FT361 vs. FT391
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Cross-Country
Joined: Oct 2021
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FT361 vs. FT391
My '56 F500 has a 1973 FT361 in it by the previous owner and it has developed a rattle at the back end of the crank. The pan has not yet been dropped for inspection yet. I do not know if or how much overhaul has been done but the overall appearance is very nice indicating that it may have had some work done.
I previously read that by simply changing the crank in the 361 to a 391 crank you increase the displacement to 391. If that is the case, this would be a great time for me to do that.
Can anyone confirm that and provide any further suggestions or tips? I am and old Y-Block sort of guy with limited experience with "newer" engines.
I previously read that by simply changing the crank in the 361 to a 391 crank you increase the displacement to 391. If that is the case, this would be a great time for me to do that.
Can anyone confirm that and provide any further suggestions or tips? I am and old Y-Block sort of guy with limited experience with "newer" engines.
Cargo Master
Joined: Jun 2014
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From: Central Florida
The 361 and 391 cranks are forged and therefore of some interest to FE performance folk. Finding a good 391 crank is getting harder. That may be something to consider as you sort this out. If you are looking for improved torque, switching to the more common FE block would not require any mods and provide a host of cost effective stroker kits that could raise the CID to 447 with a 0.040" overbore. Lots of torque there.
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He doesn't need to change the block to use a stroker. Certain other things will be a pita like the front cover bushing, flywheel/clutch, engine balance, pulleys in the front. He would be looking at aftermarket rods and custom pistons to get a low enough compression ratio for sustained heavy loads.
Cargo Master
Joined: Jun 2014
Posts: 2,212
Likes: 322
From: Central Florida
He doesn't need to change the block to use a stroker. Certain other things will be a pita like the front cover bushing, flywheel/clutch, engine balance, pulleys in the front. He would be looking at aftermarket rods and custom pistons to get a low enough compression ratio for sustained heavy loads.
Finding a usable 391 reciprocating assembly will be difficult and probably more costly. Still, he could get lucky. The OP really hasn't told us how he uses his truck yet so we;re doing a lot of guessing and assuming.
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Cross-Country
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Thanks to all who have responded. I live in the Idaho mountains and will be using the truck primarily to pull my 1964 Boles Aero 26 foot camper. Not trying to build a hotrod, don't need to go over 60 but need the torque. If the displacement increase isn't as simple as I had thought, I will be ahead to put in new bearings on a turned crank instead of spending lotsa dollars on a new crank, pistons, and rods.
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