push rods

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homeboysduster

homeboysduster

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all right,i have started to assemble me 400 all is going well but on the top end i am wondering if i need stock length push rods or shorter ones.i'm using a new set of 440 source stelth heads milled .040. the block deck is stock. i will be buying new push rods any way just wondering the length to order. and yes the rockers are adjustable,comp cam rockers!:-D
 
You have cut the heads down .040 but the head gasket you are using is probably .020 thicker than stock. that puts you only .020 off from stock, you should be good.
 
that brings up an added point. i have looked for a head gasket of min thickness so to add to my compression. the thinest is .033 thick now what ever "stock" is i have no ideal!
 
I would say you are going to need LONGER pushrods , get the engine assembled and then measure for what you need .
 
i've read the how to on measuring for the length of a push rod. can't say i understand it. something about the process confusses me could you or someone else explain it to me?
 
the factory gasket was .020. If you're going to .033 you're picking up .013 and losing .040 due to milling. You're ending up .027 shorter. That's right on the cusp of the factory tolerance. You could also throw a .010 or .020 shim under the rocker shafts. That might be easier than custom pushrods.
 
i agree with JohnRR. You need to get the heads and rockers on and use a push rod adjusting tool that will give you the proper size needed. It is best to do it the right way the first time. Places like Summitracing or Jegs may have the size you need.
 
well i guess i'll measure the length!!!! do i ues a adjustable push rod and then measure that or what? i read that you have to pump up a lifter install a adjustable rod then measure the length fully pumped then measure again fully depressed. then subtract the difference then divide by 2. is this right? or was the dude full of it?
 
homeboysduster said:
well i guess i'll measure the length!!!! do i ues a adjustable push rod and then measure that or what? i read that you have to pump up a lifter install a adjustable rod then measure the length fully pumped then measure again fully depressed. then subtract the difference then divide by 2. is this right? or was the dude full of it?
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Boy.... that sounds like a lot of fun!

I would first set up the push rods,lifters, rockers just like you are fixing to start the motor.... preload etc... then look at your rockers and see it the geometry looks ok to you. Use a marker and mark the top of the valve stem and turn the motor three times, remove the rockers and see where they hit on the valve stem. The center of the rocker needs to be in the center of the valve stem. I've got a thread on here somewhere I'll try to find for you to go with.
 
i found this page at comp cams but i still have a little hard time grasping how the rocker rolls from the intake side at base then to center at mid lift then the exhaust side at max lift. it seems to be backwards it seems to me it would start at the exhaust side and travel to the intake side?http://www.compcams.com/information/Products/Pushrods/ please forgive me but this "simple" thing driving me nuts!!!
 
dusterdon said:
the factory gasket was .020. If you're going to .033 you're picking up .013 and losing .040 due to milling. You're ending up .027 shorter. That's right on the cusp of the factory tolerance. You could also throw a .010 or .020 shim under the rocker shafts. That might be easier than custom pushrods.
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Don , do you have personal experience with the stealth heads or are you just assuming they are the same as stock replacement ?

Also shims are used to CORRECT for incorrect rocker to valve tip geometry , they are not to correct pushrod length .
 
Like John says.. shims will simply move the tip of the rocker while making the wrong pushrod work. Not really a good exchange IMO. If the rocekr geomtrry is good with the heads, then just use a checker and measure for the correct pushrods. n most cases, a longer one is needed, but you can find an off the shelf number.
 
If you're handy and have the tools, you can simply cut a spare factory one, remove 1" or so of length from the short side, thread the ID and get a peice of bolt or threaded rod and make one. Cut it at a std measurement so you can just measure the threads and the remaining bit.

I bought two of the Comp Cams kits, but I do more than one fairly regularly.
 
I totally agree with Dusterdon. You can get rocker shaft shims from Mancini. Adjustable rockers are very forgiving in this situation. When ever you cut a head or deck a block, it puts a "squash" on the pushrod, effectively making it too long compared to the original relationship. You have good rockers and they require special pushrods and I am assuming that is your next step and want to order the right thing to begin with and that is smart. If possible, you can check for proper geometry using the original rockers, shafts and pushrods. The big concern is the rocker tips contact patern with th valve stem. Actually you only have to check one valve. I use the intake on number one and I use a solid lifter to avoid a false reading because the lifter plunger sank down when the shaft is tightened. Rotate the crank and watch the rocker tip action on the valve stem as the lifter goes over the cam nose. The idea is for the contact to stay near the middle of the stem. If your does, stock length pushrods will be fine. As Dusterdon said, shimming the rocker shafts will also work to restore the relationship.
 
PFogel said:
I totally agree with Dusterdon. You can get rocker shaft shims from Mancini. Adjustable rockers are very forgiving in this situation. When ever you cut a head or deck a block, it puts a "squash" on the pushrod, effectively making it too long compared to the original relationship. You have good rockers and they require special pushrods and I am assuming that is your next step and want to order the right thing to begin with and that is smart. If possible, you can check for proper geometry using the original rockers, shafts and pushrods. The big concern is the rocker tips contact patern with th valve stem. Actually you only have to check one valve. I use the intake on number one and I use a solid lifter to avoid a false reading because the lifter plunger sank down when the shaft is tightened. Rotate the crank and watch the rocker tip action on the valve stem as the lifter goes over the cam nose. The idea is for the contact to stay near the middle of the stem. If your does, stock length pushrods will be fine. As Dusterdon said, shimming the rocker shafts will also work to restore the relationship.
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I failed to mention setting up just one on each side in my previous post. I made sound like setting the entire rocker assemblies. LOL

I have been informed that it is good to set up both back as well as both front rockers on each side of the motor (4 in all) to be on the safe side.
 
i'm sure you all know by now that this is my first "real" performance motor. i really want to make sure that i get it right the first time!!!! so let me get this right 4 rockers installed on the corners using solid lifters. use a push rod checker on all 4 corners. and measure. then measure again, then measure again. (i like to triple check). i should be ready to order the push rods!!!!:wav:
 
homeboysduster said:
i'm sure you all know by now that this is my first "real" performance motor. i really want to make sure that i get it right the first time!!!! so let me get this right 4 rockers installed on the corners using solid lifters. use a push rod checker on all 4 corners. and measure. then measure again, then measure again. (i like to triple check). i should be ready to order the push rods!!!!:wav:
Click to expand...

Yes one rocker set up at each corner of the motor. This makes sure that you get the proper length in case the block as been milled or heads and if there are in difference in length between the four you will catch it now. Have you tried set up yet with your stock push rod? Do so and take a picture of the rocker and valve (like I did) to show everyone if you can.
 
have'nt done it because i don't have a set of stock valve gear! all of that went south 2yrs ago. i'll get my push rod checker and run a test and see what i need i'll post pics when i do.
 
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