Engine build experts... 352 de-stroker?

Discussion in 'Engine Topic' started by Speed Happy '77, Mar 12, 2009.

  1. Speed Happy '77

    Speed Happy '77 Veteran Member

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    I was looking for something that could deliver decent gas mileage, low weight, high horsepower. Obviously, you make trades, but I was looking for the best I could get. So, without further ado... the 352 de-stroker (also a 348 if you don't bore .30 over).

    Uses a 327 crank with a 3.25" stroke in an SBC 400, bored .30 over (4.155). For the main journals to avoid heat issues, thick-wall bearings over bearing spacers. It uses ARP 6.202" Ford 300 cid L6 rods (forged, of course) and adapted low compression height pistons to meet the total deck height. 56 cc heads with 2.02 valves and headers, and the rest has yet to be decided.

    Hot Rod magazine did a special article on it, no worries, didn't buy it whole, they have a free team of experts who can supertune and tweak for quick delivery without lasting performance.
    http://www.purplesagetradingpost.com/sumner/techinfo/350 chevy engine.html

    Now come all my lovely questions. Spark plugs... I like non-gapping, non-fouling E3's, use them on my Camaro right now. I've also heard good things about Iridium, especially with SBC and high performance. That kind of segues into my question about heat. How tough would this motor be to cool? They claimed 11 to 1 compression, so I bet the local machine shop could make at least 10.5, and I would be running 92, not 87. More advance, quicker delivery of HP, IMHO. Lastly, camshaft. I was thinking on the low end of a moderate cam, just not mild like they installed. Does this really sound like a good setup for a 500+ HP motor? What are your suggestions for lift/duration, what type of goodies, roller rockers, hydraulic lifters, solid lifters?
    Lastly, intakes... wide bore, short stroke, big valves (I'd also polish and port the heads further, most likely), tons of flow already. What would help the most? Blower, supercharger (prefer it over a turbo, to be honest), just a cowl hood, what are your opinions?
     
  2. Americanmuscle13

    Americanmuscle13 Veteran Member

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    It's different, I guess i don't see the point? Why not build an LSx series and go injected if you're worried about gas mileage? Seems like it'd be a ton of money into a relatively average results. It'd probably rev quickly, but I don't necessarily think that it'll save you any gas mileage. 500 hp requires a certain amount of gasoline, whether it's a turbo 4 or a big block v8.
     
  3. onovakind67

    onovakind67 Veteran Member

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    There's no magic in that bore/stroke setup, it's very similar to a Mopar 383 and they weren't known for extraordinary power. This is about the same as the old Chevy 348.
     
  4. TooLateVTEC

    TooLateVTEC Veteran Member

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    If you want lightweight, good power, AND gas mileage than a fuel injected LS motor is the ONLY way to go. You can get 400+ RWHP with ONLY A CAMSHAFT.
     
  5. Speed Happy '77

    Speed Happy '77 Veteran Member

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    This is a $6,000 build, already priced out locally. Most of those blocks cost that much already. I just like the idea of 24 mpg so I can rub it in when someone says it's worthless for road trips. I wanted old school for more availability of replacement parts and easier to work on personally. What about air intakes?
     
  6. Turbo T/A

    Turbo T/A Veteran Member Lifetime Gold Member

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    If you have a good 400" block, dont waste it on making it under 400 cubes, especially if it will be mainly a street motor.

    -Carm
     
  7. Speed Happy '77

    Speed Happy '77 Veteran Member

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    I've never quite understood that. Why sacrifice RPMs for a little HP and more torque? I like the wider ratios a car can handle between gears, tons of RPM. I know that any engine can be built to those specs, but the way I learned, the safest bet was a shorter stroke. My grandfather was a master mechanic, certified to fix anything that moved... anyway, he taught my dad short stroke, big bore always won out.

    That being said, my understanding is that big bore, short stroke creates a more natural airflow, then add to that high compression on a 4-stroke. The high pressure releases, creates a pressure differential, then a natural suction going from high to low pressure so quickly. I also read up on rod ratios, and it seems to be controversial, but believable.

    I might be crazy, but I just love the idea of making a 600HP (provided I add a blower, supercharger, etc.) motor that's just roughly 350 cid without super-tweaking or wayyy over stressing a ton of parts. That and keeping the bills tiny in the build and fixing it later. I did post willing to learn, though, so here goes...
     
  8. Air_Adam

    Air_Adam Veteran Member

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    More efficient heads and a matching cam will get better fuel economy on a big engine than a medeocre heads/cam will on a slightly smaller engine.

    400ci small block with a set of Vortec heads and a can in the 218*/224* range with around 10:1 CR and a dual plane manifold would get really good mileage I'd bet, and would be a fun one to drive too. Couldn't compete with an LS1 or LT1 for fuel economy, but still would be more than reasonable.
     
  9. pdq67

    pdq67 BANNED

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    Some guys just don't get it b/c I figure he actually wants raw topend power that a shorter stroked crank engine will give along w/ a little more grunt that more cubes will give him!

    And I'm here to say that a hopped up 348" "W" pre-BB motor will actually run very well here!!! I'm talking like a "scalded-dog"!!

    He, He!! Think 350hp/348" "W" engine here..

    pdq67
     
  10. craigblock

    craigblock Veteran Member

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    Big bores are not associated with good fuel economy or emissions.

    Power comes from torque and revs. The revs won't be going up in this case because it is a pushrod engine which maxes out before the lower end will. Torque comes from the product of cylinder pressure and displacement, and the displacement is going down by 14%. The losses in the engine won't be significantly lower because little has changed; the oil pump is the same size, it has the same cooling requirements, and so forth, so there isn't much to give the torque back.

    I don't see any major benefit to the setup. Most engines are stroked for a reason: to get more power from the same rev range and cylinder pressure.
     

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