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#786454 - 02/04/07 12:26 PM Valve Lash Adjustment questions
jacktoad Offline
Getting the Wheeling Fever
Registered: 12/13/02
Posts: 92
Loc: northern california
while theRodeo's 3.1L is still apart, i've swapped in some 1.6:1 roller rockers. the distributor is not installed yet. but i did match mark it so i can install it to its original position. my questions on adjusting the valve lash during install of the new roller rockers:
1. should the distributor be installed prior to turning the crank during the valve lash adjustment process? (so that i don't lose my orientation of the distributor).
2. The install directions from Comp Cams tell how to position the engine so that it is at the correct rotation for adjustment of the intake/exhaust valve. but from reading other posts on the forum, it seemed that the rotation/position of the motor doesn't matter(unless i misunderstood....quite likely).
3. 4 of the 12 balls/spacers that came in the package will not fit onto the studs. so, is it ok to use 4 of the oem balls that i removed?

thanks once again for the continueing help and advice.

rb
_________________________
1992 Isuzu Rodeo 3.1L(now 3.4L) V6 4x4
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#786455 - 02/04/07 12:55 PM Re: Valve Lash Adjustment questions [Re: jacktoad]
Goose Offline
Getting the Wheeling Fever
Registered: 08/24/06
Posts: 25
Loc: North of the 49
As far as i can see, you dont "have" to have the distributor
in. It does make it easier since you have all marked to be in the same location. But if you dont it is not hard to relocated the distributor.
Although i am not very familiar with the 3.1L, I am assuming that if you are changing the ratio of the rocker arms you have to consider that you will have to adjust your timing, because if you increase the ratio not only are you puttin more pressure and wear on parts, but your duration of valve timing will increase.
Having said that this is a good and a bad, good because you will get more performace, bad because you will increase the wear on the head assembly(not enogh to wreck it or anthing really bad) but it is something to keep in mind.
I dont know if this really helps you, or you might know all this already, but someone else might benefit from this litle information.
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#786456 - 02/04/07 05:33 PM Re: Valve Lash Adjustment questions [Re: Goose]
Ed Mc Offline
Body Damage is Cool
Registered: 12/25/99
Posts: 1035
Loc: Poulsbo, WA 98370-8125, Kitsap...
Roller rockers work great in this application. I ran a set of Comp Cams Magnum 1.6:1 roller-tipped rockers in my old 2.8 with great results, and my 3.4 has a set of eBay El-Cheapo Small Block Chevy V8 1.6:1 roller-tips that work as well.

Note that unless you're using the stock GM camshaft, you should probably upgrade to a performance set of valve springs & retainers. The stock springs might tend to coil-bind with higher lifts.

Roller-tipped rockers will reduce wear on the valve stem and valve guide, due to reduction in the 'scrubbing' friction of stock rocker arm to valve stem. Plus they'll reduce oil temperatures and add a 'smidgeon' of extra hp, just by virtue of the roller tip.

Regarding the Q of distributor, install before or after, makes no diff; you just want to make sure you line things up to where the dist is either at TDC on compression of #1 cyl, or align to TDC and compression stroke of #4 cyl. If you have the valve covers off adjusting valve lash, it's easy to watch the pushrods go up and down and figure out whether #1 or #4 is on its compression stoke when the timing mark on the harmonic balancer is lined up to "0" on the timing scale. And of course, point the rotor to whichever cyl you line up to, #1 or #4.

Regarding proper setting of valve lash, don't get it too tight or them motor won't start! <img src="/forums/images/graemlins/scared.gif" alt="" />

For any particular valve under adjustment, make sure the other valve has started to be actuated; this means the lifter of the valve you're adjusting is, by definition, riding on the base circle of the cam.

Tighten the rocker arm locknut while "jiggling" the pushrod up and down. You'll feel the amount of clearance reduce as you tighten the locknut further. When you get to the point where the pushrod no longer "jiggles" up and down, you've reached the point of Zero Lash.

From Zero Lash, tighten no more than an additional 1 turn. Regardless of what is usually said about 1-1/2 turns past Zero Lash, that's too much and may result in a no-start condition due to the valve being held open.

I run my 1.6:1 roller-tipped rockers at 3/4 turns preload and they work just fine.

Regarding the rocker balls that don't fit, I bet if you slid them down a 3/8" stud they'd fit just fine! The factory probably slipped a few V8 rocker balls in there.

I wouldn't recommend using used ones as they'll cause additional wear on your nice, new rocker arms. New balls are cheap and readily available at most any auto parts store.

