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Old 11-13-2007, 04:41 PM
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Correct way to set valves on sbc w/ solid flat tappit camshaft?

Any good links? my engine guy is out of town and I gott ado the deed, lol...

thanks

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Old 11-13-2007, 05:06 PM
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Correct way to set valves on sbc w/ solid flat tappit camshaft?

This is from Crane Cams

Mechanical Lifters

All pushrod engines using mechanical (solid) lifters, or mechanical roller lifters, must have an adjustable valve train so that precise adjustment for "Valve Lash" can be made to match the camshaft's requirements. Valve lash is the running clearance that exists between the tip of the valve stem and the valves mating surface of the rocker arm. (It is expressed in the Crane Catalog as "Valve Lash" and on the camshaft specification card as "Valve Setting". Both terms mean the same thing.)

The amount of valve lash can vary between camshaft profile designs, being as small as .010" on some and as great as .035" on others. It is important to use the recommended valve lash when you first test the performance of the engine. You must also be concerned with thermal expansion of the engine components. (This is especially true if using aluminum alloy cylinder heads, or block.)

For this reason, Crane requires that the valve lash be set with the engine "Hot" on all pushrod engines using mechanical lifters. This will insure that the minimum required clearance (valve lash) is maintained throughout the engine's operating temperature range.

Compensating for a Cold Engine when Adjusting Valve Lash

When installing a new cam, the engine will be cold but the lash specifications are for a hot engine. What are you to do? There is a correction factor that can be used to get close. We mentioned that the alloy of the engine parts can be affected by thermal expansion in different ways, therefore the amount of correction factor to the lash setting depends on whether the cylinder heads and block are made out of cast iron or aluminum.

You can take the "hot" setting given to you in the catalog or cam specification card and alter it by the following amount to get a "cold" lash setting.

With iron block and iron heads, add .002"
With iron block and aluminum heads, subtract .006".
With both aluminum block and heads, subtract .012".
Remember this correction adjustment is approximate and is only meant to get you close for the initial start up of the engine. After the engine is warmed up to its proper operating temperature range, you must go back and reset all the valves to the proper "hot" valve lash settings.

Setting Valve Lash on Mechanical Cams

All the valves must be set individually and only when the lifter is properly located on the base circle of the lobe. At this position the valve is closed and there is no lift taking place. How will you know when the valve you are adjusting is in the proper position with the lifter on the base circle of the cam? This can be accomplished by watching the movement of the valves.

1. When the engine is hot (at operating temperature) remove the valve covers and pick the cylinder that you are going to adjust.

2. Hand turn the engine in its normal direction of rotation while watching the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake valve. (Why? Because when the exhaust is just beginning to open, the intake lifter will be on the base circle of the lobe, so the intake is the one we can now adjust.)

3. Use a feeler gauge, set to the correct valve lash, and place it between the tip of the valve stem and rocker arm. Adjust until you arrive at the proper setting and lock the adjuster in place.

4. After the intake valve has been adjusted, continue to rotate the engine, watching that same intake valve. The intake valve will go to full lift and then begin to close. When the intake is almost closed, stop and adjust the exhaust valve on that particular cylinder. (Again, when we see the intake valve almost closed, we are sure that the exhaust lifter is on the base circle of the lobe.) Use the feeler gauge and follow the procedure described before in step 3.

5. Both valves on this cylinder are now adjusted, so move to your next cylinder and follow the same procedure again. In the future you may find shortcuts to this method, but it still remains the best way to do the job correctly.

Using Valve Lash to Help Tune the Engine

The engine only responds to the actual movement of the valves. Since the valve cannot move until all the running clearance (valve lash) has been taken up, the amount of valve lash you use affects the engine's performance. For example, if you decrease the amount of (hot) valve lash, the valve will open slightly sooner, lift higher, and close later. This makes the camshaft look bigger to the engine, because of a slight increase of actual running duration and lift. If you increase the amount of (hot) lash the opposite occurs. The valve will open later, lift less, and close sooner.

This shows the engine a smaller cam with slightly less actual running duration and lift. You can use this method on a trial basis to see what the engine responds to and keep the setting that works the best. Just remember, the more lash you run, the noisier the valve train will be. If the clearance is excessive it can be harsh on the other valve train components. Therefore, for prolonged running of the engine we do not recommend increasing the amount of hot lash by more than +.004" from the recommended setting. Nor do we recommend decreasing the hot lash by more than -.008".

