Technical > Matt Shaff's Engine Shop
Rod piston issue SBC
Paul New:
--- Quote from: tcoupekyle on June 28, 2021, 03:29:58 PM ---Sooo. Thank you guys for the replies.
Called JE they said the Piston is like .275 thick (don't remember exactly thickness but it's .200 something) and said don't cut the Piston there's not enough meat. So I kept talking to JE to get a piston that would work and maybe a credit on the brand new set I already have. They basically said don't build a 434 blower motor change to a 3.5 stroke crank instead and buy a different Piston..
I called lightning rods who make the aluminum rods I have and he says taking a hundred thou off the top of the rods isn't a great idea. But he said he'd trade my 6 inch rod for shorter ones if that helps.
So that's today's breakthroughs
--- End quote ---
Yes that’s a tough combination unless you build it as 9.300 or more DH block vs the 9.025 or shorter block we did build one recently but with steel rods they are significantly thinner at the pin end
tcoupekyle:
Steel rods and it would work I think. But I got an eagle crank so I was going with an aluminum rod to try to be friendly to the crankshaft. Looks like a new crank is in my future...
What stroke you guys recommend with a 6 inch rod and any recommendations on manufacturer that ain't gonna be extremely high dollar?
Paul New:
My favorite combination is 4.125x3.625 stroke but you would clear fine with 3.75 stroke lots of 406 blown SBC’s out there
tcoupekyle:
Paul what's the dimensions on those combinations? I have to buy a crank but I have 6" aluminum rods. And I have to buy Pistons so trying to figure out what'll work.
Paul New:
With your current pistons you probably have a 1.00 compression height with a 3.75 stoke and 6” rod you would end up with 1.125 CH and with 3.625 and 6” rod 1.185 CH so that would be most likely a .125-.185 more clearance between rod and piston unless they increased the thickness of the top of the piston
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