adjustable big and small block chevy guide plates



adjustable big and small block chevy guide plates

Postby grumpyvette » February 7th, 2010, 2:19 pm

http://www.iskycams.com/pdfcatalog/2004-05/page27.pdf

http://www.jegs.com/i/Dart/301/27001230 ... tId=762684

http://www.jegs.com/i/COMP-Cams/249/481 ... Id=1355962

the heads and rockers used obviously effect the required clearance, but you'll usually want at least 60 thousands clearance on the push rods to slot measurements and you'll want to rotate the engine thru two complete revolutions while verifying that clearance, while watching the push-rod geometry as it changes as the rockers move thru their arcs

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standard guide plates

http://www.flatlanderracing.com/manleygplates.html



How to Check for Pushrod Length:
1. With the cam, crank and timing set installed, bring number 1 cylinder to top dead center on the compression stroke.

2. Install the two lifters that will be used for checking on the intake and exhaust lobes of the cam for number one cylinder.

3. Bolt the cylinder head on the block with no head gasket. (Do not torque the cylinder head, just make it snug).

4. Install the guide plate and rocker arm studs. Again, do not torque the studs, just make them snug.

5. As a starting point, adjust your checking pushrod to the same length recommended by cam manufacturer for the cam and lifter
combination you are using.

6. Install the checking pushrods in the engine.

7. Take your black magic marker and color the tips of the intake and exhaust valves.

8. Install the intake and exhaust rockers and adjust the rockers to zero lash.

9. Rotate the engine over by hand several times.

10. Remove the rockers and note the contact pattern the rockers made on the tip of the valve.

11. If the pattern is centered on the valve tip, pushrod length is ok. If the pattern is wide to the exhaust side of the head, your pushrod length is too long. If the pattern is wide to the intake side of the head, the pushrod is to short.

12. If adjustments need to be made, remove the rockers, recolor the tips of the valves, lengthen or shorten the adjusting pushrods as needed, reinstall the rockers and rotate the engine over again by hand. Repeat the process until the desired pattern is achieved.

13. Once the desired pattern is achieved, remove the checking pushrods from the engine and measure them. Take that measurement and add the compressed thickness of the head gasket being used. The sum of this will be the correct pushrod length for your combination.



Rocker Tip to Valve Stem Alignment:
1. With the cylinder head still bolted on the engine, loosely install the guide plate and studs for number one cylinder.

2. Bring number one cylinder to top dead center on the compression stroke.

3. Install the correct length pushrods for the application.

4. Reinstall the rocker arms and set to zero lash.

5. Now you want to check and make sure the rocker arm tip is centered on the valve tip. If there is any misalignment problems, the guide plate can be moved side to side or fore and aft to achieve proper alignment.

6. Once proper alignment has been achieved, remove the rocker arms and torque the studs to the proper value. Reinstall the rockers and verify that the guide plates did not move during the torquing process. Repeat the procedures for the other cylinders.

7. Due to varying tolerances in lifter bore indexing, adjusting the guide plate as mentioned above may not allow enough shift to achieve proper rocker tip to valve stem tip alignment. If this is the case, Isky adjustable guide plates may be used in the small block Ford and small block Chevy applications. Since there are no adjustable guide plates available for the Big Block Chevy, the only alternative would be to slightly bend the guide plate in the center to achieve proper alignment. Since the guide plates are made of a hardened material, CAUTION should be taken when bending the guide plate on Big Block Chevys as cracking may result.

– Tech Tip courtesy of World Products.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
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Re: adjustable big and small block chevy guide plates

Postby grumpyvette » April 6th, 2011, 11:08 am

If you find the guide plates are not exactly correct in most cases they can be bent with a plastic mallet to get them alined or cut and tack welded to the exact alignment required.
if your using the adjustable ones from DART you can use some EPOXY on the center bolt to be sure it retains alignment or TIG weld the guides off the heads as the tightened screw/bolt will keep them lined when removed from the heads,
if the push-rods don,t actually touch the edge of the guide plate slot at any time in the 720 degree engine rotation cycle, and the rocker stays centered on the valve stem, you can use the guide plates, but in an ideal world the roller rocker tips are centered on the valve stems and the push rods are centered in the guide slots. if you don,t like the adjustable rockers you can cut and re-tig weld the standard guides, or tig weld the screws in the adjustable guide plates if your concerned with them moving, Id suggest using a number stamp, with the related cylinder to identify the correct installed location for each guide

