Minimum distance between valves

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gmrocket
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Minimum distance between valves

Post by gmrocket » Tue Jan 16, 2018 3:16 am

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
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Re: Minimum distance between valves

Post by hoodeng » Tue Jan 16, 2018 3:32 am

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.

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Re: Minimum distance between valves

Post by midnightbluS10 » Tue Jan 16, 2018 7:13 am

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?

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Re: Minimum distance between valves

Post by gmrocket » Tue Jan 16, 2018 7:52 am

Parallel valves iron head max rpm 7500

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panic
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Re: Minimum distance between valves

Post by panic » Tue Jan 16, 2018 10:03 am

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.

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Re: Minimum distance between valves

Post by Rick360 » Tue Jan 16, 2018 10:04 am

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

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Re: Minimum distance between valves

Post by Momus » Tue Jan 16, 2018 11:08 am

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

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Re: Minimum distance between valves

Post by twl » Tue Jan 16, 2018 1:56 pm

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

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Re: Minimum distance between valves

Post by gmrocket » Tue Jan 16, 2018 3:18 pm

Rick360 wrote:
Tue Jan 16, 2018 10:04 am
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

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Re: Minimum distance between valves

Post by JoePorting » Tue Jan 16, 2018 4:28 pm

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

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Re: Minimum distance between valves

Post by bill jones » Tue Jan 16, 2018 5:27 pm

-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

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Re: Minimum distance between valves

Post by KnightEngines » Tue Jan 16, 2018 6:19 pm

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

I'd call .030" safe.

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Re: Minimum distance between valves

Post by jcisworthy » Tue Jan 16, 2018 6:21 pm

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

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Re: Minimum distance between valves

Post by KnightEngines » Tue Jan 16, 2018 6:40 pm

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!

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Re: Minimum distance between valves

Post by panic » Wed Jan 17, 2018 10:10 am

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

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