I am wanting to make my 79 F150 4x4 into something nice.

Currently it has a 351M in it. It runs reasonably. I have been frustrated by a chuffing or chugging noise. It is subtle and I can't pin down what it is. Right now I have no insulation in my cab, so it's easy to hear engine sounds. The engine seems to have decent throttle response and power. I don't race or do anything that requires any serious HP. I do really want an engine that sounds good, and a the rhythmic sound I get now bothers me. I know that the water pump has some play in it and haven't taken the step of replacing it yet. I have replaced a noisy alternator and PS pump as well as replaced the fuel pump. I removed the air pump and plugged the intake manifold where it attached. I can't find any exhaust leaks and I can't find any obviously loose rockers. It still has single exhaust although it has a flow master on it.

So why am I posting this on the FE forum?

I really became sold on the 390 I have in my 2wd truck. This started when I purchased a "donor" truck that had a 390 in it. When I first got it, I needed it to pass emissions. This was going to mean I had to fix bad exhaust leaks. Long story short, after breaking exhaust bolts in the heads, I replaced the heads with freshly rebuilt heads. I also ended up replacing a cam and getting aftermarket adjustable rockers for it. That engine also seemed to have "ticking" I could never trace down. The rings couldn't take the newly built heads and I ended up breaking rings and a piston skirt. Eventually I got a junkyard engine fresh out of a running truck and transplanted it into my 2wd. This engine has stock exhaust manifolds but has dual exhaust. It has an edelbrock aluminum manifold and AFB style edelbrock carb. I am very happy with how this engine runs and sounds.

Back to the 4x4. I could rebuild the 351M, I could have it built as a 400. I could have the 390 that I broke the rings in rebuilt and use it. Known issues:

I need a rear sump oil pan and pickup - I've acquired on on Ebay

I'm not sure how the FE will locate on my engine stands - i figure this is especially important since I have a transfer case and front driveline to deal with

My understanding is that the frames of F150s (not 250s) remained the same from 73 (or earlier) until 79. I know that all F150s that had 4wd 73-76 had an FE 360.

Does anybody know how different the motor mount between a 335 block and an FE block are?

I did have a hot rod oriented mechanic shop tell me a few years ago when I had them check it out, that I had good cylinder pressures in the 351M that is in the truck currently.

Pro's of going to FE:

I have heads that should be pretty good... only a few hundred miles since a machine shop had rebuilt them with hardened valve seats - they have sat unused for a dozen years

I have aftermarket adjustable rocker arms for those heads along with the pushrods that came with the set.

The cam was new... it was a Comp cams RV cam... unknown if damaged? haven't had it out to evaluate yet.

I have acquired the needed rear sump oil pan and pickup for use in 4x4


Pro's of staying with 351M:

No swap issues
having dual exhaust made might give it a better sound
If I can figure out the noise thats bothering me, it seems to run decently and not need rebuilding.

I will want to go to a 4V carb and aluminum manifold. The FE manifold looks harder to install with out leaks than the dry 335 family manifold.

Opinions?

 

Personally I would junk any 351m that crosses my path. I do know the engine stands you have wont work. You would need the stands from a FE or 6 cyl truck. The transmission would be the biggest deal.

 

I'm running a 4sp NP435 + NP205 t case.. I'm figuring I need to get a FE bell housing. I'm thinking that a FE truck bell housing shouldn't be hard to find or particularly expensive.

I forgot to put that in my known issues

 

OBT, You already have a 351/400 now. If you can hear engine tickin on a 35 year old truck the radio aint turned up loud enough.


The M can rebuilt to make a decent engine, it was an early emissions engine when they were (and still are) trying to figure it out. I don't know what your state requires for the engine to be equipped, or if they will allow an FE to be swapped in. In NC it is not a concern at all.

The FE (all same on outside) will have to have engine stands from 73-76 (not certain if 4wd are same as 2wd) FE bell, & maybe some other minor things.

Some turbo mufflers with pipes all the way to the rear exiting 3" tubes can make great but not loud sound. The M can not make FE sound, so if that is driving you, you better start working on one to swap in. If cash is limited take the truck to a shop that can help diagnose the noise.


John

 

I have swapped out different engine perches in the 2wd frames, but the 4wd engine perch set up is different than the 2wd. I haven't had the chance to find an FE F150. I'm not sure if the F250 is the same in the engine bay either?

 

For the most part 100/150s & 250 are same in the bay. Chassis is slightly larger and axles below are different with the 250.


John