SE Heads Top-end questions

[KevH]

I have a 1991 FXRS-CON that currently has 39k miles on it with a fairly stock motor. The only changes have been an EV-27 cam put in a couple years ago, Johnson lifters, a set of SE adjustable pushrods, SE 6k rpm ignition module, SE intake and a Thunderheader.

I picked up a set of Screamin Eagle Heads, Wiesco 10.5:1 pistons, cylinders, rocker boxes w/rockers, and rocker box covers (basically the entire top end) from a guy for almost nothing. It came off of a low miles 1992 Softail that he swapped an S&S engine into.

My question is how would you set this up and what cam would you run with it on my bike?

I'm in California where premium gas is 91 octane. I also don't want to create starting problems or crack my stock cases (it's a 1991). Would I need to have compression releases installed?

Here is what I have:

[Hybredhog]

  Well, as asked many times before, what's your intended use? Two up riding, you need a gruntster kind of cam, Your 27 might be OK for just you, but you should consider an adjustable ignition module at the least, & CR's wouldn't hurt for insurance. A lot of Cam manufactures have either moved on to new motors or retired (like HeadQuarter), so finding good old classics like a good 0029 or 0023 might be one of my choice's for that compression. You should dismantle them anyways and measure valve travel & spring coil bind to see what's possible, & touch up the seats. I'm sure others will have their opinions.

[JW113]

It's been awhile, so forgive the forgetfulness. I had those same SE heads on a 89". Using flat top pistons, it was also 10.5:1. So using Wiseco dome pistons, isn't the C/R gonna be a LOT higher?

Just my loose change, but a EV-27 ain't gonna be enough cam for that set up. Will ping like a mother, and hard to start when hot. I believe those SE heads are good for .575 lift, but not with those pistons I don't think. I think I'd stick with flat tops. As Jeff said, what are you planning to do with this? S&S 561 is a nice cam for a higher compression set up.

-JW

[kd]

IIRC the two sets of SE Evo heads I have are a .060 cut which gives 10.5 :1 with flat tops.  I would do a calc on those domes and a little math before using them.

[JW113]

OK that makes sense now. I found an old SE parts catalog, some helpful info:

[attach=0]

So they are 9.5:1 with flat tops on an 80" motor. Mine was 89", so yes ended up being 10.5:1. And with .060 cut, that would bump an 80" flat tops up there as well.

Says can be used with domed pistons for 10.5:1, but that is with their SE pistons. It does look those parts were all run together, so guess it was working but yes good advice, check the heads & pistons to see where the compression is going to end up.

-JW

[Hillside Motorcycle]

At a real 10.5 cr, that 38 degree closing cam will spark knock like a mofo.

[rigidthumper]

Woods 8 works well with those heads/pistons, Mik45 & a Thunderheader

[wfolarry]

At that compression I'd run a VThunder 5015.
Looking at the tops of those pistons I'm thinking the rings are shot. If you need to go oversize with new pistons you can adjust your compression lower. if you do that then you'll want to run a smaller cam.

[JW113]

Those heads, flat top pistons, and the EV-27 would be a very nice daily rider or touring bike.

-JW

[Burnout]

My cam cheat sheet says an EV27 closes the intake at 36° which would ping even worse than at 38°.

This is degrees after bottom so it's not intuitive (the piston is actually on the way back up when the intake closes), you want an intake closing around 42-45° so the static pressure does not go too high with that 10.5:1.

Measure those heads to make sure they have not been cut for flat tops, first.