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Old 12-14-2008, 07:23 AM
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Valve Lash & Cam Operation - Basic Questions

I have a 454 chevy with iron block and heads. I have a solid roller cam & lifters. Nothing fancy, just performance street stuff. I just installed new 1.7 roller rocker arms and studs.

I set the lash to 0" during the initial setup, then I ran the motor to warm it up before making final lash adjustments per the cam card. When I ran the motor to warm it up - it sounded very nice. It had that great lopey lumpy idle sound, and the valvetrain was very quiet - no noise whatsoever. Very nice.

Once I set lash (about .017"), with the motor warm, now the great lopey lumpy idle sound is nearly gone, and the valvetrain is very noisy. Still runs good though - just sounds like crap.

I understand the requirement for having some lash on a solid lifter cam, but by adding lash, it makes the cam smaller (less lift and less duration) and noiser. My question to you guys is, do I just run it this way then, or did I make some kind of mistake during the adjustments, and have to do it all over again? Is it normal for the valvetrain to make that much noise (sewing machine), and for the "lumpy lopey" idle to nearly disappear by adding lash? Would it be ok to reduce lash to .010" instead of the camcard spec of .017"?

The way I set the lash (easiest method for me with a fully assembled installed engine) was to use a remote starter switch under the hood, crank the engine and watch the intake valve rocker for the cylinder I was adjusting. When the intake valve had just closed I stop the engine, that is when I set lash for that cylinder. Seems to work ok - I think. I went back and checked a few - seems to be good - right around .015" to .019". close enough right?

I'm not cam guru - but I did learn that having lash drastically changes the valve timing and lift specs. Adding even .010" of lash makes the cam duration "noticeably" less, and the valve lift "noticeably less", hence - a smaller cam. How do I quiet my valve train, get back that lumpy lopey idle sound, and provide adequate lash to ensure a fully seated valve at high rpm?

Help...............

Lee

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Old 12-14-2008, 09:49 AM
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Quote:
The way I set the lash (easiest method for me with a fully assembled installed engine) was to use a remote starter switch under the hood, crank the engine and watch the intake valve rocker for the cylinder I was adjusting. When the intake valve had just closed I stop the engine, that is when I set lash for that cylinder. Seems to work ok - I think. I went back and checked a few - seems to be good - right around .015" to .019". close enough right?
Ayuh,...

I might be All wrong here,..
But,.. Your Method seems to be totally Lacking...

Anytime I've adjusted the valves, on Any motor,...
The sequence usually goes something like this,..

Turn the motor to TDC,... Then adjust #1 cylinder,+ whichever other intakes,+ exhaust valves that are determined by the manual I'm using,..
Then the motor is rotated to another TDC, by the timing mark on the crankshaft,..
Then several other intake,+ exhaust valves are adjusted..
This contiues til All the valves are adjusted,+ it depends on Which motor I'm working on...

Just spinning the motor on the starter, til you Think it's in the right spot,..
Just Don't sound Right to Me...
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Old 12-14-2008, 10:33 AM
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Quote:
Originally Posted by bondo
Ayuh,...

I might be All wrong here,..
But,.. Your Method seems to be totally Lacking...

Anytime I've adjusted the valves, on Any motor,...
The sequence usually goes something like this,..

Turn the motor to TDC,... Then adjust #1 cylinder,+ whichever other intakes,+ exhaust valves that are determined by the manual I'm using,..
Then the motor is rotated to another TDC, by the timing mark on the crankshaft,..
Then several other intake,+ exhaust valves are adjusted..
This contiues til All the valves are adjusted,+ it depends on Which motor I'm working on...

Just spinning the motor on the starter, til you Think it's in the right spot,..
Just Don't sound Right to Me...
I understand what you're saying. I went back and pulled the valve cover off after letting it run a bit. I checked lash on a few of the valves - they were all good - around .017" plus/minus .002". My method may not have been textbook, but the end results tell me that the lash is within the cam card spec.

Maybe I'm doing this all wrong. I put the feeler gauge between the roller rocker tip and the valve. I'm getting around .017" which is what it's supposed to be. Could I be doing something else wrong? How many other guys out there running a solid roller cam? Is it normal to have valvetrain noise and not such a lopey idle?

Lee
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Old 12-14-2008, 10:58 AM
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The way I used to do is to rotate the engine until the intake valve just starts to open then adjust the exhaust valve. Then when the exhaust valve starts to open you adjust the intake valve.

Vince
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Old 12-14-2008, 12:32 PM
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Quote:
Originally Posted by 302 Z28
The way I used to do is to rotate the engine until the intake valve just starts to open then adjust the exhaust valve. Then when the exhaust valve starts to open you adjust the intake valve.

Vince
That method is incorrect. LeeJoy was doing it right. Intake closes, set the exhaust ... exhaust opens, set the intake.
This method ensure that the cam lobe you are adjusting is on the back side /base circle.
Yes the motor will have a busy mechanical sound at idle. It has a mechanical cam that has lash in the valvetrain.
The whole concept of the Comp extreme cams is to open and close the valves as quick as possible to maximize torque and throttle response.
The trade off is increased valvetrain noise.
Yes reducing the valve lash tens to make the valvetrain quieter (to a point).
Yes by reducing the valve lash, the engine sees longer effective valve open duration and overlap which make the idle rougher.
Generally speaking you can reduce the valve lash about .008" or open it up by about .004".
The valve lash is naturally tightest when the engine is coldest and opens up when the motor gets hot. (block expansion)
So if you set the lash too tight while hot, once the motor cools you may have no lash or hung open valves when coldest. So don't get carried away.
Yes you can tighten the lash up a bit. Try .012"
Your cam isn't that big (as BBC cams go), thats why its not that lumpy at idle. I remember your motor was at the minimum as to valve to piston clearance with that cam so a larger cam that would be more "lumpy at idle" would require piston notching in your motor.

