Upside down 13 Flathead??? Anybody know?

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bigd9411

New member
I have a briggs flathead that was picked up out of a pile of blocks and it is a bit different. The air intake and exhaust ports are smooth with no lip. There is an upside 13 imprinted inside where the lifter springs go. It is an M Block and I can not find any information about this block on google. It is just the block so I have no serial numbers on it. I was wondering and hoping if anyone has any details on this block and if they have seen or hear anything about it in racing. I have an engine builder and a buddy that has worked on small engines for 20 years and don't recall seeing a block like this.

Thanks Dominic
 
Does it still have factory paint on it & if soo what color is it?
Had one that was green. I saw a model 9 on ebay forsale a while back that was
same color & it was a 60's date code. Hope this helps
 
That is what I am thinking. It may be just that more of an edge out of the corner or down the stretch. However it is rare to come across.
 
If the red paint is original, it's what we called the wka motor because it came from Briggs with a gold WKA sticker on it and that nice red paint job, definitely pre raptor and aluminum bore. It was really no different than any 5 hp block of the same time period other than the paint and sticker. Seems like it was mid to later 80' when it came out. Jon
 
It is actually. It has been untouched and I took out the governor. To me it is a mystery of if it will be a noticeable difference or no difference at all.
 
I have a similar engine red came out of junk pile in Mississippi, off a tiller.
I have the blower cover at home , when I get back ill check it.
 
The original color doesn't mean much if anything. I have had and sold two or three upside down #13 blocks. They were M- blocks. They sold well because people thought there was something special about them. They were very early, bushing, cool bore blocks, with a plunger hole for point ignition. I have access to a recycle center where I have gotten hundreds on 5hp. briggs though the years and every one seams a little different from another. If the block is in good condition send it out to a good, honest,engine builder with a good flow bench and have them tell you what they think.
 
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