Have 71 LTD SportsEdition Convertible with 400 2v which I have really enjoyed, but now the rear main seal in leaking, compression across the board has more ups and downs than the stock market, and pressure extremley low at idle. Time for major surgery, dont want to keep the 400, question now...go big 390 429 460 and has anyone any experience with this swap, issues, motor mounts etc or stay small with a performance built 302. All input appreciated. Thanx

 

If I were to downgrade I would try a 351W rather than the 302. 302 will not handle the weight properly. 351W 4 barrel is more than enough. If you want gas mileage obviously you need to drop weight - so if this is a driver car and not a show car I'd start chucking useless junk like carpet underlayment, air flaps at radiator, and many more. Every ounce counts and lightens the load the engine must haul around. I would also recommend the C-6 for the 351W as it will handle the extra weight better. Obviously going from a big to a small block figures into the weight drop from the start. In a swap I would look out for block length differences from trans. mount to engine mount and width -engine mount to engine mount. Shouldn't be much trouble. your current transmission work with a different bellhousing (don't let the guts spill when swapping bellhousings - grab the shaft and hold the trans. front pump in place with one hand). If you have a C-6 that's good. If you decide to try to do a big weight drop and drop in the 302 w/C-4 - get a Boss block or a main girdle and a cam with good low end grind. Also keep in mind transmission swapsusually require driveshaft replacement or fabrication. Keep the shafts with their respective transmissions.

 

me and my son are putting a 351w in his 64 fairlane with a c4 trans that will handle up to 300 hp with a shift kit in it. If that was my car, i would put a 351w or a 351c in it. i would take measurement on the drive shaft, but try and keep as much original as possible. what trans does it have now?

 

Not really a Ford guy, so correct me if I wrong but my understanding is the 400 is nothing more than a bored out 351C. Should have the C6 transmission. Thought finding and using a 429/460 would be easier and cheaper than the 351W. Since this a fun car and not a daily driver more interested in smiles per mile instead of miles per gallon