83fox50

So im measuring the pushrod length for my latest build, a 351 nitrous motor. Using a hydraulic converted solid lifter and a 7.5-8.7" length checker im trying to check the correct pushrod length for the trickflow heads. i had these heads on a 302, but decided to go a different route, since i know you will be wondering why such considerations.

i did some math out of curiosity and it has me stumped.

the factory 302 pushrods were 6.2535"
Trickflow 302 pushrods measured 6.700"
a difference of 0.4465"

factory 351 pushrods measure 7.5175"
Trickflow recommends 8.050 for their heads.
a difference of 0.5325"

if the only thing changing between the two engines is stock to Trickflow heads shouldn't the difference in length be the same?

also to further dispute their recommendation, today while checking the length, i got a perfect middle 30% witness mark, and the length checker measured 7.9375". this is only 0.0265" different from the following calc'd length.

351 factory (7.5175") + 302 difference (.4465) = 7.964"

Trickflow recommended (8.050") - 351 Trickflow measured (7.9375) = 0.1125"

if i haven't lost you by now with all the numbers, might someone be able to chime in on which direction i should lean toward, and what could have happened to this engine to cause such a difference in lengths? this engine has been rebuild once already, but would they really take over 0.100" off the decks? I doubt it.

and please dont lecture me about using nitrous on a rebuilt overbored motor. im well aware of the consequences.

uedlose

Go with what you measured. there so many variables when this stuff is being cast in a foundry. difference in the lifter you are using to the block who knows. if you are happy with what you came up with use it.
What is wrong with running N2o on a rebuilt overbored engine seen it done for years..

83fox50

factory bottom end out of an old work truck. atleast it only cost $75 for the whole engine.
i just have to be smart with the tune and err on the side of being conservative with how much i spray.
its not like the whole bottom end is forged.