[springer-]

Looking for some answers here folk's. What are the results when adding a 3 5/8"((+0.010") ) piston to an existing 3 1/2 " bore 80" motor(i.e compression, etc.)(Honing?). The current motor has headwork and a sub-500" lift cam. The current motor also has an upgraded ignition & Thunderheader.

3 5/8" piston are a big bore piston and require boring out the engine cases and replacing the cylinders. Depending on the piston itself it may also be setup for a stroked engine resulting in a 96" engine.

Are you really looking to put 3 5/8" pistons or did you mean 3 1/2" plus .010" pistons in the stock cylinders?

 

[springer-]

Here's the data on the pistons Springer!...JE Pistons for EVO Big Twin 3-5/8" (+0.010") Bore with Standard Stroke. I know the jugs will need honing, but the cases?

OK so based on what you supplied and not actually having seen any of it, I will try to explain what I think you have going on.

The stock bore of the 80" EVO is about 3.498" (3-1/2"). The pistons as explained above are 3.635" (3-5/8" = 3.625" but they are oversize +.010". So 3.625" + .010" = 3.635")

In order to fit that size piston the stock cylinders need to be replaced with "Big Bore" cylinders. In order to replace the stock cylinders with "Big Bore" cylinders on an EVO, the engine cases need to be bored out to accept the larger cylinder spigots.

The end result with the 3-5/8" pistons and stock stroke would be an 88" engine.

 

[springer-]

That's what I was thinking. It becomes a larger bore 88" when you bore the cylinder's and the cases. I wasn't sure about the cases, but I was certain about the cylinders. What happens when you add a stroker flywheel to the mix here. Or is it even possible with an 80" on top of the additional bore.. Thank you for the comments posted here Springer!

Best,

Glenz

First you can not bore the stock cylinders to fit those pistons. You have to replace the cylinders. The engine cases would need to be bored. To do that the entire engine must come apart.

You can not just add stroker flywheels and use those pistons. A stroker requires longer cylinders and different pistons.

If you are looking to upgrade your stock engine there are many ways of doing it but I would not make those decissions based on a set of pistons you can get or already have. There is so much more to it. If you want a Big Bore or a stroker or some combination buy the right kit to do the job. Or look at the aftermarket engines you can get that will handle the increased size better than the stock cases.

JMO, Good luck with whatever you choose.