Valve Lash Adjustment: running or not? [Archive]

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bitfactr

04-30-2010, 10:04 PM

I have a stock '70 big block Chevelle with a solid cam. I've been pointed by reliable sources to several on-line references/forums that describe the valve lash adjustment procedure. While varying slightly, all agree that it is best to do hot, once the engine is warmed-up. All also said or implied it is done with the engine <span style="text-decoration: underline">not running</span>.

The couple 70's era repair/tune-up manuals I have both say the final adjustment should be done with the engine <span style="text-decoration: underline">running</span>.

Anyone know if the accuracy between running and not running is that significant?

Thanks,
Dennis

VintageMusclecar

04-30-2010, 10:17 PM

I personally advise using the "EOIC" method, i.e. "exhaust opening intake closing" method.

With the engine at operating temp (and turned off), adjust one cylinder at a time on each bank. Carefully bump the engine over just until the exhaust rocker starts to open the valve. Stop, and adjust the intake valve on that cylinder. Then bump the engine over again just until the intake rocker has started to close. Stop, then adjust the exhaust valve for that cylinder. This method ensures that the lifter is down on the heel of the lobe.

Lather, rinse and repeat as necessary.

kwhizz

04-30-2010, 10:23 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: VintageMusclecar</div><div class="ubbcode-body">I personally advise using the "EOIC" method, i.e. "exhaust opening intake closing" method.

With the engine at operating temp (and turned off), adjust one cylinder at a time on each bank. Carefully bump the engine over just until the exhaust rocker starts to open the valve. Stop, and adjust the intake valve on that cylinder. Then bump the engine over again just until the intake rocker has started to close. Stop, then adjust the exhaust valve for that cylinder. This method ensures that the lifter is down on the heel of the lobe.

Lather, rinse and repeat as necessary. </div></div>

x 10

Ken

bitfactr

04-30-2010, 10:52 PM

Thanks for the response.

Sounds like the by far most important point is making sure the lifter is on the heel of the cam. I can see having the engine running would do this, but make the actual adjustment a bit more tricky.

The manuals (and some other soruces) describe doing multiple values at given crank position, but this sounds like the crank position will be very critical (i.e. being slightly off might result in having one of those valves not fully on the heel).

Your procedure guarantees the target valve is on the heel. Thanks for info. I picked up an underhood bump switch yesterday, so I think I'm good to go.

Thanks,
Dennis

SmallHurst

05-01-2010, 09:36 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kwhizz</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: VintageMusclecar</div><div class="ubbcode-body">I personally advise using the "EOIC" method, i.e. "exhaust opening intake closing" method.

With the engine at operating temp (and turned off), adjust one cylinder at a time on each bank. Carefully bump the engine over just until the exhaust rocker starts to open the valve. Stop, and adjust the intake valve on that cylinder. Then bump the engine over again just until the intake rocker has started to close. Stop, then adjust the exhaust valve for that cylinder. This method ensures that the lifter is down on the heel of the lobe.

Lather, rinse and repeat as necessary. </div></div>

x 10

Ken </div></div>

I thought it would be x 8 (or 7). What are you doing Ken, you have a Viper that we don't know about? <<GRAEMLIN_URL>>/haha.gif

napa68

05-02-2010, 02:15 PM

Here is a document thay applies to small block in particular but a person can take some of the information and apply it to others. I udes this procedure first on my F.I. car and what a difference! Recently, I adjusted my LT-1 and it hit the nail on the head again. This document came from a couple of fellows on the NCRS website that worked with GM back in the day. Hope this can help someone.

