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Thread: 1935 Cylinder base baffle orientation

  1. #1
    Join Date
    Jan 2014
    30 miles North of London

    Default 1935 Cylinder base baffle orientation

    Sorry it has been a while, finally getting my top end back together after finding the previous owner/restorer had fitted 55thou over pistons into 70thou over bores - yes it did smoke some, but only when it was thoroughly warmed up.
    Anyway, I thought I would put the baffles back in along with the correct sized pistons this time around and so the question - is there a particular way round the baffles should be installed ? does the small end notch end up on the cam side of the case or the genny side? Does it really matter?
    Also, in the marvellous video of the legendary Mr Bubeck stripping and assembling a later four he mentions a 7 oz max pull on an oiled piston through the bore, I can only assume this can be achieved by the use of a certain combination or types of rings, Has anyone had any experience with this requirement ?
    Thank you.
    AMCA#24040 - too many toys - not enough time

  2. #2
    Join Date
    Apr 2015


    I have attached a photo of 1935 Chief CCE1881 with intact factory baffles. Hopefully the photo answers your question. Regarding piston fitting, I imagine that Mr. Bubeck used the same process that some automobile manufacturers used to fit pistons to bores. The fitting was done without rings installed. A 0.0015" feeler ribbon is placed between the piston and the bore 90 degrees from the piston pin. A correct fit of the piston is reached when a pull of between 7 and 18 pounds is reached during feeler ribbon extraction. If the fit was too loose, a slightly larger piston would be fitted. If the fit was too tight; honing would be used to slightly enlarge the bore. If Mr. Bubeck used a pull of only 7 ounces, he may have been fitting the piston with no feeler ribbon at all. If Mr. Bubeck was using a feeler ribbon, the thickness of the ribbon would have to be known. Today, most fitting is done with accurate measuring micrometers. Piston construction/style and desired piston to bore clearance would dictate the fit clearance. It is possible that the 7 ounce pull was a piston with rings installed and in that instance, ring tension would be a factor. Measuring ring tension is not easy, and this 7 ounce pull may have been a surrogate for measuring ring tension. Piston clearance is certainly as important, if not more important than ring tension. If the 7 ounce pull is with rings installed, looser or tighter rings would have to be chosen in order to obtain the desired pull. Hopefully someone else can offer more insight.

    1935 Chief CCE1881.JPG

    I reread the question and the baffle photo is of a Chief twin and not for a 1935 Four. I don't have any good photos of Four baffles. Sorry about the confusion on my part. The piston fitting part of my response would apply to almost any engine.
    Last edited by Yellow53Chief; 06-13-2015 at 09:48 PM. Reason: I misunderstood the original question.

  3. #3
    Join Date
    Sep 2005


    I doubt it matters much. It's always good to have the correct size piston. When I put my 36 4 back together I left the baffles out. I can't remember who I talked to about this, but my motor doesn't smoke at all. I think the main reason I did this was to get more oil to the pin bushing. Stan

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