Valve Lash Adjustment

[spd4me]

I reciently adjusted my valve and wanted to see if I did it right. I've got solid lifters with Ford Mortorsport roller rockers (real pretty blue). First I warmed up engine, removed coil wire and valve covers. Bumped motor over until rocker arm was totally unloaded. Here's where I need input. I loosened the big nut first, then the inside alan wrench screw. Put the feeler gauge in and turned the big nut until gauge was tight. Then tighten inside alan screw. After that, I tightened big nut. When I tighten the big nut, it changes the gap so if I want a .25 gap, I would set the first gapping to .35 and when I did the final tightening of the big nut it would allow the .25 gauge to slip between. My question is do you make the final tightening with the big nut or the inside alan screw? I also learned that the proper lash setting can really make a difference in how smooth the engine idles.

[Brent]

This could take a while. [8D]

Do one cylinder at a time. When the intake valve starts to open you adjust the exhaust valve. When the exhaust valve starts to close you adjust the intake valve.

The allen is the locking part of the assy and the large nut is for adjustment in most cases, however, on my FE the allen is the adjuster and the jam nut is the locking assy.One of the two will lower the rocker and the other will not.
Slide the gauge in and out as you tighten the nut. When you feel the gauge get tight then tighten the lock screw as you hold the adjustment nut. With both tight check the adjustment again. You can tighten the adjustment nut a little more if you need a slight adjustment.

You can not just bump the motor until the rocker seems loose you need to do it at a specific spot on the lobe of the cam. It will be alot easier on you and on the starter if you remove the spark plugs as well. [^]

Have fun.

Brent

[excelguru]

Do yours look like this...

http://a2.cpimg.com/image/9A/B2/31884442-a5fb-02000183-.jpg

If so, the nut on the outside is the locking mechanism. The allen screw is the gap adjustment.

1. Follow Brent's instructions for "unloading" a particular rocker.
2. Check the lash to determine what the gap currently is.
3. Remove the feelers and lay them to the side.
4. Loosen the outer nut.
5. Tighten or loosen the allen screw as desired (small amounts at a time).

!!Don't waste time checking the gap at this time!!

6. Hold the allen screw still as best as possible while tightening the outer nut.
7. THEN check the gap again.
8. Return to step 3 and repeat as needed until you get the gap you want.
9. Go to the next valve and start all over.

This takes a while. It is important to understand that the mere act of tightening the outer nut will almost always change the final gap. So it's best to tighten it, then check (what Brent said). Like I said, this whole procedure takes a while. It can, however, make a remarkable difference in power.

Keith :)
Unique Motorcars (http://www.uniquecobrareplicas.com)
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[spd4me]

Keith: Mine looks like yours. I think what Brent said is right. The outer nut is what adjust the lash and the alan screw tightens it after the adjustment. I saw a TV show Horsepower TV and the guy had one of those special adjustment tools. He appeared to loosen the alan screw, turned the wrench which in turn turned the outer nut and then tightened the alan screw when finished.

[eliminator]

Do one bank at a time, another words do the right side while hot, replace the valve cover then start the engine up again let it get to operating temperature and do the other side. It is important to do the adjustment when the engine is hot not warm. A good pair of mechanics gloves would be a good investment when adjusting valves. If you have aluminum heads and or intake they cool pretty quick.

Rick

[excelguru]

After a while, the nerve endings in your fingers will die and it doesn't burn anymore. LOL.

Keith :)
Unique Motorcars (http://www.uniquecobrareplicas.com)
Southern Automotive (http://www.southernautomotiveengines.com)
Bruce Bunn (the painter) (http://www.jodecoautobody.com)

My Photo Album (http://members5.clubphoto.com/keith355593/owner-429c-1.phtml)

[Brent]

spd4me,

The set-up Keith has is the same as mine and the allen is the adjuster and the nut is to lock it. A rail type rocker will have a completely different nut and allen that is seperate from the rocker altogether. On a stud type rocker mount the nut is the adjuster and the allen is to lock it tight.

Keith is right.

Brent

[spd4me]

Brent
If my memory is right, my rocker arms are not mounted on a rail like Keith's picture. I've got Trick Flow Twisted Wedge heads and the rockers are turned all kinds of different ways. I do remember turning the outer nut to closed and opened the gap. So I guess the allen screw is what is used to tighten when finished.

[Brent]

If you have stud mounted rockers, which you do , the nut is the adjuster and the allen is the lock. The valve arrangement you have is "canted". A canted valve head angles the valves for better flow and flame travel in the combustion chamber.

Brent

[Jim Harding]

[quote]Originally posted by Brent


Do one cylinder at a time. When the intake valve starts to open you adjust the exhaust valve.

Brent,

With any amount of overlap, the intake will begin to open before the exhaust closes. It's best to be on the cam's base circle when adjusting valves.

I was taught to mark the harmonic balancer with a TDC mark every 90 degrees, and using the firing order, just turn the crank 90 degrees to the next cylinder TDC and do both intake and exhaust. This way you know both valves are on the base circle.

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[Brent]

Jim that's a good point.

My camshaft has 28 deg. of overlap @ .050 and is probably more agressive than most Cobra camshafts and truth be told 6 degrees too much overlap for my Weber setup. I usually allow the valve to open about .250 before adjusting the other valve. If you adjust the exhaust as soon as the intake rocker budges, your right, it is too soon and it will not be correct. I have drag race mentality sometimes. The camshafts we used were so crazy and installed is so many various positions we had to do them this way.

If memory serves me the last camshaft we ran was .848 lift and 345 degrees adv. dur.

Brent

[spd4me]

Jim
I've got several HP publication books on Ford Performance and Engine Rebuilding. It shows a diagram of the engine and which valve to adjust when turning the crank every 90 degrees. Bill Parham says when exhaust starts to open, adjust the intake. Rotate engine until intake valve has opened and starts to close, adjust the exhaust valve.

[Brent]

Bill is correct. I went back and read my post and I seem to suffer from dislexia when I type.

Brent