"30-30" AND OTHER OEM SB SOLID LIFTER CAM VALVE ADJUSTMENT
(Revised 09-23-2008)
By John Hinckley and Duke Williams
The traditional method of adjusting valves one or more cylinders at a time with each cylinder
at TDC is fine for hydraulics and for most solid-lifter cams, but NOT for the factory "30-30" solidlifter
cam used in '64-'65 L-76 365 HP and L-84 375 HP (FI) Corvette engines (and in '67-'69
Camaro 302/290 Z/28 engines); this cam has VERY long clearance ramps that are .017" high,
and at TDC for any cylinder, both the intake and exhaust valve for that cylinder are still on their
ramps, NOT on the cam's base circle, which is why the Service Manual for all cars so equipped
says specifically to set them "hot and running".
There is, however, a better way to adjust the valves with a "30-30" - you can set them "cold
and not running" by setting the intakes at 90 degrees ATDC and the exhausts at 90 degrees
BTDC - so the lifters are on the base circle, not on the clearance ramps. This has been confirmed
with cam lift/crank-angle diagrams and analysis of the GM drawing lobe data, and I've done mine
this way - results in a nice mechanical "singing" sound, no "clacking", it runs better, sounds
better, idle is more stable, and throttle response is improved. Several other Z/28 owners have
followed this procedure as well since we developed it, and all of them have seen the same
positive results.
Set them cold at .023"/.023". The actual measured (stamped rocker arm) ratio at the lash
points is actually about 1.37:1 (not the design 1.5:1, which is a “theoretical” number), so the
clearance ramp, which is exactly .017" high on the lobe, is all taken up at .02329" clearance;
.030" clearance with the valve closed is too loose - the ramp ends/begins before the
.030"clearance is taken up, resulting in the valve being lifted off and returned to the seat at
greater than ramp velocity. This will contribute to valve seat recession, and can cause valve
bounce at the seats at high revs - it will also be noisy.
You can adjust two valves at each 90-degree rotation point, starting at #1 TDC, turning the
crank 90 degrees at a time seven times (measure and mark your balancer first at 90-degree
intervals from TDC). Removing the plugs simplifies rotating the crank, but you were going to
change them anyway, right? Proceed as follows:
TDC #1 - 8E, 2I
90 deg. - 4E, 1I
180 deg. - 3E, 8I
270 deg. - 6E, 4I
0 - 5E, 3I
90 deg. - 7E, 6I
180 deg. - 2E, 5I
270 deg. - 1E, 7I
Start at TDC #1, then rotate 90 degrees at a time, setting at .023" cold. If you like, you can
then go back after you're done to each cylinder's TDC position and check clearance on that
cylinder's two valves, and you'll find that they've closed up to approximately.021", indicating that
both valves are still on the ramps at TDC, as I pointed out in the beginning.
Trivia - the point of max inlet lift on the "30-30" cam is at 110 degrees ATDC and 118 degrees
BTDC on the exhaust side, so the lobe separation angle is 114 degrees (angle between points of
max lift, not the geometric center of the lobe - the lobes on the "30-30" cam are asymmetrical).
Addendum (May 19, 2003)
Lash settings revised 12-14-2005
Optional indexing for Duntov cam revised 09-23-08 (#1, #6 TDC positions will not work for Duntov cam)
This procedure should also be used for the LT-1 cam. The exhaust is “on the ramp” at TDC. The inlet is
not, but just barely. With the Duntov cam this indexing procedure may be used, or both valves may be set
with the cylinder at TDC of the compression stroke. Adjusting eight specified valves at the #1 and #6 TDC
positions as discussed in the 1963 Corvette Shop manual is only valid for hydraulic lifter cams. It will not
yield accurate settings with any mechanical lifter cam because not all the specified valve’s lobes at these
two positions are on the base circle due to mechanical lifter cams’ long constant velocity clearance ramps.
This indexing procedure on page 1 may be used with ANY cam to assure that the lobe is on the base circle,
and MUST be used for cams with very long clearance ramps.
The following inlet/exhaust valve clearances are recommended with the engine cold and not running. The
difference between “hot” (engine idle speed) and cold clearance on a cast iron pushrod engine is negligible,
so clearances can be set cold, which is more convenient. These clearances are computed by multiplying
the height of the clearance ramp (which was determined from analysis of the GM drawings that list lobe data
to five decimal places every cam degree) by the 1.37:1 measured lash point rocker ratio. The computed
number is then rounded down. The factory clearances are derived from multiplying the maximum height of
the ramp above the base circle by 1.5, except the 30-30 cam. The clearances of .025"/.025" listed on the
drawing were derived from this formula, but the rationale of the published .030"/.030" is unknown. It is
speculated that the higher clearance was specified to solve idle stability problems on FI engines as the
larger clearance decreases effective duration slightly, but is definitely tougher on the valvetrain. Idle speed
on 30-30 cam FI engines should be set at whatever RPM is required to achieve stability, and this will
probably be in the range of 1000-1200
When running hard, such as sustained WOT, the exhaust valve head will heat up considerably. About 80
percent of exhaust valve cooling is through the seat, but the stem temperature will also increase, which will
cause the stem to grow and decrease running clearance. This is why exhaust clearance ramps are typically
higher than inlet ramps – to allow for more stem growth and maintain acceptable running clearance to
ensure the valves fully seat. Since the inlet valve is cooled with every fresh intake charge, its temperature
and clearance will remain more consistent over the entire engine operating spectrum.
The rocker arm nut should be tightened until a light drag is felt on the feeler of the same thickness as the
recommended clearance. Then the clearance may be verified by inserting a .001” larger gage, and if it does
not go the clearance is between the two gages, which is just right. Note that the inlet clearance specification
for the 1963 Corvette was tightened to .008” to give a bit more effective duration. This does not need to be
“factored” anymore. We recommend this tighter clearance for all 327s, and it is optional for 283s for a little
more top end power though the effect may not be noticeable. Normal engine service will usually result in
slight loosening of the clearance, and Chevrolet service recommendations from the sixties call out a lash
check every 12,000 miles as part of a normal tuneup.
Duntov cam (283) .010”/.016” (lobe clearance ramp heights: .008"/.012")
Duntov cam (327) .008”/.016” (lobe clearance ramp heights: .008"/.012")
30-30 cam .023”/.023” (lobe clearance ramp heights: .017"/.017")
LT-1 cam .016”/.023” (lobe clearance ramp heights: .012"/.017")
Note: Clearances/clearance ramp heights are listed inlet/exhaust.
Interesting facts: The LT-1 cam exhaust lobe is the same as the 30-30 cam lobe (both sides identical), but
the point of maximum lift is indexed four degrees earlier at 122 deg. BTDC. The LT-1 inlet lobe is the same
at the L-72 cam lobe (both sides identical), but the point of maximum lift is indexed two degrees later at 110
deg. ATDC versus 108 deg. ATDC for the L-72. The LT-1 inlet/L-72 lobe also has greater asymmetry than
the 30-30 lobe. The LT-1 cam was, therefore, not "all new", but incorporated two proven lobe designs with
indexing refinement to broaden torque bandwidth, and the early phased exhaust event compensates for the
small blocks' relatively restrictive exhaust port. The Duntov lobes are symmetrical and identical other than
the exhaust lobe having .004" greater clearance ramp height. At any point on the opening and closing flanks
(the portion of the lobe above the top of the clearance ramp), as measured from the point of maximum lift,
the design exhaust lobe dimension is exactly .00400" greater than the inlet lobe.

