Camshaft Piston to Valve clearances

[TooManyToys]

Have anyone measured the piston to valve clearance of a stage 2 cam in a stock motor and how much clearance did you have/allow intake and exhaust?

Stock pistons.
Piston protrusion?
Valve recession?

 

[Zeb]

It’s a real pain in the neck to measure piston to valve clearance on these motors.
I’ve done a number of Colt Stage 2 cams and here are the measurements that I run for piston protrusion and valve recession and have never had an issue.
Piston protrusion must not exceed 0.034” measured directly above the wrist pin.
Valve recession must not be less than 0.020”.


I prefer a little less piston protrusion than that, but 0.034” is max factory spec, and as long as valve recession and valve stem height is correct it will be fine.

Also, I always have run Motorcraft lifters, stock valve springs, and the updated 6.4 length pushrods.
A couple of these motors see 40-50 psi boost and plenty of rpm.

 

[TooManyToys]

I've tied it three different ways so far, one being back calculated off the lifters. I just completed another with a head installed and FelPro gaskets (0.010" thicker than Motorcraft). I've got two numbers from Colt so far, 0.030" and 0.035" P to V needed. I'm not seeing that margin especially if I used the Motorcraft gaskets. I'm using lightweight springs so as I degree around I can push down on the rockers and measure the distance to the piston. But with the lighter springs, I may be missing the compression of the system, which I ran into decades ago with the 289's, gaining 0.006"-0.008" from the normal heavier weight springs. And as I wrote that, yes the lifters are filled solid.

My protrusions are out of whack due to an under 0.010" under grind crack from the Ford reman motor. And I have a stock size crank ready to take its place. I'm used to way bigger clearances for high rev gas motors (289) so this has me nervous.

I worked up a spreadsheet of my readings from one cylinder so I can plug in the numbers to calculate where the others are. I do have one valve with a 0.018" recession, and using this method it's even an issue with the Felpro Gaskets and the reduced protrusion - with these light springs.

I may talk again to Geoff, I prefer hard numbers like you called out. Thanks for that.


Motorcraft lifters, stock valve springs, and the updated 6.4 length pushrods is what I have too.

 

[Zeb]

With the lifter filled solid, and a stock, non adjustable push rod in there, you will not get an accurate piston to valve measurement.
If the lifter is blocked all the way up, and solid, you will need 2 (one for intake, 1 for exhaust) adjustable pushrods. You will need to adjust the pushrods until the valves are closed, and there is zero lash on the rockers, with the lifter on the base circle of the cam.
If that is the way you’re doing it, 0.030”-0.035” clearance is enough, according to Geoff.

 

[TooManyToys]

Adjustable pushrod tightened to snug. That's how it's being done.

 

[Zeb]

Adjustable pushrod tightened to snug. That's how it's being done.

Perfect.
Has the block been decked? If it has, what is your deck height?
What is your piston protrusion?
What is your valve recession?
What is your valve stem height?
Nearly every, stock, unmolested 6.0 short block I’ve ever measured is very close to the factory max piston protrusion spec. If the block has been decked, and nothing has been taken of the top of the piston, I just about guarantee that you’ll have too much piston protrusion.

 

[TooManyToys]

My piston protrusion and valve recession numbers are in the image I posted above. Valve stem heights I haven't checked yet, but they were 20mm service heads untouched.

 

[Zeb]

Sorry, I missed that somehow when I replied.
I studied on it a bit here and it looks like you’ll need to have the heads worked over and get the valves set to the deep end of factory spec and you’d be fine with the Felpro gasket.
If you’re going to have the bottom end apart again to swap cranks, drop your piston protrusion to .020” and combine that with the valve recession set at 0.025”-0.027” and you could run the Motorcraft gaskets.
Some guys might holler flycut the pistons! I’d much rather run a little less protrusion, and keep the top of the piston flat, than run flycut pistons on a daily driver.

 

[TooManyToys]

I probably should have added this graph earlier. It's a comparison of measurements of an OE piston protrusion and my Motorcraft reman block. The crank is going to be replaced with a stock crank, so it should be in the correct consistency. It's just amazing that someone could screw up crank grinding like this.

