75 plymouth roadrunner 400 to 440 swap

Asked by May 10, 2017 at 02:19 AM

Question type: Car Customization

what would i be changing and what could i use
from 400 block

8 Answers


400 is an externally balanced motor, so flex plate will likely need to change. If I recall, the 400 has a short stroke, low deck but shares same block as 440. The 440 has a longer stroke. So most of intake/valvetrain/distributor can't interchange, but everything should. (it should also bolt right into same motor mounts.) You should also be able to keep same tranny, although swapping to a 727 might be worth your time if you have a stock 904. I would verify whether the motors are internally/externally balanced and make sure you have the right flexplate and/or torque converter.

1 people found this helpful.

I would keep the car original and rebuild the stock engine. Hop it up if you want to. Your car will be more valuable with the original engine.

1 people found this helpful.

i mean the car belongs to one of my friends in the army and back in high school he had it and i would use the same block but lets just say it has a giant hole in cylinder number 5 and i been looking for a 400 block but it was like looking for a needle in a hay stack


Well that is different. Like Ken said the 400 was a B engine and the 440 was a RB (raised block) engine. A 383 B engine block is also an option. There is a 400 block for sale on Ebay for $450.


Here is a source for blocks ---- http://www.indyheads.com/blocks.html

yeah i saw that it was for pick up in california & im in texas haha so i think that shipping would be alot


That car is worth doing right. Good luck!!


One last comment. Try to buy a block that is correct for 1975. There should be casting numbers that can be used to date the block.

Your Answer:


Car Customization Experts

  • #1
  • #2
  • #3
View All

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use. Content will be removed if CarGurus becomes aware that it violates our policies.