pushrods

[cmegga]

Once again looking for some advice here. i have Edelbrook rmp heads put on my 81. Im doing the cam and timing gears as well, however have a hard time with some of the small details.

Like what spark plugs will woek best with the set uo?

And what pushrods , I know they need to be .100 longer then stock. But no one can tell me exactly what the stock lenght is.

If anyine has had good result with a specific brand any advise you have to offer on that would be apreachiated as well.

 

[AKRAY4PLAY]

Oh boy, the valve train gremlins. Not worry, there are many little details to attend to with the valve train. As for your direct question about what pushrods to use and/or length; the best thing you can do is spend ten dollars and get a pushrod length guage. It is a little plastic part that slides onto the rocker stud. It will come to rest with one leg on top of your valve stem. The other leg will give you a measurement point. The tool should have one adjustable pushrod, kind of like a tierod. your cam needs to be on base circle with the lifter in place. then all you have to do is put the pushrod in and adjust to zero slack. then remove the guage tool and push rod. presto you have the perfect length pushrod to measure for your order. There are so many tolerance issues between cams, even from the same manufacturer, that inorder to get an accurate length you will need to measure for EVERY CAM!!! Getting the right length keeps you from pushing the valve sideways. The valve train will more effeciant, equals more power but not much. The best benefit is less valve guide wear resulting in an engine that does not smoke after 15,000 miles. As for what pushrods to order, going with what the head manufacturer says is generally safe. Different valve springs require different strength pushrods. Stronger may not always be better. Pushrods are kind of a fail-safe in my book. It is easier and cheaper to replace a pushrod or 50 than it is to have a piston smack a valve and waste your motor. Strange things happen like timing chains that skip or brake. You should and hopefully never have to find out what that is like. Bottom line, guage for the right pushrod and order what Edelbrock says is good! I hope you have fun wrenching and driving it later!!! Best of luck, Brian

 

[69MyWay]

Brian pretty much nailed it. Having "been there, done that" with the same Edeblrock heads, I can give you a little more detailed advice.

In a perfect world you want to see the tip of the rocker where it touches the valve stem to sit dead center of the valve stem at 50% lift. The only way you can achieve this is to lengthen or shorten the push rod.

Now, it is more critical with roller rockers than stamp steel stock style. The stock style have a large tip that makes more contact anyway, however more friction as well. The roller has a small contact point on the roller tip. What is interesting, is you are not looking for perfect side to side geometry by changing push rod length, as that is adjusted by moving the push rod guide plates around. You will have to move the push rod guide plates quite a bit to make sure they are not binding the push rods as they go through the slot either.

You have to run hardened push rods because of the guide plates. I don't know why, but stock standard ones will self destruct if run long enough in an engine with guide plates.

Edelbrock tells you in the instruction sheet what spark plugs to run. If you can't find it get back with me and I will go inspect what I am running in my small block. You can also call Summit and they will reference the Edelbrock material and send one out. I have AC Delco in my small block with Edelbrock heads, and I am going with NGK in my big block with Edeblrock heads.

Good luck. I swear you will not regret this frustration and aggravation when you feel the way that 81 pulls like a beast through the RPM band now that it will be able to breath!

 

[Jack]

Sage advice from both Brian & Chris. Stock pushrods are ABOUT 7.795" - 7.800" ... again gage with your heads & rockers ... for YOUR need.
JACK:gap

 

[motorman]

cover the top of the valve stem with magic marker and turn the engine over and you will see a pattern where the rocker tip rides. the closer to the center of the valve stem the better

 

[cmegga]

Thanks for all the info guys. This forum is always filled with helpful information that is hard to find. As this is my first project cars Im just learning as I go along.