Piston To Valve Clearance Q's??

[396_WAYS_TO_SPIT]

Ok so I degreed my cam thanks to fiat;) Now I am trying to measure my piston to valve clearance. I was told 2 different ways to do it. (1) with clay and (2) with light springs. Here is what I did. First I put 2 light springs on the #1 valves and put a dial indicator on the valve. I then pushed the valve down til it hit the piston. I got .225 ex and .180 on the in with no head gasket. Next I put clay in the 2nd hole on the piston and brought it ti tdc on that cylinder. I then installed the rockers and pushrods. I set valve lash and rotated the motor. I then pulled the head to chck what I had and it appeared that the clay moved so the reading was inaccurate. It read .055 intake but the clay lifted. I am trying to figure this out but its kicking my ass. What do I need to do to check correctly? What is the rule of thumb of clearance? some tell me .080 andothers tell me .125
396

[Moneypitt]

Forget the clay for the reason you've experienced. In order to check this clearance you must check at degreed intervals, before and after ACTUAL TDC. You do have actual tdc, right? Anyway, on the exhaust stroke, the piston rising is trying to catch the closing valve. So, you check at maybe 15* btdc, then at 12, then 10, 8, 6, 4, until the valve is closed. Then on the intake stroke, the valve opening is chasing the piston as it drops in the cylinder, so again, you check at maybe 10 btdc, then all the way up, and 10-15 after, as the piston moves away. These * numbers are a safety net and may not be necessary in your application, depending on overlap, ramp speed, etc. A ballpark mininum, that is the tightest numbers you get, should be at least .050, (IMO), although cam grinders usually list their mininum numbers on the cam card. Opinions vary, some want .100 , if you bump a hot cam up 4*, you may not be able to hold the .100 number, but something between that and .050 with steel rods, I consider safe. As the pieces come closer and closer together, record the numbers, both intake and exhaust, and you may see the difference in the closing vs. opening ramp speeds.........Hope this explains it a little bit for you...............Ray

[396_WAYS_TO_SPIT]

I am set at TDC because I still have the degree wheel attached to the crank and nothing has changed. So do I check it with the light springs method?
My cam is 258@.050,108L,.615 lift
my heads are 109cc closed chamber,.022 head gaskets,9.785 deck,close chamber pistons

[396_WAYS_TO_SPIT]

cam is set straight up at 108 lobe

[Fiat48]

Ditto. No clay. Around 8 to 10 degrees from TDC is usually the tightest point but you need to check like Moneypitt said.
Like to see .100 on Intake and .125 on the exhaust...but have gotten away with .080 and .100 as push rod deflection gives you some.
Advancing the cam tightens the intake clearance and loosens the exhaust clearance. Retarding the cam tightens the exhaust clearance and loosens the intake clearance.
Around .007 per degree on roller cams..but don't know on flat tappets.

[396_WAYS_TO_SPIT]

Ok I got that part. That doesnt sound hard at all. But my question is, Do I check with my light spring set up? Do I use rockers?

[Moneypitt]

With that cam straight up you should be able to reach Fiat's numbers, no problem. And his numbers are safer than mine, so go with em'...........Ray

[Fiat48]

Ok I got that part. That doesnt sound hard at all. But my question is, Do I check with my light spring set up? Do I use rockers?
Install light springs, your pushrods and rockers. Adjust to zero lash. Turn engine over and check piston valve clearance as Moneypitt told you. Then add valve lash to your measurement for actual p/v clearance.

[LakesOnly]

If I may make one comment, using clay may be an old method but it's tried and true, and if you rotate the motor 720+ degrees with a wad of clay on the piston crown, it reasonably measures that piston chasing the exhaust valve AND that intake valve chasing the piston. In the case of bigger cams, it also gives a good ballpark measure for radial clearance of the valve reliefs relative to the valve(s) in the dynamic orientation of the moving components in the engine's current setup.
To keep the clay from moving/shifting, put a wad of clay on the cleaned parts, then spray with WD-40 or Pam cooking spray.
With the light springs, you might want to give your clay thickness readings a cushion of a few thou to compensate for any potential reduced pusrod flex, etc...
Setting the crank orientation -10 and then +10 degrees and taking your Exh & Int valve readings (respectively) will give you a reasonable assessment also, with your current cam grind (that you just degreed).
LO

[sanger rat]

Anything wrong with using light springs and feeler gauges? I just set the lash up as it is called for. Use the feeler gauges for the amount of clearance you want and roll it over. Not real hi tech but worked for me. Beats the heck out of the playdough.

[GofastRacer]

Nope nothing wrong with that but it just tells you that the valves don't touch, it don't tell you how much clearance you have, and if you're "building" a motor and trying to squeeze all you can out of it you need to know what's going on!.. ;)

[396_WAYS_TO_SPIT]

Ok I used fiat's method along with "phil" from bergerons advice and I cam up with .140 clearance with "0" lash on the rockers and no head gasket. .140+.024+.021.185clearance. I was sweating bullets when I was checking but came out ok;) I was also told that the more clearance that you have the better, because it allows the valves to cool faster. Any comments are appreciated. Thanks for all the help fellas, I couldnt have done it without ya;) If I see any of you guys at cbbb I will have lots of extra beer for the help;)
396

[GofastRacer]

Glad you got it together!.. :cool: :cool:

[Fiat48]

Someday I'll explain the rubber band method...uses no test springs at all. But I would have to do pictures.

