lifter noise ? - Team Camaro Tech
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post #1 of 10 (permalink) Old Sep 28th, 02, 02:46 PM Thread Starter
 
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I'm a new 69 z owner I having problem with lifter noise I think , but it could be exhaust leak . I adjusted lifters per crane cams tech site . One side of motor is making noise ? sounds like coming from valve cover but could it be exhaust leak I have stock exhaust manifolds is the a way to tell if leaking? I see there is another way to adjust valves so many at tdc then it says turn motor 180 adjust some more how do you tell when you turn 180 ? sorry for all the dumb questions but I need some help from all you real mechanics out there>>
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post #2 of 10 (permalink) Old Sep 28th, 02, 03:14 PM
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If you adjusted them as per the Crane site you used the exhaust opening, intake closing method. Don't re-do that with the tdc/ do half the valves, etc method as it isn't even in the same ballpark as far as accuracy.

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post #3 of 10 (permalink) Old Sep 28th, 02, 03:15 PM
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You can isolate a noise by holding one end of a piece of hose to your ear and the other end at the suspected leak area.

Wrap your balancer with masking tape and mark the timing mark. Then carefully remove the tape and graduate it into 90 geg sections. Then replace it on the balancer and transfer the marks using a fine point permanant marker.

Use the "Exhaust open - Intake close" method to set your valve lash. When the intake valve starts to close, adjust the exhaust valve. When the exhaust valve starts to open, adjust the intake valve. It's a little more time consuming, but much more accurate.

Hope this helps a little.
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post #4 of 10 (permalink) Old Sep 28th, 02, 04:57 PM
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More to the point here, If you are using a stock 69 Z/28 solid lifter cam you need a special lashing method (the valve closing method posted above will also work) and a different lash spec than was published in the manual. I sing this song many times but very few people seem to use the correct method. The lifters will not be on the base circle at TDC for this particular cam, they will be .006 above the base circle on the clearance ramps at TDC so setting the lash at that point is incorrect. If you want the instructions and the revised lash spec with the long explanation as to why you need to set them this way, let me know and I will post it. I always set them this way and you would honestly find it difficult to hear the lifters with the engine running.

My other 302 and Corvette buddies running that "30-30" cam all testify how much better the engine sounds using this method and revised spec of .026"-.026" cold static with stock style stamped steel rockers.

-Mark.
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post #5 of 10 (permalink) Old Sep 28th, 02, 05:13 PM Thread Starter
 
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Hey Mark,

I'm interested in your valve adjustment method please post. Dave
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post #6 of 10 (permalink) Old Sep 29th, 02, 03:34 AM
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Here is the reasoning behind the revised lash spec.

The lash specs are designed to match the cam and the rocker arm ratio. The solid lifter cam lobe has a gentile clearance ramp area at the base of the lobe and a much faster lifting ramp for the portion where the valve is off its seat. Basicaly the clearance ramp is where the valve train takes up the slack as the valve lash is closing up when the lifter starts moving. The clearance ramp on the "30-30" cam is exactly .020" high on the base of the lobe. The lifter will be lifted .020" slowly until the lash is taken up and from that point on it is moving much faster up and then down until it gets down near the seat. Just before it gets down to the seat, the ramp speed will slow down in order to set the valve down on the seat gently rather than at full lift ramp velocity. This is done to avoid valve bounce, recession, and noise.

We typicaly measure the valve lash specification in the area between the rocker arm tip and the valve stem with the lifter resting on the cam's base circle. The clearance at that point is the lash spec. Since we are measuring it at the rocker arm, the clearance at the cam is mutltiplied by the rocker arm ratio. The design specs of the factory rocker arm are 1.5:1 ratio so a clearance of .020" at the lifter side of the valve train is .030" at the valve side (.020" x 1.5 ratio = .030") so far, so good! So what we are saying is we want to have the valve lash set so that all the clearance is taken up at the exact point on the cam lobe where the transition from slow to quick ramp speed occurs. It can be a few thousanths tighter and still be on the slow portion of the clearance ramp but if it is too "loose", the clearance will not be taken up while the lifter is still on the clearance ramp and the cam will be noisy, the valves will receed, the valves will also likely bounce on the seats at very high RPM as they are being slammed down at lift ramp velocity.

