Matching Rods to Pistons on build
#1
Matching Rods to Pistons on build
I need help figuring out how to match the correct rods to the pistons I'm looking to use in my build. I searched the site and didn't really come up with any threads quite on point, if I missed something please point me in the right direction...
I have a 90 Miata with a now torched 93 engine. I am having the block bored to .020.over. I had originally been looking at some Supertech pistons, but they called for rod length of 5.228" with pin diameter of .787" (20mm). It seemed like I could not locate any H beam rods that would fit that bill, so then started looking at other pistons.
I looked at Wisco .020 pistons with part no K554M785, only to find out they call for the same rod specs as the Supertechs- 5.228" with .787" pin....
I have seen on ebay several sets of these Wiseco pistons (of the same part number aformentioned) matched with a set of Eagle rods with part no CRS5233M3D...
If I'm not mistaken, that is a 5.233" rod.... How can that work? it seems like if the pistons call for a 5.228" rod, running one that much longer could cause interference with the valves and/or head? Or is it just going to up the compression ratio??
Any thoughts or help on this issue would be much appreciated!
I have a 90 Miata with a now torched 93 engine. I am having the block bored to .020.over. I had originally been looking at some Supertech pistons, but they called for rod length of 5.228" with pin diameter of .787" (20mm). It seemed like I could not locate any H beam rods that would fit that bill, so then started looking at other pistons.
I looked at Wisco .020 pistons with part no K554M785, only to find out they call for the same rod specs as the Supertechs- 5.228" with .787" pin....
I have seen on ebay several sets of these Wiseco pistons (of the same part number aformentioned) matched with a set of Eagle rods with part no CRS5233M3D...
If I'm not mistaken, that is a 5.233" rod.... How can that work? it seems like if the pistons call for a 5.228" rod, running one that much longer could cause interference with the valves and/or head? Or is it just going to up the compression ratio??
Any thoughts or help on this issue would be much appreciated!
#2
information update
So, even though I didn't get any input, I found that the Wiseco .020 pistons actually call for a 5.234" rod. And the CR is quoted at 8.5:1 with that setup (located this striaght from the source - Wiseco).
So running the Eagle 5.233" rods should actually lower the CR slightly. But Since I'm going to have the block decked, I figure it should almost even out. Stock CR for the 1.6 appears to be 9.4:1, so i figure this should still be an ok setup since I'm currently running about 8psi boost, but hoping to up it to 10-12 psi so having a lower CR should actually be ok.
So a follow up question I have if anyone is reading this and knows, is about the head gasket: I measured a spare stock head gasket I have laying around and it looks like it is 78mm.... so if I'm boring out to 78.5mm, it doesn't appear a stock sized head gasket will work... correct???
I have searched the internet for cometic gaskets and they seem to only list 80mm bores for their Miata 1.6 gaskets... I'm at a loss for what head gasket I need to get to not interfere with my larger pistons, but not go so big as to adversly affect the CR...
So running the Eagle 5.233" rods should actually lower the CR slightly. But Since I'm going to have the block decked, I figure it should almost even out. Stock CR for the 1.6 appears to be 9.4:1, so i figure this should still be an ok setup since I'm currently running about 8psi boost, but hoping to up it to 10-12 psi so having a lower CR should actually be ok.
So a follow up question I have if anyone is reading this and knows, is about the head gasket: I measured a spare stock head gasket I have laying around and it looks like it is 78mm.... so if I'm boring out to 78.5mm, it doesn't appear a stock sized head gasket will work... correct???
I have searched the internet for cometic gaskets and they seem to only list 80mm bores for their Miata 1.6 gaskets... I'm at a loss for what head gasket I need to get to not interfere with my larger pistons, but not go so big as to adversly affect the CR...
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