As many of you have endured, I have been slogging through hell with trying to determine optimum pushrod lengths.
Some background:
I have a stock 2.0 case, that I am building into a 2056. The case piston mounting surfaces have been decked. I have new Hoffman RS+ heads, going on Biral cylinders (with a slight fly cut) (and JE forged pistons). I had Tabari Andrade modify the rockers for 10 mm swivel foot adjusters, and got his rocker arm shafts and spacers.
The cam is a Webcam #86, with intake and exhaust lifts of .423. Here is the spec sheet that came with the cam.
Full Version: Pushrod Hell
I made an adjustable push rod (though have some problems with stiffness--soon to be fixed, I hope). And my antique dial gauge was acting funny until I lubed the plunger shaft.
After a couple of days, I have gotten almost repeatable measurements, with different rod lengths. I have figured out the max range of lengths before I run out of adjuster thread. With no rocker arm support spacers, that ranges from about 265 mm to about 271 mm (and I also need a longer caliper to measure rod length more precisely).
After a couple of days, I have gotten almost repeatable measurements, with different rod lengths. I have figured out the max range of lengths before I run out of adjuster thread. With no rocker arm support spacers, that ranges from about 265 mm to about 271 mm (and I also need a longer caliper to measure rod length more precisely).
Now for questions.
With some rod lengths, I have measured intake valve lift of around .440", greater than the spec (.423). Is this possible? The smallest lift I have measured is .422.
On the exhaust valve, I have measured a range of lift from .395 to .404 (spec .423). I know to expect a reduced lift on the exhaust valves, but why? Is the rocker ratio different? What should I expect to be able to get for exhaust valve lift?
I also know that alignment of the adjust with the valve stem at half-lift is important.
If I use custom-cut pushrods, can I benefit from using rocker shaft support shims? I know that with case decking, and head flycutting, I have shifted the rocker shaft centers closer to the crank center.
With some rod lengths, I have measured intake valve lift of around .440", greater than the spec (.423). Is this possible? The smallest lift I have measured is .422.
On the exhaust valve, I have measured a range of lift from .395 to .404 (spec .423). I know to expect a reduced lift on the exhaust valves, but why? Is the rocker ratio different? What should I expect to be able to get for exhaust valve lift?
I also know that alignment of the adjust with the valve stem at half-lift is important.
If I use custom-cut pushrods, can I benefit from using rocker shaft support shims? I know that with case decking, and head flycutting, I have shifted the rocker shaft centers closer to the crank center.
More questions:
Aluminum or steel rods?
And how fussy should I get about custom lengths? All the same? One length for intake and another for exhaust? Custom for each lifter (if I want to go completely insane)?
Aluminum or steel rods?
And how fussy should I get about custom lengths? All the same? One length for intake and another for exhaust? Custom for each lifter (if I want to go completely insane)?
Hang in there!
Not sure about the excessive lift numbers. I suppose some of that may be related to your gauge. (Only because you said you had to lube it - love the vintage Sears stuff).
My case was decked and I have the same HAM heads. I didn’t need shims under the rocker assemblies, but of course each build is different.
I used chromoly pushrods in my 2056. Measured intake on #1 and cut the three other intake pushrods to that spec. Did the same with the exhaust ones. Mine is a street car so I didn’t go too crazy. If I had to do it again, I’d buy an electric archery cutter to make the cuts easier to replicate.
The engine pulls really strong…you’ll love that setup
Not sure about the excessive lift numbers. I suppose some of that may be related to your gauge. (Only because you said you had to lube it - love the vintage Sears stuff).
My case was decked and I have the same HAM heads. I didn’t need shims under the rocker assemblies, but of course each build is different.
I used chromoly pushrods in my 2056. Measured intake on #1 and cut the three other intake pushrods to that spec. Did the same with the exhaust ones. Mine is a street car so I didn’t go too crazy. If I had to do it again, I’d buy an electric archery cutter to make the cuts easier to replicate.
The engine pulls really strong…you’ll love that setup
QUOTE(iankarr @ Sep 19 2021, 08:32 PM) 
Hang in there!
Not sure about the excessive lift numbers. I suppose some of that may be related to your gauge. (Only because you said you had to lube it - love the vintage Sears stuff).
My case was decked and I have the same HAM heads. I didn’t need shims under the rocker assemblies, but of course each build is different.
I used chromoly pushrods in my 2056. Measured intake on #1 and cut the three other intake pushrods to that spec. Did the same with the exhaust ones. Mine is a street car so I didn’t go too crazy. If I had to do it again, I’d buy an electric archery cutter to make the cuts easier to replicate.
The engine pulls really strong…you’ll love that setup
Thanks, Ian. I ordered a new dial gauge that might work better.
http://mantonpushrods.com/
When I did mine I bottomed the foot to the rocker then turned in two times.
I then rotated the motor until the valve fully closed and set the rod length. Since I was going chrome molly from the company above I just finger tightened the rod to fill the gap. Measured the rod, called the company above and they did the rest.
