I've been trying to put together a plan, of sorts, on what I'd like to do to my '05 1200C to improve performance, and I've been doing some research on four valve hemi heads. Here's the site:

http://www.maxtengines.com/pages/437698/index.htm

I won't post any photos, there are plenty on the site.

These were designed by the late Jim Feuling - he's the guy who, among many other accomplishments, developed the three cylinder 45 x 45 x 45 single throw crank HD engine, that was only going to require 6 new part numbers in HD's catalog.

At the last minute, HD, who had been working with him, decided not to go forward with the project, so his company did it alone. If you look around you can find some reviews of the bikes/engines, which I believe is still available if someone is persistent. Check the online archives of Motorcycle Cruiser magazine to read about it.

Anyway, I like the four valve head, not only because I'm a person who truly believes that hi tech can peacefully co-exist with tradition, making both better, with me as the beneficiary, but also because a four valve hemi head XL is not something you'd see everyday, especially if it was coupled with an 85 to 88 inch kit, and a baker six speed. And like a lot of us here, I like to be different.

Has anyone had any experience with this company, or with these heads? Or for that matter, with any of the aftermarket fuel injection systems available?

I seem to recall a discussion a few years ago about this very subject at sportster.org...

IIRC, the consensus was that those heads had a tendency to bend pushrods at high RPM because the pushrods are opening 2 springs instead of one. But then again, I might not know what I'm talking about.

You might want to do an archive search over there. I've never seen the topic pop up over here.

In a long stroke motor such as a sporty I see no benefits to be gained from going to a 4 valve set up..

A 2 valve set up works well in a long stroke motor due to swirling the air into the cylinder...

A 4 valve set up tends to tumble the air into the cylinder and works well with a short stroke large bore set up...

the only times I've seen it sucsessfull outside of these boundaries is in Top Fuel bikes.......and the Horsepower they are making has got stuff all to do with cylinder fill and they don't rev as hard as you average 883!!!!!!!!!!!!!!!!

Stevo, thanks for the input. I'm going to investigate this a LOT before I do anything.

I've thought about the "two valves being operated by one cam and lifter and rocker arm issue", and that could very well be a fly in the ointment. Pushrods, cam surface wear, cam gears, and even lifter - rocker interface could be a problem, since its common that in 4 valve heads each valve is operated by one camshaft cam, and/or lifter, rocker arm, etc. each, or at least, everything is engineered from scratch for the stress.

On the other hand, each valve should weigh less, and the springs shouldn't have to be as strong, resulting in less than double weight and spring load, because each is probably smaller than the one in a two valve head.

I do know that under the right circumstances, four valves can produce some outstanding effects, even in long stroke and/or low RPM. When Detroit Diesel develped its newest "premium heavy duty diesel" for road tractors, the Series 60, it went with an o'head cam and 4 valves per, and that only turns somewhere between 1900 and maybe 2200 RPM max.

I know that's somewhat of an oranges and apples comparison, because Diesels have vastly different factors to consider than gas, of course, and once again, that system was engineed from the ground up to be what it is.

If you get a chance, take a look at Maxtengines web home, if nothing else, for an "engine afficianado" like yourself, it will probably be an interesting look.

They put up a dyno comparison of an S&S 96 inch with the S&S heads, and the same engine with the 4 valves. They also have a pretty good assembly section that shows puttying the pistons and rotating the engine by hand to make sure of clearances and squish before final assembly, and they also address the differences needed in timing because the spark plug is now dead center instead of to one side.

Thanks again for the reply.

Interesting read....

I'd need to look at bit more closely at a few things and think about it before I could form a serious opinion of benefits/cost....

I looked at it a few years ago when the Rivera ones came out (I think it was them anyway) and as I said the only success I'd seen with them was on Fuel bikes which don't rev very high and get their HP from the nitro....

Like anything tho... it takes development time to understand and learn the benefits of each way of doing things... and often the time could be better spent elsewhere....looks like they've committed a LOT of time and are stickin to it...




I like this line tho.....very true and often overlooked in this "internet" age..

"we believe that it is good to learn the tricks of the trade. However, one must first learn the trade."



And ya gotta re-cut valve pockets for FOUR valves...that's what their plasticene procedure is to check..........still a valid an oft overlooked area of engine building.....on any amount of valves ;) ...
guesswork is NO way to win...

Stevo -

The guy on the "biker build off" on TV didn't invent the saying, but he was right to live by it - "measure twice, cut once"

Or the old adage I love most of all - "If you can't find the time to do it RIGHT, how will you ever find the time to do it OVER?"

I had a long conversation with the guy who owns Max T Engines several years ago. He 's genuinely nice guy. He was interested in building a Bonneville racer. That was just about the time I was hangning up my leathers, so things didn't go any further.

4 valve heads are normally best suited for high RPM operation. Not really a good match for a street Sportster.