Piston to valve clearance.

[Inertia]

More likely to have guide/retainer interference

 

[DART5770]

What is the valve to piston clearance? That has not been said or are the valves hitting the piston?

It would take a big change in lift at TDC to clear and then not clear...

 

[PRH]

More likely to have guide/retainer interference

I don’t have the exact number handy, but I’d expect an Ede head to have somewhere around .700” retainer to seal clearance.

 

[PRH]

What is the valve to piston clearance? That has not been said or are the valves hitting the piston?

It would take a big change in lift at TDC to clear and then not clear...

Agreed.

 

[Newbomb Turk]

What is the valve to piston clearance? That has not been said or are the valves hitting the piston?

It would take a big change in lift at TDC to clear and then not clear...

Yep

 

[fishmens67]

I bet the OP has a mile of clearance with the cam dialed in.
besides you're not making any power if the valves aren't taken the carbon off the pistons. lol

 

[RustyRatRod]

Why you degree every cam…….

The very first cam I ever degreed in……..I couldn’t figure out what I was doing wrong.
I checked and re-checked everything.
I kept coming up with it being retarded 14*.

Out of frustration I tried a different timing set.
Came out right on the money.
Well, how can that be? I must have had something set up wrong first time around, so I reinstalled the first timing set and rechecked. 14* retarded.
So I removed that set and laid the two top gears on top of each other and lined up the dowel pin and bolt holes.
The dots on the upper gears were off one tooth from each other.
The gear showing the 14* retard was made wrong.

It’s not just for performance builds……it’s also a final check that all the timing components are at least “close” to being correct.

You said retard.

 

[Newbomb Turk]

I bet the OP has a mile of clearance with the cam dialed in.
besides you're not making any power if the valves aren't taken the carbon off the pistons. lol

I’m dusting the carbon off on the exhaust side. I’m going to give myself an extra .010 clearance because I’m not 25 years old any more lol.

But yes, dusting the carbon off the piston is the most power.

 

[fishmens67]

I’m dusting the carbon off on the exhaust side.

It's hard to do it with the intake when it's the one chasing the piston. lol

 

[33IMP]

I have not read all of this thread, but,......
Unless this thing has flattops with NO valve reliefs, either the pistons are in wrong or the cam is.
My opinion only.

 

[PRH]

More number crunching……

The intake valve pocket depth on an Icon piston for a 408 is .243” deep.
The tappet lift @tdc of the intake lobe on the XE295HL, when installed at 106* C/L is .120”.
Multiplied by a RR of 1.5 puts the valve lift at .180”(and that’s not taking into account the lost motion from the way less than ideal lifter-to-pushrod angle on the SBM).
That puts the intake clearance at.060”+.
Then add in whatever the valve drop on the heads is, plus the gasket thickness.

Something has to be pretty far from the norm to have the intake valves touching the pistons(zero clearance).

 

[Newbomb Turk]

More number crunching……

The intake valve pocket depth on an Icon piston for a 408 is .243” deep.
The tappet lift @tdc of the intake lobe on the XE295HL, when installed at 106* C/L is .120”.
Multiplied by a RR of 1.5 puts the valve lift at .180”(and that’s not taking into account the lost motion from the way less than ideal lifter-to-pushrod angle on the SBM).
That puts the intake clearance at.060”+.
Then add in whatever the valve drop on the heads is, plus the gasket thickness.

Something has to be pretty far from the norm to have the intake valves touching the pistons(zero clearance).

I didn’t sign on here to do math lol.

But thanks for doing it. It makes it visual.

 

[comoxian]

These are the pistons. And I think this is the cam.

 

[crackedback]

I didn’t sign on here to do math lol.

But thanks for doing it. It makes it visual.

 

[PRH]

These are the pistons. And I think this is the cam.

View attachment 1716406067

View attachment 1716406077

Looks like the parts I used in my example.
Should have plenty of room(.100” plus).

If the cam is installed wrong by a tooth(or more)……all bets are off.

Those pistons(correctly oriented, as in the pic), that cam, Ede heads……..if the intake valve is touching the piston……… the cam is way advanced.

 

[MOPAROFFICIAL]

Hey all, been a while since I've been active here.

My 408 in my 1969 Dart had issues, and I replaced it with the build I started for my 65 Dart years ago. I decided to increase the cam from what I had in the current engine. Just called the mechanic to check on status and he informed me that there seems to be an issue with the valves contacting the piston. The lift on the cam in the previous engine was 0.519, a Blueprint crate engine. The current cam is 0.565 lift. That's roughly a heavy millimeter more lift. Would that be enough to cause an issue? I've had nothing but problems with this since I started the rebuild 18 months ago (mostly waiting for parts, wrong/damaged parts). I really just want my car back on the road.

Heads are Edelbrock Performer RPM. Is there a thicker head gasket? Or is it a spring issue? I'm mechanically inclined, and a tradesman, but not up on high performance specifics.

Hopefully, someone here with more experience than me, or my mechanic, can shed some light and get me through this.

TIA.

What type of lifter does it use, solid, hyd, roller? One way the valves are contacting the Pistons and you can't feel it when you turn the motor over by hand.. is because the springs might not be correct aka stiff enough.. and as you rev it the valves are floating ...and the Pistons are kissing them closed.
Maybe its advanced too much.. and that's usually accompanied by the worst gas mileage ever and stupid amounts of off the line torque.. and even to the point where you have low cylinder pressure because although it's filling early it's not filling completely..lol

 

[Alfajim]

Your closest valve to piston clearance on intake will be close to 8 degrees ATDC on your degree wheel, exhaust 8 degrees BTDC. As stated in this thread, it does not occur when the valve is fully open.

DC 340 is right here as valve to piston clearance actually occurs in the 8 to 10 degrees before or after TDC this is because of piston dwell time at TDC which is determined by the rod ratio, "rod length" to stroke, shorter rod to stroke, shorter dwell time, longer rod to stroke, longer dwell time.
If using clay in valve pockets to check VP it won't give the 8 to 10* clearance but the actual clearance regardless of where. If using dial indicators with heads on you can check it at all the positions before and after TDC.

 

[fishmens67]

These are the pistons. And I think this is the cam.

a mile of clearance unless the cam is installed incorrectly. I don't believe it would run very well in the incorrect position it would take for interference.