Going with a Andrews EV27. How much difference will I see w/ a port and polish? Any thoughts?

10,000 mile 98 Heritage, SE a/c and ignition, Vance and Hines longshots

 

The power is in the heads.

Then the cams.

Do both, and after the carb is jetted correctly, you will notice a BIG jump in power.

Ported heads with stock cams make a big enough difference as it is.

~Joe

 

Porting will gain you a lot if it's done by a competent service. Polishing has fallen from grace somewhat. Getting a balance between flow and velocity is the critical thing. If you aren't building an all out engine then there are a decent amount of shops that do street porting job which usually consists of "pocket porting" 9the area in the valve bowl) and some port work. This works well on a lot of street engines. Increasing compression will give you a good boost because it offsets the compression loss when longer duration cams are installed. Hope this helps.

 

I completely agree. I would only say ANY porting done will gain over stock.

A nice street port with a stock cam is REALLY nice.

really nice power jump. If you add a cam, fight the urge to go "too big" on the cam....big cams suffer in real world riding situations.

If you want a nice power jump, have the heads street ported, possibly a slightly larger cam, and take the time to tune the carb in. With a nice exhaust and low restriction air filter...you will be happy.

~Joe

 

We have the end-all expert on porting and polishing here on this site. I hope he chimes in here. His name is Kirby (prodrag1320). Anyways, he's the professional drag racer who does headwork for a living and owns pissloads of trophy's and Harley national records. Theres all sorts of ways and shapes to increase airflow that I will never understand but I seem to remember him saying that polishing properly ported heads on low RPM motors like Harley's was a bad thing....but I may be nuts. Something about the rougher texture of the walls of unpolished heads help to increase how the fuel mixes with the air charge. Again, I'm just babbling here. Hopefully Kirby shows up to answer whatever crap I just pissed out at you guys.

 

That's the same babble I understand to be true! It's all to do with shape and getting good airflow to suit the rest of the engine. We had a top head man near here (he race-tuned Mike Hailwood's TT winning Ducati in the 70s) who when tuning the R100 BMW twins fitted smaller inlet valves and reduced port size to improve performance! Both a black art and a science.

My inclination would be to phone a good head man, talk through what you want, then post your heads to him. You already have an excellent suggestion....

 

Evo's respond well to compression and GOOD portwork as "The Evo section" (knowledgeable) members are advising. Speak to the experianced builders as also being mentioned and also keep an opening for a guy named John Sachs that does my work, even good builders listen when he speaks, the thing I like about him is he won't push a customer into the overkill garbage for your street engine and taylors your need for your application and riding style, not just a ported head. Traveler mentioned this same "the urge" syndrome in his last post and talk in depth with your potential headporter and determine if you are a valued customer or a number to them.
By the way, that EV27 is a proven addition and no guessing there, very easily into the 85-90 hp range with some headwork and compression.

 

Here's my real world experience with my FLHS with EV27 cam, SE a/c, SuperTrap slipons (18 discs), Dyna2000 module, and tuned CV carb: There is a slight gain in horsepower with the street porting on stock heads, as compared to just a decent valve job. Which occurs at rpm's that are not routinely reached with everyday riding. Unless you like to rocket from stoplight to stoplight. I've had two upper ends done, the last with the street porting, and that's what the dyno runs showed.

Is it worth the cost? Hard to say. It usually is one of those MAWs (might as well), when you're into the engine. I agree that bumping the CR to 9.5:1 is a good way to increase power without a loss in driveablility, as the stock EVO has a pathetically low CR. As I know of no one that runs regular (87 octane) in their HD's (even though The MoCo says it's okay in my owner's manual), there isn't any increase in fuel cost if you're running premium gasoline right now.

 

spend your money elsewhere, a small bump in compression will compliment the ev27 much better than a port and polish,

 

What is the best way to bump the compression and keep reliability?