I'm getting some valvetrain noise and i'm wondering if i should go with a different pushrod length. I believe the block was decked and shaved for 10.8:1 compression but i dont think the heads were milled. It has cometic head gaskets and currently stock length pushrods. I figured maybe i'd need some 7.425's but i dunno with the head gaskets and decked block. Also i think the cam has XER lobes, could it just be their ramp rates causing the valvetrain noise? Any help would be greatly appreciated, i dont know a whole lot about cams/valvetrain specs. EDIT: got some more info from the previous owner, The block was decked for square and flat as he used Cometic head gaskets. Not sure how much was taken off.Also, He specified piston at .000. he didn't want them sticking out of the hole. The heads were shaved .020. With the heads being milled .020 and then the cometic gaskets which are .030 thick which is .024 thinner than stock right?, so i'd say that it's at least .045 less than stock total.

 

depending on how much it was decked the 7.425" are what you want

 

I would think that a tad taller than stock would do the trick.

 

this is what i dont understand, if it was decked, why a longer pushrod? If material was taken off of the block or head, i would think you might need a shorter pushrod if anything?

 

well....how much was it decked? You might want to find out if the heads were milled. What is your current CR?

 

that's the problem, i'm not sure how much it was decked, i'm trying to figure out the exact specs, i dont think the heads were milled at all tho. I guess i'll prolly just end up trying some 7.425's and see what happens

 

Also depends on the base circle of the cam. a stock length rod might work in your case either way. The 7.350's are what I run in my milled .030 with a smaller basecircle on my 244/248 cam.

 

That's the other problem lol i cant find the specs on the base circle of the cam online anywhere, i'll have to call them tomorrow and see if a tech can tell me. My question is, i get how a pushrod too short could cause noise, but would running too long of a pushrod make the same noise? Cause i basically have lifter noise, like all my lifters are ticking, but they are new so they shouldn't be bad

 

Chances are it is the same size as the stock one that came out.

 

Are they stock replacement lifters or Comp R's?

 

They are Comp's OEM replacements, not the Comp R's

 

The best way to do this is get a push rod checker, 0 lash it and then add amount of preload desired. Read that and compare to your current p-rod.
Only then will you determine the proper length.
It is easy to calculate diferences on cam only setups but once you start changing valves and decking and milling, actual measurement is the right way.

 

Yeah that's prolly the route i'll have to go. Where do they sell those? Can i pick one up at an auto parts store or will i have to buy one online?

 

off my head, I know Thunder has them.

 

7.425 is what you want. Good luck.

 

alot have said that, but since the block is decked, it makes me wonder if i might need shorter pushrods. If the block wasn't decked then i could see the 7.425's being what i need.

 

http://www.ls1speed.com/catagory.cfm...in%20/%20Heads

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i talked to a tech at thunderracing and he said to check my preload with a dial-indicator with the current pushrods to see if i need a defferent length. Cause he said, like i expected, some valvetrain noise is expected with a high lift cam, especially cams with aggressive ramp rates like the one i have.

 

got some more info from the previous owner, The block was decked for square and flat as he used Cometic head gaskets. Not sure how much was taken off.Also, He specified piston at .000. He didn't want them sticking out of the hole. The heads were shaved .020. With the heads being milled .020 and then the cometic gaskets which are .030 thick which is .024 thinner than stock right?, so i'd say that it's at least .045 less than stock total.