kwhizz

05-02-2010, 10:13 PM

Great Info...................

Ken

Chevy454

05-03-2010, 12:20 AM

Mr70

05-03-2010, 08:48 PM

This method has worked very well for me.

69Tom

05-03-2010, 09:25 PM

In addition to this thread, I have a question: on an engine that is driven regularly, getting normal street useage, how often should one adjust one's valve lash? Or is there no way to really say?

Just trying to get an idea how often I'll be wrenching on my L72
It's not that I have any problem with doing so--just want to get an idea as to what to expect.

VintageMusclecar

05-03-2010, 10:14 PM

Once break-in has been completed, you shouldn't have to check the valves any more than maybe once a year, esp. with an OE cam.

69Tom

05-03-2010, 10:52 PM

Excellent. I like the idea of a yearly adjustment. Perhaps I should get one of those too. <<GRAEMLIN_URL>>/burnout.gif

bitfactr

05-04-2010, 12:00 AM

Thanks to everyone who responded.

The engine I'll be adjusting the valves on is an LS6, stock rebuild, using a CompCams regrid of the original LS6 cam. (I have the cam card and can provide the numbers if it would be helpful, but the card is at home.)

If I understand the info given by napa68 about the adjustment for a "30-30" cam, the procedure will also work with my engine. I'm guessing the LS6 cam does not fall in the "30-30" category (please correct me if I'm wrong), and shouldn't require the "30-30" procedure, even though it would work.

I was going to follow EOIC method described by VintageMusclecar. It sounds like it would accomplish the same result (providing the LS6 cam isn't like the "30-30"). It seems a bit more friendly for those less experienced.

Thanks,
Dennis

napa68

05-04-2010, 12:17 AM

Speaking for myself, I like adjusting on a cold engine. I have found the specs they give for a cold engine hits the spec just right for a hot one ( I checked one of mine before and after)
Best of luck.