Warning:

"Tight Lash" camshafts cannot deviate from the recommended hot lash setting by more than +.002" increase, or -.004" decrease. "Tight Lash" cams are those which have recommended valve settings of only .010", .012", or .014" on the specification card. These lobe designs have very short clearance ramps and cannot tolerate any increase in the recommended valve lash. The extra clearance can cause severe damage to valve train components.
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Old 11-13-2007, 08:56 PM
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I bring both valves closed and set it that way is that ok?
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Old 11-13-2007, 09:26 PM
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Quote:
Originally Posted by Joshua Lee
I bring both valves closed and set it that way is that ok?

On camshafts with near stock duration numbers you can set them with the motor at tdc on the compression stroke of each cylinder. On engines with performance cams you need to use the method that Guy posted. The only thing I do different is that following the firing order I'll do all the exhausts and then all the intakes. I find you turn the engine over less times.
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Old 11-14-2007, 08:05 AM
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My question is this....(just got my first solid roller engine).....how do you know when to stop turning the adjusting nut...in other words how hard should you have to pull to get the feeler gauge out from between the valve and rocker arm? The reason I'm asking is because mine were set by the builder, however since winter is coming up and the mud bog season is over he wants me to back off all of the rocker arms so the springs don't sit for an extended period of time in the open position and I'll have to re-set them this spring.
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Old 11-14-2007, 02:08 PM
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Everybody's touch with feeler gages is a little different. Before you back off the rockers take your feeler gages and see what you currently have to gage what your builder uses. Also you only need to back off the ones that are in their cycle, you'll find that there's only a half dozen or so of them. The rest can stay where they are so long as you don't turn the motor over.
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Old 11-14-2007, 02:18 PM
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How hard should the pull be on the feeler gauge? I could think of a thousand funny ways to answer that, but I won't, try this, like running a brush through your hair! Some resistance.

Why not just give each plug hole a shot of trans fluid and one or two down the carb bores and call it a day. Are you worried about moisture or valve spring tension? To close the valve if going to take about 3 or 4 turns on a wrench.
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Old 11-14-2007, 02:22 PM
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they are 944 comp springs with 600+ pounds of open pressure...it weakens the springs to have them sit open for any period of time.......... dont' want to drop a valve next spring...............
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Old 11-14-2007, 02:29 PM
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If you have to adjust them again in the Springtime, then just back them off untill the pushrods are quite loose. That will tell you that there is no tension on the valve spring.

The more information that you supply the better answer you get. I would still give them a splash of trans fluid so the valves don't stick. (you probably have aluminum heads on that thing too!)
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Old 11-14-2007, 04:26 PM
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The spring won't be affected over the winter, leave the roller adjustment alone.

When the lash is adjusted correctly the correct feeler gauge will be difficult to insert between the rocker and valve tip and difficult to pull out. It will take a bit of a tug. No other way to explain it. The absolute MOST important factor is adjusting the valvetrain HOT. Hot as in it's at full operating temp. What we will do is lash all the valves hot, let the engine cool and the next day check the valves cold. We note the lash when cold, it will be tighter, and then from that point on check and adjust the lash with the engine cold and to the cold lash specs. Much easier in the long run. The first hot lash setting though will likely require you to reinstall the valvecovers at least half way through if you are not experienced with the process. If you don't get them all hot lashed within 15 minutes I'd refire and heat up the motor.

Much better to be on the slightly tight side of the lash setting than loose. Running a brush through your hair is WAY too loose.
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Old 11-14-2007, 06:48 PM
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Thats the way mine are... Like you almost have to big a feeler gauge.. Then when hot they "roll" in and out...

GOOD POST!
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Old 11-14-2007, 07:39 PM
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Joshua, if the feeler gauge rolls easily in and out when hot, they are too loose.
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Old 11-14-2007, 08:16 PM
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Im dumb... other way around, lol
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Old 11-28-2007, 02:03 PM
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Im gona try this again tonight, lol... Last time I messed with the valves I bent one the next day (I dont think it had anything to do with my settings, but still) lol....
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Old 11-28-2007, 02:34 PM
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With roller rockers I slide the feeler side ways so that you don't get a rolling effect as the roller will actually let you have the lash to tight and the gauge will still roll in.Pulling the gauge across the stem eliminates this tendencey.Also both valves may be adjusted at TDC compression for each cylinder as both valves will be on the base circle of the cam at this time.A method I have used often is start at TDC #1 set them,rotate crank 90 degrees, go to the next cylinder in the firing order set it. And continue thru the firing order this way till all are set.
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