When I did mine I bottomed the foot to the rocker then turned in two times.
I then rotated the motor until the valve fully closed and set the rod length. Since I was going chrome molly from the company above I just finger tightened the rod to fill the gap. Measured the rod, called the company above and they did the rest.
Any other comments?
BTW, I did get advice from Len Hoffman, who suggested that for my "mild" 2056 build, stock aluminum pushrods will work. That means shimming the rocker shaft towers to optimize the adjuster to valve stem alignment at half-lift.
BTW, I did get advice from Len Hoffman, who suggested that for my "mild" 2056 build, stock aluminum pushrods will work. That means shimming the rocker shaft towers to optimize the adjuster to valve stem alignment at half-lift.
If all you need is a shim that is the way to go. I wouldn't buy a shorter set.
One way to get you in the ball park is to set the valve adjuster a few turns out and then rotate the cam to 50% lift with the adjustable pushrod roughty at stock length. From there you will start to mess with shims under the rockers to adjust the valve stem and adjuster to be perfectly inline. This will require you messing with both the rocker stand shims, the pushrod length, and the valve adjuster. Keep repeating the measurements (0, 50%, max lift) and check alignment at 50% each time. Eventually you will find a combination of shim, pushrod length, and valve adjustment (adjuster stick out) that nets close to the correct max value and is perfect at 50% lift.
Couple things:
* your range of acceptable lift is valve lift +/- 5% (.444, .402 is your acceptable range)
If you can get greater then .423 of lift - AWESOME.
*At 50% lift your valve stem and adjuster need to be in the EXACT same plane. This means 50% of whatever number you are using from the first bullet, not 50% of the cam card. If not, keep making adjustments even if it means you sacrifice some of the max lift at the first bullet point (so long as you are in your acceptable range.) If you cannot get the pushrod to give you acceptable range at lift AND perfect alignment at 50% of that lift, that is when you need to add a small shim under the base of the rocker arms. Try and get it without the shim if you can. This should go without saying, but when you use a shim on one rocker, you need to shim all the rockers.
*Your micrometer needs to be in a place that is in perfect alignment with the plane of the valve stem. Post pics of your setup. If not, your measurements will not be repeatable. I like to go off the valve spring retaining cap. I try to put the micrometer on the same location of each cap.
It will take a LOT of trial and error to get the first one. It will take very little time to get the next 7.
Make SURE that the end caps of the pushrods are the exact same as the end cap of the adjustable pushrod you made.
If you don't have a metal lathe handy, cut the pushrods just SLIGHTLY long, and then get them to the perfect length with a file or grinder. Remember, no amount of grinding in the world can save a pushrod cut .01mm too short.
You probably know this but this is really important. You need to have ALL cylinder leveling, head space and CR adjustments made prior to starting pushrod length.
You want steel pushrods, not aluminum. Using steel you will be able to set zero lash, which makes adjustments MUCH easier.
Zach
* your range of acceptable lift is valve lift +/- 5% (.444, .402 is your acceptable range)
If you can get greater then .423 of lift - AWESOME.
*At 50% lift your valve stem and adjuster need to be in the EXACT same plane. This means 50% of whatever number you are using from the first bullet, not 50% of the cam card. If not, keep making adjustments even if it means you sacrifice some of the max lift at the first bullet point (so long as you are in your acceptable range.) If you cannot get the pushrod to give you acceptable range at lift AND perfect alignment at 50% of that lift, that is when you need to add a small shim under the base of the rocker arms. Try and get it without the shim if you can. This should go without saying, but when you use a shim on one rocker, you need to shim all the rockers.
*Your micrometer needs to be in a place that is in perfect alignment with the plane of the valve stem. Post pics of your setup. If not, your measurements will not be repeatable. I like to go off the valve spring retaining cap. I try to put the micrometer on the same location of each cap.
It will take a LOT of trial and error to get the first one. It will take very little time to get the next 7.
Make SURE that the end caps of the pushrods are the exact same as the end cap of the adjustable pushrod you made.
If you don't have a metal lathe handy, cut the pushrods just SLIGHTLY long, and then get them to the perfect length with a file or grinder. Remember, no amount of grinding in the world can save a pushrod cut .01mm too short.
You probably know this but this is really important. You need to have ALL cylinder leveling, head space and CR adjustments made prior to starting pushrod length.
You want steel pushrods, not aluminum. Using steel you will be able to set zero lash, which makes adjustments MUCH easier.
Zach
Thanks, guys. While I am waiting to get my new dial gauge, I decided to see what would happen with stock rods and shims under the rocker shaft supports. I tried a pair of washers as temp shims, .075" thick.
I installed stock rods first in #1, in both intake and exhaust.
I measured .401-403 on the exhaust valve and .422 to .426 on the intake.
And the alignment of adjusters and valve stems at half-lift look very good.
And I got similar results on #2.
Once I get my new dial gauge I will confirm measurements and make decisions about rods.
Once I get my new dial gauge I will confirm measurements and make decisions about rods.
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