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Nice, streetable, wide 308 2V torque curve

Discussion in '308/328' started by AZDoug, Dec 20, 2019.

  1. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
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    This is thru full exhaust, with air cleaner and accessories on the motor. No special gasoline, needed, either.
    Doug
     
  2. dhalter

    dhalter Karting

    Aug 2, 2009
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    that looks nice. so how did you get there?
     
  3. derekw

    derekw Formula 3

    Sep 7, 2010
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    Looks very nice, look forward to hearing about the secret sauce...
     
  4. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
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    360 crankshaft and 85 MM cylinder barrels, and better cams.

    The 2V head just doesn't breath as well as pent valve head, though., which shows as the torque starts falling off above 5500 RPM.

    Doug
     
  5. derekw

    derekw Formula 3

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    Web cams or CATcams? Profiles? Carb or injection changes? Timing curve?
     
  6. cavallo_nero

    cavallo_nero Formula 3

    Nov 3, 2003
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    Your lowest torque numbers are more than most of our engines' max torque - for Normally Aspirated, well done.
     
  7. jim rosenthal

    jim rosenthal Karting
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    Sep 10, 2006
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    More particulars, and where do you get a 360 crankshaft? When you go to 85mm cylinders, do you have to sleeve the block or just bore it out? I recall reading that the cylinder bores are Nikasil- I would think you would sleeve it or bore it out and recoat the Nikasil and hone it? And what do you think this set of curves would look like with 4-valve heads?
     
  8. sltillim

    sltillim Formula 3
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    I see the top of the sheet says corrected power - so is this estimated crank or wheel?
     
  9. Ferraripilot

    Ferraripilot F1 World Champ
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    May 10, 2006
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    That is at the crank. Sadly mine was only ever dyno'd on a dynojet.

    Good stuff Doug. Glad you finished this project!

    For documentation for others who might be interested in similar projects. Mine used 83mm bore with 360 crank, I did quite a bit of head work using larger ID intake valve seats, larger intake valves with nail head profile, minor bowl and throat work on intakes only (flow was up 10%+ at lifts above .200), ports were not altered, 34mm carb chokes, carb jetting was changed quite a bit in that the main jet was about a 135 with a 165 air corrector, Cat cams with .425 or so lift and 245 dur @ .050, 10.4:1 JE pistons, stiffer valve springs, total ignition timing was 36-37 degrees all in by 4500rpm ish, made 274bhp at the wheels (Dynojet), so about 320+ flywheel.
     
  10. derekw

    derekw Formula 3

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    Surprised you used stiffer valve springs as the originals are too stiff and CAT cams sell softer sets with their cams.
     
  11. Ferraripilot

    Ferraripilot F1 World Champ
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    Stock springs can not handle that much lift, or it's very borderline with stock springs (can't quite recall, been a while). I sourced a set from a great place in Australia. Seat pressure is only not much higher but they can handle the lift more comfortably.

    I hate to say this, but I had an unpleasant experience with Cat Cams springs a while ago with another engine because the springs were not strong enough, had valve float all over the place despite their recommendation. I love their cams but do not trust their spring recommendations.
     
  12. derekw

    derekw Formula 3

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    Thanks for the heads up on the springs. The many stories of these engines reving to 9-10krpm suggest the originals are too stiff.
     
  13. mk e

    mk e F1 World Champ

    Oct 31, 2003
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    Yeah, stock springs have enough extra seat pressure to handle boost to about 15psi and float at about 18psi I'm told, not sure what that translate to rpm wise........but I'm pretty sure they won't handle much additional lift safely. They are also not up to current spring standards....I've pulled a few heads apart now and everyone had at least a few bad springs so I would not use them in anything but a stock build.
     
  14. sp1der

    sp1der Formula 3
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    Guess we used the same source for valve springs, also got the titanium retainers, I believe this is where superformance get the uprated parts from as well
     
  15. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
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    I bought my crank at GT parts about oh, 6 years or so, ago. It was fresh out of a 360 motor. All it needed was a bit of polishing. I think i paid about $2K for it
    New sleeves, block had to be bored for the larger sleeves. The original '79 308 sleeves were cast iron. New sleeves are Nikasil

    A 4V head would extend the torque curve and thus the power curve, the max tq won't go up much, but higher tq at higher RPM will give you more power at higher RPM.

    If you compare a 360 dyno graph vs my graph, you can see where the 2V head starts to fall on its face above 7K RPM. More, lighter valves on the 360, extend the RPM range and increases the air flow., even though max Tg isn't that much different.
    Doug
     
  16. derekw

    derekw Formula 3

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    348 and 355 cranks also work with a little machining. My 348 crank was only $200
     
  17. thorn

    thorn F1 Rookie
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    How much was the machining?
     
  18. derekw

    derekw Formula 3

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  19. sp1der

    sp1der Formula 3
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  20. jim rosenthal

    jim rosenthal Karting
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    Do you get the increased stroke with the 348 and 355 cranks, and is it as much as the 360 cranks gives you? I don't have comparative bore/stroke information for all these motors, although I do have it in a book for 308/328..
     
