sbc 4.125 stroke with small journal 5.85 ??
08-11-2011, 02:01 PM
#1
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sbc 4.125 stroke with small journal 5.85 ??
My concerns (stroker small block Chevy, 4.125" bore X 4.000" stroke with 5.850" rods) are mostly related to rod angularity and cylinder sideloading with this combo. And of course, ring seal, piston and cylinder wear over time (mostly street driven with minimal track time on a road course to sort things out from time to time).
Crazy idea, but if a 4.000" stroke in a standard deck height block is likely to cause reliability problems over time...... Rather than destroke...... What about a tall deck block and longer rods? No, not one of the big buck store bought 9.325" raised deck blocks. Something homebrewed and taller.
With my present 4" stroke crank and 1.170" comp. height pistons, but with a taller deck and longer rods......
7.5" rod = 1.875:1 rod/stroke ratio...... Need additional 1.65" deck height (10.675")
7.0" rod = 1.75:1 rod/stroke ratio...... Need additional 1.15" deck height (10.175")
If I scrounged up a set of identical blanchard ground 1-3/4" thick cast iron honing plates for SBC, machined the water passages into them, brazed them to the decks of my block with yellow brass rod and then bored out all 8 cylinders and cold sleeved it with taller sleeves down through the honing plates before milling the new, higher deck to allow the pistons to be at zero deck...... Would that destroy the rigidity of the block?
Instead of brazing the deck plates to the block, could the deck plates be installed permanently using dead soft copper head gaskets between the plates and original block deck surface along with long studs passing through them (for the heads) that thread into the original block?
In theory, it would allow me to run rods around 7.5" long and get a rod/stroke ratio of 1.875:1 . But with a taller deck block without a raised cam as well, would cam lobe to rod clearance be worsened over what it is now? Or clearance at the bottom of the bores?
What do you think?
I have found a source for 4340 H-beam rods 7" long (170 cu. in. MOPAR slant 6 application) which might be adapted with a little work. Custom rods 7.5" long and having the big end sized for a 2.1" 350 sized rod journal might be insanely expensive, though?
Yes I know...... Will need to make spacer plates for the intake, longer pushrods, deal with distributor length,etc. But is this homebrewed tall deck, long rod 427 Chevy small block idea feasible or worth doing?
I already have my block, crankshaft, 5.80" rods and pistons. Am waiting on pushrods until I have the engine together to measure and see what I need. So the pushrods are a wash pricewise, but would need spacer plates for the intake, longer rods and the machine work to install deck plates and sleeve the block to do this.
Crazy idea, but if a 4.000" stroke in a standard deck height block is likely to cause reliability problems over time...... Rather than destroke...... What about a tall deck block and longer rods? No, not one of the big buck store bought 9.325" raised deck blocks. Something homebrewed and taller.
With my present 4" stroke crank and 1.170" comp. height pistons, but with a taller deck and longer rods......
7.5" rod = 1.875:1 rod/stroke ratio...... Need additional 1.65" deck height (10.675")
7.0" rod = 1.75:1 rod/stroke ratio...... Need additional 1.15" deck height (10.175")
If I scrounged up a set of identical blanchard ground 1-3/4" thick cast iron honing plates for SBC, machined the water passages into them, brazed them to the decks of my block with yellow brass rod and then bored out all 8 cylinders and cold sleeved it with taller sleeves down through the honing plates before milling the new, higher deck to allow the pistons to be at zero deck...... Would that destroy the rigidity of the block?
Instead of brazing the deck plates to the block, could the deck plates be installed permanently using dead soft copper head gaskets between the plates and original block deck surface along with long studs passing through them (for the heads) that thread into the original block?
In theory, it would allow me to run rods around 7.5" long and get a rod/stroke ratio of 1.875:1 . But with a taller deck block without a raised cam as well, would cam lobe to rod clearance be worsened over what it is now? Or clearance at the bottom of the bores?
What do you think?
I have found a source for 4340 H-beam rods 7" long (170 cu. in. MOPAR slant 6 application) which might be adapted with a little work. Custom rods 7.5" long and having the big end sized for a 2.1" 350 sized rod journal might be insanely expensive, though?
Yes I know...... Will need to make spacer plates for the intake, longer pushrods, deal with distributor length,etc. But is this homebrewed tall deck, long rod 427 Chevy small block idea feasible or worth doing?
I already have my block, crankshaft, 5.80" rods and pistons. Am waiting on pushrods until I have the engine together to measure and see what I need. So the pushrods are a wash pricewise, but would need spacer plates for the intake, longer rods and the machine work to install deck plates and sleeve the block to do this.
08-29-2011, 06:42 PM
#2
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As much as I like to be creative and inventive there is that threshold of practicality when choosing to experiment in the search for more power. What your proposing to do is going to cost you as much money as a new block. The reliability and integrity of the block would be compromised as well. To sleeve the block to accommodate a set up as your discussing diminishes the deck integrity as well Also a standard gen 1 and 2 block wont accommodate a stroke of without a smaller rod on the big end. Your cam to rod clearance being the biggest obstacle. What you need is is a raised cam and deck block to do what your proposing. Simple as that.
