHARGER]

At least you can save it.

[tparker]

So, for those of us not experts in machine work and such, why are the original so important? Why can't you replace them, or why is it not ideal? Is it cause it wouldn't be worn to match the block side? Or something else?

[Rich G.]

The main caps are put on the engine and then align bored. If you replace a cap it's almost certain it won't be in line with the other caps causing the bearing to be either to tight or to lose. Which will lead to bearing failure, low oil pressure and then boom!

[1973Barracuda]

On a 360 I had, a main cap came off and put a hole in my oil pan. Dropped the pan, inspected it. No real damage to my crank.got a new cap, and bearing, got some plasti gauge, reassembled it, torqued it, measured. It was ok. Put it back together. Ran for seven years. Just sold the motor.

[jimynick]

On a 360 I had, a main cap came off and put a hole in my oil pan. Dropped the pan, inspected it. No real damage to my crank.got a new cap, and bearing, got some plasti gauge, reassembled it, torqued it, measured. It was ok. Put it back together. Ran for seven years. Just sold the motor.

LOL! Take some of the money you got for that engine and dash out and buy a few lottery tickets as your luck seems to be strong!! 

[pyro273]

   My luck would have just been the opposite and I would have ended up with a hole in my block from a seized piston........