I'm a detail guy, so this is what's driving me nuts, and by proxy why I can drive you nuts.

First, I'm really trying to not do anything with these 70k mile heads if I don't have to, an expense I don't need to have. So doing the P-V checks with Colt saying it would be an outlier for the cam to not work - and my highest protrusions being in spec and my valve recession in the middle of the range has me going nuts with the numbers I'm seeing. And that's what I'm hung up on. If I thought this cam was going to need rework, I would have gone to a milder cam or stock.

This just doesn't make sense to me, especially in context when you've been able to run this cam with:

Piston protrusion must not exceed 0.034” measured directly above the wrist pin.
Valve recession must not be less than 0.020”.

Was that with Motorcraft gaskets?

Because with the 0.010" thicker Felpro this should be a breeze.

Unless this crank grind is so screwed up that they move the indexing not only with the last two journals but the timing as well.

Sorry for the headache.

 

[Zeb]

1st off, you’re not driving me nuts. It’s refreshing to see someone paying attention to details. I see too many guys that have no idea what anything measures, assemble the motor and then wonder why they have issues.
2nd, I can’t read that last graph you posted. It’s too blurry on my phone.
3rd, I should have been more clear when I originally posted piston protrusion and valve recession #’s. Those specs are “supposed” to work with a Stage 2 cam, BUT I HAVE NEVER MEASURED/RUN A MOTOR THAT HAS THAT MUCH PISTON PROTRUSION and a Colt Stage 2 cam.
Every motor I’ve put a Colt Stage 2 in we’ve set it up with 0.026”, or less, piston protrusion, and 0.025”-0.028” valve recession, used Mahle gaskets (same thickness as Motorcraft) and been fine.
If you don’t want to mess with the heads, and you’re taking the bottom end apart again, just take some off the top of the piston to get the clearance you need.
My Excursion has 0.009”-0.015” piston protrusion, and delipped pistons. Do the math on what the compression ratio is.....Starts just fine, but does white haze a bit for the first minute or two when it’s below 30* ambient temperature.

 

[TooManyToys]

Let's see if this works on this forum.

First image

The top table is data from an OE block, the bottom table from my Ford Reman motor.

Second image

I plotted both the piston protrusion and with those results got curious about the stroke of the crank. It looks like they mis-indexed the crank when grinding. I never saw anything like this before during my engine building prior and didn't check the crank for that before putting the bottom end together. All journals measured in-spec for diameter.

 

[Zeb]

Let's see if this works on this forum.

First image

The top table is data from an OE block, the bottom table from my Ford Reman motor.

Second image

I plotted both the piston protrusion and with those results got curious about the stroke of the crank. It looks like they mis-indexed the crank when grinding. I never saw anything like this before during my engine building prior and didn't check the crank for that before putting the bottom end together. All journals measured in-spec for diameter.

I’d be ok with the variation on David’s motor.
The variation on Jack’s motor would tick me off. I doubt I’d want to run with it.

 

[TooManyToys]

Jack would be me. I talked to two crank grinders who weren't happy with it either but said it shouldn't be a major problem. I ran the truck with that crank for 70k and about 8 years. I can't put it together like that. I have no problem with doing somethings outside the norm, and maybe that crank would have continued on, but every time I'd drive the truck I'd be thinking about it.

 

[TooManyToys]

......
Every motor I’ve put a Colt Stage 2 in we’ve set it up with 0.026”, or less, piston protrusion, and 0.025”-0.028” valve recession used Mahle gaskets (same thickness as Motorcraft) and been fine.
......

And thanks for giving those values, that gives me direction.

 

[Zeb]

....but every time I'd drive the truck I'd be thinking about it.

You’re as bad as I am.
Here’s how I like a set of pistons to measure.

