340 to 360 swap

ok guys, currently have a 70 duster running a badly hurt 340/727 cast crank I believe.

Question is I bought a 74 360 complete with dampner and flexplate. Can I use my 340 converter or do I need to buy new convertor?

The 360 is assembled with correct dampner and flexplate already just dont know what trans it was attached to

IIRC, the 360 imbalance is one-of-a-kind. Check the various B&M flexplates to see if one compensates for the 360engine vs. 340 converter.

A cast crank 340 is externally balanced too so you can either get a B&M flex plate for a 360 with a neutral balanced convertor and knock the weights off the 340 convertor. Or just get a 360 convertor. Depending on the rest of the drive train a convertor change can be to your advantage.

If you knock the weights off make sure you only knock off the imbalance weights only.

OT there might be a slight difference in the fore/aft spacing of the DR block ears & possibly a difference in the space between the block ears on that same side so check that out & some spacers/washers will take care of that as needed. there are (2) "center sump" 360 pans that I am aware of, the sump(s) ain't exactly center (are more toward the front) but are referred to CS pans as opposed to front "van" or rear "truck" sump pans. On the "392" the sump starts ~4" from a line vertical plumb down from the very front pan lip and on the "876" pan the sump starts ~2". both sumps are ~8" long & they take different oil pickups. visual on your 340 sump/compare it to what you have on the 360 to see if you will be in the clear. Having the eng "almost" dropped all in is definitely not the time to have an issue there!. As said keep the 360 dampener as is up front & do what you need to do to keep the rear part of the external 360 balance on the 360 as it needs to be.

340's and 360's use the same motor mount ears, 273's and 318's use another.


But 340 oil pans will not fit a 360.

Noted, thank you

All small blocks use the same passenger side motor mount...the 340/360 use a different driver side mount then the 273/318....

I have a spare B&M flexplate for an external balanced 360 /w 727 if you need it. I'm also in Michigan.

Thank You, How much do you want for it and where are you located? I'm in the Detroit area