So...what is the rpm redline on my 390FE engine? I was thinking it is pretty low...say around 5000-6000rpm? Or could it be lower/higher with the mods I have made to the engine (please see signature)?

Very interested to find out...as I do not want to push my FE to hard or worse push my 4spd tranny/drivetrain to hard. FYI...I do not currently have a tach...but took the truck up to 50 or 51mph in third the other day and it seemed like it wanted more...but again...I'm not wanting to break anything.

Thanks for any input.

 

i would think around 5,000 to 6,000 rpm deoending on if your crank was balanced and how far the cam can take it., i wouldnt rev it much higher than 6 grand

 

With your performer cam you'd have no reason to go over 5,000rpm. Any higher is slowing things down and chancing a break.

 

I agree. The Performer manifold really isn't gonna give you much top end. If you had the performer RPM I would say an occasional, short, trip to 6000 would probably be OK if your valvetrain/cam will let you get there.

-Scouder

 

i'd agree with all the above. go buy a tachometer, and you'll probably discover while it will rev to 5500 or 6, it won't feel like it's doing anything past about 5 grand.
had sevral fe powered vehicles over the years and while im sure big cammed big headed engines can use the extra rpm's most everything else is just empty revs after 5500 with 4800 to 5000 probably the norm for most engines.
which brings me to gearing. i had years ago, a 71 f 250 2wd. it had 3.73 in the dana rear and i put in 4.56 gears. with the tall stock type tires it had, it wasn't over geared to drive but really made no difference.
now the 68 i currently have, has 3.50 ( or 3.55 i always mix them up ) gears and i'm willing to bet it's as quick as the old 71 i had. i think it's due to the fact that the mellower gears actually let the engine pull and uses the engines torque rather than just revving it up faster, where theres not any more to be gained ( in a mild to medium engine that is ) .
i'm thinking i'll leave my gears alone, and some day when i re build the 360 or make it a 390 i'll just be a happy camper up to about 5 grand.........probably less.
anyway, thought i'd mention the gearing thing as it makes a big difference in how high an fe really even needs to go.
back to waiting for my carb spacer to come in the mail so i can try that out.........lol..........never ends.........

 

I get the same feeling about my setup. I think the 4.10s are almost slowing me down. I might even run out of gear before 1/4 mile with the 255-70-r16 tires.

I'm sure the 4.10s help a bit with the 0-60, but with my torque curve I'm thinking of going to 3.55s, my truck rarely leaves 3rd gear, unless I come to a complete stop or just stomp on the throttle below 40 MPH. Seriously, I can round sharp residential corners at like 10 MPH, and it will stay in 3rd without struggling.

My only concern is the towing. If I ever get my big **** boat, I may still want the 4.10s. Although, I'm starting to think I could pull more than I can stop even with 3.55s...As you can see, I've been thinking about this, since I might consider a gera change when I get some sort of locker for the Dana 60 rear.


As for redine, I agree most stock or mild FEs stop making power before 5000rpm.

 

Your swinging enough crank to get by real well on 3.55s Greg. I don't think 4.10 gears are slowing you down but you won't be hurting too bad with 3.55s.

At 110MPH with 4.10 gears and your tires you will be turning 5034 rpm.

At 110MPH with 3.55 gears you will be turning 4359 rpm

At 65MPH with 4.10s you will be turning 2975rpm

At 65MPH with 3.55 gear you will be turning 2576rpm

If you were strictly a drag racing dude I would say to get 4.56 gears to get best times and still live on the street but you want to tow that boat so that would not be cool.

If you listen real close when you are towing your boat you might hear the 446 laughing at it.

A 3.73 gear might be the best compromise though. Its all up to what you want.

 

3.73s and a GV OD.....add the ARB Air locker and I could easily drop another $4k in this cash bucket :-) With 3.73s and a 22% drop with the OD, it would run like 2.91 gears when cruising.

It's amazing how much I've put in this truck but how much left I want to do....amazing or depressing, not sure which yet.


BTW, most of the boat I'm looking at are running 496 or 502 CI motors...some are running twin Big Blocks :-)

 

6 speeds would be cool. They just cost too much. An AOD or TKO would be cheaper.

 

I don't think the A0D is any cheaper after getting the adapter and beefing up the A0D to handle the FE torque.

 

ive got a question about my 75 f150's rearend gears the guy i got it from said the rearend gears had been changed so he could pull more with it, will that be good or bad for raceing

 

Prolly good, since to tow more you need lower ratio-higher numerically -gears, which is what you need for racing. Doesn't make you faster, but it makes you quicker.

Putt

 

Sean,

I've got a question for you. I feel like I' m running a little high on engine RPM's? I'm running roughly 3800 to 4100 RPM's at 75 mph. My truck tag says I have 3.55s but who knows. someone could have changed them? I have a 390 with a C6. Talk about wanting a AOD. Man, at 4100, GULP, GULP, GULP. Not passing too many gas stations am I?

Ken
68 F100 390
74 Bronco 351W

 

This is all GREAT info...Thanks! I guess I should install a tach...sooner than later. Will certainly help save the FE from any damage...from my heavy foot!

The only thing...is that it "really" pulls hard when going in 3rd @ around the 50mph zone...FUN!

Will be real interesting what my final rpm will be at 65mph and 75mph when I install the tach.

Can anyone do the configuration for me? Here is the info: 3.50's turning 32x11.50R15.

 

MKPJ1


You can't be running 3.55s with that rpm at 75MPH. Unlesss yo uhave some very short tires.

What size tires are you running? DO you feel that your speedo is accurate?