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Running Valves on Solid Lifter Cam
I just ran my valves last night on my 427 T/O. I am running a solid lifter cam and roller rockers. Engine was cold but I always check my valves before I adjust them. Last night my clearances were more like .017 rather than the .020 I thought I had set them at before.
The last time ran my valves I apparently set my valves a little closer than I had thought, because each valve was set at almost the same clearance .017-.019. If I had set my valves hot last time (and I think I did) shouldn't my clearance be off the other way (.021-.023) cold? Clois Cam specs are 607 lift and 248 dur with 106 lobe centers and recommended gap is .020 |
Clois,
I think it depends on many factors including aluminum or cast heads, aluminum or cast block, as well as what rocker arms you're using. I'm running a cast block with aluminum heads and Erson rockers. I've found that I can set mine at .010 cold and that corresponds nicely to .020 hot. I have a nice little "interview article" that was conducted with, if I remember correctly, Doug from Precision Pumps and a couple of other guys. It makes a couple of general recommendations of cold lash vs hot lash based on the above considerations. I'll find it when I get home tonight and either post a link or retype the pertinent info. Chris |
Thanks Chris,
Sounds like you and are are probably running the same heads and Sig Erson roller rockers. |
Clois,
Here's a link to the interview I mentioned: http://bellsouthpwp.net/b/s/bsprowl/...erArmFAQs.html Not as much detail as I thought but it's still pretty helpful. Chris |
Thanks Chris,
I had actually printed that article some time ago. Just needed my memory jolted a little. Clois |
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 is 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. Iron Block Iron Heads Add .002" Iron Block Aluminum Heads Subtract .006" Aluminum Block Aluminum 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. Crane Cams |
Thanks Jeff,
I can confirm that with my alum Edelbrock heads/iron block my valves were in fact off between .005 and .008 due to the cold vs hot settings. Clois |
The thing I worry about while adjusting valves hot is the 'cooling factor'. And first of all, what IS 'hot'? Engine water temp doesn't mean the heads, block and valve train components are at full operating temperature. Oil temp is a much better guide to determine when your engine is 'hot enough'. Then as you move through the adjustment procedure are the last valves cooling down and changing their clearance as you adjust the first ones?
I don't know, I prefer the 'cold lash' setting myself. |
Excaliber,
I agree with your concerns. If you do all 16 valves at once, the engine will have cooled a lot by the time you get to the last valve. I suggest taking your best guess at the cold lash setting. Set all 16 valves cold. Then take the car out for a good long run allowing water and oil temps to come up to normal. Get it back into the garage and as quickly as possible recheck the lash on just a couple of valves. This should tell you the difference between your hot lash and your cold lash. Let the car sit and cool overnight and then the the next day you can reset all the valves to the newly calculated cold lash. Of course you would want to always set your cold lash when your engine is at roughly the same temperature. That is, if you use the above method to find the proper cold lash on a 50 degree day, your results would be different than if you did it on a 90 degree day. Chris |
From experience my valves are at .009 cold on an iron block/aluminum head package. That gives me .018 hot. A buddy with an aluminum block sets cold at zero to hit .016
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When setting the valves on eny engine I like to use the same process. I set the intake valves when the exhaust valve on that cylinder starts to open. I set the exhaust when the intake on that cylinder starts to close. This will always make sure that you are on the base circle of the camshaft. I have found that on most aluminum head cast iron blocks that you need to subtract .003 to .004 when setting the valves cold. On aluminum heads and blocks I have found that you need to set the valves about .010 to .012 tight. This will vary a little with the head thickness, valve length and block height. On cast iron heads and blocks I will set the valves about .002 loose. These specs have always worked well for me. good luck, Keith Craft
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KC, I always worry about valve overlap and that MAYBE I won't be on the exact base circle. But hey, I'm just paranoid. :D
I use the distributor rotor and harmonic balancer method myself. Setting both valves on one cylinder at time and turning the engine over with a 'breaker bar' and socket. Following the firing order from number one... |
Response to Excalibur: Valve lash
Quote:
When we set lash at the strip we do it hot with the engine running. That way we get a more consistent and accurate setting. We don't have to worry whether or not we have it TDC. |
Setting those valves with engine running. I've done it, HATE it! Oil splash all over the place, to much for me, but clearly the BEST way to really dial in the lash.
I recall setting a Chevy engine that way (ONCE :D ) and the darn rockers were shooting oil well over the fenders! What a mess that was. :LOL: |
Reply on setting valve lash
Excalibur, you're right about the oil. It can get a little messy, especially if you don't protect the fender wells and fenders. I admit its not one of the most pleasant things to look forward to but it can have big payoffs. I guess sometimes you just have to get dirty. I guess thats why a lot of 'em don't use solids anymore.
Take care, Bob:) |
After many years of adjusting valves--on everything from farm tractors to top fuelers--the most accurate setting is atained with the engine NOT RUNNING, and set at what ever temperature that you use
On the top fueler, funny car(Keeling&Clayton California Charger) and pro-stockers, we had a cold setting for assembling the engine and we final adjusted after warm-up-- Anyone should be able to run the valves on a V-8 OHV engine in less than 5 minutes--------if anything has moved significantly you have a problem and the valve adjusting exercise turns into a bigger job. Jerry |
Sideoiler,
Worrying about the ambient temperature will not be a concern if you're finding only a .002 difference between your hot lash and your cold lash settings. Depending upon your head, valve, block, rocker arm combination, the difference between hot and cold lash can be significantly higher. Some people may find a difference of up to .025 or so. In those instances, a difference of 40 degrees in your "cold temperature" can be significant. Here's just one example of someone encountering a difference of more than .018. http://www.network54.com/Forum/74182/thread/1146187108/ Chris |
I have been using the method described by Keith for several years now. That is, adjust the intake valve when the exhaust is just beginning to open and adjust the exhaust valve as the intake is just totally closed. This way you are sure that the cam is at it lowest point. Trying to adjust both valves on the same cylinder at the same time, at/close to TDC, can yield bad results if you off TDC by a little bit.
Wayne |
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