The JDM collection grows... and Dixie has some competition for my time. | Page 4 | The Z Club of Great Britain
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The JDM collection grows... and Dixie has some competition for my time.

Discussion in 'General discussion' started by richiep, May 2, 2021.

  1. toopy

    toopy
    Z Club Member

    I have to say Rich, the amount of research you put into these projects and the subsequent work that follows is pretty inspiring, i wish had the money, time and inclination to follow suit! :D
     
    SeanDezart likes this.
  2. richiep

    richiep
    Z Club Member

    I like to know what I’m letting myself into! On the money front, I probably need to slow down. The credit card balance is now making me wince.
     
    SeanDezart and toopy like this.
  3. Col-b

    Col-b
    Z Club Member

    Hi Richie i just checked my engine although its a 1975 it the 18RGU so less power any tips on getting more power without changing cams etc would be appreciated :conf2:
     
  4. richiep

    richiep
    Z Club Member

    Without opening the engine up, it's pretty much exhaust and carbs - a tubular manifold and suitable exhaust, and swap the Mikuni 40s that come as standard for 44s or similar (Dellorto/Weber/OER 45s, etc.). Also, you may have the non-rebuildable carbs, so tuning them for power is a no-go. You could track down some of the earlier ones if that's the case so that re-jetting, etc. can be done.

    From what I can make out from my research so far, the pistons are the main tool for controlling compression and thus much of the power potential in these engines. The RG heads are not suitable for major skimming like L-series heads can be. 1mm is apparently the absolute max. I presume with the twin chain setup, things are much more sensitive in terms of chain tension, and messing with head thickness could be more risky. The higher compression piston options are domed beasts that come up into the chambers, with big valve reliefs. That's how you get into the 11:1s, etc.

    The twin cam head I have for my build is a Yamaha RGU version. I think they may have a deeper chamber, which might contribute to the lower compression. It will be interesting to see what I can do with a bit of playing around with it. Bigger valves apparently make a big difference, and as mentioned before, it looks like its had new oversize seats put in, given the step in the "throat cut" in the top of the port below the seat.

    Also, see what smog crap you have on the engine - recirc valves, carbon canister, etc. A lot of that could be done away with probably.
     
  5. Col-b

    Col-b
    Z Club Member

    Cheers Rich i will do. I have Solex carbs can these be tuned and can i do away with the standard air filter by adding carb trumpets for more air ? and as you said there seems to be a lot of smog crap on the engine
     

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  6. Col-b

    Col-b
    Z Club Member

    To be honest i would not know where to start and knowing what was smog control will check you tube etc
     
  7. richiep

    richiep
    Z Club Member

    Those are the non-rebuildable Mikuni-Solex carbs. Tops are different to the tuneable ones. The emissions stuff is that spaghetti of hoses and valves around the place. You’d need to do some research too with respect to what you can get away with removing. This is probably the advantage I’ve got - because I’m building an 18RG, it will be bare bones - nothing there that strictly doesn’t need to be. The RA25 is also a simpler car than the 28, so less ‘stuff’ in the bay overall! That might help you further down the line because then I’ll know what it will run with and what you don’t need!
     

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