How much can I pre-load my hydraulic flat lifters?

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Posted: Aug/22/2019 at 4:58pm

? 0.345 inch too long pushrods is my immediate un-researched un-substantiated reaction ?...

Rockers are too high up on the Studs... but that is just a "off the cuff" comment for discussion, ok ?

7.700 inch Long where the Pushrods I used...

BUT... 1969 Block ( 9.175 vs 9.208 nominal ) and maybe .045 inch milled heads,

but those 2 things only account for .080 difference in pushrod length...

aftermarket Elgin Camshaft and Hydraulic Lifters...

On-hand Perf American Style Book has these stock AMC Pushrod length values, not gospel...

7.767 inch long +/- 1968-69 ( 9.175" Block Deck Nominal )

7.800 inch long +/- 1970-71 ( 9.208 Block Deck Nominal ) individual rocker stud heads

7.820 inch long +/- 1972

Maybe get a pair of adjustable pushrods to do a little "investigating" ?

Edited by PHAT69AMX - Aug/22/2019 at 5:00pm

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Posted: Aug/22/2019 at 6:16pm

And to muddy the water even further...

Here's something from 1969 that I only recently came across:

( quote)

( per 1969 Hurst Performance Research Mechanical Engineer Bob Tarozzi )

( and Car Craft and Vic Edelbrock building a Clone S/S AMC 390 )

"... the ( stock rocker ) stud boss ( on 1969 AMC Cylinder Heads )

has to be machined down 3/16" to keep

the bottom of the ( roller ) rockers from hitting."

( end quote )

The Point being to keep the Roller Rockers LOW on the Stud...

-----

On the topic of AMC's and Roller Rockers,

found this 1969 Cra Craft article interesting

because amoung other things they mention milling

the 1969 Head Rocker Stud Bosses down by 3/16" ?

and I wondered why ? They make NO MENTION of Pushrod Guideplates,

and understanding is NO GUIDE PLATES are needed with the '69 heads,

and they DO MENTION that Stock Stamped Rockers Arms

and Stock Stepped Rocker Studs somehow align the Stock Rockers ?

Huh ?

? Maybe they were saying the Stock Stamped Rockers could "Rotate"

some amount towards the front and rear of the engine direction,

"Crossways" I guess ?...,

if the stock rockers were higher up on the stock studs and

up above the larger diamter lower portion of the stock studs ?

Whereas, Trunion Pivot Roller Rocker Arms can NOT...

-----

Excerpt from PART 3 of 4 - VIVA AMX ! - OCT 1969 - CAR CRAFT

Car Craft builds a clone '69 Hurst S/S AMX car with help from Edelbrock

( quote)

Once we pulled the valve covers the problem was quite apparent, even if the solution wasn't.

On the two cylinders in question, the exhaust rocker arms had parted company

with the pushrods, and the #8 rocker stud had sheared itself off. For those of you

who are not familiar with the AM engine, the rocker arm mechanism is similar to the

Chevy V8; a stamped steel rocker arm pivoting on a stud and ball arrangement. The AM

stud, in stock form, was designed to be used with a hydraulic lifter camshaft. The

lower portion of the stud has a shoulder that locates the ball, which determines the

height of the rocker arm, and proper preload on the hydraulic lifter. In our case,

we were using a solid lifter cam, with a smaller diameter base circle and different

length pushrods. The slot in the bottom of the rocker arm is slightly wider than the

major diameter of the stud, ( i.e. that portion below the shoulder ) which aligns the

rocker arm laterally. With the solid lifter cam the ball registered itself above the

shoulder, with a resulting loss of lateral support for the rocker. The only solution

was to use a different type of rocker arm and stud arrangement. We couldn't use

Chevrolet or small block Ford rockers, as these engines have a 1.5:1 rocker arm

ratio; AM engines have a 1.6:1 ratio.

-> At this point we called Hurst Performance Research for a possible answer to our

problem. Bob Tarozzi had been the chief trouble shooter for Hurst when they built

the original 52 Super Stockers for the factory, and was quite aware of this

malfunction. His solution, and ours, came from Crane Engineering in Hallendale,

Florida. They had designed a special set of aluminum rocker arms supported by

individual needle bearing shafts, with the required 1.6:1 ratio. A special rocker

stud, also designed by Crane, has to be used in conjunction with the aluminum rocker

arms. Because they are made from aluminum, the Crane rockers have a much beefier

cross section than the stockers, and the stud boss has to be machined down 3/16"

to keep the bottom of the rockers from hitting. Crane can supply a cutter to do this,

or the head can be set up in a mill.

( end quote )

Edited by PHAT69AMX - Aug/22/2019 at 6:26pm

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Posted: Aug/22/2019 at 7:33pm

I have never used 8.125 pushrods that I can remember. Most of my builds with rollers end up in the 7.900 range with iron heads on early blocks and up to 8.00 on late blocks depending on cam and base circle. I had one block NOS tall deck with aluminum heads that took 8.100 to get correct. I think that one had .100 taller valves though. I really think you should run your half lift geometry again. Your pushrods are way too long. It also sounds as though your machinist owes you a regrind to the next under and a set of bearings. Have them use the correct specs for the AMC engines.

