Hello everyone and thank you in advance for sharing all your experience and expertise. I recently purchased a 93 E350 Quigley with a 351W. The lower end is toast, so I'm going to build a motor. Since its a heavy utility/adventure rig that'll tow heavy on occasion and speeding most of its time in the Colorado Rockies, I'm looking to build out the motor to have great low end torque with the best mpg's possible, From what I gather, I need to build a high compression motor- buy a 94 or newer roller short block, some aluminum heads with small ports and fast flow. My current 351w is an efi, and I plan on using as much stock parts off my junk motor. Do I need anything else to accomplish this at a budget level? I would like to convert it to MAF as well. Do I need to put different pistons or cam in it?

 

I found myself in a similar situation to yours a couple of years ago. I had purchased a 1994 high top van and the motor would barely run. When I tore it down I found melted pistons, etc. I'm surprised it even ran! (I knew the motor was toast when I bought the van.)

I was converting the van to 4x4 and as part of the project rebuilt the engine. It had a 351w roller block in it. I purchased a short block from a mass short block manufacturer out of Tyler, Tx, MABCO and built the rest myself. I had the block built to stock specifications. I then replaced the stock cam shaft with a low end high torque cam: https://www.summitracing.com/parts/CCA-35-510-8. For heads I went with AFR's SBF 185 St Enforcer Heads 64cc. I measured and got the right push rod lengths along with Comp Cams hydraulic lifters. The rest of the engine is stock. I am controlling the engine with Stinger Performance's PiMPxs Standalone Engine Management (Sequential EFI). I converted the wiring to sequential and kept the speed density.

Like you I thought a switch to MAF would be the way to go. Unfortunately you need to get a 1996 (or so) 5.0 computer and then remap it for the larger displacement of the 351. The remapping of the computer is an entire art all in itself. It can be done and people have done it. I did find a MAF sensor on a van local to me, but the rest of the donor's intake plumbing was toast. Finding the rest of the plumbing to go with the MAF can be extremely difficult given the age of these vehicles and the lack of good donors in the wrecking yards in my area.

The engine is a power house. I have it paired with a 2017 F150 6R80 6 speed automatic transmission and have the shifts mapped to take advantage of the low end torque and power. I run at around 1900 rpms at 70 mph. Shifts are oriented at moderate and light throttle for early shifts to keep the engine turning slower. My van is 7900 lbs and I can tell you this engine setup makes the van feel MUCH lighter than it really is. I have no idea how much power the motor is putting out, but it is PLENTY for anything I've encountered. I have tuned the engine as much as I know how and can tell you that big motor is not fuel efficient in any way. I get 13.5 going down the free way at 70+. I get 13 around town running the A/C. I get between 10 and 12 in extremely rugged rough off road terrain. I saw over 14+ on a tank a couple of times and a tail wind was involved. If I was in a situation to run 60 for an entire tank on a relatively calm day I believe the fuel mileage would increase to around 15 based upon what I've seen in my travels. At lower speeds in stop and go traffic and off roading situations the weight of the rig is the big reason for the fuel burn and at highway speeds the high top wind drag penalty is the reason for the fuel burn. No way around it with this setup.

I personally don't think building a high compression motor is necessary. The engine has so much power as is running on regular gas. Given how much I drive it and the cost of premium fuel I am so glad I built it and tuned it to run on regular unleaded. My wallet definitely appreciates it!

 

Thank you for the reply Bd96a3. You’re exactly the person I’d hope this thread reached. I’m also looking at purchasing through mabbco motors. How was your experience with them? I haven’t pulled the trigger quite yet, but I’m thinking I’ll have them build a 94’ roller block, upgraded flat top pistons, gt40 heads, and an rv cam. I was thinking of some nice aluminum heads, but I don’t have space to build a motor(only have a street to swap motors atm (if you know someone willing to let me use they’re shop near Denver CO for cash or barter, let me know!)) and I’m not positive I’ll get my moneys worth from aluminum heads anyhow.

 

The experience was good. I have no reason to complain. Have you done a lot of research on the GT40 heads? I seem to recall they really didn't make much difference on a speed density setup. I could be remembering wrong on that. Anyway, I decided the GT40 heads weren't worth the money for the limited improvements they were supposed to make. Hopefully your experience will prove those recollections wrong!

 

From what I gather the gt40 are a huge upgrade to the stock heads. The 62cc combustion chamber plus I think 180cc intake. Along with the flat top pistons, I should be sitting around 9.5-1. I know the aluminum heads are much lighter and dissipate heat much better. I have a bit more to consider because I don’t have a place to work. I live in my camper at an rv park and the owner is already giving me looks with the van not moving since arrival. I’m looking into renting space, but haven’t found anything under $2500. So I could get a long block with the gt40 installed, and have a short list of work to get it into the van. Rather, buying a short block, then building it… somewhere. Plus the gt40 upgrade is $600 compared to $1,200-2,600 for anluminum heads. Always, if you or someone else has a better idea for me, I’m all ears. Another thing that’s a big problem is Mabbco won’t have the motor to me for a month or two. I would like to have it going… yesterday! Ha

 

I'm running a 429 in my '78 4x4 Ford E250 Chateau wagon with a C6 and NP205 behind it. I just love it to pieces, and, it LOVES fueling stations. _ haha
Prior to that build, I had converted a '75 E250 Club Wagon to 4x4 and it had a 351w. That 351w engine was a workhorse.
On a long hard pull towing a 26-foot travel trailer up a long steep grade, the 351w wouldn't go as far up the grade befor downshift as the 429.
In my '77 F350 Crew Cab pickup 4x4 converted, I am running a balanced and built 300 inline Six Gasser with holley 4-bbl.

I run mid-range cams, because when climbing those long grades, I'm running the engine in it's power band from 3,200 to 4,500 rpms.

I think you will be happy with whatever you choose, as the 351w is a go-to engine.