Quick question for the forum members ...

I understand the benefit of hydraulic lifters (as opposed to solid lifters) is that they 'self-adjust' ... the oil pressure causes them to internally 'inflate' to the appropriate length .... [This is beneficial because otherwise there is a mechanical adjustment that must be done with solid lifters to take out any slack in the valvetrain ....]

The question is how much of a range is there between a collapsed lifter with no oil pressure and a 'fully inflated' lifter with standard operating oil pressure ...?

I understand that the stock lifters may be reused on most 'bolt-in' cams ... which have a base circle the same radius as the stock cams ... (although often adjustable push rods are used for convenience of the installer as the rocker covers do not have to be removed) ....

- I understand when heads are decked (milled) to increase compression it would lower the rocker arm ...

- Changing the rocker arm geometry from stock 1.65 to 1.725 ratio rocker arms would also seem to change the geometry somewhat ...

I noted the MoCo's 'perfect fit' pushrods come in stock length, +0.030, -0.030, and -0.060 .... What would be the respective applications ...? Wondering if there is more than sixty thousandths' range in the lifters why it would be necessary to change the length of pushrods in a particular application ...?

I guess having seen a few problems reported with adjustment or breakage / slippage of the nuts it might be preferable to go with perfect fit pushrods instead ... as long as the proper ones were selected ....

THX in advance for your experience / insights ....

R/
'Chop

 

There is probably around .200 inches of travel/take up in the hydraulic lifter, they are set to around .120-.150 deep. The perfect fit push rods are to compensate for milled heads, aftermarket cam base circle differences, different head gasket thicknesses and whatever else can change the rocker to cam relationship including rockers. I would agree that the simpler the part the more reliable it is, but like you I have not heard of any issues with adjustable length push rods. I used the SE tapered when changing my cam and they were very straight forward to install and set up. The adjustables are only $20 to $50 more than perfect fits so if you screw up on your measurement with the perfect fit you have blown your savings and maybe even worse your weekend ride.

 

I had heard the nuts on some adjustable pushrods can develop cracks ... and that when installing them you had to ensure the hydraulic lifters had filled with oil (or you would screw up the pushrod adjustment) ....

I suppose if you just take your time and follow the procedures to a "T" you will be good ... but, on a solid pushrod, there are no nuts to crack ....

THX for the input JE ...

R/
'Chop

 

The thing with adjustable pushrods is if you like to fiddle with the engine.

Till I got things pretty much where I wanted them I probably took the rockers cover and supports off several times. Seemed like I would do one thing at a time as I learned this engine and its quirks. And have to do the pushrods again and again.

I also now use Smith Brothers Easy Install because the last itme I put the rockers back together I didn't want to full around with the top end anymore. Got, at least that, like I want.

 

I think you have it figured out. Remember that the PF pushrods only have to compensate for the radial difference in base circle; 1/2 the diameter. Further more it doesn't really it doesn't really matter if they compress the lifter plunger to .110" or deeper; many run adjustables .020"-.030" off the bottom.

The SE Quick Install Tapered pushrods were the ones that had some poor quality adjusting nuts that were prone to cracking but that problem seems to have been limited to the early production; haven't heard much about that lately.

I would agree that, unless one plans to be in/out of the cam chest, non-adjustables are teh way to go. If you are sure about your measurements, Smith Brothers will make a set to any length.

 

https://www.hdforums.com/forum/touri...am-swap-5.html

I don't think this is the first post like this that I've seen ....

R/
'Chop

 

It happens but not very often; I wonder what pushrods parakiller was using? I have taken to putting a drop of blue loctite between the face of the retaining nut and the base nut; not on the threads. Just tryin to "stick" the two nuts together. If the loctite gets on the threads of the adjusting nut, it takes forever to loosen/readjust should that be necessary.

 

God... Ain't THAT the truth

 

I will never have adjustables. It's too simple of a job reusing the stock ones. They weigh less and there is no chance whatsoever of them coming loose.

 

For me it was heads milled 0.060.
cometic 0.030 gasket. Stock is 0.045 I think.
That comes to 0.075 less that stock.
Woods 7H ,then Woods 400 cam.

Then chased valve train noise till I came to Woods Lifters, which I put in exactly as Bob Woods said.

Somewhere during all this I read where S&S, I believe it was S&S, setting up video using strobes and slow motion showing the pushrods flexing and moving around as the engine ran up and down the rpm range.

So there is more to pushrods than just the length.
And why I now have Smith Brothers Easy Install which are not at all like Jiffy types.
7/16 on the bottom tappered at the top and heavy wall chrome molley.
I just love the sound of Chrome Molley. If I was younger and had a new Daughter---- Oh Well.

In fact one needs little Elf fingers to put these things in.

Very Stout pushrods seemed the way to go to me.