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https://www.youtube.com/watch?v=o5is9BsH5OU

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Posted: Aug/23/2019 at 2:36pm

Welp. Sounds like I may be buying some new pushrods. Even if the problem is low oil pressure, I should have the correct pushrods in there, too. I know no one has said "Rang-a-Stang, you have the wrong length pushrods and need to replace them" but logic dictates, most probably, i have the wrong length pushrods and that will need to be corrected. I really appreciate all the information/time you guys are giving me.

I measured with a home made adjustable pushrod and a venier caliper. This is the process I used:

This is the only time I have ever done this, so no doubt that I screwed it up.

When I was reading about measuring for proper geometry, I read a lot of good stuff about the comp cams pushrod measuring tools:

https://www.summitracing.com/parts/cca-7703-1?rrec=true

Any advice here? this is a good one? Sucks?

Also, when I measured the first time, the intake was off. Can I get an accurate measurement with the intake on? I really don't want to pull the intake to put a solid lifter in...

-My thoughts: mark valve tip, install tool at 7.900, install the rocker with .030 pre-load, set the valve cover on the top, crank it for a few seconds to establish oil pressure, remove the valve cover/rocker, check the mark, adjust the tool, repeat until mark centered. I assume I can measure intake on cyl 1, then verify it's the same at Exhaust on cyl 1, and go order pushrods, right (in other words, I don't need to do all 16 valves)?

I have not touched my rig this week and probably won't for about another week. I am also fighting some other un-related issues.

Edit: Just finished reading your second post this page, PHAT69AMX. I thought the HS rockers took this need to sit lower sitting into account and was why they had that nice big chamfer at the bottom you asked about. My stud bosses were not machined at all; I just unscrewed the stock/shouldered/non-adjustable studs, and loctite'ed/screwed in the ARPs. When I open my valve covers, I will take LOTS of pictures and post them up.

Edited by rang-a-stang - Aug/23/2019 at 3:16pm

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Posted: Aug/23/2019 at 3:18pm

69 ambassador 390 wrote:

...It also sounds as though your machinist owes you a regrind to the next under and a set of bearings. Have them use the correct specs for the AMC engines.

I am heading toward that as well. I will be calling him next week to discuss.

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Posted: Aug/23/2019 at 4:49pm

Agree, the chamfer on the HS Rockers should take care of the bottom clearance.

No intention to suggest your Stud bosses need milled down.

Just I stumbled across that 1969 article lately where it is mentioned and had not heard that before.

Was more of a "reinforcement" to the logic to keep rockers low on the stud.

Also Different brand rocker studs have different contours at the Hex, and

imho the ARP Studs you have are some of the better ones, I used the same as you have

and I did -NOT- machine my single stud AMC Cyl Head Stud bosses down either.

Agree with the video, at half lift, 90 degrees between valve stem and Rocker "centerline"...

-BUT-, and -NOT- that I know... one thing I thought different than in that video,

the imaginary "centerline" used is from the Trunion Center to the VALVE TIP / Rocker Tip Roller CONTACT PATCH

-NOT- to the Rocker Tip Roller CENTERLINE... or at least that is what I "thought", not that I know.

-BUT- that difference right there WOULD result in a shorter required Pushrod, would it not ?

What might be the dimension from the Rocker Tip Roller centerline to the FACE of the Tip Roller ?

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Posted: Aug/23/2019 at 6:25pm

Another question about that video...

A .355 inch change on the Pushrod Side does -NOT- equal a .355 inch change on the Valve Side, does it ?

The Rocker has a 1.6 Ratio, right ?... so .355" (* 1.6) on the Pushrod side is .568" on the valve side ? and

a .355" (*1/1.6) change on the valve side is only a .2218" change on the Pushrod Side ?...

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Posted: Aug/24/2019 at 1:05am

rang-a-stang - if ya can, get and post a picture strait on as possible from the end like this drawing

of your current Rocker and Pushrod in place, valve closed, with about .030" Lifter Preload

so we can see what the existing Geometry looks like with what you already have...

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Posted: Aug/26/2019 at 2:04pm

PHAT69AMX wrote:

rang-a-stang - if ya can, get and post a picture strait on as possible from the end like this drawing

of your current Rocker and Pushrod in place, valve closed, with about .030" Lifter Preload

so we can see what the existing Geometry looks like with what you already have...

WilCO. Will probably be sometime during the week of 8 Sept. Going on a road trip this weekend (not in my 401). Wife would be really upset if I wrench this week because if I pull the jeep in the garage, her car goes in the driveway. It's warm this time of year and she is not a fan of getting in her dark grey pathfinder after it's been sitting in the sun all day. Wacko

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