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Author Topic:   Rocker arm geometry
V8 Thumper
Gearhead

Posts: 4681
From: Phoenix, Arizona
Registered: Dec 2001

posted 06-26-2002 08:08 AM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
...should be checked with zero lash, correct?

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jkilroy
Gearhead

Posts: 1808
From: Vicksburg, MS
Registered: Dec 99

posted 06-26-2002 10:28 AM     Click Here to See the Profile for jkilroy   Click Here to Email jkilroy     Edit/Delete Message   Reply w/Quote
Are you talking about juice cams or solids? Solids I check with zero lash and then back them off. Juice sticks need to be properly preloaded and then checked. They you drive it.

------------------
Jay Kilroy
68' Fastback GT 390
"No such thing as a cam thats too big"

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66bluefb
Gearhead

Posts: 521
From: Okla.City,Okla.
Registered: May 2002

posted 06-26-2002 02:38 PM     Click Here to See the Profile for 66bluefb   Click Here to Email 66bluefb     Edit/Delete Message   Reply w/Quote
V8 Thumper,I`m getting ready to put my H/S roller rockers on when I get my harden push rods from Summit.What do you mean by zero lash? Thanks,Tony

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V8 Thumper
Gearhead

Posts: 4681
From: Phoenix, Arizona
Registered: Dec 2001

posted 06-26-2002 06:59 PM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
No guys, not rocker arm adjustment, but geometry (determining pushrod length). Solid cam, of course

Lash is the clearance between the valve stem and the rocker arm tip, with zero being, well, zero

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bluestreek
Gearhead

Posts: 1724
From: Athens,GA
Registered: Jul 2001

posted 06-27-2002 01:47 AM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
Start with the lifter on the flat of the cam lobe with zero lash. For perfect geometry, the roller tip should sit on the valve tip about 1/32-1/16" from center, toward the stud side, and should only travel about 1/16-1/8" across the center of the valve tip at full lift. If there is too much roller travel, or the roller gets too close to the edge, the valve train and guides will catch hell!!

[This message has been edited by bluestreek (edited 06-27-2002).]

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V8 Thumper
Gearhead

Posts: 4681
From: Phoenix, Arizona
Registered: Dec 2001

posted 06-27-2002 07:44 AM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
Thank you

How's your motor comming? With your roller, have you determined just how much longer they need to be? Trick Flow says +.450 for my solid flat cam, but I'm not going to rely on that number. Maybe as a starting point with my length checker; I've changed too many paramaters to just order a set without doing a full-blown geometry mock-up first.

Have you had any dealings with Trick Flow tech support? I wasn't real impressed

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bluestreek
Gearhead

Posts: 1724
From: Athens,GA
Registered: Jul 2001

posted 06-27-2002 12:06 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
Your right. Trick Flow tech is kinda slow but you can also call Summit tech, since they own TFS.

I had a delay on my 331 because they had to order some metric rings for my forged pistons. The rings are in and the assy is getting clearanced and balanced as we speak.

The guy I bought my used TFS heads from included a set Trick flow 7.350 (.080 wall) pushrods that he used on a solid tappet cam. The heads were used for about 5000 miles and the guides still checked out great! I'm gonna do a mock check on the heads to see if I can use them with the roller lifters.

Spend as much time and money as needed to get the valvetrain right. It will payoff BIGTIME in the long run.

Did you decide to use a windage tray or main girdle?

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V8 Thumper
Gearhead

Posts: 4681
From: Phoenix, Arizona
Registered: Dec 2001

posted 06-28-2002 09:28 AM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
Tray yes (FMS-Boss 302), girdle no (Mexican block )

Depending on, well, a whole bunch...

let me know how those pushrods mock up with your roller. I don't think they'll work (too long) and if I haven't already aquired a set, I'd be happy to take those off your hands

[This message has been edited by V8 Thumper (edited 06-28-2002).]

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n2oMike
Gearhead

Posts: 2831
From: Spencer, WV
Registered: Jan 2001

posted 06-28-2002 09:51 AM     Click Here to See the Profile for n2oMike   Click Here to Email n2oMike     Edit/Delete Message   Reply w/Quote
Rocker Geometry...

The roller on the rocker arm should be centered side to side. If it's off too far, the guide plate may need to be cut in half to center each rocker on the valve tips. Often, one can get by with elongating their mounting holes to allow the plate to slide side to side. At times, flipping the guide plate over even helps.

As for back and forth motion... The roller should be centered on the valve tip, and should have no more than 0.080" sweep as the cam goes through it's lift cycle. hydraulic lifters don't work well for this due to their compressability w/o oil pressure
To do this test, a solid lifter will need to be acquired (or fabricated). you can take the guts out of an old hydraulic lifter and fill it solid with epoxy or something
As an alternative... One of those soft 'checking springs' can be substituted for the regular valve spring, and will often keep a hydraulic lifter's plunger from depressing too much during this checking process.

Vary pushrod length until the roller is centered, and sweep is under control. If pushrod length can't get the geometry where it needs to be, you'll have to try different rocker arms. they vary from brand to brand The earliest Trick Flow TW heads were designed around a CHEVY rocker arm, which is a little shorter from the fulcrum to the tip. Some manufactures will recommend certain brands of rockers.

To give you an idea how much 0.080" is, 1/16" of an inch is 0.062". The top of the valve stem can be colored with a marker, and the movement can be recorded by where the marker ink gets rubbed out.

Good Luck!

------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220

[This message has been edited by n2oMike (edited 06-28-2002).]

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