Bigger valves

I searched all through the forums and didn't see anything about valve sizes. If I missed it somewhere ... sorry.
I'm putting my motor back together after floating a valve at higher rpm, bending the front intake valve and then the guide broke and got sucked into both cylinders and hammered the pistons and heads up (pistons more than heads). 80 in, EVO with EV-27 cam, 42 Mikuni, pipes and single fire ignition.
I've got some 10.1 JE domed pistons that I am going to use and maybe a higher lift cam like a Crane Hi-Roller H310-2 with a .550 lift. Going to roller rockers, SE high rev springs.
Wondering if I should go to bigger than stock valves. I have the jugs being bored and ready to do the heads.
The JE pistons are only .005 over. Would there be any advantage going to bigger valves than stock?
Thanks for the help.

Oh we get into some fun stuff here, cowboy 140 (I love it) but the simple answer is no, bigger is not always better. For example, we tried 3 different intake valve sizes on my 100" engine (peak HP @ 7200 rpm) on the flow bench & with the biggest ones, the flow actually went down. And you must always think "system" rather than individual parts - you can buy the best parts on planet earth, but if they're not designed to work together in harmony, you just spend a lot of $$$.

The combustion chambers in the heads will need to be worked to match the shape of the 10.1 JE domed pistons or you'll have flame-travel problems & the ignition timing will be hard to get right. I'm no expert on that particular engine, but I do know what works, what doesn't & why. 1st you should consider the rpm range you actually use - peak HP dyno numbers are good to know, but valves big enough to flow all the engine can handle @ 6000 rpm are too big for lower rpms, as the mixture velocity is too low for a good "cylinder fill" & real world torque will suffer.

And one major factor you have to consider is the valvetrain - only so far you can go before you start bending pushrods with a BT because the pushrods are not on the same vertical plane. Look @ a Sportster or a 4-cam BT & you'll see what I mean - 1 cam for each valve & the pushrods running straight. Harleys love the mid-range, so for a street/road bike, it just makes sense to me to use it. If you want to rev like a Yamaha, buy a Yamaha !!

Thanks Art

I appreciate all the info and knowledge. Absolutely you want to set it up for the rpm range that you'll be using most. I like to just cruise and don't drag race but there are times when I want to twist in on and go fast for awhile then back off of it. I do quite a bit of highway driving though at higher rpm's.

I'm open to all suggestions and opinions because if I knew it all ... I wouldn't be askin'. So on what you've told me I'll just put some new quality stock size valves and save money on the oversized seats. I know enough to "clay" the heads when I get them ready to check for clearance but not sure how to shape the heads to match the domed pistons so maybe I could visit JE's website and get some info there.

Thanks again and if anyone else has suggestions or info that could be used ... I'm all ears.

Yes - you'll get a lot more benefit by cleaning up the heads with respect to the ports & combustion chambers than by going to bigger valves. A good way to go is to measure both intake ports, find the larger of the 2, clean it up, then make the other one match. Then do the same to the exhaust ports. You'll have to remove some material, but you don't want to "hog 'em out" - just whatever is necessary to smooth 'em out. And you do not want to polish the intake ports - that only works when the only goal is top end flow. A slightly rough surface helps the incoming air & fuel mix better as it breaks up "laminar flow" along the port walls & you can make the mixture "swirl" into the cylinders.

Matching the pistons & combustion chambers is extremely important - when they're not matched you get "detonation" - one of the causes of "pinging" (the other is "pre-ignition"). JE does know how it works & there are several factors, including the fact that domed pistons push the mixture away from the center of the cylinder. And especially with a "loose" piston-to-wall clearance setup, the edges of the pistons & the rings get cooked quick. When the mixture isn't concentrated in the combustion chamber, burning mixture goes down the cylinder walls past the pistons/rings. Not a pretty picture.

Thanks

For the help and advice guys. As far as components matching an 80 in. evo the popular set up used to be the EV-27 cam, 42mm Mikuni and unrestricted pipes. That was supposed to be the ticket for a dependable daily rider with a little more balls than stock. I was sort of ok with that until the valve float problem and thought since I was starting over. I would try the higher compression, hi rev springs and maybe a different cam etc. so if I wanted to run it through the gears now and then I would get that 'tingle' it would be there.

Will post how it runs when I get r done just in case I get lucky and do something right.
Appreciate the help!

Whoever told you unrestricted (as in straight drag) pipes was wrong. And while Mikuni makes a great carb, the 42 is actually a bit too big. I wouldn't spend the $$$ for a 40 mm version, but that setup targets high rpms & a powerband that's only about 1500 rpm wide. The EV27 cam has 34 degrees of "overlap" (time period when the intake valve is opening before the exhaust valve has closed) & that's enough for "reversion" waves coming back up the pipes to go all the way thru the cylinders & get into the intake manifold. And since your're dealing with an "odd-fire" engine (firing order = 315-405), what comes up the front & rear pipes arrives @ the manifold @ irregular intervals.

What you often see is one cyl. running rich & the other running lean because of that. And also "standoff", usually in the 4500 rpm range. Run the bike on the dyno with the air-cleaner off & you see a fog of air/fuel mixture standing just outside the carb throat - "reversion" is literally blowing mixture out. It gets drawn back in & blown back out over & over again so fast all you see is the fog & needless to say, you can't get the carb tuned right in that range. Unless you go to the source of the problem & using quality slip-ons mufflers or @ least baffles in the straight pipes, break up those reversion waves so they have less effect.

