351 to 390 swap [Archive] - Classic Cougar Forums

: 351 to 390 swap

September 1st, 2001, 11:17 PM
I was wondering if someone could help me? I've got a 70xr7 with a 351c,2v /fmx the motor needs rebuilt bad . I've got a strong running 390 4v out of a 75 truck, it runs good would the swap be real hard,will the tranny bolt up or any major modifacations needed or would it more worth my while to rebuild the 351. thanks straycat22

September 2nd, 2001, 05:54 AM
There will be a boatload of changes necessary to perform this engine family swap.

The motor mounts may be different. I think the FE engine family uses different ones. I've never dealt with FEs so I can't be sure.
The transmission bellhousing pattern is different. A 351C uses a small block pattern. The FE uses its own round pattern. Being your cat already has an FMX, FMX trannies have a bolt-on bellhousing. You may be able to scrounge up an FMX to FE housing, but it will be hard to find. Then there's the tranny input shaft, convertor,.... If you use the tranny from your truck, you will solve this problem but will start others. The mount, Neutral safety switch, driveshaft...
The exhaust system will have to be changed. Well, at least the headpipe.
Radiator hoses.
Accessory brackets if the components aren't the same from your truck to your Cat....

Do you see where all this is going? It would be much simpler to just rebuild the 351C. A 351C has the potential to be a powerful engine. With a careful selection of parts you're all set. Rebuilding your Cleveland will probably be the quickest, cheapest, and easiest solution for you.

What you may want to consider is to trash both the 351C and the 390 and put in a 351W. Don't laugh. With the aftermarket heads they have these days, and the avalability of stroker kits for 351W, you can turn it into a powerful 390+ inch motor and have a smaller, lighter and easier-to-work-on package to boot! Windsors use normal small block mounts, use the same small block pattern tranny as your 351C, have more speed parts available, and are easy to find.

September 2nd, 2001, 07:07 AM
Years ago I did a swap going the other way, 390 to 351. You have to change every thing as nothing fits at all. I still have that 70 351c 2v engine that I posted under parts for sale for $200 if you need one. Its been awhile since I've been to Lansing but if I remember its around 3hrs away if you needed it.mm

September 2nd, 2001, 10:18 AM
thanks guys i'll probably rebuild the cleavland or shop around for 351w,i just put the 390 in my 77 f-250 boy was that a headache had to relocate motormounts,powersteering,oilfilter, custom exaust then after all that the dana60 rearend goes out on me.I .definately dont want to go thru that again. thanks for the info This is just what i wanted to know before getting started .straycat22

September 4th, 2001, 06:39 PM
Stray Cat 22, You must not have heard me. I said I had a good 351 c for $200. Its been rebuilt a while ago. If you want to spend a grand or to to redo yours be my guest. mm

September 6th, 2001, 10:27 PM
modifiedmark i did not reply cause i thought i might push back doing anything to my cougar until this winter, but your right it would be alot cheaper to go your route. I'm not sure how to get in touch with you to find out how to get the motor let me know. straycat22

September 6th, 2001, 10:44 PM
Check your mail as I sent directions how to get in touch. mm