Engine What Are Some Tips To Build A Long Lasting Reliable 347!!!

Discussion in 'Fox 5.0 Mustang Tech' started by fiveohlover, Jan 29, 2014.

  1. if you are short on cash, then do yourself the favor of letting the pros set up your short block. remember you want to do this once. the best cheap way to go is to get a solid foundation, aka the short block, and use stock heads, intake, exhaust etc. for now, and upgrade when you have extra cash again.
    Grabbin' Asphalt likes this.
  2. I built mine from a stock 289 block. I have a good machinist. I had him do all the block prep etc and install the crank. I took over from there. the entire rotating assembly is Eagle and ARP studs or bolts throughout. Heads are AFR, cam is an ed curtis custom, manifold is edelbrock, topped with a holley and fired by an MSD system.

    as long as you start with a good foundation, and pay attention to detail, you should be fine.
  3. [​IMG]

    THIS^^ Says to me that there was probably nothing at all wrong with the components used but that the entire assembly grenaded due to being WAY too lean.

    Some of you guys that build and tear down motors like Legos can confirm or deny.
  4. that is a possibility, Would being lean lead to a valve dropping down? cuz thats what happend
  5. The secret to building a long lasting and reliable 347 is easy......don't build a 347. They, by their nature aren't designed for this purpose. The 302 based stroker kits are designed to add torque and horsepower, not sustained reliability. The rod angles are too excessive for high mileage duty. Going with a 331 stroker is better for longevity and sticking with the 302 is better still.

    If you want cubes and are starting from scratch anyway, start with a 351W block and build from there. The block is wider and therefore their rod angles are far more forgiving than that of a 302W.

    I have yet to see anyone produce a 347 kit capable of sustaining what I would call high mileage.
  6. yeah it does seem like the mixture was rather lean. as for it causing the issue, no. he said he dropped a valve, which means either a bad valve spring, or the valve itself broke, and unless the motor was running really lean, that wont be the cause of his broken motor.

    that depends on what you consider high mileage. a properly built 347 should go about 100k miles before you should have to go through it these days. i also agree that a 331 would be a better combination if you want a long lasting engine, and it doesnt lose much to the 347 in the area of actual useable power output.

  7. While I don't think there's a magic equation to calculate exactly how much more wear each individual combination is contributing to, I will say that it seems the higher displacement/longer stroke combinations contribute the most. This is based on both the results I've seen from running and broken engines after a few miles and simply by doing the math.

    Of all the 347's I've seen running around, I don't think I've ever seen one with more than 50,000-miles on it. Generally, the car ends up sold or broken, (to become someone elses problem as made apparent in this thread) or a different combination is built before any of them see any sort of mileage. I have on the other hand seen pics of ones that the owners assumed were running fine, only to find visual evidence of excessive piston skirt scuffing, and/or cylinder bores polished to a mirror finish from wear in a relativity short period of time. The angle of the rods in a stroker kit puts a LOT more stress on the cylinder walls and piston than your standard 302 does. This fact is irrefutable. How much additional stress is really going to depend on how much the rod angle is increased.

    This was exactly the reason I chose my 331 over the 347. While I know it's not going to knock out 200,000-miles like a basic 302, it should be good for a good portion of that and most certainly will outlast a 347, while providing as good, if not better performance characteristics in return. That 15lbs/ft of torque I miss out on with the additional displacement is more than made up for by the "revvy" nature of a more square bore vs stroke combination and additional longevity of a less stressful engine combination.

    In the end, I decided the performance vs longevity ratio of the smaller stroker was an acceptable compromise for me to live with.
    Noobz347 likes this.

  8. I've seen detonation break valve stems a time or two. Not saying that's exactly what happened but I think I recall the OP indicating that one of the valves broke in a peculiar spot.

    It's not always the head gaskets that give first even though we usually hope that they do.

  9. DART block for the MFW! :rock:
  10. how can you guys tell it running lean? because the pistons or what?
  11. if you look at the coloration of the pistons, you will see that towards the edge of the piston a white coloration. this indicates a lean condition in that area of the flame front. that indicates an overall lean condition. what you are looking for is a consistent color across the piston, and you want a dark charcoal look.
  12. I have a bbk fuel pressure regulator, is it more of just adjusting it to get more fuel to richen it up?
  13. If yours is a Mass Air car, then just bumping up the fuel pressure to richen it up on the top end probably won't cut it. The ECU will sense that it's too rich at idle and part throttle driveability and just adjust the injector pulse width to compensate. What's in it for injectors, fuel pump, etc. Was the car previously dyno tuned? If so, were you given any paperwork showing an A/F ratio?
  14. No dyno tune, not a dyno tuner in 200 miles of my place that i know of. Got 30lb squirters, and a 190lph. And i dont know how to measure A/f Ratio
  15. Oh and its got no egr, and a chip not sure what brand though
  16. I think when you get it back together, it wouldn't hurt for you to install a wideband A/F ratio set up. AEM, Innovate Motorsports, etc make some nice, reasonably priced kits.

    ....then I'd drive it the 200-miles for a proper dyno tune. That's a lot of money wrapped up in that engine to be gambling with. It seems silly to risk it over $100 worth of fuel and a few hours of your time.
    A5literMan likes this.