WATCH VIDEO
http://www.youtube.com/watch?v=DxROQtv7 ... dded#at=31

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pictured above you see the last rocked badly out of alignment with the valve center line,
a good example why you need adjustable guide plates, this rocker if left too run off center like this, on the valve stem tip , will quickly destroy the valve guide and rocker
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BEEHIVE SPRINGS and FORGED STEEL ROCKERS GIVE A GOOD DEAL MORE ROCKER TO RETAINER CLEARANCE
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lets be clear, before going further, if your rockers bind on the rocker studs or push rod guide plates, and you have verified proper rocker geometry, with the correct push rod ;length, your describing the rocker binding at location (B) not location (A) or (C) , location (A) is frequently the result of using the wrong adjustment nuts with your rockers, this tends to bind the upper rocker slot to the sides of the adjustment nuts,frequently when you swap to a different style to use a rocker stud girdle.
location (C) can be avoided with BEEHIVE type valve springs and retainers OR machining rockers for additional retainer to rocker clearance.

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if thats the case the push rods or the rocker studs or the guide plates are wrong for the application OR you never had the cast rocker bosses in the heads correctly machined for the screw in studs

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standard screw in rocker studs to use with or without guide plates require the rocker stud boss be machined for required clearance
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EACH type of engine and every set of rocker guide plates and studs will effect how far the rocker boss must be machined for clearance but on most sbc engines the boss is machined down about .360, CHECK WITH YOUR MACHINIST AND HAVE THE PARTS AVAILABLE TO MEASURE
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there ARE screw in rocker studs that can be used WITHOUT machining the bossed but they CAN NOT be used with guide plates and DO frequently result in cracked rocker bosses.

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stock cast rocker bosses must be machines to gain clearance for guide plates and screw in studs

MUCH MORE INFO HERE

viewtopic.php?f=52&t=181
as a temporary measure to get you rolling you can clearance the existing guide plates, but its very unlikely to allow exactly precise push-rod and rocker alignment on the valve stems.


what you really should do is order these

Dart 27001230-4 - Dart Pushrod Guideplates

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viewtopic.php?f=44&t=2839&p=7344&hilit=adjustable+guide#p7344

viewtopic.php?f=52&t=155
viewtopic.php?f=52&t=399
IN most cases the stamped guides that come with most cylinder heads will be very close to correct, but at times youll need a custom spacing, you can do that buy buying adjustable guide plates or by cutting and welding the stock guide plates if its required.
Ive always used a TIG WELDER to lock the guide plate alignment and used the cylinder number STAMPED on the guides so they don,t get mixed up as to location if you need to cut and re-weld push-rod guide plates and to get the alignment correct you obviously need them clamped in place with the rocker studs so the heads and rocker studs act like a heat sink and because a TIG has very localized heat your not going to anneal the slot for the push rods on the other side of the heads rocker boss.


ON MORE REASON IN AN ENDLESS LIST OF REASONS WHY A GOOD TIG WELDER IS A VALUABLE ASSET TO MOST SHOPS TOOL LIST


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as to the welding splatter , some modeling clay in the oil drains, and several layers of tin foil under the guides , and around the valve springs and a vacuum cleaner to suck up any stray micro crud and a couple magnets placed under the area being tack welded will catch any stray crud

and a die grinder with abrasive wheel makes a clean up tool on the welded seam, after the guides are tacked and welded once off the heads

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Ive used either one of these two products, applied on clean dry threads by dipping the stud threads just prior to assembly on those threads, waiting a minute for the stuff to start to get tacky,then screwing them in for decades

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Ive never had a leak or loose stud, never had any issues removing them if required ,with the proper socket and breaker bar later either,
BTW, remember to visually verify the stud length and cut them a bit shorter if required you don,t want the lower end protruding into the intake port and any threads doing that do NOTHING to increase the stud rigidity but they sure can reduce port flow rates if left sticking down into the air flow path
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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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