So I measured for pushrod length on the engine I’m building. I keep getting 2 different lengths. I’m using the comp cams pushrod length checker with a base length of 6.8” and 0.050” per turn. For the intake I’m getting 10 turns for zero lash. For the exhaust I’m getting 9.75 turns for zero lash. I’ve done it many times trying to see if there was an error on my part and I keep getting the same numbers. So with that being said, should I run the same length pushrod, or get separate lengths for intake and exhaust? I was looking for a 0.070” preload and here’s the numbers I came up with.
intake: (10 x 0.050”) + 6.8” + 0.070”= 7.37” intake rod length.
exhaust: (9.75 x 0.050”) + 6.8” + 0.070= 7.3575” exhaust rod length.

the length options I see from tsp are 7.350”, 7.375”, and I already have 7.4”. Should I just run all 7.375” rods and call it a day?

 

Where did the camshaft come from? Did you try measuring another cylinder to see if you get the same results?

 

That’s why I use Manton pushrods, they will make them any length no fee. You can get 16 different ones if you want.

most don’t take the time to measure correctly. They just do one or two and call it good.

What lifters are are you running?

 

camshaft is a btr centrifugal truck cam. No I haven’t tried another cylinder yet. I’ll try another cylinder tomorrow and see what the results are on that. Just wandering if someone else had run into this before.

or they don’t even measure at all. I really don’t want to get different length rods but I will if I have to. Wouldn’t the only real difference using the same rod for both (assuming my measurements are correct) just a slight difference in the preload? And the lifters are ls7 style lifters from Texas speed.

 

I used those in my custom engine but the short travel lifters required .035 Preload and and the Short block decks where not square from GM.
Everything about that build was a pain in the ****...

 

LS7 lifters are a lot more forgiving, but I don’t trust them and run Johnson link bars And their pre-load is as mentioned above.

 

I measured for every single one on mine, thought it was weird but they all came out consistent and used diff sizes for intake and exhaust sides to get what preload i wanted. Called up manton and they shipped them next day air for no extra charge. They also have different sizes and tappered ones than the usual ones all the online places stock if you have the head clearance to run stronger/larger ones.
i would just make sure you mark them incase you forget or someone in the future takes it apart as most just toss all the p-rods into one big pile..

 

So I measured the passenger side and these are what I got

#2 ex- 9.75
In- 9.75
#4 ex- 9.5
In- 9.75
#6 ex- 9.5
In- 9.75
#8 ex- 9.5
In- 9.75

seems consistent that there’s a 1/4 turn difference between intake and exhaust lengths except on the number 2 cylinder. Guess I’ll measure the driver’s side and see what numbers I come up with for those.

 

No harm in running 2 different lengths to get the correct preload if needed.

Definitely check the other side to be sure that's all you need.

 

would there be any harm to running the same length rod for everything? If I ran a 7.35” rod then on the 9.75 turn valves they would have a .0625” preload and on the 9.5 turn valves they would have a .075” preload. That’s a difference of 0.0125”. And I believe both of those preload numbers are within the acceptable range of the ls7 style lifter.