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383 stroker valve stem problem

 
Mongoose78
I love my Chevy Chevette!
Posts: 16
Joined: 06/12
Posted: 06/26/12 09:49 PM

I have a 383 stroker in a 78 vette.
It has set of procomp heads a Howard's hydraulic roller cam
I am running 1.5 roller rockers. I have been hearing some lifter noise
But not to bad . Took a rocker arm off to check it out and saw the valve stem
Is pitted and some the edges of the stem are pretty bad. the motor only has
About 2400 miles on it  Anybody's help would be appreciated thanks  

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waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 06/27/12 05:59 AM

take pictures... contact procomp.. if the heads were completely assembled..

if the valve adjustment was a little on the loose side.. it could hammer the tip of the rocker arm on the top of the valve stem.

post the pictures here also...  use photobucket..   we would like to see the face of the rocker arm also.

do you know what kinds of valves that got installed...   regular steel...  stainless steel.. titanium

there are a few valves that require LASH CAPS to prevent damage to the top of the stem from impacts from the rocker arm.  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 06/27/12 03:48 PM

+1 Wayne

Sounds like the cam is so big it's actually making the valve spring bounce.

I think there's not enough valve spring to control that valve spring bounce.

Check to see what valve springs you have with the cam. See if they are matched to each other.

Just one other thing. Did the roller tip stop turning and hammer the valve stem?

I wonder if they just used a stock replacement valve. Not a hi performance valve material. Material is too soft especially the exhaust valves.

I've seen this happen on valve stems that where worn out also a lot of miles. I've actually seen the valve mushroomed over on the seats from too much valve spring pressure on a stock replacement valve, especially the exhaust valves.

A solid lifter cam, where the adjustment was way too big.

You really have to look things over. To determine what happened first. Good luck...  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 06/27/12 06:53 PM

Mongoose78:

There is another thing that can hammer the valve stems to death. If the valve train geometery is incorrect. If the rocker arm is too far to the back side of the valve or too close to the front of the valve stem it will hammer the valve stem.

How to tell if they are too close to the edge of the valve stem. Look at the top of the valve stem and see where the mark was left by the rocker arm the roller side of the rocker arm. There should be a mark where the rocker arm was hitting the top of the valve stem. Like I said look it over very closely and you will find your problem...Good Luck...  

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Mongoose78
I love my Chevy Chevette!
Posts: 16
Joined: 06/12
Posted: 06/28/12 03:02 PM

Thanks for the info looks like the geometry is to far to the bottom of the valve stem going to try lash caps and a shorter pushrod and see what that gets me thanks again for the help everyone  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 09/29/12 08:57 PM

Welcome Mongoose78:

Yeah that's the one place that will destroy you money and hard work in a heart beat.

Bob  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 09/29/12 10:23 PM

Mongoose78

I think they didn't use a Stainless Steel Valve. You can machine a Stainless Steel intake or exhaust valve and emerge it insalt water,and it should not pit a SS valve...I can't believe they did something like that.

I would remove all the rockers and take a picture of them all. If it's only one or two valves then they are using Chitty valve material..What P/N on the pro-comp heads? I have guys bring them in for rebuild or just to freshen them up. I know we usually replace all the valves in any competition head. Grin  Cool

Bob  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 09/29/12 10:25 PM

Mongoose78

Can you send the P/N of those cylinder heads? I can look them up and see what valves are standard and what options they have for valves.

Bob  

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Pontiacman2
Moderator
Posts: 8956
Joined: 09/08
Posted: 09/30/12 03:26 PM

Sounds like it maybe a valve train geometery problem.




1 The first step is to install a solid lifter and an       adjustable pushrod. Mark the tip of the valve with a marker.
Verifyvtgeometry1

2 Install your rocker arm and set it up with zero lash. Rotate the crankshaft clockwise several times. Remove the rocker arm. The contact pattern of the rocker tip will be where the marker has been wiped away from the valve tip. The pattern should be centered on the valve tip, and as narrow as possible. If it is not, experiment with varying the pushrod length to yield the best pattern.

Verifyvtgeometry2

3 Rotate the crankshaft clockwise several times. Remove the rocker arm. The contact pattern of the rocker tip will be where the marker has been wiped away from the valve tip. The pattern should be centered on the valve tip, and as narrow as possible. If it is not, experiment with varying the pushrod length to yield the best pattern.
Verifyvtgeometry3

4aPushrod Too Long: Notice how the pattern is wide, and shifted to the exhaust side of the valve tip
Verifyvtgeometry4a

4bPushrod Too Short: Notice how the pattern is wide, and shifted to the intake side of the valve tip.
Verifyvtgeometry4b

4cPushrod Length Correct: Notice how the pattern is narrow and is centered on the valve tip.
Verifyvtgeometry4c  
Pontiacman2
Pontiacman2

Professional Hi-performance engine builder

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 09/30/12 04:04 PM

Thanks Pontiacman. Those pictures are always worth a thousand words.

Bob  

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skyeking
I mow my lawn and find Chevys
Posts: 2738
Joined: 08/09
Posted: 10/02/12 05:07 PM

Hi People,
 Good to see that basic common lodgic
 can never die...All the best...Down under blunder...  
skyeking

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Pontiacman2
Moderator
Posts: 8956
Joined: 09/08
Posted: 10/02/12 05:47 PM

Icon Quotepepsi1:
Thanks Pontiacman. Those pictures are always worth a thousand words.

Bob


Your welcome bud.  
Pontiacman2
Pontiacman2

Professional Hi-performance engine builder

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