Just ask for some for a 1990 Chevy S-10 with 2.8 V6, and you won't confuse the Parts Dude!! <img src="/forums/images/graemlins/lol.gif" alt="" />

G'luck with your performance mods, I think you'll be pleased with the results, once your computer "learns" the new parameters.

You're going to want to check/adjust minimum idle air speed and T.P.S. voltage after any performance mod such as this, as it affects airflow thru the engine and will throw off the stock settings.

If your rig idles or runs strange after the mod, that's the reason for it.

HTH..........ed
_________________________
'90 Troop 3.4 LS
'89 Troop RS (Has Valve Issues, needs Counseling)
HI, I'm Ed and I'm a Trooper-holic!
Keep On Troopin'......
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#786457 - 02/04/07 06:49 PM Re: Valve Lash Adjustment questions [Re: Goose]
mlclark Offline

Isuzu Moderator
Registered: 04/11/00
Posts: 7268
Loc: Ventura County *****
but your duration of valve timing will increase.

Unless I am mistaken, I am pretty sure duration is a function of the camshaft, not the rockers. There will be more total lift, but the valves will still open and close at the same points in time.

Michael
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#786458 - 02/05/07 06:59 PM Re: Valve Lash Adjustment questions [Re: Ed Mc]
jacktoad Offline
Getting the Wheeling Fever
Registered: 12/13/02
Posts: 92
Loc: northern california
Quote:

... you just want to make sure you line things up to where the dist is either at TDC on compression of #1 cyl, or align to TDC and compression stroke of #4 cyl. If you have the valve covers off adjusting valve lash, it's easy to watch the pushrods go up and down and figure out whether #1 or #4 is on its compression stoke when the timing mark on the harmonic balancer is lined up to "0" on the timing scale. And of course, point the rotor to whichever cyl you line up to, #1 or #4.
...
HTH..........ed


yes, helps quite a bit thank you. though i wish i could be more confident that i am at TDC-compression #1 cylinder. i had a very long pencil down through the #1 spark plug hole as i turned the crank. pencil rose as the timing marks aligned, and the rockers were not 'in motion' during the final ~25 degrees of the rotation. i took this to be the correct position. but if this is not correct, or if there is a way to 2x check, i have not put the rocker covers back on yet.
_________________________
1992 Isuzu Rodeo 3.1L(now 3.4L) V6 4x4
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#786459 - 02/05/07 07:57 PM Re: Valve Lash Adjustment questions [Re: jacktoad]
Ed Mc Offline
Body Damage is Cool
Registered: 12/25/99
Posts: 1035
Loc: Poulsbo, WA 98370-8125, Kitsap...
Sounds like you're there, however there's always the Stone-Age way of determining if you're on the compression stroke or not:

Stick your finger in the spark plug hole or very loosely thread in a spark plug. When you're on compression stroke you'll hear hissing and if that plug is the only one installed, you're going to feel the resistance increase as it approaches TDC.

The fact that neither rocker was moving, however, is pretty good indicator that the cyl in question was on its compression stroke.

Once you've established that, it's a simple matter of aligning the timing mark on the harm. bal. to Zero and you're there!
_________________________
'90 Troop 3.4 LS
'89 Troop RS (Has Valve Issues, needs Counseling)
HI, I'm Ed and I'm a Trooper-holic!
Keep On Troopin'......
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#786460 - 02/06/07 11:32 AM Re: Valve Lash Adjustment questions [Re: Ed Mc]
JohninLV Offline
Getting the Wheeling Fever
Registered: 01/21/03
Posts: 90
Loc: Las Vegas NV
Valve springs are important. I would toss the OEM springs and go for a set of early gm 327 springs and retainers. it is easyer to do it now. I have had the stock trooper springs brake and get so weak that they mushroom the end of the valve stem from bounsing on it. I get them on EBay.
http://cgi.ebay.com/ebaymotors/550-Lift-...emZ180080936882
they closely match the 3.4l HP springs.
While your in there replace the valve stem seals with vitrons, intake and exhaust. Fel-Pro or GM will work.
After doing all this right the first time you may never have the pleasure of removing the valve covers again.

John in LV
_________________________
3 90 Trooper V-6's, 5 speed, 4.3L TBI, 31" BFG AT's, Fender Flairs, Bored intake, 1.6 roller rockers, MSD Coil, Jacobs Omni ignition. Heavy duty torsion bars, Rancho 9000 Shocks CAN'T SPELL, TO OLD TO LEARN, GOD BLESS YOU IF YOU CAN.
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#786461 - 02/07/07 12:06 AM Re: Valve Lash Adjustment questions [Re: mlclark]
Goose Offline
Getting the Wheeling Fever
Registered: 08/24/06
Posts: 25
Loc: North of the 49
Mlclark is right my bad...
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