I've posted some lately, and decided to start a new thread about my attempt to make my engine run acceptably, and in the process, gain some power.

The starting point is a stock 79 351m with 73,000 miles on it. I bought it for $1500 a dozen years ago and it did not run well. Couldn't hold an acceptable idle. Surged up and down in rpm and basically was not smooth under high vacuum conditions. past half throttle was OK. I replaced the intake manifold with a stamped steel turkey tray type gasket figuring I had a leak. I put a GM style one wire ignition on it to rule out spark problems. Gave up trying to fix it and just used it to haul wood. I had the carb idle circuit adjusted pretty rich and when cold, it would idle smoothly. Smooth idle is pretty important when jockeying through the trees in a woodlot in creeper, especially when it's only two wheel drive. It's a four speed manual with 4.10 gears. It started leaking pretty bad from the rear main seal, and recently I've been getting wood at a place where ridiculous leakage is unacceptable.

So I tore it down. I found the cam lobes on 1 & 2 exhaust valves smoked. The others didn't look exactly healthy. Main and rod bearings showed copper. Pistons and bore visually looked fine. Very light carbon ridge at the top of the cylinder. Valley pan I installed had oil on top of it so obviously it wasn't totally sealed. After cleaning the intake valves and seats, they looked for all practical purposes, new. I lapped the exhaust valves because I had lapping compound on the shelf, and they did not look new, although very good.

I said cheap. I found an Edelbrock 2172 clone cam with lifters and double true roller adjustable timing set for about $130, so that's what the beast is getting. I already had a Holley 600 carb, so I sprung for a Weiand 4v intake. When I'm done, I will be looking at a low compression 4 barrel with a cam never offered, running out stock exhaust manifolds and crossover into a free flowing 3" muffler dumping in front of the rear axle.

Doing the math and testing the valve spring compression, I found that I can't use the valve rotators on the exhaust valves. I'm ordering some retainers that should give me more room for the lift. Most likely I could use intake valve spring retainers, but hopefully what I'm ordering is a sure thing.

As of right now, the engine is on a stand. Rod and main bearings are in. Cam is in. While installing the rod bearings without removing the pistons, I pushed a piston down a little (up in the bore, engine upside down) and the top ring cleared the deck. Did I say minimal ridge? Had to borrow my brothers ring compressor to get the piston back in the bore.

This afternoon I installed the timing gears. I have no degree wheel, nor do I have a dial indicator and BS to mount it, so whatever the gears say it is, is what it is. I set it 2 degrees advanced.

While cleaning, painting and installing a new front seal on the timing cover plate, I thought to myself that this item is not particularly impressive. I noticed threads not flush where the water pump bolts to it. Touched it with a mill *******. Installed the plate and water pump and noticed that the gasket between the plate and pump was on my work cart. F. R&R pump. The second time I torque the pump bolts, one of them pulls the threads out of the plate. I'm thinking about brazing a nut on the back side, and if I do one, I'll do them both. Anyone have this happen to them? I don't feel like dropping another chunk of change when I have torches. I would probably MIG the bugger in hopes of keeping it cool to minimize warpage, if I had a MIG welder. I'd feel better about buying a new plate if I hadn't already installed a seal in this one. I'm actually pretty handy joining metals, but I'm thinking that keeping the seal cool while heating the plate might be a PITA.

This is where I'm at. Sharing my world. I would post some pics but my military spec Kyocera flip phone isn't set up for this PC yet. I'm still getting used to Windows 10. I think it's 10. Where is "my computer". Lol.

 

Palmrose2,

I'm in the process of helping my oldest son rebuild a 400 for his '78 F-150 - also on the cheap!

For what it's worth I think you're correct that to MIG weld a nut on the back would be best. Do you have a friend with a MIG welder? Take all of two minutes!

 

I agree - tack weld it. And make sure you have a bolt in the nut so there's no chance of welding the threads.

As for the seal, how 'bout laying a wet rag over it? Wet, not damp.

 

Used a wet rag, heat shield, and ran a bolt through and snugged them to make the nuts square for initial "tack". I brazed them and didn't want to take the chance of possibly wetting the bolt with bronze. It was actually quite a job. Warped the snot out of it as expected and so I had to spend time massaging it with hammer anvil and bench vice. Chased the threads with a tap, and was meticulous about getting every bit of glass flux from the brazing removed. Of course I knew it was gonna suck before I started.

Brazing a couple tacks on a 5/16ths nut. Think about that. By the time you heat the thing up to tack it, you could invest another 30 seconds and be done.

 

My plan is to use the air intake stove and duct work to feed it warm air, though it seems a little restrictive for this engine as built. Do you guys think that just the exhaust intake crossover will be enough for COLD weather driving?
For the exhaust I intend to use the OEM manifolds and crossover. The crossover pipes join each other in a nice V orientation. They are 2.25" and the "collector" is 2.5" and about 18" long. I've got some stuff in the cart at Summit but haven't pulled the trigger. 2.5"x3" adapter, some 3" pipe, a Walker #22636 3" in and out muffler, a 3" mandrel bent ell. I figure with this and some hardwear I can dump the exhaust in front of the right rear tire. The muffler is what Walker calls heavy duty and looks like it would be at home slung under an F700. I'm shooting for low back pressure without all the noise. I'm sure I'll get some just because of the short exhaust run.

 

I don't think that just the exhaust heat crossover in the intake manifold will be enough.

That's exactly what I have on Rusty and it takes forever on a cold morning to get warm enough so it won't bog. I really, REALLY nead the exhaust stove as I have the rest of the inlet air plumbing, including a good Air Cleaner Temp Sensor, but don't have the stove. And when the choke comes off and the outside temp is less than 20 degrees it is bog city until I've driven at least 10 miles.

 

I've now painted my ex manifolds and stove high temp cast iron gray. My wife asked what the stove was as it was just laying there, not installed. I told her and she said it looks like it's rusting out. It is a little feathered around the bottom where it lays against the manifold. My response to her was I know it's rusted some, that's why I painted it. Finding a good stove for a truck manufactured well over thirty years ago, I'm sure would be a challenge.

 

Yes, stoves are pretty much gone. I'm hoping to recreate the one I have in stainless.

 

Pics of my mild porting on the exhaust side. I looked and looked for a cross section of a D5AEA-2-A-? to no avail. I think there is a coolant passage near the exhaust valve stem so grinding was minimal.








OEM exhast bowl D%AEA-2-a-?

 

Seems like I read somewhere that it isn't a good idea to port match manifolds on a street engine. Supposed to help with reversion. As it stands, my intake manifold runners are smaller than the head intake ports, and my exhaust manifold openings are larger than the head's exhaust ports. Gaskets are pretty close to the larger ends of aforementioned mating surfaces. Arguments?

Got a re-curve kit coming with springs and adjustable can. I'm sure that will be a fun project.

I've had extra time to play with this because of my job, but I'm coming up on the time for 60+ hrs a week for a few months. It will be 70+ with this project not finished.

I still can't post pics straight from my phone. Blah.

 

A little exhaust manifold clean up.





Before





after

 

More ex port pix.



before





after

All I did to the intake was blend the bowls and shave the guides a little. I've read too many places where you can make things worse, so I took a minimalist approach. Besides, I ain't racing.

Just BTW. As near as I can figure, with everything I've read, this 351M came from the factory with 8.3 to 1 compression ratio. I've read a LOT, but I could still be wrong.

 

I'm going to try to quantify this.

Cam, lifters, and springs. $175
Gaskets and plastigage. 75$
6" egg shaped burr. 28$
Rod and main bearings. 75$
Weiand intake manifold. 220$
600 CFM Holley. 0$ but would have been 320$
Double true roller timing set 50$
Exhaust components (some stainless) 180$
Correct thermostat. 6$
Adjustable timing kit and timing tape. 43$
Paint. 20$
Anti freeze 25$

Project is dragging while I'm waiting for cam springs, so I'm kind of kicking myself for not popping the pistons out, breaking the glaze, and installing rings for 40$. If I would have gone down that road, I would have done Tim's oil mods too.

It looks like I came up with $1,257.00

Delete $320 and $40 cause I already had the carb and I'm too lazy to even put in new rings, and my cost is around 900$ Even though I have a perfectly functioning 2 1/4" single exhaust system, I can't, in good conscience, reuse it.

P.S. I'm not sure I would have messed with the timing kit, but was leaning that way after some research. The deciding factor was my discovering that the vacuum canister on my not even broke in, but well out of warranty, aftermarket GM HEI distributor was smoked. The resistance to airflow through it isn't much more than that of a good filter mask. SMOKED.

 

That's cheap. Hope it works as expected.

 

Palmrose2,

You've got the right idea on the exhaust. Round off the edge of that plateau just a bit and get rid of that air injection bump helps a lot! I'll be curious how you like the cam, so let us know!