347 Vs. 302

[fdlrc]

My son wants to rebuild my old 74 Bronco. It has the original 302. His question to me was whether or not to replaced the 302 with a 347 that he found, or rebuild the 302? First of all, we are keeping the original engine no matter what he does.
I know nothing about 347 engines, and whether it would be a good choice or not. We can pull up dozens of articles from Mustang guys and hotrodders, but that doesn't answer what I'd like to hear from you guys with real world experience and the 347. That is:

1. Is the 347 as a reliable street engine as the 302? We're talking street use application.

2. I've never had a stroker engine, but I imagine the torque available, and where it is in the RPM band, is why many of the Bronco sites only offer, or talk about, either the 302 or Coyote engines. Not much, if any, talk about the 347.

3. My first inclination is to rebuild the 302 as a roller cam engine, or keep it aside, and replace it with a 351W roller.

I know if we built this 302 to the same specs of my Ford Racing Boss 302, that's in my 57, he would like it. The only difference would be Boss has 4-bolt vs. 2-bolts mains in my 302 that puts out a whopping 140 HP.

So, I'd like to hear any real-world experience and opinions regarding the 347.

[59meteor]

I can't say much about the 347 SB Ford striker package, but I have been running a 331 striker 302 in my 78 Fairmont for the past 5 years. Unlike a 351w swap, all your existing 302 externals (accessory brackets, headers , oil pan etc) can be retained, plus the 351w engine is physically larger and heavier. Depending on what you want from the engine and vehicle, the 347 may be a great choice, but if you want a mild cruiser vehicle, a race built engine will not likely make you happy. I understand that to package the 3.40" stroke of the 347, the wrist pin hole in the pistons is into the oil ring hooves, and may cause some oil consumption issues, but that is info that I have only heard 2nd hand. The 331 uses a 3.125" stroke, and the pistons do not have the wrist pin/oil ring issue. Probably the 331 I have in my Fairmont would be more aggressive than what you are looking for a street vehicle, but my pump gas, flat tappet cam 331 puts a smile on my face.

[CobraJoe]

I built a 347 , zero clearance stroker for my Daytona Coupe, and it was a great motor. It was very reliable and made plenty of power. The old oil consumption issues are pretty much a thing of the past as modern piston and ring designs have eliminated this problem. The 347 will make more torque than you could get from the 302.
Another good choice would be stroking a 351W to 393-408, stroking to a 427 seems to work well in trucks from what I'm told as they use a a long stroke (heavy) bottom end which limits them to lower rpms.

[FiveSevenLiter]

Great picture Rory.
My brother pulled his stroked Windsor in his 64 Fairlane, and replaced it with a 347.  Ran 11.9's on street slicks and headers open.  Pulled well, pump gas, no overheating issues, I am sold on them.  No brainer when it comes to time messing with different components.  The Windsor went into my other brother's Ranchero.

[fdlrc]

Thanks guys. Am I to assume one builds a 347 using a 4-bolt main vs. a 2-bolt main block?

[rmk57]

  That would depend on how high you want to spin the engine. I'm not sure on the safe limits on a 2-bolt 302 block.

[59meteor]

On my 331, the first block was a factory hydraulic roller lifter block from a 5.0L Mustang, after a few years of drag racing, when we pulled it apart for a freshen up, we discovered the main webbing cracked, and when the front main cap was removed, it broke in 2 pieces. Luckily I didn`t make many more 1/4 mile passes, it likely would have destroyed everything in the engine.  As much as I would like a Dart aftermarket block, I think I would rather put the money towards getting the Fairmonts chassis upgraded to be legal to run 9s, and put the FE engine back in again. So we found a good earlier 1974 302 block, which has a bit more material around the main bearing area, and added a main cap girdle. 3 years of racing later, it`s still running good, although I should pull it apart this winter for a look over. Since I run a flat tappet cam, I don`t rev it super high, typically dump the clutch at 6200-6600 RPM, shift at 6800, and cross the finish line around 7000, 7200 on a killer pass in good weather. I am sure in a street car, or even an automatic drag car, the 5.0 block would have been fine for a long time. At least at the power level I am at, and naturally aspirated.

[silverbird#58]

[quote author  -  in the 58 ford  you could have some fun ,   
                         a small club sedan  with 331  fe block   bored over to get 340 ci
                            add coae 6090-d  heads     or the new alloy units would be better .     and im sorry  the FE 331 could be made a  real runner too ,  just ford never went this route.

[59meteor]

As much as I love FE engines, personally if I wanted an engine that small, I would go with a 302 o 351W. Much lighter, smaller, and easier to get parts for. But if I wanted something around 390 cubes or bigger, FE would be my choice. Now concerning the stroker small block, I now have a 347 for my Fairmont , but it`s not the more common configuration. A buddy made me a deal too good to pass up, so I sold my 331, and bought this new engine, all brand new, with only 1/2 dozen dyno pulls on it. It`s a big bore (4.125" ) Dart SHP block, so it gets it`s 347 cubes, by using the same stroke crankshaft as a 331 using a .030" over 302 bore. Hopefully the local dragstrips are open next year, as I am itching to see how the new 347 runs down the track. As for the original posters Bronco, I can`t imagine any downside to a stroker kit, other than costs, but since most Broncos have plenty of gearing, a stock or near stock 302 would likely be fine too.

[fdlrc]

I think we will rebuild the original 302. Up-grade to aluminum heads, Ford HP cam - convert to roller cam and lifters. Basically what I put in my 57, which seems perfect regarding street-ability and good low end torque.

[Ford Blue blood]

I'd look in the yards for an under 100K motor out of light trucks, Mustangs, Crown Vics etc.  They are barely broke in at that point.  It would cost less then the heads/cams and parts for the rotating assembly, never mind the cost of machine work....just saying.

[fdlrc]

That is a good option as we have time. We haven't even started the body and chassis work.