Really need some assistance here, sorry about the length of post.

Setup is stock bottom end LM7(gen III) with 70K, New Mamo AFR205's cut down to 55CC, Cometic .040/3.906 gaskets, Yella Terra rockers, Joshnson 2216ls link bar lifters, and a custom cam spec'd by Tony (.595/.596, 214/216 @.050, Comp HR lobes). Engine made no noise prior to new top end.

Measured for pushrods 3 times using comp tool, ordered custom rods from Manton 11/32 .120 wall (7.60 Int/7.62 Ex). Average fell within the range specified by Johnson .035 +\- .010. First startup, valvetrain was what I felt was very loud. After engine warms, it gets worse, and develops a squeak on #7. Verified all rockers are receiving good oil flow, No exhaust leaks, and not an issue with PCV over pressurization (valve covers are off while running).

Contacted Tony to get his opinion, he suggested that I was short on the pushrods and had me run a couple of checks. He came back and said that the length appeared to be within range. By my math, I agree (M8X1.25 = .049 per full turn of bolt, Zero lash to 22ftlbs was .75 turn = .03675 preload).

Here is where my issue comes in...Due to running the Yella Terras, I have to back off both rocker bolts on each cylinder to get to zero lash, so I only measured the intake rockers. Using EO/IC, in order to check the exhaust I would be damn near full pressure on the Intake springs. I am not willing to back off on the bolt and place all that pressure on the aluminum threads in the head as I back it out. I am concerned about #7 exhaust specifically, I believe it has too much preload based on my original measurements. I setup my dial indicator while #7 was at TDC on compression stroke and made my measurement, came up with .045, but I am not sure this correct, as I am not on the base circle of the cam.

So the question is, can I expect this measurement to be fairly accurate if I am not on the base circle? If it is accurate, I am on the extreme edge of the spec provided by Johnson, and I am concerned with thermal expansion I am running too tight which may cause the noises I am experiencing....

Thoughts?

Pulled all rockers on passenger side, inspected all pushrods, etc, nothing found that was out of the ordinary, no rubbing or clearance issues that I can see. Lifters were all rolled and lubed with redline assembly lube prior to install.

 

I can answer your question no I wouldn't feel comfortable with my measurements for preload not being on the base circle of the cam lobe. I have never done it with yella terra rocker setup. However if you search hard enough there is a whole write up on how a person does this successfully with Yella Terra rockers.

 

Did you call manton to verify your findings. Comp tool uses gauge length so you have to add +.010 to the final number. The guys at johnson have lots of tips and knowledge and slightly altered desired preload and final number with my measurements and it seems to be quiet. Cant hear much over the 102mm intake though but no valvetrain noise jumps out at me.

 

Also I'm not sure why you are having problems measuring. First off, you shouldnt back off the bolt, you tighten until the rocker is snug. it will have slight side to side play and zero play up and down. I installed and torqued a rocker on both sides of the girdle so it wouldnt flex and measured. Turn the engine over and make sure jts on base circle otherwise readings will be skewed.

 

Math is off. Turns on the bolt do not equal preload. One full turn is actually .076 not .049. 3/4 turn is .055-.060 preload.

If you got .045 via dial indicator NOT on base circle then very likely you are closer to .055-.060 preload.

 

comp tells you its .050

This technique requires the use of a COMP Cams® Hi-Tech™ Pushrod Length Checker. These are marked with a standard length stamped in them. This number represents the gauge length of the part (.140" gauge diameter) with the two halves screwed completely together. Extending the pushrod one rotation lengthens the gauge length .050". For example, a pushrod stamped 7.800 and screwed apart one rotation would be 7.800" + .050" = 7.850" gauge length. Therefore you would order the part number from the catalog that matches this gauge length, since gauge length is how they are listed.


Edit: Nvm you are talking about the rocker bolt not the tool

 

Manton Rods were within .003 of what I ordered, everyone was measured prior to install. Comp tool was measured with a calibrated 8" caliper.

Not sure you are understanding what I am attempting to do, rods were already measured, installed, and engine started. I am attempting to verify that the preload matches what I measured for. I have to loosen both bolts on the yella terras due to the shaft between them. I understand where zero lash is.



[QUOTE=Darth_V8r;20251159] Math is off. Turns on the bolt do not equal preload. One full turn is actually .076 not .049. 3/4 turn is .055-.060 preload.

If you got .045 via dial indicator NOT on base circle then very likely you are closer to .055-.060 preload. [QUOTE]

Darth,

glad you chimed in. I am a bit confused, metric fasteners move in 1 full turn the same as their thread pitch, 1.25 pitch converted to inches is .04912. Can you explain how you arrived at .076? Not doubting you, just trying to understand where I made my mistake. Also, I understand what you are saying about turns vs preload, but if the valve is closed, and I back off the rocker bolt, find zero lash, then retorque, why am I not just re-establishing the preload on the lifter?

 

Try using the light checker springs.

 

[quote=babydeuce]Manton Rods were within .003 of what I ordered, everyone was measured prior to install. Comp tool was measured with a calibrated 8" caliper.

Not sure you are understanding what I am attempting to do, rods were already measured, installed, and engine started. I am attempting to verify that the preload matches what I measured for. I have to loosen both bolts on the yella terras due to the shaft between them. I understand where zero lash is.



[QUOTE=Darth_V8r;20251159] Math is off. Turns on the bolt do not equal preload. One full turn is actually .076 not .049. 3/4 turn is .055-.060 preload.

If you got .045 via dial indicator NOT on base circle then very likely you are closer to .055-.060 preload.