  21. bill308

    bill308 Formula 3
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    Hi Jim,
    I believe the following is the progression of crank strokes.
    308 71mm
    328 73 mm
    348 75mm
    355 77 mm
    360 79 mm

    Hi Doug,
    Thanks for posting your dyno results. The following chart compares my 3.4 to your 3.5 liter engine. As far as I can tell, the key difference in engine builds is likely bore size. I think you used (Norwood?) 85 mm sleeves and I used 73 mm (328 Nikasil) sleeves. The bigger bore should enable better breathing. My dyno results show an output dip in the 4700-5700 rpm range. I now believe this is due to how the dyno was being operated, so likely not real. Multiple dyno runs on a 1700 cc, Cosworth BD, on the same dyno, shows a remarkably similar dip, in the same rpm range. Based on this data and my observations during the test, I feel comfortable in interpolating and extrapolating the dotted line curves for my results. Your curves helped a lot. My engine builder does not like to test a new engine low in the rpm range.

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    Your engine is 3.5/3.4=1.03, or about 3% bigger in displacement. This yields a 268/256=1.047, or about a 5% increase in torque. Your 268 lbft torque peak is at about 5300 rpm and my 256 lbft peak occurs at about 5800 rpm. This is the result I would expect on a carb constrained (34 mm chokes) engine. The bigger engine produces more torque but runs out of breath sooner at high rpm. Both should be very nice street engines. Personally, I would prefer your engine for the street.
    There is more to be had with a better air filter assembly. With OE air horns and no the air box cover, my engine showed up to 30 more hp over a significant range.

    Bill
     
  22. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
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    Thanks for the info. i will analyze this a bit further.
    FWIW, i suspect that tq dip is due to something else, let me think about that.

    Is your exhaust stock, and if not, how is it modified? You may be getting a reversion of some type (possibly dyno caused) causing your car to run either too lean or too rich in the dip. Do you AFR data on your run, also? I know Webers are infinitely adjustable, but damn, there are an infinite amount of permutations, and knowing what to do to correct an AFR imbalance in a certain RPM band takes a lot of experience, time, skill, talent and emulsion tubes, etc.

    I will post some dyno graphs from a chev V8 that had tremendous change in tg, in certain RPM range just by a mild exh mod, when i get back next week.
    Doug
     
  23. bill308

    bill308 Formula 3
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    Hi Doug,
    We had a pretty good discussion on 308 exhausts here:

    https://www.ferrarichat.com/forum/threads/big-bore-exhaust-manifold-for-2v-engines.608093/

    This thread shows photos of my engine and the dyno test setup. The dyno headers used 1.88 OD primaries on a 4 into 1 design. Most folks believe the primaries are too large in diameter and should be in the 1.37-1.63 inch OD range, to maximize exhaust scavenging. David Vizard emphasizes that this exhaust pulse is much more powerful than the pumping action produced by the downward travel of the piston. Note that these exhaust pulses arrive at the intake valve just after it begins to open, hence the importance of low lift flow. The pumping pulse occurs later and includes the time when the intake valve is fully open. So, we have a strong pulse at low lift and a long duration, weak pulse, when the intake valve is fully open. My takeaway is that my test headers were likely not optimum.

    The good news is that your results show the OE exhaust headers are fine at the power levels we are dealing with. The folks at Caribou Engineering told me the OE exhaust headers are pretty good. Like you, I will use the OE tri-Y headers with a sport muffler. If this system works at 3.5 liters, it will work at 3.4 liters, and I don't have to do a custom exhaust. This is very good news as the OE headers are well insulated and offer sniffer tubes for idle mixture setting.

    The following chart is a little busy but shows data from 4 engine tests, 3 of which were run on my engine builders dyno. While I only show one of my Ferrari runs, with the full air filter assembly, my other runs show the same dip. Tim's Cosworth BDR shows a similar dip on all of its runs. At a sweep rate of 300 rpm/sec, the dip lasts about 3.3 seconds during testing. Surprisingly, my Lotus Twin Cam (LTC) data does not show this dip.

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    We did not record AFR data during testing, but did monitor it's value on real time display. The leanest we saw at wide open throttle (WOT) was 0.88 lambda. To keep testing costs reasonable, we minimized dyno testing, only ensuring a controlled initial break-in and safe operation at WOT. Low and mid range operation are in the ball park. Final tuning will be done on the road.

    Bill
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  24. mk e

    mk e F1 World Champ

    Oct 31, 2003
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    I think you hit it spot on with the exhaust. The dynomation simulations I ran for him pretty much duplicated his issue using the exhaust he has and eliminated it with a mod modern tri-y design and that was with the software holding the AFR constant (EFI vs carb). The best I could tell the dyno headers had both the primaries and collectors go completely out of tune together at about that 5200 rpm point but worked well up top to make the peak numbers really good.
     

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