345 swap in place of 304, '70 800

A

Ari

New member
good evening all,

have a '70 800, 304/bw11/dana20. I'm interested in swapping in a 345/727/dana20 from a '73. I think its presumptuous to think this is a simple bolt-in swap, maybe it is, but I’m curious as what type of modifications to the transmission cross member and motor mounts would be needed to accomplish this exchange. Any body done a swap like this?
 
Personally, I know of one person for sure, scott sinner who has done this swap. I think he had a thread or two regarding this on the binder bulletin, now binder planet. Since your 800 is already set up for a v8, the engine swap will be the most easy and straight forward portion of the job. The tranny swap is where you will run into the most amount of headaches, butt-scratching and fab work, but it isn't rocket science.
 
Be sure to remove and save all components regarding the 727 shifter, nss system, etc. From the sii donor, the bw 11 shifter stuff in the 800 is completely different as it mounts to the tranny.

Ya also need to provide a transmission cooler of some sort. If you run an air-to-air only cooler on that install, I'd highly advise ya also install a thermostatic control to the cooler plumbing so it doesn't run too "cool", especially in a "cold start" mode.

No oem s800 radiator had a tranny cooler segment installed due to the "external" heat exchanger those used. I've not tried to plumb the bw 11 heat exchanger to a 727, of course that is "possible"...but since most of those rotted away or plugged up (coolant side) many years ago, I've never had an opportunity to try out that theory! And since the bw 11 torque converter is "air cooled", that heat exchanger May not be the correct capacity to run with a torqueflite without some help.
 
Well it sounds like I should quite hesitating and just go for it; should make a good thread anyhow. The previous owner replaced the heat exchanger when they rebuilt the bw and was able to squeeze a cooler in front of the radiator, doesn’t look like it was very fun so at least that is out of the way. He did a very clean job of it by the way. Should start the swap next month, wish me luck.
 
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