Hi all ., have read the previous discussions regarding milling to bump up comp. ratios and there is a lot of info. but im still left with a simple question regarding my own particular situation.
Im doing a top end rebuild on a 1990 FLT EVO motor including .,
replacing the lifters with Johnson V2303 , Andrews EV27 cam , CV carb. stage upgrade and intend to use the original pushrods .

My question is ... is it ok. to simply mill the heads to get the oem comp. ratio from 8.5 / 1 to a more effective 9.5 / 1 comp. ratio ?

 

You can do it that way, or use dome top pistons. Just realize you can't put it back on once you take it off.

 

I'm sure we had a similar question on this recently. I would be surprised if you can increase CR that much by machining the heads. I certainly wouldn't, that's what pistons are for!

 

By original pushrods do you mean non adjustable I don't think you can use them if that's the case

 

Thanks all ., havent visited the machine shop yet but will keep you advised on this.

 

.030 Cometic head gaskets are a good start.

 

It's worth it to CC the heads first. Then when you make your cuts you can get them both the same. This can help make a little more power, plus a little smother engine!!
John

 

I agree with grbrown and miacycles. I don't think you'll be able to go from 8.5 to 9.5 by milling the heads, but having the shop cc them would be a good start. IMO have them shaved to be equal cc's but as close to stock as you can, and throw a set of hc pistons.

While I prefer adjustables, the ev27 cam is usable with stock pushrods. If you shave .010 off the heads, the pushrod will be .010 deeper in the lifter. The hydraulic lifters have more than enough room to absorb something like .010 or .015 difference. But its still something to keep in mind when you start decking the heads...

 

Go to Night rider.com. There's some great info on what you're wanting to do.