H-D knows all this stuff & that's why stock cams have very little overlap & there's a crossover pipe in most exhaust systems - break up reversion in the exhaust, equalize what's left over on the way up the pipes & don't have both intake & exhaust valves open long enough for reversion to get all the way thru the cylinders & into the intake manifold. With the cam you've got, the intake valve starts to open 20 degrees before the piston hits TDC on the way up on the exhaust stroke, but the exhaust valve doesn't close down until 14 degrees after TDC when the piston is on the way back down on the next intake stroke. You can make the exhaust going out help pull fresh mixture in @ the same time too, but only in a narrow rpm range.

It's one of those deals where what works @ the racetrack doesn't on the street. I use reversion to my advantage in one application & by changing pipe diameter & length you can target any given range, but unless you can convince God to change the laws of physics, that range is only going to be about 1500 rpm wide on a Harley. So get some good slip-on mufflers or @ least put some good baffles in the pipes - reversion is killing useable street power.

Absolutely right

You know your stuff Art!
What I started with when I got the '95 Fat Boy was a stock compression 80 in. Evo with long stepped down Hooker pipes, and EV-27 cam and adj. pushrods, CV carb that had been re jetted. I was getting reversion and it was ruining my day because with the K&N air cleaner the gas mist that was hovering about 2 inches away from the carb was diluting the oil on the a/c enough that it would blow down the oil tank and onto my jeans and I ended up smelling like gas everytime I rode it. I then went to the 42 Mikuni hoping to solve the reversion (didn't know what it was then) problem. Took it to the H-D dealer and had it dyno'd and jetted. It ran fine but still had the reversion issue. I put a Forcewinder type cone a/c on it and it forced the reversion back into the carb and I wasn't happy with the look but was bettern than smelling like gas.
A couple of weeks ago I was messing around and overreved it. It coughed, started ticking and then knocking. Shut it off and trailered it home. Took of the heads and found the front intake valve bent and a piece of the guide had busted off and it went into both cylinders and hammered the pistons and heads up a little. The springs and keepers were still in place.
I wanted to go with higher compression (because I heard it was better) and ended up with the 10:1 JE domed pistons. The jugs are being bored to fit the .005 over pistons and I need to replace the valve ang guide so that's what started this whole mess. :witsend: Sorry this is so long. Now I have the EV-27 (which I suspected had too much overlap) the Hooker pipes, Mikuni and Crane Hi-4 single fire ignition. That's why the question of bigger valves camce up. I'm trying to get a cam/valve combination that will help the pistons work better. Like I said ... you know what you're talking about!
Thanks

Reversion is a function of cam timing & exhaust system - changing the carb and/or air-cleaner won't make it go away & I've seen a 4 HP drop on the dyno using a Forcewinder. And stepped pipes are really tricky to get right - there is no "one size fits all" deal. I have a set for one engine that are a combination of my design & Darrell Bassani's CAD-CAM technology - they work on that one engine, but only on that one engine & were I to change cam timing, they wouldn't work in the rpm range I want.

I won't give away the details 'cause we intend to set more Land-Speed-Records & I don't want the competition to know what I'm up to, but what happens from 5500-7200 rpm is the reversion waves going back up the pipes hit the exhaust port & back of the exhaust valve just as it's opening or while it's open & then bounce back down the pipe. That creates a low-pressure area behind the exhaust valve & during the "overlap" period, helps exhaust flow out & fresh mixture flow in @ the same time. The "stepped" pipes allow exhaust to expand on the way out & act somewhat like a funnel for the reversion going back up, targeting the waves right @ the exhaust port.

But as I've said, you can only make the "reversion effect" work for your benefit in a narrow rpm range & were I to set the rev-limiters on my 1649 cc (100 c.i.) Sportster-based race engine & on my 883 Sportster @ 4500 rpm, the 883 would win. And my 1200 cc setup for the other street bike would trounce the race engine too. At 5500 rpm on the race engine all h*** breaks loose & at 7200, it's making 167 HP with one carb & racing gasoline - no nitrous or blower. We do have a couple silly gas setups, but haven't used 'em yet. Want to break our own record of 180.025 mph 1st Then go after all of Carl's Speed Shop's records - we've beat 'em before too - went 14 mph faster on the same track on the same day with a 19" smaller engine I just need to find that tree $$$ grows on - done spent all my "mad money" :-(

Higher mechanical compression ratio does not automatically = more power. Cylinder pressure is what makes power & the mechanical CR is just part of it. Cam timing is a key too - when the intake & exhaust valves open & how long they stay open makes a huge difference in how much compression you actually have.

You've got to get the combustion chambers in the heads worked to match up with those pistons - that's crucial & if not done, the engine will never run right. The EV27 cam you can live with & will give you a really strong mid-range, but bigger valves you do not want & you've got to get an exhaust that breaks up reversion. The tricks we use @ the racetrack for top-end HP do not work on a street bike.

Thanks Road King

I went ahead and ordered an Andrews EV-5 cam. Wish I had seen your post first or I would have checked out the one you mentioned. Got a good price on it and couldn't pass it up. If it doesn't work out I can maybe put the EV-27 back in.
Appreciate the help guys.