Replacing heads

[dodj]

Swapping out the heads this weekend. 452's are off. Anything you should do to the block surface before putting on the new heads? Wipe with solvent? a light sanding? 
Also, the tops of my pistons are mostly black, aluminium showing around the edges. Normal?

[Chryco Psycho]

Piston tops are normal
 Clean the surface , well solvent , very fine sandpaper is ok too .
 What heads are going on & what gaskets are you using ?

[dodj]

What heads are going on & what gaskets are you using ?

Stealth heads and cometic gaskets. PRW stainless rockers. The PRW's came with two adjustable push rods. Don't know how to measure with them yet though. I thought I would be just using the stock ones. I should replace the p-rods too?

[Strawdawg]

I would.  I would use the adjustable rods to find the correct average length for each side and then order a set of custom made ones if the length is different from the stock factory pushrods

[dodj]

Any good links to an article on how to measure for correct pushrod length?

[Strawdawg]

first, the instructions  from PRW   https://www.prw-usa.com/files/pages/pdfs/32-prw-mopar-rockers-stainless-steel.pdf  (think those are the right ones)

Now you can find a jillion articles on setting them up   https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=measure%20correct%20pushrod%20length

For the average street engine with hydraulic lifters, I tend to simplify it quite a bit.

First, I set the adjuster screw so that approximately one thread has emerged on the exit side of the arm (pushrod side).



Then I make sure that the valve that I am going to check is on the base circle of the cam so that the valve would be completely closed if the pushrod was installed and adjusted.

Then I put the adjustable rod in making sure the bottom end is in the center of the lifter and the upper end is positioned to mate up with the adjuster screw.

Next, torque the rocker shaft assembly to the specified range.

I adjust the length of the pushrod until there is zero pre-load on the lifter.  You can tell this by spinning the pushrod between your finger tips...when there is a resistance to turning, it is ready to start depressing the plunger in the lifter. 

Now you have to loosen the shaft so that you can remove the pushrod and measure the length with a caliper.

Take that length and add 0.030" for pre-load to obtain the final manufactured length.  Write it down.

Then you go down to a valve on the other end of the head and do the same thing.  Hopefully, it will be very close to to the first one you did.

Repeat on the other head.  Hopefully, they will be about the same length as the first side.  If so, take an average, and order a set of pushrods from Smith.

If they are right on a stock set of pushrods, then you can just buy a set of them.

I have forgotten how many tpi the PRW adjusters are but one turn will be something like 0.040" depending upon pitch so you have the ability to make up for small variations if you want to.  I don't like to see more than 1.5 threads emerging thru the rocker, myself.

CP will hopefully see this and offer his comments.  I will be glad to defer to his thoughts as he has done a lot more of these than I have in the past few years

[Chryco Psycho]

Good advice ..... I would follow the advice overall .
 I would not use stock pushrods even if the length is correct as most builds have higher spring pressure requirements & the stock rods may not hold up .