383 Rocker Arms

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Tsully

Tsully

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When I bought my B’Cuda it kept hearing a slight knock at idle and would go away around 1500 rpm’s. I have adjustable rockers and was wonder if it’s normal for them to “knock” at idle or if the spreader spring is to weak to keep it from walking? I haven’t adjusted them yet wanted advice beforehand. I’ve had sets on a race car before but it was in Small block chevy and had no knock issues and I’ve owned other mopars with stock rockers and no issues. Was contemplating getting a stock stamped set and place these aside until I build the 451 stroker or Just leave them on adjust and drive! Sorry the pic is from a video of me pushing over the arm and it wouldn’t let me upload it.

Motor now is 60 over 383 with 516 heads and a mild cam.

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I don't have an answer, but what brand rockers are those? Look similar to 273 rockers.
 
You didn't mention if it was a solid cam or hydraulic. The rocker adjusters appear to be be backed off almost all the way. Most applications with a hydraulic cam run in the middle of the adjustment, or a bit on the top side to avoid pump up. I'd adjust them.
 
Demonic said:
You didn't mention if it was a solid cam or hydraulic. The rocker adjusters appear to be be backed off almost all the way. Most applications with a hydraulic cam run in the middle of the adjustment, or a bit on the top side to avoid pump up. I'd adjust them.
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Hydraulic...I checked them by turning the pushrod when both valves are closed and they were not binding or felt to loose but like I said originally I'm not use to adjusting Mopars...I've lots of experience with Chevies'.

I'm getting ready to change the valve covers out and take those Mr Gasket Chrome don't get you home ones off and put a set of MP Black Aluminum. Once I change them I will go back and check the valve lash see how far off they are.
 
It looks like the pushrods might be long, that’s a lot of thread showing through the top.

Jake
 
xLURKxDOGx said:
It looks like the pushrods might be long, that’s a lot of thread showing through the top.

Jake
Click to expand...

I’ll pull them out and measure them, never thought they might too long. The guy I bought it from said the heads haven’t been cut or block decked.

Isn’t there a way to check PR length needed without pulling the heads and checking deck height?
 
Tsully said:
I’ll pull them out and measure them, never thought they might too long. The guy I bought it from said the heads haven’t been cut or block decked.

Isn’t there a way to check PR length needed without pulling the heads and checking deck height?
Click to expand...

Yes. Pull the pushrods and measure them.
 
Tsully said:
I’ll pull them out and measure them, never thought they might too long. The guy I bought it from said the heads haven’t been cut or block decked.

Isn’t there a way to check PR length needed without pulling the heads and checking deck height?
Click to expand...
I can tell you that if they’re too long they’ll make a tapping noise. I dealt with this a few times.

Jake
 
As a big off topic note, there Gutenberg’s the MP covers carefully and equally all around. They are easy to crack at the far ends.
 
The pushrods length has to be correct to get the correct geometry on the rocker as it travels up and down on the valve tip.
A set of 3 pictures of the rocker tip on top of the spring while the spring is holding the valve closed, mid lift and full open is what you will need. Also, before you start taking the pictures, oh need to remove the rockers, clean the valve tip, take a black sharpie marker and color the entire valve tip. Then reinstall the rockers.

Starting from the valve fully closed, rotate the engine so the valve opens and closes. Take your pictures and then remove the rockers to photograph the valve tip that will show the scrub area made by the rocker tip.

WOW! That is a lot right?!?!

But this is getting it done right.
 
rumblefish360 said:
The pushrods length has to be correct to get the correct geometry on the rocker as it travels up and down on the valve tip.
A set of 3 pictures of the rocker tip on top of the spring while the spring is holding the valve closed, mid lift and full open is what you will need. Also, before you start taking the pictures, oh need to remove the rockers, clean the valve tip, take a black sharpie marker and color the entire valve tip. Then reinstall the rockers.

Starting from the valve fully closed, rotate the engine so the valve opens and closes. Take your pictures and then remove the rockers to photograph the valve tip that will show the scrub area made by the rocker tip.

WOW! That is a lot right?!?!

But this is getting it done right.
Click to expand...

Not at all if that’s what it takes to get the correct valve lash!!!

Like I said I’ve done the Chevy’s with no problem because they can be adjusted while running...but this time I don’t want to do something stupid like bend a PR or worse a Valve!!!

What about the spring the keeps the rockers separated...they feel really weak when the valve is closed the rocker moves with little effort?

Thanks again for all the advice!!!
 
