Howdy...I have a spent 351M and am looking for any suggestions/mag articles/literature to turn this sick puppy into a hoss tire spinning 400. I have read the "Down $ Dirty" article from hot rod '98, but that engine went to a street machine, I am looking for a mudding/trail running/4-wheeling/fun machine with lots of low end torque and good horse. The article was a good read and the price and hp and tq numbers were good, what changes would you wrench heads recommend if any? Would I be happy with this engine in my '79 bronco? Thanks for the info, i know this issue has been addressed a gazilion times, I just want to do this right the first time!

 

OK so you want to build yourself a Real Truck Motor, Here's what I would do.
Take a get yourself a 400 Crank for your engine and then order yourself some .030 over 351c 12.5 to 1 bumpy top piston's . Send the block to a good machine shop have them boil out the block and have it bored for your pistons and then have them Deck your block to .010 with the piston's rods and crank assmebly your going to use.you'll have to bush the pins in your rod for the 351C pistons but shouldn't be a problem for them to do at this time.
Having everything balanced would be a really good thing to do at this time but not nessesary for street use. Just one of those things I'd do for peace of mine.
For the cam I'd look at one of the real torque monster towing cams out there.


When you get everything back from the Machine Shop you'll have to test fit the heads. Without the head gaskets place the head on the block ( Do NOT bolt them down )and bring the piston to top dead center and watch to see if the head moves, If it does then you have to find out what part of the piston is touching the head, and have the head massaged ( grind that spot a little ) so it makes no contact with the heads.And you'll have to do that to each combustion chamber on each head.Usally there's two core vents by the plug hole that need to be smoothed out some.

Now that you have everything ground so nothing hits you'll have to check Valve clearances.So with the cam installed set-up one cylinder with pushrods and rocker and lightweight springs (Aces Hardware Spring box) on your valves.Now as the intake valve startes to open push valve down by hand to see how close the valve is to the piston. And then do the same with the exhuast valve as the piston comes to top dead center.You'll need a dial indicator set up to check this But I look for at least .080 Clearance on intake valves .125 on the exhaust valves.
You may have to adjust cam timing to get sufficient Clearances.

OK with that done it's time to look at the Intake & Exhaust ports. Gasket match the intake to the heads And do the same to the exhaust ports to manifolds or headers.

And then add the external oil line from the port by the oil filter to the port on the back of the motor to help oil the mains.

Now you have a 400 With some snot.( In pretty much Stock Form )

And if this has to much compression for you, You can opp for flat top pistons for 9 to 1 comp.with your open chamber heads. But with either piston you end up with 409 Cid with this set-up.
Have Fun

 

Shazam, you the man! Thanks for the info and time!! I have never done anything like this before- how much time and money (ballpark it)can I expect with this? What kind of hp and tq numbers can I expect at the tires? What kind of cam would you recommend? Thanks again!

 

Oops! I forgot to ask you about heads. What's up with the aussie heads? are the stock heads from my 351M alright to use? I know i will save money using my own, what can i expect to pay/ where do i get some/ are these aussie heads worth it? What advantages do they provide? Thanks again!!