Ok I am by no means a professional engine builder and I have never rebuilt a flathead, but everyone's gotta start somewhere ! I have a 8cm block that is cracked in 3 cylinders and I have practiced on it, but only with different cutters in the router and the technique in general.... I probablly should have done all 8 cylinders in it but I felt I was ready- I checked my deck surface with a straight edge from my machinist ( I worked for him as a kid so I'm not completelly in the dark here ) my deck surface is just a bout a good as they come -- ( .0015" is the smallest feeler gauge I have and could barely wiggle it under the straight edge in a couple places. ) I'm not saying there is no chance I will have the block decked, but if I do It'll just be a tiny ammount . I wanted a .125 releif so that's were I set the router at ( all said and done it's .128-.130 after sanding and polishing ) I used the big boere head gaskets to mark the boundries of the relief ( only after all head bolts were in to hold it ) . After I got the relief cut I thought I needed to open up the chamfer around the valve seatso I used a cutter then sanded it - I polished it with felt polising fobs and finished with loose cloth ... I rechecked and none of the cuts intrude into the fire ring of the head gasket at all, there is roughlly a 1/32 - 1/64 ledge that sticks out past the gasket so I'm good there. I have not had the seats cut with a 78 degree bowl hog , or done any port work yet - so of course the seats havn't been ground either. My block hasn't been bored yet so I didn't go over board where the relief meets the bore ( I'll clean it up as nessiarl after the bore ) I figured I should do my relief work first so if I screw up I throw a bunch of cash for machine work out ! I think It turned out good, but I'm no expert. Please feel free to tell me what I did wrong, how bad I screwed up, and what you think I should have done different. I' have broad shoulders so don't hold back . Thanks in advance . This is the drivers side - the other side isn't finished yet
Much better than the factory whack job! They just ran a big wheel edge-wise across the high spot, no finesse at all.
Wow. Thanks guys. I was kinda expecting I really screwed up and couldn't see it! And yeah it looks way better than the 1 block I have with factory releif.
Welcome to the world of flatmotors. I'll stir this up a bit on tech aspects so this will become debatable. I am of the opinion that there should be more of a definition barrier between the valves. The port job pictured shows that the divide area between the I and E valve has been moved up about half way between the two valves. This allows the intake air flow to escape into the exhaust port during the overlap where as a port divider will redirect more of the incoming air flow into the cylinder to promote a more efficient burn. My suggestion would be on the next engine to leave more material between the valve guides and then taper the center ridge down to a point as it goes to the cylinder. This is a example of what I am suggesting.
****, While I do not want to say anything against the fellas first relief job I am in total agreement with you. What you describe is exactly the way that I was taught to do it and with the same logic in mind. Of course I could disagree if it will open up thre discussion a little bit. OOne thing different that I have done in the past to what is pictured in your post is to slightly radius the edge @ the cylinder. Not major just knock the sharp off of it to reduce hot spots in the combustion chamber. There that ought to open it up a bit.
Looks like you did a very nice job. I have always questioned the benefits of doing that though . Is the loss of compression vs flow worth it? Would removing the same amount of material from the head/chamber flow better? Does the incoming air/fuel mix actually make that tight of a turn?
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