Tim

69 Post Sedan

05-04-2010, 01:00 AM

The first time I set my valve lash, I do it when the engine is hot. Once it has cooled down, I check them and write it down. My Nova was about .002 difference when it was cold.

bitfactr

05-05-2010, 05:52 AM

Great ideas and advice all around. Thanks.

I was all set the do the adjustment tomorrow morning. I just looked at the specs for my cam. It is a CompCams, Part # 11-671-4, Engine: CB Nostalgia LS-6+, Valve Adjustment: Intake .012, Exhaust .012. Again, the engine was rebuilt to as close to original specs as possible, and this cam was selected as being the closest.

The 70's era manuals I have, while not listing the valve adjustment for the 70' LS6 specifically, lists the other solid cam big blocks (ex. L78 from multiple years, the '71 LS6 from the Vette, etc.) with lash in the range of .024 - .028.

I didn't expect such a drastic difference in the lash on the contemporary CompCams regrid; it seems to be about half of the original. Should I be concerned about this?????

I don't have the specs on the original LS6 cam, so I don't know how different the CompCams regrid is, but I included the rest of the CompCams specs here:
Valve Adjustment: Intake .012, Exhaust .012.
Gross Vale Lift: Intake .544 Exhaust .539
Duration @ .015 Tappet Lift: Intake 276 Exhaust 283
Valve Timing @ .015: Open: Int 29 BTDC Exh 76 BBDC
Valve Timing @ .015: Close: Int 67 ABDC Exh 27 ATDC
Duration @ .050: Intake 239 Exhaust 246
Lobe Lift: Intake .3200 Exhaust .3170
Lobe Separation 112.0
Specs for cam installed @ 108.0 intake center line

Lastly, I read in another thread that it would be a good idea to disconnect the "power" wire from the distrubutor when using a bump-switch from underhood to crank the engine to be absolutely sure the engine doesn't start. Would simply disconnecting the coil wire from the distributor do the trick?

Thanks again,
Dennis

firstgenaddict

05-05-2010, 03:09 PM

I just pull the coil wire.

bitfactr

05-05-2010, 03:19 PM

Thanks for the confirmation on cutting the power firstgenaddict. Just tested my bump-switch and all is well. I'm taking it out now to warm it up.

Chevy454

05-05-2010, 05:37 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bitfactr</div><div class="ubbcode-body">Great ideas and advice all around. Thanks.

I was all set the do the adjustment tomorrow morning. I just looked at the specs for my cam. It is a CompCams, Part # 11-671-4, Engine: CB Nostalgia LS-6+, Valve Adjustment: Intake .012, Exhaust .012. Again, the engine was rebuilt to as close to original specs as possible, <span style="color: #FF0000">and this cam was selected as being the closest.</span>

The 70's era manuals I have, while not listing the valve adjustment for the 70' LS6 specifically, lists the other solid cam big blocks (ex. L78 from multiple years, the '71 LS6 from the Vette, etc.) with lash in the range of .024 - .028.

I didn't expect such a drastic difference in the lash on the contemporary CompCams regrid; it seems to be about half of the original. Should I be concerned about this?????

I don't have the specs on the original LS6 cam, so I don't know how different the CompCams regrid is, but I included the rest of the CompCams specs here:
Valve Adjustment: Intake .012, Exhaust .012.
Gross Vale Lift: Intake .544 Exhaust .539
Duration @ .015 Tappet Lift: Intake 276 Exhaust 283
Valve Timing @ .015: Open: Int 29 BTDC Exh 76 BBDC
Valve Timing @ .015: Close: Int 67 ABDC Exh 27 ATDC
Duration @ .050: Intake 239 Exhaust 246
Lobe Lift: Intake .3200 Exhaust .3170
Lobe Separation 112.0
Specs for cam installed @ 108.0 intake center line

Lastly, I read in another thread that it would be a good idea to disconnect the "power" wire from the distrubutor when using a bump-switch from underhood to crank the engine to be absolutely sure the engine doesn't start. Would simply disconnecting the coil wire from the distributor do the trick?

Thanks again,
Dennis </div></div>
Well, you got some bad info on the cam...the cam you have is a tight lash cam, hence the 12/12 setting, whereas the original was 24/28 like you posted...not only are the cam specs themselves different than the original 143 cam, but the different lash characteristics will change how the engine sees the camshaft as well...I also see that it has a 112 LSA, whereas the original was a 114, which means a tad lumpier idle as well as a bit less vacuum...it's imperitive that you set the lash to the cam card, though, because tight lash cams are a bit more finicky due to their lobe designs.

