Minimum distance between valves

[gmrocket]

What's the closest you can get away without them clipping each other?

For titanium , which does not have as much thermal expansion as stainless.

[hoodeng]

What type of head do you have? valves parallel or canted to each other? if canted what is the included valve to valve angle?
Material does not effect valve to valve clearance to a large degree.

Cheers.

[midnightbluS10]

I didn't read all of this yet so I apologize in advance if it isn't what you're asking about. The first one has some info on thermal properties of stainless vs titanium vs inconel. The second link is the same link posted in the first thread(valve to valve minimum clearance).


valve to valve minimum clearance

Want to know how close you can run the valves to each other?

[gmrocket]

Parallel valves iron head max rpm 7500

[panic]

I think with parallel valves we're talking about "ringing clearance", the locus of much hula-hoop orbital motion the valve head has at speed before tangency.
The static clearance can be nearly zero.

Part of the question is:
1. what is the stem length to the guide at full length
2. how long is the guide
3. how tight is the guide fit
Obviously, a short valve with low lift in a long guide can be really tight.

I've seen .060" described as safe, no personal experience.

[Rick360]

Lots of variables to consider for a definite number.

Just the geometry of the parts makes these factors to consider and geometric minimum could be calculated with this information.
- guide clearance on both valves
- distance from lowest part of guide to seat
- length of guide
- lift at peak overlap

How much a given valve can move side-side can be measured also ... with no springs raise valves to peak overlap lift and pull valve heads apart to measure gap then push together and measure gap. That'll tell you how much room you have. I'd want to keep a few thou extra too, and add more clearance as the stem diameter decreases.

Rick

[Momus]

Does it matter if they brush? Lots of other parts operate with intermittent contact.

[twl]

I use .060" as a general rule of thumb.

[gmrocket]

Lots of variables to consider for a definite number.

Just the geometry of the parts makes these factors to consider and geometric minimum could be calculated with this information.
- guide clearance on both valves
- distance from lowest part of guide to seat
- length of guide
- lift at peak overlap

How much a given valve can move side-side can be measured also ... with no springs raise valves to peak overlap lift and pull valve heads apart to measure gap then push together and measure gap. That'll tell you how much room you have. I'd want to keep a few thou extra too, and add more clearance as the stem diameter decreases.

Rick

i checked those measurements before, they are...

.027" between valves when seated with a little slop in the guide..about .001 more than it should be
guide to seat is 1.425", its not a tall head so that helps
11/32 stem
2.00" guide length

dont know cam yet so did a check at .500" , spread distance increased to .0385" and pinched together it was .0155"

these were run like this and no problems. im moving the guides in the heads they are going in and would like to get them as close as possible so everything fits better. reducing it to .020" is what i would like

[JoePorting]

Generally I shoot for .035". Haven't had any issues with it.

[bill jones]

-here a link to an older speedtalk thread that might convince you of what you need.

http://www.speedtalk.com/forum/viewtopic.php?p=25838

[KnightEngines]

I've had them touch & leave witness marks at .020" - 11/32 stems, stainless valves, iron heads, 8000rpm.

I'd call .030" safe.

[jcisworthy]

I know someone who ran his drag race engine to 10K with .027 and no issues.

[KnightEngines]

Valve weight & valve train control come into it, if you've got rigid Ti valves & perfect valve train control then you could probably run at .020" or even less, but if something is less than perfect you'll have problems!

[panic]

Rather than waste my time answering questions, I'll just let someone else do it.