SBM 340 Rear Main Cap

[ironmonger]

I have a 340 block with no mains. I was hoping I could use 318s. My machine shop just informed me the rear main is too short.
Nobody makes one. Anybody have any suggestions? At least, any help on specs and dimensions to have one made?

First post, have mercy, thanks

 

[Bennoel 10]

Place an ad in the parts wanted section. 340 main cap appear on and off.
Good luck

 

[Professor Fate]

Yes, the 318 main caps are shorter than 340 caps, but are still useable- just not as strong, but in a non-max street build the difference is negligible.
To use the 318 caps you need to use the 318 bolts, shorten the 340 bolts, use a main stud kit, or use hardened washers under the heads of the 340 bolts (this is what DC/MP used to accommodate the differences in their windage tray main bolt kits).
No matter which route you opt for, the block will need to be line honed or bored, depending how close the tolerances work out.
A good thread on the subject:
340 main caps

 

[ironmonger]

The problem is the rear main cap.

 

[autoxcuda]

buy the old Mopar Performance 4-bolt complete set of main caps and cut down the 2nd bolts. guy here sells them.

 

[ironmonger]

thanks, i was thinking of buying some aftermarkets and just cutting off the ears. Now I know that will work.
But still need a rear cap

 

[Professor Fate]

The problem is the rear main cap.

And it gets dealt with as stated above.

 

[toolmanmike]

Place an ad in the parts wanted section. 340 main cap appear on and off.
Good luck

I have a 340 block with no mains. I was hoping I could use 318s. My machine shop just informed me the rear main is too short.
Nobody makes one. Anybody have any suggestions? At least, any help on specs and dimensions to have one made?

First post, have mercy, thanks

Exactly, start a wanted ad if you are looking or look through the sale ads. Just because an ad is old enough to be closed doesn't mean the parts have been sold. Like this one, contact the seller through a personal message and he may still have the parts you need.

[FOR SALE] - 340 engine main caps

 

[Newbomb Turk]

Call Kent Ritter and buy caps from him. Buying used caps is a crap shoot at best and not matter what it will be a ***** to fit them.

Kent will have something.

If you don't have his phone number PM me and I'll give it to you.

Kent is a very great guy. He will hook you up.

 

[gzig5]

thanks, i was thinking of buying some aftermarkets and just cutting off the ears. Now I know that will work.
But still need a rear cap

I have some cap options for you and sent you a PM.

 

[MOPAROFFICIAL]

I have a 340 block with no mains. I was hoping I could use 318s. My machine shop just informed me the rear main is too short.
Nobody makes one. Anybody have any suggestions? At least, any help on specs and dimensions to have one made?

First post, have mercy, thanks

Do not use 318 main caps they're not beefy enough. 340 caps are all taller. Look for aftermarket caps

 

[ironmonger]

Call Kent Ritter and buy caps from him. Buying used caps is a crap shoot at best and not matter what it will be a ***** to fit them.

Kent will have something.

If you don't have his phone number PM me and I'll give it to you.

Kent is a very great guy. He will hook you up.

I don't have his number can you give it to me?

 

[Newbomb Turk]

I don't have his number can you give it to me?

Check your PM’s.

 

[gzig5]

Here are four rear main caps from different size LA engines. Bottom to top: 1965 273, late 80’s 318, 19?? 340, X- block 340 with 360 oil pan configuration. I lined up the block surfaces and the web thickness, bolt bosses, and oil pump surfaces are nearly identical. As far as I’m concerned, there isn’t a lick of difference between any of them. And from a strength strand point, the front and rear mains don’t carry nearly the load that the middle three do. That’s why when they put four bolt mains on the XNR blocks it’s only the middle three to get them. Supposedly the 340 has thicker web on the middle three than the 318. Maybe tomorrow I’ll pull out the rest of the middle mains and compare them to one another and take some measurements. I did that a couple years ago, and it didn’t seem to me that the differences were very significant at that time.