With that said, your Comp camshaft will still work fine...

SS427

05-05-2010, 06:17 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chevy454</div><div class="ubbcode-body">With that said, your Comp camshaft will still work fine...
</div></div>

When the engine was rebuilt, this was the closest cam to original specs that could be found according to Total Engine in Bloomington, MN. Can't be all bad as in stock configuration other than a bore increase, distributor recurve and carb magic by Eric it produced 475 horse and 483 ft lbs of torque. I called them and asked them about these settings. He suggested warming the engine and checking all the clearances the way they were set currently. Make sure they are all consistant with each other and none were way off which could point to a lobe issue. He also suggested setting them at .012-015 saying that you will increase low end power at .015 but lose some on the top end. I am not sure it really matters on this engine as it is not driven much anyway.

bitfactr

05-05-2010, 06:47 PM

Rob, Rick,
Thanks for the input. No complaints with the cam being different than the original LS6 [I think I can suffer with only 475 hp :)]. I just wanted to be sure that such a different lash setting was correct.

I followed the EOIC method and have the driver side done. Most were in the .012-.013 range, though a few were more loose than that. The adjustment went well and pretty quick and I double checked them. The hardest part was getting the bump-switch connected to the starter when the engine is hot. Taking it back out now to warm it up again for the other side.

Thanks again,
Dennis

Chevy454

05-05-2010, 07:23 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SS427</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chevy454</div><div class="ubbcode-body">With that said, your Comp camshaft will still work fine...
</div></div>

When the engine was rebuilt, this was the closest cam to original specs that could be found according to Total Engine in Bloomington, MN. Can't be all bad as in stock configuration other than a bore increase, distributor recurve and carb magic by Eric it produced 475 horse and 483 ft lbs of torque. I called them and asked them about these settings. He suggested warming the engine and checking all the clearances the way they were set currently. Make sure they are all consistant with each other and none were way off which could point to a lobe issue. He also suggested setting them at .012-015 saying that you will increase low end power at .015 but lose some on the top end. I am not sure it really matters on this engine as it is not driven much anyway.</div></div>

Just curious Rick, headers or exhaust manifolds? Would you mind sharing where it peaked??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bitfactr</div><div class="ubbcode-body">Rob, Rick,
Thanks for the input. No complaints with the cam being different than the original LS6 [I think I can suffer with only 475 hp :)]. I just wanted to be sure that such a different lash setting was correct.

I followed the EOIC method and have the driver side done. Most were in the .012-.013 range, though a few were more loose than that. The adjustment went well and pretty quick and I double checked them. The hardest part was getting the bump-switch connected to the starter when the engine is hot. Taking it back out now to warm it up again for the other side.

Thanks again,
Dennis</div></div>
Cool...I actually snag the wire on the firewall, where it's covered by the wire gutter. I betcha before long you'll be able to do it in your sleep!

bitfactr

05-05-2010, 09:24 PM

All done. The EOIC method that VintageMuscleCar first mentioned worked great and I can't imagine doing this without the bump-switch. The passenger side had more loose ones. I put them all at 0.12. It's quieter and smoother now, yet still has that lump in the idle that Rob mentioned. In fact, it got lumpier and the engine idle dropped about 150. Had to readjust back up to 750. Runs and sounds great. Yes Rick, I actually drove it. Not just up and down the driveway, but actually on the street <<GRAEMLIN_URL>>/smile.gif

Rob, I think it was dyno'ed with headers, but Rick would know for sure. I have the output chart (somewhere). I'll locate it later this evening and post the numbers.

Thanks again everyone.
Dennis

SS427

05-05-2010, 10:33 PM

Rob,
Dennis' motor was run with manifolds not headers. The next LS6 motor they did for me was assembled identically but used headers instead and it was 492 hp if I recall correctly. So far we have built three of these and all were between 475 and 492 hp. The builder still owes me a case of beer as he said this engine would never break 450 hp with manifolds (and I said it would) and he has done it three times now.

Peak horsepower was 475.1 at 6100 rpm and torque was 482.9 at 3700. Average was 462.4 hp, 393.8 trq at 4500 rpm. They made a total of 7 pulls.

