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RCrombie

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  • My Project Cars
    1953 M37cdn
    1978 280z

Converted

  • Location
    Ont, Canada
  • Interests
    All things that go, fast or slow

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  1. Triple Carbs are very common on straight sixes, such as those found on Datsun L series motors. No problems with one throat per cylinder, although you have to make sure that each carb is balanced first, and that the opening of the throttles are synchronized. Otherwise you get poor off idle performance and a shaky motor in low rpms. For the 2.4 litre six cylinders, carb throat sizes in the range of 40-45mm were used depending on how how the motor was built. I built several engines running DCOE webers, and they work well, but were rather finicky. They didn’t play so nicely with modern fuels, and requires a systematic approach to tuning them as there are idle jets, main jets, emulsion tubes and air correctors that all have a theoretical impact somewhere in the power band. They would require a balance tube for things like the vacuum advance, but otherwise it wasn’t necessary for a smooth running engine. On the Dodge sixes with the shared intake ports, three single barrel side drafts like Moose has would work well. Maybe improvements could be made on the intake manifold to shorten the length of the runners, depending on available space. I don’t know if it has been mentioned yet, but six cylinders sound GREAT with individual carbs. Adds at least 20hp to the butt dyno. Anyway, I spent a lot of time tuning triple carbs and so I can ramble about them enough to bore most people...
  2. The one I purchased had a couple different rubber ends you could use, but you’re right that if the throat of the carb isn’t round or if you have something projecting up into the airflow then you may need an adapter to get it to seal. velocity stacks aren’t necessary though. They work well as long as you can hold a steady RPM. With the Weber’s, you would tune them at idle when the linkage was slack, then at a steady rpm when the linkage was slightly taught. If you already have on of these synchrometers in your toolbox, give it a try. If it doesn’t work, you’re not out anything. Cheers Rob
  3. I used to spend quite a bit of time synchronizing triple carbs on a Datsun, and I found the best tool for the job was this style. It doesn't restrict the airflow to the carburetor to measure the flow(that can cause issues too), and it gives you a number value to match between your carbs. You can also adjust the sensitivity to measure off idle sync which can be more important (and more often affected by a worn linkage).
  4. That’s a cool machine! I would love to see a video of it in action. I see you’re north of the border, where abouts? I’m in the Ottawa area. cheers Rob
  5. Very nice M! I have a Canadian M37 that is currently half disassembled. A truck like yours motivates me to get to work on it.
  6. You say the truck has been sitting for many years. Sometimes you can have a bit of surface rust develop which causes the disc to stick to the pressure plate or flywheel, and it will cause these symptoms. Pulling the truck in a lower gear with the clutch depressed will usually free it up, and you’re good to go after that.
  7. To the best of my knowledge, the 25” Canadian engines used brass tubes. I have taken 3 out, and they all came out without much fuss. At least one of those I can personally guarantee hadn’t been touched since the 1960s. I would hazard a guess that any galvanic action going on must be pretty minimal.
  8. You might have better luck asking this question on the maple leaf up forum or perhaps g503 forum... the members there have a lot more knowledge about the specifics of ww2 dodges etc. cheers, rob
  9. Hi all, I’ve been lurking on this board for a while but I want to chime in here since I have tinkered with efi on the Nissan straight sixes, and I have been keeping it in mind for my M37 as well. First off, with these engines being what they are I certainly wouldn’t worry about the crank flexing to any degree. That’s generally a problem with high RPM harmonics in race engines, and it wouldn’t be a timing issue. It would be an issue with main bearings and the crank breaking. I have triggered an L6 with a 36-1 trigger wheel from the crank snout with great success, that was hitting easily twice the RPM these flatheads top out at. When I did my conversion, I found you needed to have a very rigid bracket for the VR sensor or any shake would cause issues with loss of signal. Similarly the missing tooth wheel had to have very little runout as well. Secondly, I think injecting the fuel just after the throttle body is the way to go to get around the issues with Siamese port engines. Generally with siamese ports you have to do some very odd timing to get port injection to work, and end up running into other problems as well, such as very short injection pulses. Another thing to remember is that the latest generation of injectors is miles better than the TBI injectors of the 80s-90s, and you can run very large injectors (1000cc or more) with great driveability using megasquirt/ micro squirt. Anyway, I think these engines would certainly benefit from some form of modern efi, and a coil on plug ignition, or wasted spark using a coil pack. Tuning is not difficult either, although it does take some time simply driving in different conditions and tinkering as you go. I say go for it! I plan on it down the road as well. My 2 cents. Rob
  10. Green would be corroded copper. Copper core plugs?
  11. Hi Chuck, the M37 should have 16” rims with a Budd bolt pattern. They are two piece locking ring rims, and are not the same as split rims. Cheers, Rob edit- whereabouts are you located?
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