I'm looking at putting a fmx transmission behind a 351w to go,into my 54 customline project. I tried a sbf c6 and it was to long, can someone please tell me the length of the c6 compared to fmx?
What length either one would be can be different depending on its original application. The small-block C6 was pretty much limited to trucks/vans (outside of the rare early '70s hi-po 351C cars) and if those used a one-piece driveshaft or were longer wheelbase were pretty long. It's probably possible to change the output shaft and tailhousing to a shorter set from a car unit. Behind a 351 it'll be nearly bulletproof, but it does come with a large downside. The C6 has a very high internal resistance (to the tune of a nearly 50 HP loss) and is a serious mileage killer. They were the reason most mid-'60s Ford trucks got such lousy fuel economy... The FMX was Ford's choice for the 351 as soon as it came out. Some full-size car versions could be longer, best bet is to look under Mustangs/Fairlanes, some Granadas. Considered a medium-duty trans, not really a good choice for performance applications. Considerably more complicated compared to either the C6 or C4, and Ford limited HP to 300 or less usually. They're a bit of an orphan these days, with the least aftermarket support. Used as designed and within it's power limits, it is a dependable trans. FWIW, I installed a 351W/FMX out of a '71 LTD into a '56 Ford car and had no issues with space. It's essentially the same size as the '50s Fordomatic. Don't ignore the lowly C4. While Ford limited it's use to 302s or smaller motors, not trusting it behind the bigger 351 (although Ford did use that combo around 1980 in some cars, but the 351 had been smogged down on power to 302 levels by then), on a very mild 351 build they can live. Upside is there's everything you need to upgrade to big power in the aftermarket. You'll have no space issues here as these are very compact. And like the FMX, it's considerably more efficient than the C6. The BEST choice would be an AOD which will add overdrive. Again, if big power is your goal, some beefing up of the stock trans will be highly recommended. If you're not already a member, ask this over at the '54-59 Ford social forum. Go here... 1952-59 Ford Social Group | The H.A.M.B. You will have to 'join' to see the posts. In the upper right corner, click on 'thread tools', then click 'join'. Somebody there has done each of these swaps and can furnish more detail...
C-6 on 351-4V, FMX on 351-2V, & C-4 on 302 & down in late 60s & early 70s. I had a late 70s wagon with a 351W & C-4 as crazy Steve said. If you are building serious power there used to be an add in the National Mu&t*ng Racing Association publication by a company that builds the C-4 in varying strengths up to really big numbers.
Great information here as I’m looking at a car with a stock 351C / C4 combo. (I don’t think either unit is original to the car). I had reservations about it.
Yep, it is. They moved the ATF pump from the rear to the front (no more push starting one) and addressed a few other issues, but they're brothers, not cousins... LOL
Crazy Steve nailed it. Give a lot of thought to the AOD. You'll want a wider (2") band, an A+ servo and a handful of other improvements, but any competent aftermarket parts supplier has most of that available. The FMX flexplate from the 351W works with the AOD and you can sort out which torque converter by consulting with your local trans parts house supplier or reputable rebuilders. FWIW regarding that 351W, you can go with factory heads (D0OE heads from '69-70 or some later, better breathing versions are okay) but you'll benefit from grinding out the thermactor humps inside and matching the runners to the intake and exhaust manifolds. Better yet, bite the bullet financially and get aftermarket aluminum heads that breathe better without the humps, have bigger valves and save you some weight. If you want to use the Duraspark II ignition, get the Motorcraft box, not aftermarket version, and don't get lazy on making sure you've got several good sources of grounding EVERYTHING -- frame to body to battery to alternator housing. Keep posting so we know the next episode and can cheer you on.
The early transmission had two pumps, one front and one rear, just like most other automatics of the day...the rear pump went away in the 60s, like with most other automatics of the day.
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