[396_WAYS_TO_SPIT]

Someday I'll explain the rubber band method...uses no test springs at all. But I would have to do pictures.
When you have some free time bob please email me the pics and please explain. i soak all the info that I can. I want to help people like the way you and art helped me.......
mrfierman78@hotmail.com
Michael

[steelcomp]

Anyone ever bother to chceck weather or not the valve pocket in the piston is square with the face of the valve?? :idea: :D

[396_WAYS_TO_SPIT]

Glad you got it together!.. :cool: :cool:
I just hope it stays together :2purples: we'll see on saturday. Sunday is the planned lake testing. I still have to get a pyrometer and install it. Cheap insurance;)
396

[396_WAYS_TO_SPIT]

Anyone ever bother to chceck weather or not the valve pocket in the piston is square with the face of the valve?? :idea: :D
hmmmm, good idea!!! Please explain yourself comp??????
396

[Fiat48]

Anyone ever bother to chceck weather or not the valve pocket in the piston is square with the face of the valve?? :idea: :D
It doesn't matter if it's square or not when you have a "mile" of clearance.

[396_WAYS_TO_SPIT]

It doesn't matter if it's square or not when you have a "mile" of clearance.
bob,I just let him talk :D I have a good machine shop that did all of my machining and they told me I was good;)

[steelcomp]

Sometimes heads get rolled over or "angle milled" for more compression. Also, some heads come with unusual valve angles that don't quite match the piston. If you're trying to squeak every last pony out of youe deal, like a pro stock, this is the kind of little detail you try and make sure you don't overlook. There's a number of ways to check, but the idea is that if the valve and pocket aren't square, one) you're giving away compression, and two) if you do tag a piston with a valve (and at 10.000rpm it happens more often than you might think) you'll most likely bend the valve. :D

[steelcomp]

It doesn't matter if it's square or not when you have a "mile" of clearance.
You sure about that??? :idea:

[Fiat48]

And most pistons reliefs are not square to the valves anyway in the first place. Why guys that get piston to valve contact always see "eyebrows" on the pistons. Even on stock motors.

[steelcomp]

bob,I just let him talk :D I have a good machine shop that did all of my machining and they told me I was good;)
I was just making conversation...no big. You're right, 396...you're good.

[steelcomp]

And most pistons reliefs are not square to the valves anyway in the first place. Why guys that get piston to valve contact always see "eyebrows" on the pistons. Even on stock motors.
I was just adding some insight as to the level of detail that can be gone to when trying to max out a motor. Dosen't apply here...obviously. :coffeycup
Didn't mean to interrupt.

[Stab-n-Steer]

If the clay method is done properly it is the best method in my opinion...
I take modeling clay, add some motor oil and nead it up real well. This makes the clay much less sticky. I then apply it to the the piston and rub more oil on the valve side (This keeps the clay on the piston during disassembly). I then assemble the head with gasket (not sure why you wouldn't include the gasket as it will add up to .040" of clearance). After removing the head I take a razor knife and carefully slice the clay down the center of the valve pocket and remove half of it. This gives you a visual section of where the valve is in pocket. I use a special depth gage with shortened legs to measure clearance but you can use calipers if you are careful not to push into the clay too much.
The clay method may be old fashion, but it gives you a true snapshot of what's going on...
S&S

[sanger rat]

Cutting the clay down the middle doesn't show what what your valves are doing on the edges of the valve reliefs. That is where I had problems when I put 2.25's in my heads.

[Jet City]

If the clay method is done properly it is the best method in my opinion...
I take modeling clay, add some motor oil and nead it up real well. This makes the clay much less sticky. I then apply it to the the piston and rub more oil on the valve side (This keeps the clay on the piston during disassembly). I then assemble the head with gasket (not sure why you wouldn't include the gasket as it will add up to .040" of clearance). After removing the head I take a razor knife and carefully slice the clay down the center of the valve pocket and remove half of it. This gives you a visual section of where the valve is in pocket. I use a special depth gage with shortened legs to measure clearance but you can use calipers if you are careful not to push into the clay too much.
The clay method may be old fashion, but it gives you a true snapshot of what's going on...
S&S
I respectfully disagree, I feel measuring with a travel dial as Moneypit and Fiat48 outlined not only offers better accuracy (measuring hard points with travel dial vs. clay with calipers + no guessing where the thinest spot is), but will also help you identlify exactly where in the rotation the least amount of valve clearance is. I also don't use a gasket, easy enough to just calculate the gasket thickness back in.
Obviously people have been successful with both methods for a very long time, I just favor the travel dial method.

[Stab-n-Steer]

Cutting the clay down the middle doesn't show what what your valves are doing on the edges of the valve reliefs. That is where I had problems when I put 2.25's in my heads.
Actually it does. Sorry, I should have been more descriptive. When I slice the clay down the middle I remove one half carefully (the oil really helps to release the clay without distorting it too bad) then I inspect how the valve sets in the relief. I then measure clearance on the clay still on the piston, remove that and inspect the relief clearance on that side... Always has worked for me. I have never had a valve touch a piston and have caught clearance problems with this method...
S&S

[Stab-n-Steer]

I respectfully disagree, I feel measuring with a travel dial as Moneypit and Fiat48 outlined not only offers better accuracy (measuring hard points with travel dial vs. clay with calipers + no guessing where the thinest spot is), but will also help you identlify exactly where in the rotation the least amount of valve clearance is. I also don't use a gasket, easy enough to just calculate the gasket thickness back in.
Obviously people have been successful with both methods for a very long time, I just favor the travel dial method.
Hey, respectfully accepted! Just my opinion and what works for me. We all know about opinions, they are like belly buttons, everyone's got one! The nice thing about the play doe method is if you're just building a runner motor and not a full out race motor it is very fast and easy. You don't even need to measure unless the visual gives you reason for concern...
When I was in high school I worked for a Speed Shop and was taught this method and have used it ever since... Prior to having all the proper tools, this was the only method I could use... Now I got all the tools but still use it!
S&S