Nos681 wrote:

Has anyone played with the 351w speed density ecm found on trucks?

Yes, extensively since I bought my Lightning new in 1995. They vary a bit by year, but one thing is for sure they don't like many mods to the motor. You can have a custom cam ground to keep it somewhat happy, but there's a lot better EFI options nowadays depending on what you are looking for.
 

Last edited by Raymond_B (4/24/2021 11:45 AM)

TKOPerformance wrote:

The first thing a lot of Lightning owners did was convert the system to mass air.  That's still a viable option.  The problem with SD is that its only going to tolerate small change in airflow without going wonky.

And it was EXPENSIVE! I and several friends tuned quite a lot of SD trucks several made it in to the 10's and faster, but it was always working with one hand behind your back.

Now there's a plug and play Megasquirt that connects right to the EEC-IV 60 pin connector giving you both engine and trans control. My how times have changed
 

Nos681 wrote:

Years ago, I drove a friend’s F350 while my truck was getting repaired.

The difference was noticeable to the 289 in Mustang.

However, I saw the fuel gauge drop just driving around town and it had SD on the 351w.

Probably a waste of time to consider I guess.
Thanks for sharing your experiences.

Could be torque and gearing, but yeah if you were considering it for your Mustang or something no way Your A9L is waaaaaay more flexible!
 

I wold talk to a cam company to get the best matched cam, but in general the biggest thing to consider is LSA.  You're going to want to be in the 112 degree range to keep the computer happy.  The 351s were WAY under cammed.  Even the Lightning, which had a GT40 top end had a peanut cam in it.  A cam swap and switch the mass air in those trucks could shave a full second off the ET.  Personally I'm a fan of Crane Cams.  They answer the phone when I call, and I've always been happy with the cams they've sent me. 

On trucks, keep in mind that most 250 and up trucks have 3.73-4.10 gears, so that's another reason for the bad mileage, and they are heavy.  This is why Diesels gained popularity, even when they were making all of 135HP; the mileage and longevity were significantly better.  Now the gas trucks get better mileage, but you don't want to tow heavy with anything other than a Diesel.