Polling for push rod length used with Harland Sharp Roller Rockers

[87LtdT]

I am working to quiet a 218/212 cam with HS roller rocker arms. Have purchased the Morel lifters and need to order push rods.

It appears the length I'll need is 7.900" or 7.925" which seems too short compared to what I've heard others use.

Am hoping to find somebody that has done this before me with good results to compare notes with...especially regarding push rod length, adjusting screw depth, and lifter pre-load.

Thanks, Bob

 

[84BuickGNYorkPA]

Pretty sure that the rod length will be slightly different for each motor. This is where a push rod length tool would come in handy. FULL THROTTLE SPEED - Item Description Page
The variation will come from the tolerances getting stacked up, crank centerline to deck height, cam centerline to crank centerline, face of head to centerline of rocker shaft etc.

Chuck

 

[87LtdT]

Thanks for your quick input Chuck.

I am aware of that and have the adjustable push rod...but 7.900" appears to be about an 1/8" shorter than typical...a lot more than "slightly different" IMO.

As a result, I am losing confidence in what I have done to come up with that number.

Bob

 

[84BuickGNYorkPA]

FULL THROTTLE SPEED - Item Description Page after seeing this, I understand your concern. So you may want a 2nd set of eyes check your measurements...

Chuck

 

[Slow91z]

How can you say slightly shorter than normal, when there is no normal...Many Many things will effect pushrod length including whether you are using Roller Rockers or Stock Rockers, what headgaskets, block decked, heads milled, lifters.

This is why EVERYONE needs to measure before getting pushrods, there is a wide range that you could end up needing.

 

[87LtdT]

I agree that there is a range based on all the components involved that will dictate the length of push rod required...however, the dimensions that these components will vary from one another should all be pretty small numbers...and I'm an 1/8" shorter from what most guys use....which seems like a relatively "big" difference.

Now are "most guys" just purchasing 8.05" push rods without checking?? Could be I dunno...

But I appreciate the info that others share...whether I already am aware or not... I am certainly not an ace mechanic so worry I may be doing something wrong, omitting something, etc.

One thing that might be different is lifter adjusting screw position. HS tells me optimum location of the adjusting screw is 2 threads below flush (.100"). I wonder if the T&D adjusting screw is the same?? Could be 8.05" pushrod is perfect for T&D setup but too long for HS.

Anybody know for sure T&D adjusting screw recommendation??

Bob

 

[SNOWBIRD]

If your deck and heads have been cut you could be pretty close with the morels if useing morels and T D rockers....dont know about harland sharp

 

[84BuickGNYorkPA]

T&D rockers, the screw should be flush, one full turn is .050 which is the limit of tolerance, per instrutions. I got custom rods so my set screws at the "correct geometry" which is flush. My final length was 8.175 with 1.65 roller rockers.

Chuck

 

[Slow91z]

I agree that there is a range based on all the components involved that will dictate the length of push rod required...however, the dimensions that these components will vary from one another should all be pretty small numbers...and I'm an 1/8" shorter from what most guys use....which seems like a relatively "big" difference.

Now are "most guys" just purchasing 8.05" push rods without checking?? Could be I dunno...

But I appreciate the info that others share...whether I already am aware or not... I am certainly not an ace mechanic so worry I may be doing something wrong, omitting something, etc.

One thing that might be different is lifter adjusting screw position. HS tells me optimum location of the adjusting screw is 2 threads below flush (.100"). I wonder if the T&D adjusting screw is the same?? Could be 8.05" pushrod is perfect for T&D setup but too long for HS.

Anybody know for sure T&D adjusting screw recommendation??

Bob

My Harland Sharp's are pretty flush with the bottom of the rocker.

I'm not trying to get on you for asking, that is not my intention...I just think most people don't realize how far off they could be if they don't check the length.

 

[87LtdT]

Thanks Chuck...at first I thought that your post might have cleared up things but then it didn't. Assuming the T&D and HS rocker arms are in the same location (an assumption I am unsure of) and T&D advised flush then that would account for .100" difference (in the correct direction) because HS recommends 2.0 threads (.100" @ .050" per thread) below flush. So I thought that might account for the approx .100" I am "short" by...

But then when seeing you ended up with 8.175" rods...it put me back to square one...

I see you are a machinist...I am an engineer. How much stackup variation do YOU think there is in push rod length considering decked blocks, decked heads, cam bore location, and other manufacturing related tolerances??

And now another thing I am wondering about is the "flush" end of T&D rockers in the same plane in space as the "flush" end of HS rockers??

Bob

 

[87LtdT]

I agree 100% with you Colin...instead of just purchasing a "standard" push rod we need to know the length required.

What is typical amount of material removed during block or head machining?? .010" ?? .020" ??

Am sending you a PM as well.

Bob

 

[Lee Thompson]

Bob

Call me--765-602-0997