Pushrod Length - PRC 225 Head
Thread Starter
Teching In
Joined: Apr 2014
Posts: 15
Likes: 0
From: Michigan
Pushrod Length - PRC 225 Head Measuring my pushrod length. Just trying to make sure these numbers I'm coming up with seem reasonable.
Currently set up with:
LS1
PRC 225 as cast heads-62cc combustion chambers
Cometic .40 Head Gasket
Morel 5315 lifters
Torquer V2 cam
Stock Rockers + Straub Bushings
Tried this on the #1 cylinder intake and exhaust valves with identical results.
With the comp checker threaded out 12.25 turns, and rocker snugged down....I still have play at the rocker tip. Threading the checker out an additional 1/4 turn (12.5 total) all play goes away. This would be zero lash correct? Or is more accuracy than .25 of turn required (such as 1/8 turn)? Probably a stupid question, just trying to get it right.
With that....I get the following length before accounting for preload:
(12.5)(.050)+6.8=7.425
I see a wide range of preloads being shouted for these lifters, but .045-.050 appears to be acceptable with an aluminum block/head.
That gives me 7.475" with .05" of preload.
Am I on the right track? Thanks.
Currently set up with:
LS1
PRC 225 as cast heads-62cc combustion chambers
Cometic .40 Head Gasket
Morel 5315 lifters
Torquer V2 cam
Stock Rockers + Straub Bushings
Tried this on the #1 cylinder intake and exhaust valves with identical results.
With the comp checker threaded out 12.25 turns, and rocker snugged down....I still have play at the rocker tip. Threading the checker out an additional 1/4 turn (12.5 total) all play goes away. This would be zero lash correct? Or is more accuracy than .25 of turn required (such as 1/8 turn)? Probably a stupid question, just trying to get it right.
With that....I get the following length before accounting for preload:
(12.5)(.050)+6.8=7.425
I see a wide range of preloads being shouted for these lifters, but .045-.050 appears to be acceptable with an aluminum block/head.
That gives me 7.475" with .05" of preload.
Am I on the right track? Thanks.
TECH Apprentice
Joined: Oct 2015
Posts: 310
Likes: 24
Measuring my pushrod length. Just trying to make sure these numbers I'm coming up with seem reasonable.
Currently set up with:
LS1
PRC 225 as cast heads-62cc combustion chambers
Cometic .40 Head Gasket
Morel 5315 lifters
Torquer V2 cam
Stock Rockers + Straub Bushings
Tried this on the #1 cylinder intake and exhaust valves with identical results.
With the comp checker threaded out 12.25 turns, and rocker snugged down....I still have play at the rocker tip. Threading the checker out an additional 1/4 turn (12.5 total) all play goes away. This would be zero lash correct? Or is more accuracy than .25 of turn required (such as 1/8 turn)? Probably a stupid question, just trying to get it right.
With that....I get the following length before accounting for preload:
(12.5)(.050)+6.8=7.425
I see a wide range of preloads being shouted for these lifters, but .045-.050 appears to be acceptable with an aluminum block/head.
That gives me 7.475" with .05" of preload.
Am I on the right track? Thanks.
Currently set up with:
LS1
PRC 225 as cast heads-62cc combustion chambers
Cometic .40 Head Gasket
Morel 5315 lifters
Torquer V2 cam
Stock Rockers + Straub Bushings
Tried this on the #1 cylinder intake and exhaust valves with identical results.
With the comp checker threaded out 12.25 turns, and rocker snugged down....I still have play at the rocker tip. Threading the checker out an additional 1/4 turn (12.5 total) all play goes away. This would be zero lash correct? Or is more accuracy than .25 of turn required (such as 1/8 turn)? Probably a stupid question, just trying to get it right.
With that....I get the following length before accounting for preload:
(12.5)(.050)+6.8=7.425
I see a wide range of preloads being shouted for these lifters, but .045-.050 appears to be acceptable with an aluminum block/head.
That gives me 7.475" with .05" of preload.
Am I on the right track? Thanks.
TECH Senior Member
Joined: Jun 2016
Posts: 22,308
Likes: 3,625
From: Central Cal.
I think your correct on the preload. What I'd do is install the rocker with no pushrod in the hole and start the bolt. As soon as it starts to thread mark a dot at the 12:00 position and then turn the bolt while counting how many turns it takes to seat the rocker arm on the pedestal by tightening the rocker arm hand tight. Lets say you did this and got 13 turns to seat the rocker arm on the pedestal. Now with the lifter on the base circle of the cam install your pushrod checker tool with what you think is the right length for zero lash and then install your rocker arm. Start your bolt again and the dot should be at the 12:00 position. Now tighten the bolt and count the turns. If you get to thirteen and there is still play then the pushrod is too short. If you do not get to thirteen turns then the pushrod is too long. If you get to thirteen and all the play is out of the rocker arm you have the correct length at zero lash. Measure this then add the desired preload and order your pushrods. I like to measure with a dial cailper and measure for overall length.