The problem comes from the actual measured rocker arm ratio of the factory style stamped steel rockers. The design spec is 1.5:1 ratio but the actual measurement is closer to 1.37 instead of 1.5 so the lash spec must be changed if you use stock style rockers. Now, if you are using the stock rockers, the best spec is determined by mutiplying the lift ramp height (.020") by the "actual" rocker arm ratio (1.37) and you get .020" x 1.37 = .0274" which is the MAX lash spec you would want. Set the valve lash at .026"/.026" COLD.

WARNING! You CANNOT, repeat, CANNOT accurately adjust EITHER the inlet or exhaust valves of the 30-30 at TDC because BOTH the inlet and exhaust are on the ramps. If you adjust at TDC your actual running clearance will be about .032" to .033", but the MOST you want is .027". Adjust the inlets at 90 degrees ATC and the exhaust at 90 degrees BTC. Lay this out on paper and you will see that you can adjust two valves at every TDC point as follows:

TDC#1 8E, 2I

90 4E, 1I

180 3E, 8I

270 6E, 4I

0 5E, 3I

90 7E, 6I

180 2E, 5I

270 1E 7I

Start at TDC #1 and adjust 8I and 2E, then rotate 90 degree and continue with the valves as indicated. Set them at .026"/026" cold with the engine not running. You can also use this method for the LT-1 cam, but you can adjust the inlet at TDC if you like because of the LT-1 cam's shorter inlet duration and clearance ramps. Recommend .021"/.027" cold clearance with the LT-1 cam to adjust for the actual 1.37 ratio at the end/beginning of the clearance ramp. Mark your balancer at the ninety degree points with tape. Do it as accurately as you can, but if you're within ten degrees, it's okay.

To visualize the reasoning helps. The adjustment follows the firing order 1-8-4-3-6-5-7-2. The idea here is for you to get the engine on a firing position TDC for a cylinder, lets say #4 for example, and then figure out that the cylinder that was previous in the firing order(#8) will no way be on it's intake ramp and the cylinder that is next in the firing order(#3) is no way going to have it's exhaust valve on ramp. This is how I can easily remember which rocker to adjust without writing it down. Once you get the concept(takes a while) you might not need the sheet of paper anymore.

Feel free to ask questions if you need clarification.

-Mark.
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post #7 of 10 (permalink) Old Sep 29th, 02, 02:30 PM Thread Starter
 
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Mark,

How do you tell when 90 & 180 degrees, I know tdc is straight up on timing mark , how do you tell where 90 & 180 etc.. is at ? Dave
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post #8 of 10 (permalink) Old Sep 29th, 02, 05:35 PM
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You can do it with a pre-made stick on timing tape or a piece of string or a cloth measuring tape or a metal tape measure.

The 90 degree points are at half way around from the timing mark, and then on either side, half way between the timing mark and the opposite mark you just made.

Buy a timing tape from the speed shop that fits the diameter of your damper (either 8" dia or the smaller one which is about 6-3/4" or so, I forget right now) and wrap it on the balancer long enough to be able to make some marks on the balancer with a sharpie as the tape will fly off when you fire up the engine Make marks at 90*, 180*, 270* and another mark at the 36 degree mark that you can use for setting your total timing (not for setting valves). I like to make a line that extends on to the front face of the damper with the numerals on either side of the line so you do not get them confused later.

Piece of string works in a pinch as long as it is not the type that can strech. Just wrap it around till it overlaps and mark the point of overlap with a sharpie. Hold the marked ends torether and the very bottom of the loop is 180* and if you fold it again, the bottom of the 2 loops are the 90* and 270*. Acurate enough for this purpose. The pre-made timing tape is probably more accurate.

One of these days I am going to write up a procedure to make your own timing tape using cloth medical tape, a couple of drafting squares and a ruler. That one is very accurate and works for any size balancer on any engine. Probably would need a few pictures to go along with it. One of these days. Only so much time...

-Mark.
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post #9 of 10 (permalink) Old Sep 30th, 02, 01:04 AM
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Mark,

Very good explanation on ramps, GM wanted to save the valvetrain as much as they could, hence, the lash ramps.

Our fellow Mopar dealerships, in their Direct Connection catalog, sell a 3X5 decal of the valve adjustment. Can be applied to under the hood, or your toolbox and apply lamination over it.

I find, as suggested, a Sharpie mark in the appropriate places on the balancer is good enough for adjusting the valves. In fact, it takes less time to adjust all 16 than using the EO-IC method.

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post #10 of 10 (permalink) Old Sep 30th, 02, 06:36 AM
 
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Excellent info, I just printed it so I can keep a copy handy. Thanks for sharing it with us.

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