For anyone with access to a dyno, it is one of the better things I have done. They set the carb, timing, valves, etc, make an average of 7 pulls after breaking in the engine and carry it live on the internet so guys like Mark Mitchell could watch his engine dyno run live from California. All this for $250!!!! All I have to do is drop it in and run with it.

Dennis..................YOU DID WHAT???????????? Just kidding, they were meant to be driven. Besides, if I know you, you drove it for 1/2 hour and will clean it for 4 hours! <<GRAEMLIN_URL>>/wink.gif

Chevy454

05-05-2010, 10:54 PM

Interesting that there was only a 17hp difference. Also interesting that the hp peak was so high...my LS6 peaked around 5700 I believe, but that was with the Crane blueprint cam...the Comp piece listed above would certainly move the peak higher.

Ditto on the dyno...I see it as cheap insurance.

bitfactr

05-06-2010, 04:41 AM

Thanks for posting the numbers Rick. Saves me searching for them tonight.

Some of the more loose rockers were probably around .015, maybe more. After reading your earlier post, I thought perhaps I should have set them all in the .014-.015 range, since the engine really never gets out of the low end. But the quieter engine, yet better sound, resulting from .012 is nice.

Though driveability felt like it needed a tune-up again, other than just resetting the idle. I'm guessing this isn't uncommon after valve adjustment.

Rob mentioned the tighter lash cam being more finicky. I'm wondering about the margin of error I have in the adjustment. I tried to set it where the .013 would not slide in, .012 would with drag, and .011 easily. So, in theory, my settings should all roughly be between .0115 and .0125.

At would point would a "too tight" adjustment be a problem (i.e. if a valve was set at .010 or tighter, what, if any, damage could occur?)

And, no, I'm not done cleaning it yet <<GRAEMLIN_URL>>/smile.gif

Belair62

05-06-2010, 07:38 AM

This is easier to write down
#1 Cylinder TDC then adjust
Intake - 1,3,4,8 Exhaust - 1,2,5,7

Rotate 360 degrees to TDC #6 cyl firing position and adjust
Intake 2,5,6,7 Exhaust 3,4,6,8

Put valve covers back on. Wash hands. Go for a ride

Mr70

05-06-2010, 03:01 PM

Do we really have to wash our hands?

Chevy454

05-06-2010, 03:53 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bitfactr</div><div class="ubbcode-body">Thanks for posting the numbers Rick. Saves me searching for them tonight.

Some of the more loose rockers were probably around .015, maybe more. After reading your earlier post, I thought perhaps I should have set them all in the .014-.015 range, since the engine really never gets out of the low end. But the quieter engine, yet better sound, resulting from .012 is nice.

Though driveability felt like it needed a tune-up again, other than just resetting the idle. I'm guessing this isn't uncommon after valve adjustment.

Rob mentioned the tighter lash cam being more finicky. I'm wondering about the margin of error I have in the adjustment. I tried to set it where the .013 would not slide in, .012 would with drag, and .011 easily. So, in theory, my settings should all roughly be between .0115 and .0125.

At would point would a "too tight" adjustment be a problem (i.e. if a valve was set at .010 or tighter, what, if any, damage could occur?)

And, no, I'm not done cleaning it yet <<GRAEMLIN_URL>>/smile.gif

</div></div>
Comp could tell you the exact tolerance number for that lobe, but .004" +/- won't hurt a thing. We've played with lash a lot in our Pure Stock class, and although it's a different lobe, we've gone from .020 to .030+, and COPO Pete has deviated more than that on his ZL1...we're stuck with the stock cams, but that's not always the perfect cam, so you have to try and work around it.

69Tom

05-06-2010, 04:44 PM

Guys, what valve lash measuring tool would you recommend?

This has been an interesting thread. Very informative.

Dennis, glad to see you're out exercising the car after all that work!

bitfactr

05-06-2010, 05:17 PM

I bought two sets of feeler gauges; one straight, and a second with a slight angle at the last 3/4". I tried the latter first; they were a pain. The straight set worked better for me.

I did read about "go/no-go" feeler gauges, where the first 1/2" or so is .002 less. I was constantly going back and forth between .011, .012 and .013. The go/no-go set would have been great to have. I'll be ordering a set for next time.

The other thing that consumed time for me was getting the bump-switch hooked up. It's difficult to reach the S terminal on the solenoid on a hot engine without getting burned, which I did. I'm considering some type of temporary, very well insulated, lead I could install while cold.

