'74 351 to '97 302

[HPTGreyGhost]

Re: '74 351 to '97 302

Cool. Looks like we are about on the same page with the wiring. Thanks for the help. I do have 1 remaining question on the subject at this point. I'm going from a raw wiring situation to a harness hopefully, so I'd like to make sure my thoughts are clear on how it should work. Is Pin 6 providing power forward to the ignition switch or is it receiving power? I would think it sends power from starter connection forward so that the only wires going from the engine to the dash would now be in this bundle? Please confirm if you can.

I'll talk the water pump pulley and pump off Saturday and hopefully start compression testing with a fully battery. Look for updates

 

[E4ODnut]

Re: '74 351 to '97 302

From your diagram it looks to me like pin 6 is a large pin, which would indicate a main power lead from system battery and alternator to supply all loads on that system. Following the R/Pu wire from the plug, it goes to one side of the 60 amp main harness circuit breaker. This also connects to the output terminal on the alternator and to the 20 amp circuit breaker for the fuel pumps. The other side of the 60 amp breaker connects to the battery via the main terminal on the starter drive solenoid. With this arrangement, the circuit breaker provides protection from the battery only. I suppose the logic here is that the alternator probably only has a 60 amp output so it's not likely to exceed that current under fault conditions.

I'm assuming that the pin 1 wire will go to a negative bus for all your other loads on that system, and that the Pin 6 wire would go to the ignition/start switch and the fuse or breaker panel for the other loads on that system. I stand to be corrected on this but if you have a wiring diagram for your boat you should be able to check it out.

Hope this helps.

 

[E4ODnut]

Re: '74 351 to '97 302

My turn for questions.

Does the engine use a return to tank fuel line as well as the suction line?
Do both low pressure and high pressure pumps look the same?
Is the fuel cooler separate from the high pressure pump, or is the pump inside a cooler assembly?

 

[HPTGreyGhost]

Re: '74 351 to '97 302

Cool.

Updated Pics

Weekend update: I can't get to the plugs because the stupid headers block access. Horrible design. I need a 5/8 socket that I can attach a wrench on because there isn't room for a swivel or the socket wrench or an extension. In lieu of looking for a socket, I decided I'd take the headers off. Well that didn't go so well. As you can see from the pics, the 4 bolts that were out were easy to take off but the 4 bolts that were recessed on this header design have fused to the headers and are near impossible to remove. I tried sockets, I tried EZ outs, I tried a heat gun. Next step is a torch and if that doesn't work a pneumatic die grinder? Some pics are included so you can see what i'm dealing with. Note the guy I circled in red. You can't even see a head on it.

I did not see a fuel return line but that's a good question. I'll double check. Pic "K" will give you a good shot at the secondary fuel pump. To me it looks the same as the primary fuel pump in pic "N". The fuel pump sits on top of the cooler.

According to this parts diagram, the fuel pumps are different: 3857650 and 3858714 or 3858261.

 

[E4ODnut]

Re: '74 351 to '97 302

Cool.

Updated Pics

Weekend update: I can't get to the plugs because the stupid headers block access. Horrible design. I need a 5/8 socket that I can attach a wrench on because there isn't room for a swivel or the socket wrench or an extension. In lieu of looking for a socket, I decided I'd take the headers off. Well that didn't go so well. As you can see from the pics, the 4 bolts that were out were easy to take off but the 4 bolts that were recessed on this header design have fused to the headers and are near impossible to remove. I tried sockets, I tried EZ outs, I tried a heat gun. Next step is a torch and if that doesn't work a pneumatic die grinder? Some pics are included so you can see what i'm dealing with. Note the guy I circled in red. You can't even see a head on it.

I did not see a fuel return line but that's a good question. I'll double check. Pic "K" will give you a good shot at the secondary fuel pump. To me it looks the same as the primary fuel pump in pic "N". The fuel pump sits on top of the cooler.

According to this parts diagram, the fuel pumps are different: 3857650 and 3858714 or 3858261.

I'll bet you're glad the engine is in the shop and not in the boat right now.

You're photos were a bit "stacked up", so it was hard to tell where the borders are.

I use a 3/8" drive, 6 point 5/8" deep socket, shortened as much as possible and still have decent contact with the plug and tapered a bit at the spark plug end. I use it with a Snap-On universal joint (because they are relatively small) and a short extension. Work just fine, but the clearances are tight. Now is the time to get those manifolds off and checked out. From the looks of the rust on the rest of the engine it could probably use a thorough inspection.

It's very possible that you don't have a return to tank line. Perhaps the low pressure pump just charges the cooler(cooler/surge tank?) and the high pressure pump draws from and returns to this cooler/tank. I think that Mercruiser may do something similar, but I stand to be corrected.

 

[haulnazz15]

Re: '74 351 to '97 302

I think a simple box-wrench is usually the easiest to remove the spark splugs. The spark plug sockets/swivel works, but it's usually more of a pain to work around the manifold.

 

[HPTGreyGhost]

Re: '74 351 to '97 302

Ok... Ez outs sockets, drilling, fire, nothing worked. So we pulled the engine out the back of the truck and took a sledge hammer to the exhaust. We hit the risers and it broke off the manifolds around the bolts. Yea!

Now we were able to get a compression guage on her.
#1: 110
#2: 0
#3: 110
#4: 120
#5: 135
#6: 120
#7: 120
#8: 120

Poor #2 had no compression. We think the exhaust valve may be stuck open or a lifter is broken. We were going to put some air through it to test, but the air came out #4. I guess we need to turn it over a bit more. I'll probably just pull the valve cover off and look first.

I'm beginning to think there will be a lot to replace on this engine. I know the freshwater pump needs to be replaced and the exhaust and the valve covers. It's old, oil wasn't debris free and I'm starting to think a new 350 MPI may be the way to go. I just don't want to drop a couple thousand in this engine and only get a season out of it and need a new engine next year. And the rising cost of ford parts and availability has me a little spooked. What would one of these ECUs cost if it went bad - $1000? Thoughts on my plan ahead? Am I right to want to repower all new or should i dredge forward on this project?