I finally took the Iroc for a ride last nite after the repower and it runs pretty good for a first run. I am concerned at all of the valve noise I am hearing tho (tick tick tick). The ticking sounds like a friggin old honda! Its not too loud but definately noticable when the hood is popped. I just can't seem to get the valves adjusted properly tho. The Chilton manual says to back the nut off until no backlash is felt on the PR, then tighten till all backlash is gone and THEN one full turn. I have seen some of you guys post that you should do a full turn just as soon as any resistance is felt at the pushrod. Thats how I adjusted them and gave about 3/4 turn at that. I can just barely "wiggle" the tips of the rockers when the adjustment is completed. Is this still too loose? Needless to say, I was afraid to do a full turn on the first run or so. I just figured better too loose then too tight! I have also heard that a roller motor is noisy like this anyways. I am running Comp pro magnum roller rockers, Comp high energy PR and it has guideplates. Well, time to go pull some valve covers I guess, yahoo...

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Mike C
88 Iroc 5spd
355 TPI, AFR 190s and lotsa other mods
86 Iroc in pieces!

 

i spin the push rod between my fingers while tightening the rocker nut when the push rod stops spinning i go another 1/2 turn or so. you have to watch you don't over tighten and make the lifter start spinning when you do it this way. make sure the valves are closed and the lifter is primed.

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ICON Motorsports
1st & 3rd

 

Well the best way to do it (IMHO) is while the engine is running with the valve covers off. I back off the nut until that valve starts tapping. Slowly tighten it until it stops then go another 1/2 turn.

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92 Z28 L98 350
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Ported stock heads, XR270HR-10 cam, TES headers, Crane AFPR, Flowmaster catback, MSD ignition components.
Best ET 13.5@105 mph
"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)
Click here to see my car at Truspeed.org

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I'm with Blade. Adjusting on a warm, running engine is as precise as you'll get. Unless you do a lot of them cold, it can be a little tricky to determine whether the lifter is collapsed and the adjsutment is too tight, or if the lifter is holding oil and the adjustment is right.

Incidentally, with high-bleed lifters, the ONLY way to adjust them is with the hot/running method - no exceptions. So if you're running Rhodes lifters, start it up and pull the covers.

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Later,
Vader
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"I cannot take this any more... Saying everything that I've said before..."
Adobe Acrobat Reader 4.0

 

Mike, there are several different ways to adjust the valves and all of them will work as long as you follow 'that particular' procedure exactly.

Some ways are easier to do than others, though. The most critical part of the whole operation is to make absolutely sure the lifter is on the base circle of the cam lobe you're adjusting - that's the real key.

GM's Service Manuals show one way requiring you to move from side to side of the engine; some guys like doing it with the engine running (kinda messy even with clips installed and one guy recently reported a engine/oil fire doing it that way).

Camshaft companies offer procedures that differ slightly from each other and magazine Tech articles recommend other variations.

Over 25 years, I've tried them all and have settled on one which is bullet proof and since it works for me, I've stuck with it.

I prepared a file showing the step by step that I send to guys who put up posts just like yours - Wish I had a dollar for each one I've emailed out. I'm going to email it to you - and to anyone else that's interested.

One thing most guys over-look; if the engine has been run before, when re-adjusting the valves, take all the tension off the lifter and wait about a minute. This allows the plunger, which would be somewhere in mid-travel, to rise to the top of the lifter and contact the retainer ring/clip. Then, when you remove all lash in your search for 'zero lash' you'll have an accurate starting point.

You'll be looking for somewhere between .020 and .060 preload. Noisy lifters means the too little preload and lousy idle means too much.

Most articles and recommendations I've read say to slowly tighten the adjusting nut while spinning the pushrod between your thumb and index finger until slight resistance/drag is felt. Problem with that is that which is a slight drag to one person may not be to another. I alway move the pushrod up and down, up and down, as I slowly tighten the adjusting nut. When I reach the point where I can no longer move the pushrod up or down, I know I'm at zero. To each his own though.

I always follow the camshaft maker's recommendations as to the number of turns required for proper preload. They designed the ramps on the cam and know how much preload is required for the lifters to run properly on the lobes. Different profiles have different style ramps and require a different preload.

Keep us posted on how you make out.

Hope this helps.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9



[This message has been edited by JakeJr (edited January 06, 2001).]

 

Hey thanks alot fellas, this really helps out! Yeah, I definately was getting frustrated trying to adjust them when the lifters were collapsing, I could tell at times I just wasn't even close cuz I could actually see the valve start moving. Special thanks to Jake here for such a detailed explanation too!

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Mike C
88 Iroc 5spd
355 TPI, AFR 190s and lotsa other mods
86 Iroc in pieces!

 

How exactly do you keep the oil down when adjusting the rockers with the engine running? What exactly is this part and how does it work? I've got a noisy rocker and I figured i'd switch out to roller tips but I want to know exactly how to keep it from getting messy with the engine running. Thanks.

 

Hydraulic lifters need .020" to a max of .060" preload. From zero lash tighten the rocker nut 1/2 turn to 1 full turn.

If you have a dial guage you can accuratly set them for .020" preload.

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Stephen's racing page

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
454 Big Block buildup now in progress for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
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Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

I've been involved in various forms of racing a long time, most of which involved solid-liftered big and small block Chevy's. The easiest (and least messy) way to adjust hydraulic lifters is very similar to adjusting solid-lifters. With the engine not running, and after determining the valve you want to adjust is closed (this has been discussed in other posts), loosen the adjusting nut slightly enough to slide a .002 or .003 feeler gauge between the rocker and the top of the valve. Then ever-so-slightly tighten down the adjusting nut (while sliding the feeler gauge in and out) until you feel the gauge get tight, or pinched. Pull the gauge out and then tighten the adjusting nut 1/2 turn more (for performance type driving) to 3/4 turn more (for 'stock'). That is all it takes. No more trying to tell when your fingers are actually spinning the push rod. This really works and the only time I ever had any problem was on my '88 GTA when I had to trim the feeler gauge with tin snips so it would clear the guides on the rocker arms.
jms