Many Roller rockers tend to be quite noisey at idle. A friend here has a very simular 454 BBC motor to yours using a Comp Magnum solid street roller simular to your cam and Crane energizer aluminum roller rockers. It is quite busy sounding at idle just as you discribe ("sewing machine").
Some others have said tha the Comp Pro magnum roller rockers tend to be a bit on the noisey/busy sounding side at idle as well.
I've found Scorpion roller rockers to be the quietest roller rockers I've used or heard at idle.
It is possible to create a mechanical cam that is very quite at idle by employing much much tamer/slower valve action on and off seat. At the expense of power and low speed torque. There is no free lunch.

Last edited by F-BIRD'88; 12-14-2008 at 12:55 PM.
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Old 12-14-2008, 12:55 PM
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Quote:
Originally Posted by F-BIRD'88
That method is incorrect. LeeJoy was doing it right. Intake closes, set the exhaust ... exhaust opens, set the intake.
This method ensure that the cam lobe you are adjusting is on the back side /base circle.
Yes the motor will have a busy mechanical sound at idle. It has a mechanical cam that has lash in the valvetrain.
The whole concept of the Comp extreme cams is to open and close the valves as quick as possible to maximize torque and throttle response.
The trade off is increased valvetrain noise.
Yes reducing the valve lash tens to make the valvetrain quieter (to a point).
Yes by reducing the valve lash, the engine sees longer effective valve open duration and overlap which make the idle rougher.
Generally speaking you can reduce the valve lash about .008" or open it up by about .004".
The valve lash is naturally tightest when the engine is coldest and opens up when the motor gets hot. (block expansion)
So if you set the lash too tight while hot, once the motor cools you may have no lash or hung open valves when coldest. So don't get carried away.
Yes you can tighten the lash up a bit. Try .012"
Your cam isn't that big (as BBC cams go), thats why its not that lumpy at idle. I remember your motor was at the minimum as to valve to piston clearance with that cam so a larger cam that would be more "lumpy at idle" would require piston notching in your motor.

Many Roller rockers tend to be quite noisey at idle. A friend here has a very simular 454 BBC motor to yours using a Comp Magnum solid street roller simular to your cam and Crane energizer aluminum roller rockers. It is quite busy sounding at idle just as you discribe ("sewing machine"). I've found Scorpion roller rockers to be the quietest roller rockers I've used or heard at idle.
Hey F-bird:

howz it going buddy? Yes you are correct about my piston to valve clearance being tight (last winter I redid the motor with new cam, etc) I had to set the cam 2 deg off to get more clearance. Anyway, I think I will try reducing lash to about .012" - but only after hearing more feedback from different guys to make sure I'm not going to screw anything up.

Also, you said that when the engine is "cold" that lash with reduce itself and be "tighter", and when "warm", lash would be "looser". Are you sure that's true? I thought it was the opposite of that. I just read something from a mfr's website that says to add .002" lash on a cold engine with iron block and heads. To me that means that when the iron engine is warmed up the lash gets "tighter" not "looser".
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Old 12-14-2008, 01:09 PM
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Quote:
Originally Posted by leejoy
Hey F-bird:

howz it going buddy? Yes you are correct about my piston to valve clearance being tight (last winter I redid the motor with new cam, etc) I had to set the cam 2 deg off to get more clearance. Anyway, I think I will try reducing lash to about .012" - but only after hearing more feedback from different guys to make sure I'm not going to screw anything up.

Also, you said that when the engine is "cold" that lash with reduce itself and be "tighter", and when "warm", lash would be "looser". Are you sure that's true? I thought it was the opposite of that. I just read something from a mfr's website that says to add .002" lash on a cold engine with iron block and heads. To me that means that when the iron engine is warmed up the lash gets "tighter" not "looser".
No you won;t screw it up. And when they say add, they are refering to taking a little lash out. Tighter when cold setting the valve lash. BBC's and most other V8's tend to open up the valve lash as the motor becomes hotter. As long as you stay within my/Comp Cams guide lines for varying the valve lash from the cam card specs, you're fine. .008" tighter to .004" looser valve lash from cam card is an effective "tuning method" used with mechanical cams to dial in the best effective running valve timing. Too loose, pounds the valve train, to tight causes a loss of cylinder compression when the block is coldest. Like in the winter.
Try it for yourself. Set one valve to say .020" with the motor hot hot hot.
Then let it cool right off stone cold. (next day) and check the "cold valve lash" on that cylinder. You'll see.
Setting valve lash (developing a "feel for it") is much like playing a musical instrument. Practice makes perfect.
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Old 12-14-2008, 05:13 PM
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And if you set em hot and reacheck em cold you'll know what the expansion limits are and you can set em cold next time and stop burning your self.
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