Quote:

Darth,

glad you chimed in. I am a bit confused, metric fasteners move in 1 full turn the same as their thread pitch, 1.25 pitch converted to inches is .04912. Can you explain how you arrived at .076? Not doubting you, just trying to understand where I made my mistake. Also, I understand what you are saying about turns vs preload, but if the valve is closed, and I back off the rocker bolt, find zero lash, then retorque, why am I not just re-establishing the preload on the lifter?

It's geometry. Your rocker ratio is 1.7. But your fulcrum is the valve tip. So you tighten the bolt at 1.7 off the tip. The pushrod moves 2.7 for every 1.7 the bolt moves. .048 x 2.7 / 1.7 is ~.076.

If all you're trying to do is validate what you have, loosen the bolt, find dead soft touch. Mark the bolt at 12:00. Tighten it till it hits home. Do not torque. Just take up the preload. You will know when you got it. If you are now at 6:00, you have .038 preload.

 

I've never determined PR length with Yella Terra rocker arms but couldn't you just bring the piston up to TDC with the rocker arms hand tight and the PR checker installed onto a lifter and determine zero lash? I would think once you've done this you just add the desired preload to the length.

 

Yes but I do not use tdc. I use exhaust open intake closed plus 90 degrees

 

[QUOTE=Darth_V8r;20251200][quote=babydeuce]Manton Rods were within .003 of what I ordered, everyone was measured prior to install. Comp tool was measured with a calibrated 8" caliper.

Not sure you are understanding what I am attempting to do, rods were already measured, installed, and engine started. I am attempting to verify that the preload matches what I measured for. I have to loosen both bolts on the yella terras due to the shaft between them. I understand where zero lash is.





Ahhhh, there it is, exactly where I screwed the pooch. I did not consider the rocker ratio. Thanks for clearing that up.

When I checked them for Tony, I went zero lash to 22 ftlbs, got 3/4 turn, by your description, I would be over .057.

When I initially measured using the comp tool, I torqued the rocker, ran the checker up to zero lash, pulled and measured (overall length with a caliper, then added my .035 for the recommended preload). Manton took my overall measurement and built my rods. They all cam back within .003 or what I told them.

It sounds like I am bottoming out the lifter, or damn near.

 

I prefer the EOIC method and I'm guessing that the Yella Terra's throws a wrinkle into the mix because two rockers are held down on a shaft but I'm not seeing how that could be an issue though.

 

I don’t see any issues with your initial length measurements. It sounds as if you are thinking there was wild variation from cylinder to cylinder? There shouldn’t be.

Maybe try the counting turns stuff on cyl 1 to see if it either verified your initial setup or not.

Sometimes I think a guy should invent a rocker bolt with a vernier on it.....

I have YT rockers. After setting up the geometry for roller tip pattern on the stem, I did just like you with the checker and calipers. I wasn’t working with short travel lifters. .060” preload. Trick flow pushrods. End to end, ended up with 7.45 length.

Milled AFR 205’s as well. 60cc chambers. .050” gaskets. So am a little puzzled about the length of 7.6X?

Anyway, mine was far from quiet. Ran excellent though. Just pulled it all apart after 20k miles. No issues.

Lastly, a squealing noise doesn’t sound good.

Ron

 

Ron,

Initially, I measured cyl 1,2,7 and 8 both intake and exhaust. I did this because I can see when the roller is on the base circle. #7 exhaust was on the high side of the average, which is why I am concerned. It is the cylinder I think I hear the chirp from. I pulled the intake and valley cover today, cylinders 1,2,7 and 8 lifters and cam lobes all look good.

Johnson short travels are physically shorter than factory lifters, and require a longer pushrod.

Thanks for your input, I appreciate it.

Jack

 

Got it on the lifters.

Can you rig rig up your dial indicator to measure when you are on the base circle? I made a small steel plate to bolt down using the valley cover bolt holes.
You would measure on the end of the pushrod. Bunch of monkey motion to set the indicator up. But I’ve done it.

Then just re-do your measurement.
Leave the pushrod out on the rocker you aren’t working with.

After that, since you now know you are on the base circle, put your real pushrod in and try the count turns thing.

Its always hard to localize where a sound is coming from. Got a stethoscope? Even a piece of rubber hose works.

Roller rockers are noiser than stockers.

Good luck!

 

TDC on the wrong stroke would have you setting up during overlap and get you too short on rods

 

Funny you should mention this, I have been all over this sucker with the stethoscope. The only place I can localize too is on cyl #2 on the outer block near the timing cover, but under the waterpump inlets to the block. I do not get anything at the head, timing cover, or even from the rockers themselves.

Jack

 

Yeah its important to know its the compression stroke. You'll know it too because the air will push your finger out of the spark plug hole but if its not then the air escaping around the exhaust valve.

Although I still prefer the EOIC method for setting up my valve train the quickest way on an LS engine is to get NO.1 at TDC on the compression stroke and tighten exhaust. rockers 1, 2, 7, 8 and intake rockers 1,3,4 and 5 to 22 ft lbs then rotate the crankshaft 360° and tighten exhaust rockers. 3,4,5,6, and intake rockers 2,6,7 and 8 to 22 ft lbs.

 

Dont use the bolt turn x metric threads. rule. You wont get an accurate measurement.

3/4 turn will give you about .050-.060 preload.

You want it super accurate use a long reach micrometer or weld a tab on a spare pushrod.

The main issue is, you're working with a triangle, not 2 parallel lines. Thats why the bolt turn x threads per inch idea doesnt work. Especially on heads with a different valve angle that have been heavily milled.

But also id get rid of the alum rocker arms.