I have a bone stock 360 with 56000 original miles in the 74 ford highboy that I just bought. I'd like to make it a 390 with lots of low end grunt and some decent HP. Good thing I have an FE, right? Haha. I know I need to change the crank and rods for 390 versions, but what about pistons? I think I read somewhere that I should use the stock 360 pistons for better compression. Is this right? Will I have any clearance issues with the valves? I'm not sure what version of heads that are on the truck, but I'm thinking that I should get some porting done and a 3 angle valve job. Can/should I get some better valves? I have a streetmaster intake that I bought on ebay already, and I'm thinking I should get a 650 4bbl carb to put on it. Does that sound about right? I'll also be running headers and 2.5 inch duals. I'm also wondering what kind of cam I should run. I'm not looking for a high RPM screamer, more like something that I can pull stumps with. I will be using the truck mostly on the street, but will be pulling a 6000-7000lb trailer with it a few times a year. I'll also be using it to play in the mud. It has 35 inch tires on it now, but I'm thinking of going down to 33's for some cost savings. It has 410's in dana 60's (it has a high pinion dana 60 swapped in the front) and a 4 speed manual transmission. I'm currently in Iraq and would like to have all the parts ordered and waiting for me when I get home to do the work, so I'm trying to get this build mapped out now. I'm also wondering what ignition set up I should run...Am I missing anything? Any and all suggestions and help are welcome and much appreciated. Thanks!

 

First and Foremost Thanks so much for putting it all on the line for our Country. now IF it were me and you can find one I'd skip the 390 Crank(3.78") infavor of a 410/428s crank(3.98") that would give you a 410Cid which produces hellacious torque. and at lower RPM IF you have to bore it .030 over you'd end up with a 415Cid Big Block FE

 

Scott, Have you ever pulled that trailer with the setup that you have now? It should be a stout puller already. With 4.10 gears behind a 360 it ought to pull that weight with ease. Those big tires can make trailer handling a little ruff. You don't want it swaying all over the road.

You are talking about maybe a 5mpg truck, that big horse is gonna eat a lot of hay by the end of the day. IMHO


John

 

court1100f, Thanks for showing your support but you have the wrong guy, haha. While I have served as a soldier here before, this time around I'm working as a civilian contractor mechanic. This trip is all about the money! hahahaha. John, I haven't even driven the truck at all to be honest. I bought it on ebay (dont worry, my father checked it out for me in person) while I was here and won't be home until July to see/drive it in person. I don't plan on using the truck as a daily driver, so I'm not too concerned with milage. Mostly, its just going to be used for raising hell and hauling a trailer here and there. This truck is mostly being built to be my toy, so I'd like to have one hellacious motor if I can. I considered the 428 crank too, but I don't want to spend tons and tons of money on the motor, because I have a budget in mind for the truck, and I still would like to buy selectable lockers for the front and rear. Now, if I could find a 428 crank for a decent price, what length rods would I need and what pistons would I have to use? I really dont want to spend 1800 bucks on a balance rotating assembly from SCAT. Know what I mean?

 

no need to spend money on the balance, use a correct flexplate/flywheel for 80.00 The cranks are pretty cheap now with the forged chinese stuff rolling out like doughnuts. 390 Truck pistons with the 390 rods and your in business. Several choices in pistons with reasonable prices.

 

Agreed just get the correct Flexplate/Flywheel..........although I think some Car 390 pistons would yield higher compression thus higher performance wouldn't they??? As apposed to the truck pistons just depends on what the current bore is but depending on how crazy you go with an overbore you could get as much as a 420Cid out of it at .060 over or as little as 410Cid wth the stock bore thats totally up to you and depends on the engine block in questions ability to withstand the over bore but YOU can damn sure have fun with that motor and you don't have to break the bank to build it either

 

Scott, I don't think you comprehend what you have there now. The FE is a torque monster out of the box. Any FE in front of 4.10 rears will pull a house down the road.

A lightly sweetened 390 will do all that you want as you have described. You wrote in your first post that you didn't want a lot of Rs. FEs make power off idle and darn few factory setups would ever reach 6000 rpms without floating the valves.

It's your money to spend, but you have your whole life ahead, slow down, enjoy it.



John

 

John, I think you and I are on the same page. I dont want to blow a ton of money on a 428 crank or crazy race parts. I do appreciate everyones input though! So lets just say that I want a mildly built 390.... as far as the bottom end goes, what is the most economical, feasable route for turning my 360 into a 390?

 

What the he!! is all this flexplate/flywheel jazz?

The SAME flexplate (C5AZ6375D) is used for ALL 1965/71 cars with 352/390's. ALL 1965/76 F100/350's with 352/360/390's.

C6 or C-O-M makes no difference...it's the same for both.

The only difference between a 352/360 flywheel (C5AZ6375K) and one for a 390 ( C5AZ6375L) is the pressure plate's bolt circle diameter.

352/360's use a 11" clutch on a 12 3/8" bolt circle.

390's use an 11 1/2" clutch on a 12 7/8" bolt circle.

The 352/360 flywheel can be used in place of the 390.

My truck has a balanced and blueprinted 390 I built from the original 352. The same 352 flywheel has been in there since 1965.

The same two flywheels were used on 1965/76 F100/350's, 1965/71 on the cars.

I've typed over 100 posts here on FTE listing all the specs of these two flywheels and flexplate...I would think...one of y'all would have read one of them!

Geez!

 

Bill, I think he was referring to a 428 crank, that one is different.



John

 

Scott, basically you start with a 390 crank and rod set and order pistons accordingly to overbore size.

There are others here much more knowledgeable than me that can tell you what cam and intake to run to make your house mover move a bigger house.


John

 

360's rarely require an overbore, and with 56k on it I seriously doubt you'll need one. I had a 360 with 4.10's and it pulled good enough, and it got about 8-10mpg. Going to a 390 is a very good choice in my opinion. Better mpg, more power, etc. 650 carb sounds good, and really you dont need high flow heads for tq. So I wouldnt worry about spending the extra bucks on porting.

Anybody know the compression the truck 390 runs at? cant remember off the top of my head.

 

yeah Bill and this is just common sense to most of us!!! and you took things a little bit out of context no disrespect intended. but the original comment focused around the 428 Crank not the standard 352-390 Cranks it's a given they use the same flywheel/flexplate since it's the same Crank Essentially with their respective strokes of 3.52"/3.78"/or 3.98" being the only difference.

 

Me thinks you should have done the reading on this one Bill

 

Where does it say anything here about 428's?

All is see is references to 390 pistons/rods.

Sorry...if I took it out of context, but y'all ought to make yourself a little clearer.