Hey all, got a question for you. I've got a '74 F20 High Boy with a good runnin 390 and a 4 speed. I have the opportunity to put a 460 with a C-6 in it. Now I know that there is no replacement for displacement, but will I get that much more power from the 460 to make up for the swap? I also know that you can do a whole lot more with the 460 (stroke it, ect.). Just want to get some input from others before I make up my mind. Thanks.

 

The 460 comes with more inherent potential for power. It comes with more torque and easily can be stroked to way over 500 cubic inches.

A lot depends on what year 460 you can get. Is it a pre 1972 with 360 HP, or a lowly smog dog from the mid 1970s that makes less than 200 HP? The potential is still there, but you have to do a lot more to bring it out.

The C-6 eats about 75 HP. If your 390 runs strong and does what you want it to do, leave it. If you have future plans to build a monster stroker, go for the 460.

 

[QUOTE=scroob]. The C-6 eats about 75 HP.


Can you explain this?

 

Its static loss when the pressure plate and clutch come together there is no loss . A firm connection as if it had been welded together. A automatic tranny relies on fluid and turbin fins found in the torqe converter no real hard connection . Thats why u hear the term locking converter most dont lock up . So there is loss . I am not sure how u measure this maybe a dyno and i am not sure exactly when in the pull the 75 comes into play probably more on the bottom end of the pull rather than the top of the pull which means everything on the street .I am positive Scroob will know the details. This is a basic overview.

 

There is also a parasitic loss in the pumping of the fluid thru the tranny also... power thats being used to pump the fluid instead of turning the wheels

 

I pulled a 390 and 4 speed out of my truck (73 F100 2 wheel drive), and replaced it with a 460 and C6. I noticed very little if any performance gains at low RPM's. I had no idea a C6 ate up 75 HP. It may be time for me to divorce the C6 and go back to a 4 speed. Does anyone know what I will need besides a bellhousing, and fly wheel? Will the z bar from the 390 interchange? I still have all the stuff from the 4 speed that was in it as far as the plate that bolts to the frame, Z bar, clutch pedal, etc. The 460 that I have is an 84 model if that makes any difference. I also wonder what if anything I would accomplish by putting a shift kit and/ or a stall converter in, and just leaving the C6.

 

I will never believe a 75 hp loss thru the C-6. Hell, even a 4-speed has to lube the bearings and gears and the lube is a hell of a lot thicker(dense). The only way I would believe any power loss claim was to see the dyno numbers. First bare engine and then the C-6 and then a 4-speed if possible. The rear wheel hp numbers don't show anything like this kinda of loss. I dragged raced a '69 428SCJ for years, first with a 4-speed and then with a C-6. Ets were identical, mph was about 1 1/2 mph lower. That don't add up to any 75 hp. BTW the truck I had before the 460 and C-6 was a '68 F250 390 4V with C-6 warmed over with factory parts only(mainly GT heads) and with the camper onboard and the race boat in tow I always ran off and left my racing partner's 460 with C-6 with only his camper onboard. Don't under rate the FE engines.

 

Bear, why do the serious drag racers all run overbuilt C-4s or Powerglides?

 

I wouldnt have it any other way than a c-6 in my truck, I hate shifting in a truck....thats what a sports car is for...

 

scoob, I ran the C6 because that's what I had and it was ready to go. However I will admit to a C4 converter modded to fit a C6(10" with a 2500 stall). Never knew anyone to run anything but C6's with big blocks and C4s with the small blocks. In fact I saw a couple of very broke C4s with very strong 335 blocks in front of them. Then again I quit racing cars in the late 70's and turned to boat racing to spend to much money on.

Icicle, I agree that for heavy loads on the truck such as a camper or behind the truck, boat or quad trailer with 6 quads; an auto is the only way to go. On the boat ramp a stick is the pits.

 

I always see drag racers in various forums looking for C4 bellhousings for the big block pattern. They want the C4 because it doesn't eat so much power. Nowadays, a C4 can be built to handle 800 HP. Sorry if my question was misleading.

 

scroob; I haven't been to a drag race since the early 80's and haven't paid any attention to what people run anymore. I was aware that the BB Chebby guys liked to run the Powerglides behind their motors. Didn't know the Ford boys had gone that route. I'm retired now so have found that I still have an interest in many things, but alot of the technowledgy has passed me by.

 

While it is possible to run a C4 behind a 460 I would not recomend it. I asked this question on a Ford tranny only site once. If the vehicle is built for the strip or even just crusing they seem to think its ok. But if you do any work, towing etc, it will not hold up as well.

 

tmyers; I agree with you. Once in a place far, far away(Colorado) and long, long ago(1970). I was moving from Wichita, Kansas to Spokane, Washington with a Ford U-haul truck. With the 18' box full and towing my race car on my flatbed, while climbing out of Fort Collins, Co. up to Cheyenne, Wy. One very steep hill BTW and on the floor for that poor old 390 all the way, when we stopped at the top at a pull out the C-6 seemed to be glowing a pale pink and you could feel the heat off of it when you looked under the truck. Of course the pipes were glowing too but that was one warm tranny. Even after that, it took us all the way to Spokane. Of course the wife was following in the '69 428SCJ Torino Cobra, so if I had broke down wouldn't have been stuck anyway(figures, when you can't get stranded 100 miles from nowhere everything works).

 

The c-6 can waste up to 60-70 hp through parasitic losses. Anybody who has rebuilt one can attest that it takes a lot of muscle to turn the shafts inside when it's put together. The c-6 takes the most HP of any auto to run, but it is also the easiest to fix. By replacing the thrust washers with torrington bearings you can take back about 30 of those HP. As for preference it is all in the owner. I personally like autos in town and wherever I have to drive slow. Out on the open roads, I hate them. I will take a stick over auto anyday in the mountains or hauling super heavy. We used to have a F-150 with 460/c-6 and another with 351M/4 spd. On level ground the 460 would flat blow the 351 away, but once you hit the hills that 460 better get out of the way. Not only would the 351 outrun it and get 12mpg loaded with identical or more weight, it wouldn't overheat doing it. Whereas the 460 would build so much heat that you would eventually have to stop and cool the tranny and motor off. Now granted that it was summer and the temps were 100+ in the shade and we were pulling roads that are now considered scenic back country tours. However, when you grow up driving in places that are 180 miles between gas stations, you gain appreciation for the old 4 spd. As for boat ramps and such, if you have the granny, you can always slip the clutch a little. Just my experience. As for the 390 vs 460, I would take the 390 anyday unless it was in the snow, deep mud, or sand. Those places auto's with big blocks really shine. As long as you don't mind 3-5 MPG at $2.20 a gallon.