Valve Lash Adjustment: running or not?

[bitfactr]

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]

I just pull the coil wire.

[bitfactr]

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]

<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 &quot;power&quot; 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]

<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]

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]

<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]

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 [img]<<GRAEMLIN_URL>>/smile.gif[/img]

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]

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! [img]<<GRAEMLIN_URL>>/wink.gif[/img]

[Chevy454]

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.