1969 302 swap but thinking abt 331 stroker

Discussion in 'Technical' started by pil1sbury, Nov 29, 2015.

  1. pil1sbury

    pil1sbury MavBoy living life

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    I haven't posted in awhile but I did a 302 swap out of a 1969 mustang. I bored it .30 over and a few small upgrades so she's a healthy 307ci. I need to now rebuild my C4 and my rear end, and I need to do some under hood upgrades my radiator just isn't doing much so I'm looking at a champion 4 row with electric fans I have some more to do.

    After building the motor and driving it for 2 months I'm really considering a 331 stroker kit for more power. We do a lot of street fun in my area I'm not gonna be running with the top (750-900hp cars but mainly mustangs) but I'll hold my own with the mid range guys.
    Any of y'all have any tips on a 331 stroker?
     

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  2. 71gold

    71gold Frank Cooper Supporting Member

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    build a 347...about the same money and a lot more fun...:yup:
     
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  3. groberts101

    groberts101 Member

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    What size and the expected power level.. and more specifically where in the Rev range you want that power to show up.. should be the biggest determining factor on what kind of motor to build.

    Basic rule is that smaller motors are more tractable with fewer suspension mods required since they have less torque. But they need more gear and converter when you really want to start lowering et's. Bigger motors need more suspension and can get by with less gear and converter to easily hit the same et with greater civility.

    Speed costs.. how fast you wanna go?
     
  4. greasemonkey

    greasemonkey Burnin corn

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    I'd just upgrade the 302 with Afr heads a custom cam. Some good headers and exhaust and N2o.
     
  5. pil1sbury

    pil1sbury MavBoy living life

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    I thought I've read that a 347 is a good power making motor but didn't last long.
     
  6. greasemonkey

    greasemonkey Burnin corn

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    My 347 is around 15 years old. But, if I had it to do over I'd go 331 if my only option was a stock block. If you can afford a dart or boss block. Go big bore 347. Basically, there are two options on the 347 I guess I should say. A small bore long stroke and a short stroke big bore. The latter of the two seems to be the most desirable but, requires an aftermarket block.
     
  7. groberts101

    groberts101 Member

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    That old myth was caused by the early "stock crank strokers" and un-optimized piston designs(bad oiling/rail designs) of years ago. Plus, many guys didn't know how to build them any different than other motors to help mitigate the potential issues. Then you add the mechanically inept morons and teenagers who don't know how to warm up an engine properly before they load it under power and what do you have? Burnt, leaked, and puffed oil.

    From a geometry comparison standpoint(rod angle, bearing/cylinder thrust wall loading) the 347 is no better or worse than many other old motors.

    The bigger issue is that many people underestimate the value of a good "stroker specific" piston design. The shorter deck height doesn't lend itself as well to bigger strokes which often leads to piston rock/skirt loading and dropout/protrusion past the bottom of the bores(into the crank case). A "good piston".. $$$.. fixes almost all of these issues. Short skirt, high ring location with no oil ring spacer and thinner rings help last a good long while. Good pistons are worth power up on top and even across the board too.
     
  8. 71Mavrk

    71Mavrk Member

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    Eagle rotating assembly and Icon Pistons in my 347.

    Notice the bearing edge wear. I replaced them with ones that were not so close to the edge of the journal.

    I had to pull the engine after 1,000 miles. She burned a LOT of oil. Turned out the shop forgot to install the baffle under the PCV valve. (What a pain)

    Cost for a 331 v 347 is the same. I went for the cubes.

    No problems with the engine now.

    Micah
    image.jpeg image.jpeg
     
  9. pil1sbury

    pil1sbury MavBoy living life

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    I think I'm going with 331 might add a pro charger or something later. It's not on my first to do I need to do everything to get the bugs out like rebuilding my C4 putting a big starter installing MSD and I need to put a 4 row radiator with electric fan
     
  10. rotorr22

    rotorr22 Member

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    If you seriously plan on adding forced induction or nitrous at some point, spend the extra $$$ on a Boss or Dart block.
     
  11. greasemonkey

    greasemonkey Burnin corn

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    Tci makes a nice kit to rollerize that c4 btw.
     
  12. groberts101

    groberts101 Member

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    This is exactly right. Also need to keep in mind that the compression you choose now can be severely limiting to the amount of maximum allowable boost used later on. Best to stay at around 9:1 or even lower unless you want to be running alcohol or race gas everywhere you drive it to prevent detonation. Boosted motors have extremely low tolerance to detonation and scorch pistons before you even know what hit you.

    With a Boosted application.. you'd at least want a 6 pinion front carrier in that thing. Stock 3 pinions can break pretty easy.
     
  13. OLD GOOSE

    OLD GOOSE Member

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    There is no substitute for cubic inches
     
  14. junrai

    junrai Member

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    power and go fast equals LOTS of money potentially I know I started out going to build a 347 stroker with a stock block. I wanted it to hold up because I heard about the short life for the 347 so I bought ALL KINDS of goodies forged this forged that Hbeam rods BRAND new everything except the block even a girdle to hold it all together and I was up to $10k for a measly lil 500HP I asked my engine builder what was holding me back from running with the 1000hp club and he told me lets see.........youre block so I decided to get myself a dart block and go all in with a 363 stroker all in oil pan to carbs without the msd dizzy and msd box Ive spent $13100 the dizzy and box ran me about another $1200 so going fast can get VERY expensive VERY fast

    as far as life span goes I cant say just yet as mine isnt done yet. Ive read that the 347 is a snotty motor that can be lots of fun but tough to get along with on the street depending on cam choice. I read somewhere the 363 is supposed to be easier to get along with on the street and have a longer life span
     
  15. OLD GOOSE

    OLD GOOSE Member

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    devil's advocate - if you want big horsepower cheap go ls1 - tons of mods for them 500 hp very easy to do fuel injected very streetable if someone asks "'why did you put it in a Ford ?'' say ''The Hemi blew up"":rofl2::stirthepot:
     
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