 

[TooManyToys]

Last night before going to bed in my head was "this guy is going to ask how I'm checking PP", so I broke out a segment of one of my upcoming videos on this situation.


https://youtu.be/HeMGtC2xano



And if you want to see my interpretation on the disaster I'm dealing with and you've got 40 minutes to kill .... I actually grabbed a discussion from you guys on this site for this vid before I joined the site, so I might as well post it here.


https://youtu.be/gHSTd_Wvjnk

 

[Zeb]

Last night before going to bed in my head was "this guy is going to ask how I'm checking PP", so I broke out a segment of one of my upcoming videos on this situation.


https://youtu.be/HeMGtC2xano



And if you want to see my interpretation on the disaster I'm dealing with and you've got 40 minutes to kill .... I actually grabbed a discussion from you guys on this site for this vid before I joined the site, so I might as well post it here.


https://youtu.be/gHSTd_Wvjnk

I’ll check those videos out sometime.

 

[TooManyToys]

No real need to review them.


Again, thanks for giving me the values you use on your engine builds. I'm going to go back to my motor and install standard rate springs to see if my checks come out close to Colts numbers. As I said earlier, years ago I tried the light springs and my numbers were a little off, showed too tight. And maybe that's were these sweeps are off.

You mentioned people putting motors together and never checking clearance. It may be for the average guy the methodology is too involved to get their head around. Hey, I've having a hard time here and I've done it before decads ago.

But I'm more of a numbers guy, give me a spec and I'll run with it. In that vein, I took your numbers and Colts comments and tried making up a calculation that might work for those people. I rather have it this way too.

Your building motors for customers in a safe way, and that's how I would do it too. In fact, plugging my numbers in with the FelPro gaskets, there's a couple of valve locations I need to get to for a 0.051 factor, and that's where I'll go.

Anyone who may want to use this, it's an unproven calculation but I believe it would work, but only for this camshaft. And you still need to know what your piston protrusion and what every valve recession value is.


On another note, in the current market have you had experience with Melling valves? I got one intake valve to check in these heads. Slightly different tulip head, 2 grams lighter.

 

[Zeb]

No real need to review them.


Again, thanks for giving me the values you use on your engine builds. I'm going to go back to my motor and install standard rate springs to see if my checks come out close to Colts numbers. As I said earlier, years ago I tried the light springs and my numbers were a little off, showed too tight. And maybe that's were these sweeps are off.

You mentioned people putting motors together and never checking clearance. It may be for the average guy the methodology is too involved to get their head around. Hey, I've having a hard time here and I've done it before decads ago.

But I'm more of a numbers guy, give me a spec and I'll run with it. In that vein, I took your numbers and Colts comments and tried making up a calculation that might work for those people. I rather have it this way too.

Your building motors for customers in a safe way, and that's how I would do it too. In fact, plugging my numbers in with the FelPro gaskets, there's a couple of valve locations I need to get to for a 0.051 factor, and that's where I'll go.

Anyone who may want to use this, it's an unproven calculation but I believe it would work, but only for this camshaft. And you still need to know what your piston protrusion and what every valve recession value is.


On another note, in the current market have you had experience with Melling valves? I got one intake valve to check in these heads. Slightly different tulip head, 2 grams lighter.

I like what you put together on that sheet.

The way I look at the work I do, I warranty it, and neither the customer nor I want to deal with that hassle so I’m going to to the best job I can. Plus I couldn’t live with my conscience if I were to cut corners.

I have not used any Melling valves. The machine shop I work with sticks to SBI most of the time.

 

[Zeb]

Here are some numbers you guys might find interesting.
Bone stock, unmolested 6.0 short block that I measured and tore down today.
These numbers are starting at the front of each bank and working toward the rear.
4 numbers for each piston.
Piston protrusion Top of wristpin bore to top of piston
#1 0.026” 0.025” 1.391” 1.392”
#2 0.026” 0.022” 1.391” 1.391”
#3 0.021” 0.027” 1.390” 1.390”
#4 0.024” 0.025” 1.392” 1.392”
#5 0.026” 0.025” 1.390” 1.390”
#6 0.023” 0.023” 1.392” 1.3915”
#7 0.024” 0.026” 1.3905” 1.3905”
#8 0.024” 0.026” 1.3915” 1.392”


I’ve never measured a stock 6.0 with that little piston protrusion.