In the process of replacing stock heads and cam to AFR 180's and xe262 comp cam. Talking to other backyard mech's they mentioned measuring for correct pushrod length. Thats one thing I havent seen a lot of discussion on here in the forum when heads and cams are replaced. Is this something I missed and should be seriously considered? I am planning on using [new] standard length pushrods.

 

My Holleys required +.100. Aluminum heads are a little taller.

 

Mine used stock length pushrods. Set the valve at mid lift and look to see if the rocker sits in the middle of the valve stem. :cheers:

 

Proper rocker alignment will depend on the correct pushrod length. There is a adjustable pushrod tool that is inserted as a regular pushrod and you adjust the length untill you get the correct rocker alignment. I would think you could rent or purchase at any speed shop. I would also call the head mfg and get a spec on the pushrod that was designed for you heads.
Edl

 

I had to go .100 longer with my AFR heads. It will extend your valve guide life if this is properly set. Beg, borrow, or steal (not really) a tool for this and your valves will be much happier


[Modified by Gordonm, 8:54 PM 1/17/2003]

 

Summit has the pushrod length checkers for about $10. Well worth the $$ to properly check for correct length. Otherwise, your geometry could be off and high RPM's and bong goes the rockers or valves.

 

So this is something that needs and should be done when changing to a different head other that stock replacement. I'm new to enternal engine work so trying to learn as I go. There just hasen't been much discussion of this on the forum. Is it just me or quite a few other people not aware of it and should be?

 

Good question Zoom,
I burned a lot of time trying to get mine right. The builders (Lingenfelter, Vizard) say the tip of your rockers should swipe across the valve stem tip from the top 1/3 across the center to the bottom 1/3 and back again as the lobe moves the lifter (up & down). This will minimize valve guide wear from forcing stem at bad angles/geometery against guide. Very important in a regular use street motor. Anytime you change or machine cylinder heads and change gasket thickness pushrod length should be checked.
Tried using adjustable pushrod to measure required length with block in car but finally gave up - should be done with engine on stand. Bought pushrod checker tool from ProForm ($25) and was very easy to use with instructions provided. Stock rods measured ~.060" too long. Wanted a secound opinion so I bought the Moroso pushrod checker (~$25 Summit) and measured stock rods ~.050" too long using easy to follow instructions provided.
So rather than spend big $$ for custom rods I bought Trick Flows .050" short (7.750") from Summit for $85. Surprise, my new 7.750" rods measured 7.764" - only .036" shorter. I'm hoping these new rods will loose the black coating/finish and shrink to 7.750" with use so there can be a happy ending to this story. After setting valve/lifter preload the rocker tips looked pretty good using a light up close to highlight contact with shadows.
Yes I'm also surprised at the lack of disscusion on push rod length by this forum. But really too few hot rodded cars are driven to ruin enough valve guides to make it a crisis topic. We all want to go fast NOW!;)