Who knows the answer?

[Evo1]

Mother Harley knows but she ain't talking!

I have a set of Screamin Eagle Evo heads. They come with valve springs (part # 18223-98) that the recommended max lift is .620. However the specs on the heads say the max lift is .575. Why? I called Mother Harley and they were annoyed that I called and refused to give me an answer, said I was engine building hence no answer. Well yes, I guess I am, sort of.  It really ticks me off that after I spent my money to buy genuine HD parts they don't have the common courtesy to answer a simple question about their product! Any way, does anyone out there happen to know the answer as to why the discrepancy in the max lift?

[springer-]

Only a guess but maybe the valve guides are not cut down and the valve seals interfere at .575".... I'd have to measure to be sure.

[stroker800]

  The valve springs are allowed to compress a certain distance due to there length , this is in comparison to the length of the valve stem. As stated it sounds like you are gonna run out of travel due to the guides in the heads,you could run atravel test on the heads while on the bench.
Dave

[wfolarry]

One of the problems with those heads is the way they advertise the #'s so people think it's OK to stick in a big cam & go. Nothing could be farther from the truth. If you plan on running a big cam you need to check all your clearances: valve-valve, retainer to guide & spring travel. Don't go by what's in the book or you'll get yourself in trouble. Those heads can be made to perform well they just need a little TLC.

[Evo1]

I was thinking at one time of running a W6H, but have since decided on something with much less lift. Possible choice are a W6, EV13 or 23.  The bike is a flhtc so I think that the 27 probably would not be the best choice for low end torque. Any way, why couldn't HD tell me this? I really don't think that they are in a position to be dumping on their customers, IMHO. Rant off.

[Hillside Motorcycle]

Most dealers are parts sellers/jiffy lube centers.
Get too far outside that, and things can get fuzzy for them.
Didn't used to be that way.

[Evo1]

Hillside, it wasn't the dealer I was talking to, it was the Motor Company direct. I got as far as the enginering department. I wouldn't expect a dealer to know.

[PanHeadRed]

EVO, like the other pos't say say, you are dealing with two seperate issues.

1. What the springs can handle.

2. What the assembled heads can handle.

Theres lots more to what the heads can handle then what springs are installed.

[lionsm13]

Only the Shadow Knows

[Evo1]

Pan, I understand that there are design limits, I was asking the designers of the part about the limits and why......simple and reasonable question. If it was because the valves would hit each other, why couldn't they just say that. That is all I was after.

[Evo1]

Only the Shadow Knows

And he ain't talking either!

[Evo1]

I think maybe I've confused the issue somewhat. The design limits are no longer an issue (however I am still curious). What really bothers me is that HD was annoyed with my request and refused to answer. The answers and willingness to help that I get from the people here are outstanding, just the opposite of HD!

To everyone here, hats off to you!

[96dynabagger]

While Harley's answer is unacceptable (I mean you buy heads separately, of course you're engine building, and by selling them they are encouraging you), it seems pretty clear from your post that the limit for the springs is .620 and for the heads is .575.  If you put the two together, you are limited by the heads.  You may be able to modify the heads to match the .620, and I can see their reluctance to get involved in THAT issue.  It should have been handled a bit more diplomatically by Harley employees. 

We engineers can be a cranky bunch, that's why most customers aren't allowed to talk to us.   

[Evo1]

Hey 96dyna,

The heads come from the factory with those springs allready installed, so I think it is a fair question.

[Evo1]

Also, I wasn't asking how to modify the heads, just why the difference in the lift capacity. I would not expect them to tell me how to modify the heads.  If the springs are rated for a .620 lift, I would assume that would be for a stock EVO head. So what is differant with the SE head that would cause the max lift to be limited to .575?