Those are Crane ductile iron rockers. Good stuff for flat tappet and hydraulic roller setups.

The springs just keep the rocker arm where it should naturally want to be, against the shims against the rocker shaft mount pads. S/F....Ken M
 
You can get new springs between the rockers. There not very strong to begin with. I don’t know what there rate is supposed to be though.

If you have done Chevy adjustable rockers before, then this is a no brainer. And you'll just need to know the lash setting of the cam being used. Stock cam? The lash info should be in a service manual. That is something I do not know off hand.
 
rumblefish360 said:
The pushrods length has to be correct to get the correct geometry on the rocker as it travels up and down on the valve tip.
A set of 3 pictures of the rocker tip on top of the spring while the spring is holding the valve closed, mid lift and full open is what you will need. Also, before you start taking the pictures, oh need to remove the rockers, clean the valve tip, take a black sharpie marker and color the entire valve tip. Then reinstall the rockers.

Starting from the valve fully closed, rotate the engine so the valve opens and closes. Take your pictures and then remove the rockers to photograph the valve tip that will show the scrub area made by the rocker tip.

WOW! That is a lot right?!?!

But this is getting it done right.
Click to expand...
You can take the pushrod out of the engine and throw it across the garage and it will not effect the rocker arm to valve tip geometry in a shaft mounted rocker arm system. Changing the pushrod length will only effect the rocker arm adjusting screw to pushrod angle, and could hamper the pushrod/adjusting screw oiling.

B3 Racing Engines LLC - Mopar Rocker Arm Geometry Tech

Looking at the pictures of the rocker to pushrod area, it looks like the top of the pushrods may have been getting hot. This could be due to the pushrod being too long and the oil supply not hitting the pushrod cup correctly. I'd be checking the pushrod cups and adjusting screw balls for deterioration.
 
Not sure what CAM is in it...the guy I bought it from lost the card...all I know its a flat tappet Hydraulic Comp Cam. It starts falling on its face around 5k...that's what got me to thinking something might be out of adjustment...I mean a stock cam will go to 5500 before falling. It's got a decent chop at idle, the guy said he thought it was in the .280-.290 range, I'll never know until its pulled and checked.

I'll get the correct pushrods then work my way back.

Thanks again for all the responses!

Todd
 
You have to start with what I said followed by what IQ52 wrote.
(Because if the scrub pattern was off, that would suggest ether a wrong length pushrod and/or the shaft that the rockers ride on needs to be moved.)

When you said you needed to lash the rocker arm, that instantly says to me (and probably most here) that you have a mechanical cam. Solid flat tapper of a roller cam with solid roller lifters.

Off hand, I can’t think of any big block Chrysler ever having need any gap between the rocker tip and the valve stem.

It was always a zero lash setting.
 
rumblefish360 said:
You have to start with what I said followed by what IQ52 wrote.
(Because if the scrub pattern was off, that would suggest ether a wrong length pushrod and/or the shaft that the rockers ride on needs to be moved.)

When you said you needed to lash the rocker arm, that instantly says to me (and probably most here) that you have a mechanical cam. Solid flat tapper of a roller cam with solid roller lifters.

Off hand, I can’t think of any big block Chrysler ever having need any gap between the rocker tip and the valve stem.

It was always a zero lash setting.
Click to expand...

Sorry I should have stated zero lash is what I'm after, as it is a Hydraulic flat tappet.

Thanks again for all the help!

Todd
 
Actually, with a hydraulic cam, there should be a preload setting, of whatever, say .020 for example. S/F....Ken M
 
EchoSixMike said:
Actually, with a hydraulic cam, there should be a preload setting, of whatever, say .020 for example. S/F....Ken M
Click to expand...

They are Crane Doctile rockers...I took a closer pic of them and there is a funky symbol on them that is on the Crane pic I googled!

I read that also about the .020 preload, but was getting confused since I wasn't familiar with adjustables on a Mopar.
 
i had a stock type adjustable rocker arm rub on some over size springs as they went through their stroke , that was found during a check on trip scrub test on a hyd cam .
 
A little update since the last posting... I was able to get back to work on the Cuda after a hiatus and this is what I found!!!!

Now I’m at a loss...because I adjust the exhaust until the pushrod would barely turn the backed off just enough for it to spin without any drag...all this was done on a cold engine. One of my concerns is before I made the adjustment...the lifter felt weak...meaning i could push it very easy with the rocker arm. Am I creating to much preload when I adjust the arm as i described? Or is there something else going on I’m missing?

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