351m/400 Big Block In A 69 Bronco?

[jeremy69bronco]

I bought my first EB about 4 months ago. I rebuilt the little 302 that was in it and im just not happy with it. I have a 351M out of a 79 bronco. Has anyone ever put one under the hood of a EB?

 

[bobtail]

I once had a 76 Bronco that I squeezed a 460 into (same size as a 351M) and let me tell you it was way more trouble than it was worth. I had to relocate the brakes and power ones would not fit, had to beat the crap out of the firewall and never was able to fit tall valve covers, had to cut off the shock towers, modify the steering & trans linkage, create a new trans crossmember & driveshafts, custom radiator, adapt the engine accessories (alt, ps) and purchase L&L conversion headers from Jeff's Bronco Graveyard.

By the time it was done I could have just rebuilt the 302 and been in better shape for the street, the only good reason for adding a 460 should be for racing in the mud or sand drags. I'll see if I can post some pictures of the truck here soon for those who are interested.

 

[Bronco1978]

One of the secrets to the 66-77 Bronco was the relative light weight.....a 351M is way heavier and bulkier than a 289/302 and wont rev as high either,that and their lousy track record of oiling system problems and you are better off with a 351W...it fits better (its a little taller) and factory EFI is available as a potential upgrade.The smaller 289/302 was such a great "team" with the smaller Bronco configuration,its overall hard to beat......

The whole reason for the 351M/400 in the 78/79 Broncos was,#1:It was now based on F series trucks (and their FE engines were laid to rest in 76),and #2:The high weight of the trucks demanded a "torquier" and more "durable" engine.Thanks to development of the 302/351W during the 80s(EFI,computer controls),they became acceptable for use in full size heavyweights...that is after some seriously bad years of below par performance.

I would say overall the 289/302 was by far Fords best engines....fuel efficient,long lasting,low maintenance,very flexible for usage in trucks,Mustangs,Cobras,family cars... the Cleveland based 351/400M engines may have been smooth and long lasting,they were far from being as "flexible" in their applications (in car use they were gutless,in truck use they were just par,and no sportscar or Mustang were ever graced with a 351M/400 engine).

 

[upnorth]

I had a buddy spend a lot of late nights and money rebuilding a 351M. When he was finally finished with the rebuild, installing which was a pain and a seriously gentle break-in period we hopped in his bronco and went to see what parts the new engine was going to break. After 20 minutes of testing I started planning on a 351W. He had better overall performance with the 302 with headers and cam. The engine ran like a top but just didn't have the holeshot feel that the 302 had. As for top speed, who knows, neither one of us really wanted to see if it would actually keep the tire side down at 100mph.

Now that I have my 351W in unfortunatley we don't live near each other anymore to do some head to head testing but my 351W whips the old 302! Better gas mileage also.

 

[Big John]

[-X Don't mess with the 351M /400 engines. I put way to much money in a 400 for my 1977 F250 and it still isn't right. I have used 302's, 351C, and 351W in my Broncos . My favorite was the 351C but it ran a bit too hot when at higher altitudes. I switched back to my 351W which is more manageable. You will have too many problems trying to adapt the 351M/400 to your early Bronco.

 

[67halfcab]

1st thing to note is the 351m/400 is a small block motor, it just happens to share the big block bolt pattern for tranny's.

Although they are not mainstream they can be great engines and part of their problem is they came on the scene at a time when automakers were gearing them toward emissions standards more so than performance.

Follow this link I think it is one that everyone should read.

http://www.projectbronco.com/Technical_Art..._the_rumors.htm

Just me $.02