what is the stroke of the 2U crankshaft? I pulled the pan off my 76 f-150 4x4 and found it has a 2U crank ground .010" under. The people I bought the truck from told me that they rebuilt the 360 into a 390, but I dynoed it and it only had 199hp at the wheels (thats with headders, edl-perf intake, comp268h, and a holley 650dp). Does that seam low, even for a low comp 360?

 

What kind of transmission?

Did you get an AF ratio with the run?

Measure the stroke, that will tell you if it is a 360 or a 390.

EDIT, Oh sorry, acording to my literature a 2U is a 390 crank.

 

my truck has the np-435 4-spd. The af was a little rich but not too bad. that hp seems prety low if it is a 390. it has full 2.5"duel exh with the 1.75" headders and flowmasters, should'nt that alone get it above 200rwhp. I'll do a comp test tomarow and post back.

 

the stroke is 3.78". I would believe dyno with auto but it does seem a tick low. Torque is what is important in a truck.

 

the torque peakked at about 320flbs it was a pretty broad torque curve. I wonder if who ever rebuilt it used the wrong pistons? I'll check the head casting #s tomarow.

 

i'm going to guess right now that yours heads will make you think twice because ford was goofy with all there casting ****.

 

Jocky, if the fellows who rebuilt your engine used what are usually sold as 390 'truck' pistons, then you have about 7.6 to 1 compression. Runs fine on regular, but doesn't help in the power dept. at all. The Comp cam is junk, IMO, and it's too small. The Edel Perf intake only saves you some weight, it doesn't help power or torque in any way. The Holley is on the small side as well, if power is what your after. How much more power do you want, where in the curve do you want it to happen, and how much can you spend ? Is this truck for towing, commutting or off roading ? Tell us more and we'll help. DF

 

7.6 to 1! thats lower than most turbo motors. Come to think about it i have a cuple of t3 turbos laying around. I'm leaving next monday to collage so I wont have much time or money to do any thing major, this thing just has to get me to school every day.
Arnt 390 truck pistons the same as 410 pistons?

 

Jocky, yes, they are the same. DF

 

The 410 had a 3.98 stroke and used the same rods as the 390: So to keep the piston down in the bore the 410 pistons had the wrist pins set higher in the piston. If you put them in a 390 with a 3.78 stroke (like ford did for trucks) you get really low CR. So they aren't the same as 390 pistons.

 

so I basically have a destroked 410. What will the compression be if I ad a 410/428 crank, and would it be a bolt in?

 

You can directly swich out any FE crank. the 410 and 428 were externally balanced. If you can find a 410 or 428 crank with the flexplate or flywheel. yu will be set. . The rods and pistons from your 390 will work if they are in good shape. The only problem would be if your engine is a 360. Then you will need 390 rods(The 360 has longer rods because of the short 3.5 stroke). I don't know if 360 pistons will work with this setup.Others here will know for sure. Just make sure you have a 390. With the heads off measure the stroke by taking a measurement at BDC then another at TDC. The difference between the two measurements is the stroke. Example: BDC = 4.00 and TDC = .22 then you have a 3.78 stroke(390) . Hope this helps.

 

Can I just swap in a 410/428 crank & flywheel, or would I have to get it ballanced? I might re-ring it some time soon and it would be nice to have an extra 20 cubes.

 

Assuming it does have the 410 spec pistons, yes you could just swap the 410/428 crank and flywheel. It would not be ideal but it would work.

If it doesn't have the 410 pistons you will get some really cool bent and broken stuff.

You could also look at my post "410 pistons again".

 

always have it balanced anytime you change out any of the rotating parts.