Questions about milling Evo heads
 

Hello, this fall I went from a sportster to a 98 electraglide, I love the ride of the new eglide, but the power is not the same. I have purchased and plan to install an andrews ev 27 cam, and I plan to either change the pistons or mill the heads to get somewhere around 9.5 to 1 compression. I can mill the heads myself, and this would save alot over buying pistons and boring the cylinders.

I have read that milling the heads about .050 and using a .030 head gasket, will get a compression ratio of about 9.5 to 1.

The first question would be, since we are dropping the valves about .060, will this cause valve to piston contact?

The second question is will an adjustable push rod go short enough to make up the difference in dropping the heads, what brand, type is recomended.

Thanks, for any replies.

Ina 98 you should have no problem with valve-piston clearance, but as with any modification I always reccomend checking clearances when done. You should CC the heads as some EVO heads can vary and making them equal can go a long way in vibration reduction. Ddjustable pushrods will be fine as they have more than sufficient adjustment for your application. Before you reassemble your top end be sure to drill out the oil drain holes in the rocker box to 1/8", it can help with any potential "oil misting" problem. Hope this helps.
P.S. Go to your profile and post your location, that way if you really get into trouble a local member may be able to help. Of course if you are in the witness protection program then you might not want to do that. LOL

First of all thanks for your service to our country, second thanks for the reply. I have updated my location as well.

I thought milling the heads .050 would be okay, it is always good to have another opinion or two to make sure. I just don't want to have to buy a new set. I really have not decided if I want to mill or bore yet, I will probably make the decision after getting the heads off and taken apart to see if valve guides need to be replaced. I will also be doing a compression test before disassembly, to help make the decision. The only mods that I currently see that have been done is a K&N filter, bike has about 26,000 miles on it. I will also clay the motor when assembling.

Ramping up the comp ratio on Evos makes a big difference.....I ran a1996 Dyna at 10.5:1 with Keith Black pistons and an EV46 cam and it just flew!! 76HP and 75 torque as I recall.

Just wanted to mention this. First, I am NOT an expert but I am repeating information that was given to me concerning the EV27 cam. Though it is an excellent cam for stock, stage one motors, it is my understanding that because of its overlap, it is a poor choice for an Evo with bumped up compression. Just wanted to throw that out so others with actual knowledge can chime in.


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When I did my 88 FLHTC with a stock 80 ci in it, I had the deck & heads shaved to get rid of minor warpage. I used a CV-13 cam which comes on lower so I could launch off the start & get that heavy pig rollin! I am not a light weight, sitting at 325 pounds of ex army beef so the combined weight is high.
The bike rips, loads of power, good on fuel & still has a stock bore!
I have a CV 40 & lightly baffled pipes on it.
Another consideration would be a good ignition!
Hatch.

Thanks for the replies. When, I was looking at cam choices on nightrider, which seems to have alot of information on performance. On this site, there is a horsepower gallery that lists various dyno runs with different bikes and compression ratios. I chose the ev 27 because of cost and the fact that it pulls hard from 2000 to 5000 rpms. There is a dyno run on the same site were an evo with an ev 27 cam, and 10 to 1 compression, it made 84 hp and was the highest for the ev 27 cam.

Having said all of this, Bikerlaws post concerns me. I am no expert either, maybe someone that is, will chime in. I have already ordered the cam so maybe I will just install cam, inner bearing and lifters for now, to see what it does.

Thanks for your service Hatch, sounds like ev 13 worked good for you.

Tony

Spanner, hows the ev 27 in the wide glide?

My heads are ported and milled .060 and I run a Wood 6 cam, which I believe is the closest Wood equivalent to the EV27. Since it's a dresser and not a race bike I don't bother with a dyno and all that, but my seat-of-the-pants dyno tells me that it's a great combo.

I was thinking of doing this in the near future. Possibly going with larger pistons. Are you running stock pistons?