Thanks Rob for letting me know that I have some room for error without causing damage. I'm wondering now if the minutes I took in hooking up the bump-switch and popping the valve cover, was enough to have the engine start to cool and effect the adjustment. The rockers were still hot to the point I could only touch them for a split second with my finger tips, so I'm not too worried.

bitfactr

05-06-2010, 05:29 PM

Forgot. The multiple valve adjustment procedure that Belair62 mentions is like the procedure described in the '70's era manuals I have. I was going to go with that, as it should certainly work, but when I started to post, the EOIC method seemed a little more goof-proof for a first timer. But thanks for the info.

TDW

05-06-2010, 05:53 PM

The other thing that consumed time for me was getting the bump-switch hooked up. It's difficult to reach the S terminal on the solenoid on a hot engine without getting burned, which I did. I'm considering some type of temporary, very well insulated, lead I could install while cold

I installed a small plastic block on the firewall of my Nova just for that purpose. It is an original GM part, but I don't remember what it was from. Basically, just a block with 2 studs and a mounting ear. I ran a #10 wire from the starter to one stud, the other stud is where I hook one of the leads on the remote button. The other lead on the remote just hooks to the Pos side of the battery. Works great.

Chevy454

05-06-2010, 06:26 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 68Tom</div><div class="ubbcode-body">Guys, what valve lash measuring tool would you recommend?

This has been an interesting thread. Very informative.

Dennis, glad to see you're out exercising the car after all that work! </div></div>
I just use a feeler guage, plus a wrench, and an allen wrench...(I've got poly locks). I've always thought I'd buy a go/no-go guage, but once you get a feel for doing it with the feeler guages (that I already had), you can do it with your eyes closed.

Belair62

05-06-2010, 07:13 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mr70</div><div class="ubbcode-body">Do we really have to wash our hands?</div></div>
No Rick...you can keep yours dirty. But the rest of you really should.

markjohnson

05-06-2010, 11:04 PM

I don't know if you have Roller rockers or not, but just in case you do, it is much more accurate to slide the feeler gauger in from the side to prevent the roller tip from rolling and giving an inaccurate measurement. Something else I've always wondered about is if anybody else here feels that you lose some of solid lifter sound (that "clackity" sound) when you upgrade to aluminum roller rockers. It's always seemed to me that the thick aluminum body of the roller rocker possibly dampens that particular sound. Anybody else ever pick up on this or is it just me?

Belair62

05-07-2010, 12:26 AM

I think it is a bit quieter Mark. I have rollers and I just feel my way thru and don't go in sideways !

05-07-2010, 01:36 AM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: markjohnson</div><div class="ubbcode-body">Something else I've always wondered about is if anybody else here feels that you lose some of solid lifter sound (that "clackity" sound) when you upgrade to aluminum roller rockers. It's always seemed to me that the thick aluminum body of the roller rocker possibly dampens that particular sound. Anybody else ever pick up on this or is it just me? </div></div>

Same deal for me too. But then again, my wife says I'm deaf. <<GRAEMLIN_URL>>/grin.gif

Wayne

Mr70

05-07-2010, 02:46 AM

<span style="font-style: italic">"Something else I've always wondered about is if anybody else here feels that you lose some of solid lifter sound (that "clackity" sound) when you upgrade to aluminum roller rockers."</span>

We argued this exact subject at one of our cruise nights last year.Walt switched to Al.,& when he pulled up,some even thought he switched over to hydraulic.
Definitely a different sound then previous.

Verne_Frantz

05-07-2010, 04:22 AM

I guess I'm just old fashioned, lazy or I just don't want to remember what "sequence" some proven procedure dictates. I just do each cylinder at a time.
I loosen both, then bump it around until the gauge is loose, then I tighten the nut until it's good, then bump it again. If it gets loose again, I tighten it down again. I repeat that until the after the last bump, the feeler gauge won't go in. I know I've covered the base circle that way and the lash isn't too loose or too tight. That's just easier for me then having to remember some IOECOEICOCIC 90deg, 180deg, 360deg ++ -- thing. Once around the block and I'm done and I don't have to remember a thing about "how" I should remember how far to turn it or which valve to run around the car and find or worry about forgetting one.

I do them cold and add .002 to the hot spec. Maybe I should add more on the exhaust then the intake, but that's the way I do it. I really don't think +or- .001" will matter on a fun car.

Verne <<GRAEMLIN_URL>>/smile.gif