I recently installed roller tips on my 71LT-1. Following the instructions from the chassis manual, I rotated the engine manually and adjusted the intakes and exhuast in sequence using a feeler gauge (.024" intake, .030" exhaust). Now, it is my understanding that I need to normalize the engine temperature and re-adjust the valves again as the clearances change due to thermal expansion. My question is this; while the engine is running do I simply place the feeler gauge between the rocker and spring and adjust so that the feeler gauge just fits or is the adjustment similar to hydraulics where the rocker is adjusted down to zero lash (no rattle)?? Any comments would be appreciated.

 

Do it as you did for the initial setup, but this time while the engine is hot. As much as I love the "engine running" method for hydraulic lifters, the solids must be adjusted with the engine off.

 

Check with the manufacrurer of the rockers. They should recommend adjusting the clearances either hot or cold. I wouldn't think you would need to do it twice.

But then agin I've never adjusted roller rockers!

 

iron heads and iron blocks the setting will change little or not at all. alum heads and iron block clearance will grow about .004,and alum heads and alum block clearance will grow .010 when hot. also any rocker arm that used a poly lock system should be adjusted .002/.003 loose,tighten the lock nut and then tighten down the rest of the way by just turning the adjustment nut. this will lock the poly lock tight. the top of the studs should also be machined flat if you are using stock chevy studs. :chevy


[Modified by clem zahrobsky, 12:21 PM 3/20/2002]

 

tsw71, why must the solids be adjusted with the motor off??

 

Solids are supposed to be adjusted hot. With mine I get the engine up to running temp and then take off the valve cover on one side, with the engine off, do the valves one the one side then put the valve cover back on, get it back up to temp and do the other side.

You can do them with the engine running but it makes a mess.

Do a search and you will see some good info on this subject fro the not too distant past.

 

If I do it with a hot engine (not running) this means that I must find TDC (#1 firing position) again and rotate manually to adjust the valves in proper sequence. Seems like a lot more work than is required?

 

I called Comp Cam and asked about adjusting the valves cold and they told me that the setting given on tha cam card was only a ball park figure. If I wanted to change it a little it wouldn't matter. I could tighten up the lash or loosen it if I wanted. I always adjust my valves cold to keep from burning myself and adjust them to card specs and let the hot setting fall where it wants. I would never adjust them twice.
As for turning the motor over in the firing order you can do it by setting TDC, then BDC then TDC and finally BDC. Only 4 half turns adjust certain valves along the way.

 

With Hydraulics, you have a much larger margin for error. While it is possible to do the same with solids, it lacks the precision that you need to get them right. Keep in mind that you can tune a solid cam for performance by adjusting the lash tighter or looser for top end or low end power, and even then you're only talking about an adjustment of maybe .006" in either direction at the most. Much more than that could begin to have a damaging effect on the valvetrain. I have the roller tip rockers on both of my solid cam cars and can say that getting the correct lash is already a problem since the roller makes getting the proper feel a bit difficult sometimes. Doing this with the engine running would only make it harder and less likely give you precise results.

 

Check out this site for info. to all your questions :
http://www.centuryperformance.com/valveadjustment.htm

For mech. lifters, the engine 'must' be off to insure correct lash adj. Why ? - because the lash varies while the engine runs (i.e. valve-in vs. valve-out)

Good luck ! - sounds like a "sweet" engine :cool: :D

 

mulchie - I have a mech. cam and 1.6 comp cams roller tips. What told you to set them at .024/.030? It's way to wide and it will beat the heck out of your stem tips and rollers. The old 30-30 cams are junk from the past.

IMO - Once you start setting them for the 10th time you will find that cold or hot the values change very little. So I get my motor up to temp and let it cool till it warm to the touch. I'm not going to burn my self or drip oil on hot headers to set the valves. I would just pick a number like .020 feeler gauge. That gives plenty of lash margin and it eliminates the loud bashing you going to have with .030 You don't have to be right on in crank shaft degrees. I bump mine with the starter and it never stops right on. So 10-20 degrees either way doesn't make any difference.

Your low side of the cam is big in number of degrees. So your concern is just adjusting the rockers at the loosest point. You never have to be right on. Which is 20 Degrees + or - on the crank. The best thing to do is invest in Allen Locking nuts and if your need to a stud girdle and then valve adjusment is more of a check because they rarely move.

Big lash numbers like .024-.030 actually make a hot cam less radical at the sacrfice of beating your valve train to death. Low lash numbers like .012 - .018 increase duration and lift of a mechanical cam. My Crane cam card called for something like .014 and .018. It mellowed out and ran better at 20-22.

Guy that have been around solid cams for years don't worry about exactness. My .022 measurement might be measured by another person as + or _ .002 compared to me. Its how much drag you consider right when pulling out the feeler gauge. The real reason that it can't be done on a running motor is: If I place a feeler gauge in place how would you ever be able to determine if your not actually starting to lift the valve off of the seat with everything in motion? If you tighten down the nut and you have a hard time pulling the feeler gauge out your actually starting to compress the valve spring.

 

I am going through this now. Adjust with engine hot and off. Do the rotation method it works well and does not make a mess like running the engine will.
I have adjusted mine 3 times since my install of the cam. The last time the settings stayed fairly close to true (1000 miles).
And I too have a 71 LT-1 now with a 282S cam.

 

Here's something that you can do... And it's actually not that difficult and takes in the hot/cold setting issue.

1. Get the engine running up to temp.

2. Shut engine down, and set the lash on both the int/exh of one cylinder according to specs on cam card.

3. After the engine is cold, using feeler gauge get the new valve lash settings of the cylinder you had set in step 2. This will show any variance between hot/cold setting.

4. Set the remaining int/exh using the new measurement in step 3.

Presto - alot easier then trying to set them all hot.


[Modified by 70PurpleLS7, 1:39 PM 3/20/2002]

 

I know have some issues on finding TDC. My manual says to find TDC in #1 firing position. Furthermore the chassis manual goes on to state that finding TDC in #1 can be determined by manually rotating the engine. If the #1 valves don't move when approaching TDC then you are in the #1 firing position. Is there a sure fire way to determine TDC in #1 firing position? Where will the distributor rotor be pointing; to #1 or #6. Thanks

 

The distributor rotor should point to the #1 position. You can also tell without even removing the distributor cap by watching the #1 rockers. As the number #1 intake valve closes, watch the timing mark on the balancer. It will coming back around to TDC soon after the intake valve closes.

 

Thanks. I originally adjusted them starting from TDC #6 (oops). After TDC in #1 I will be looking for the #1 exhaust valve to begin opening as I rotate the engine again.

 

that's correct.


Tom :cheers: