Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties Difference between UL cylinders?

Difference between UL cylinders?

Moderators: Curt!, Pa

Post Wed Dec 06, 2006 8:27 am

Posts: 74
Location: Wichita, KS
I have been talking to a legendary engine builder here in Wichita about building a big inch stroker. He is suggesting boring to 3.5 and using Evo pistons. I know that is MAXIMUM but hey! ya gotta pay to play right? Anyway I was reading something here (I think) that indicated to me that there was an actuall wall thickness difference between UL and ULH (11 fin vs 13 fin?) castings. I have a set of 11s for this project, casting 120-38. Not having a set of 13 fins and an outside mic to check I thought I 'ld ask you experts. Thanks.

Post Wed Dec 06, 2006 8:49 am

Posts: 801
Location: Planet Earth
I have a set of 11 fin UL cylinders that are bored out to 3.4575, approx .020 over 3.4375 which is STD for AFTER MARKET ULH pistons not HD pistons. When measuring the thickness of the cylinder at the cutaways for the cylinder base bolts using Cottens method of measuring, I get varying thicknesses between .075 to .090. This is generally but not always the thinest part of the cylinder. One of them also has a couple of areas bellow the lower fin that are slightly thinner than the cutaway areas. If I was to bore these cylinders out to 3.5, the thinest areas of the cylinder would be .050 or there abouts. That might be dangerously thin. I have measured another set of 11 fin UL cylinders I have and one of them has the cylinder base cutaways machined a lot higher up the cylinder and would be slightly thinner than .070 if bored to the same size as my other set.
Suggest you search the Flathead section to see if you can find Cottens posting on this and I highly suggest that your cylinders be measured before you have them bored that large. If you are going to stroke the motor I would think you would want the strongest cylinders you can use.


Post Sun Dec 10, 2006 9:04 am

Posts: 1643
Location: Interlaken, NY USA

Does anyone know what our sponsor's product can be safely bored to?? New metal might be the perfect choice for a big inch big twin. Just a thought.
Dr. Dick

Post Sun Dec 10, 2006 12:00 pm

Posts: 536
Location: Wa, USA
Our sponsor would have to have product available for this to be a possibility. My engine builder and I have both been hearing "we will have some soon" for over a year now. I have given up and will be using my old sleeved 11 fin jugs.

Post Sun Dec 10, 2006 5:58 pm

Posts: 349
Location: Champaign-Urbana, IL
That't too bad about the Flathead Power cylinders ... MAS Classics has also apparently given up their plans to produce cylinders ... Their prototypes are up for sale on the website. Maybe somebody ought to be talking to whomever is casting those Made in India 45 cylinders?


Post Wed Dec 13, 2006 6:46 pm

Posts: 325
Location: Viola, WI

ya'll are right guys, we haven't had any for awhile now. not to make excuses but how many of ya'll were in the middle of the two biggest storms to come our way last year? hurricane rita tore up the foundry we were using to do the cast iron parts so we had to go looking for another one. we have been thru a half dozen places and finally we hope we found one that can do it. we had some test castings done and they looked real good.

the problem is most of that stuff has to be still done by hand and not many of them can do that any more very good. i can find you foundries all day long that can do automated pours but hardly none that can do what we need. as we speak we are having 20 or more sets cast to machine up. hopefully we'll have some decent ones here shortly. we had 20 sets already cast a few months ago and had to return all of them because of poor quality control on the foundries part.

we wont sell anything just to sell it if we wouldn't own it ourselves. if we cant sell quality stuff, it wont get sold and thats the way i look at it. if you want to fault me for that, well go ahead.

Post Wed Dec 13, 2006 8:02 pm

Posts: 2677
Location: Los Angeles, CA
Pa sed,
hurricane rita tore up the foundry we were using to do the cast iron parts so we had to go looking for another one.

Maybe you should try Motor Castings Company. They cast the originals for Harley and they are still in business. That way you could even have the MCC hallmark on them as originals did.

Motor Castings Co
414-476-1434 Fax: 414-476-2845
1323 S 65th St, Milwaukee, WI 53214

Post Wed Dec 13, 2006 9:50 pm
Pa Site Admin

Posts: 5552
Location: Ohio USA

Pa said what Chris ? :? Pa

Post Wed Dec 13, 2006 10:22 pm

Posts: 2677
Location: Los Angeles, CA
Sorry, I confused admin with Pa

Post Thu Dec 14, 2006 7:18 am
Pa Site Admin

Posts: 5552
Location: Ohio USA

Pa-simers is contagious ! :wink:

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