The pistons got kissed (pics)

[mnbigblock]

Hey there fellow Mopar fans. This is my first real post, but I have been a extremely active reader of this forum for many years now. This site is great and I finally decided to stop being lazy and start participating.

I rebuilt my 440 back in 2002 with the following parts
Stock crank ground and balanced.
Stock rods.
SpeedPro "Sixpack" replacement pistons.
the block was overbored 30 over, no milling (that I know of)
906 heads had pocket porting, was machined for larger exhaust valves, and other normal reconditioning work done to them.
The cam was a Hughes grind (HEH3237BL). Lift= 0.540/0.547. Duration= 232/237. Intake/exhaust.
Too many other parts to list but ask if knowing could help you understand whats going on.

The engine never ran right. The motor ate the first cam within 100 miles , then I replaced the cam and stock rocker arms with the current cam and crane ductile rockers (based on Rons recomendations for them).

My question is what could have caused the valves to hit the pistons like that?
Too much lift? Too much duration?

And do you think I can reuse the pistons?

Be gentle on me, I am learning this as I go.  :icon_smile_big:Thanks a ton guys and gals.

[firefighter3931]

Welcome to the site....about time you started posting ! 

I'd have no problems reusing those pistons....the Speedpro slugs are just about indestructable. 

Did you measure the piston to valve clearance when the cam was installed ? It appears that the valves floated and kissed the slugs. What valvesprings were used with this cam ? How high did you rev it ?


Ron

[mnbigblock]

Mistake number one,I did not measure the piston to valve clearance. I just took someone else's word for it that they would not be a problem. (I was doing all of this for the first time and only 18 years old.)
Mistake number two, I also did not measure the pushrod length. I just ordered stock length.
I did however use the valve springs that hughes recommended. As for how high I reved it, I never could get it above about 4k rpm. I always figured that the first cam that got wiped messed something up on its way out.

Think the heads are worth rebuilding, again? I am tempted to just get some new stealth or eddy heads, but that would just about max out my car spending budget for a while.

[frederick]

Hi,

My question is what could have caused the valves to hit the pistons like that?
Too much lift? Too much duration?

Can be caused by valve float or using to big a cam.
Too much lift isn't the problem, max lift occurs when the piston is halfway down.

So the answer is too big a cam for the engine.
There are two options;
-smaller cam
-make the valve pockets bigger

Either way I'd still measure the piston/valve clearance.
The way I did it is open one hydraulic lifter, take the parts out, and shim it so you can't compress it anymore.
Measure how far the pistons are down on each cylinder.
(On my engine biggest difference was 0.020")
You'll want to measure the p/v clearance on the cylinder which comes highest up the bore.
Take the normal springs of the valve and put on a very light spring you can compress by hand.
Put the cylinderhead on and an old headgasket.
(preferably the same type as the ones you're going to use)
You'll have to reset the preload of course, since there won't be any with the shimmed lifters.
Take shimmed lifter and measure the p/v clearance on the intake and exhaust valve on that cylinder.
Keep in mind minimum p/v clearance doesn't occur when the piston is at TDC, so turn the engine over measuring every few degrees.
You'll quickly notice where minimum p/v clearance occurs.
If you've overshot it, just turn the engine back at least 20degrees, before rotating forward so you can take up the slack in the chain.


If you're keeping the head I'd renew all intake valves if I were you.

BTW edelbrock and 440 source heads have larger valves than your 906 taking up even more p/v clearance.


Strange that you couldn't rev it above 4k
How's the timing chain?
Camshaft was degreed properly?

Cheers,

Frederick

[mnbigblock]

The timing chain is a new MRE double roller that I installed "dot to dot" with the cam when installing both the first cam that wiped and also the next cam. So in essence I guess I did not degree the cam and just assumed that everything would be as specified.
On the initial cam I used stock stamped rockers, I wonder if they just couldn't deal with the fast ramp speeds on the hughes grinds and caused some valve float?
With the second cam I did switch to the ductile Iron rockers, but if the damage was already done to the heads/valves/valve seats from the first cam I suppose that could cause the inability to rev beyond 4K? 

Thanks for the tips on checking piston to valve clearance. I will check that before I take the bottom end apart.

Probably time for a smaller cam either way. At 18 yrs old I was a little to influenced by all the muscle car mags out there and though I needed to have the biggest cam I could squeeze in there. Probably cant trust the cam, the pushrods, or the lifters anymore anyway 

[AKcharger]

Depending on how the 1st start attempt went and breakin you might have eaten the cam due to oil. If you get some time might want to read the sticky post on flat tappet cams and oil...really opened my eyes!

Good luck

[Cooter]

NEVER "Take someone's word" for things..Especially when it comes to your hard earned money and engine...I even double check the machine work when the block comes back from the mach. shop...You would be surprized at how many engines get "Rushed" through machine shops when you CLEARLY stated "Take yer time, I'm NOT in a hurry"...