Old-timers secrets for setting valve lash

Old-timers secrets for setting valve lash

Author
Discussion

gt5s_1985

Original Poster:

703 posts

224 months

Tuesday 21st October 2003
quotequote all
Hi,

Last night I re-set the valve lash for the second time in a month because I'm an idiot and used the wrong dimension the first time... This is my first engine with solid tappets (a Ford 351C) and I'm still trying to figure out a foolproof procedure for setting the lash the first time.

This is a more time-consuming process than I think it ought to be because I can't consistently set the lash to where I would like it to be - I have to use a sort of trial-and-error. Tighten down the roller rocker and check lash... Too tight? Loosen it up. Too loose? Tighten it up. Measure again. Loosen. Measure. Tighten. Measure. Tighten again. And so forth.

Is there anyone out there who has been living with a solid-tappet engine for years and has found a method for setting lash in 5 minutes that allows you to set the lash you want instead of measuring the lash you have acheived to see if it is in spec?

TIA

Incorrigible

13,668 posts

229 months

Tuesday 21st October 2003
quotequote all
I'm not familiar with the 351, does it have adjusters on the rocker arms ? Is this what you're on about ? If so adjust the clearance at TDC on the compression stroke screw down on the gauge before locking the lock nut this should take up the backlash in the thread

If I've missed the point entirely sorry

gt5s_1985

Original Poster:

703 posts

224 months

Tuesday 21st October 2003
quotequote all
I think that the setup is the same one you are familiar with and describe. There is an allen set screw in the middle that tightens down the roller rocker, and the lash is set by the outer nut.

I set the desired lash with the out nut, then, while holding this nut in place, tighten down the set screw in the middle. The problem is that I don't think I can tighten the set screw sufficiently just using an Allen wrench, as I can tighten the outer nut somewhat. So I back off slightly the allen nut, then tighten down the outer nut (which tightens both nuts) hoping to return the allen nut to its previous location. This is somewhat of a trial and error process, and I end up repeating it a half dozen times until I finally get the lash I am looking for.

If I had a diagram, this would be so much easier to explain, so thanks for your patience.

ZR1415

17,999 posts

217 months

Tuesday 21st October 2003
quotequote all

You could try asking on this site as the 351 cleveland is a Mustang engine,,hope this helps.
www.mocgb.co.uk/

Incorrigible

13,668 posts

229 months

Tuesday 21st October 2003
quotequote all
Again only guessing but can't you hold the allen screw in the right position with a key while tightening the outer (I assume locking) nut

sheepy

3,164 posts

217 months

Tuesday 21st October 2003
quotequote all
Similar problem with the B-Series engine in my MG (assuming I've understood you right). The tappets are made with a threaded rod which has a slot in it for a screwdriver. Slacken the lock nut, turn to the required cleareance and then you have to hold the screwdriver steady whilst tightening the locknut (Is this the same idea?)

Assuming I'm right, then this is what I do:

Slacken lock nut and tappet

Inset feeler guage which is a fraction thicker than I want

Tighten tappet with screwdriver (or allen key for you) until the feeler guage is held in place between the tappet and valve-stem

Tighten lock nut whilst holding tappet as still as possible

Pull feeler guage out (needs a bit of force)

Voila: clearance is spot-on, move on to next valve.

There is a tool called "Click-Adjust" which apparently incorporates both the screwdriver bit and the spanner for the locknut. I've never bothered, but apparently it's useful for when the end of the tappet becomes dished through long life. It may be possible to get one with an allen-key head.

Sheepy

RichB

45,530 posts

252 months

Tuesday 21st October 2003
quotequote all
sheepy said:
Similar problem with the B-Series engine in my MG
I was going to say surely you can't have problems adjusting the tappets on an MGB, but reading on I realise you don't Rich...

Mr2Mike

20,143 posts

223 months

Wednesday 22nd October 2003
quotequote all
gt5s_1985 said:
I think that the setup is the same one you are familiar with and describe. There is an allen set screw in the middle that tightens down the roller rocker, and the lash is set by the outer nut.


This dosen's sound like any setup I have ever seen. Generaly the screw is used to set the clearance(lash), and the outer nut is used to lock the screw in place. If this is the case then you ned to understand how tightening the locknut affects the clearance. Normaly as you tighten the locknut, the clearance increases slightly as the screw is forced hard against it's threads. In order to get the correct clearance after tighening the lock nut, you need to set it very slightly tight.

gt5s_1985

Original Poster:

703 posts

224 months

Thursday 23rd October 2003
quotequote all
Thanks for the suggestions... For posterity, I think I found an easier method when I set the other half last night.

I determined how much clearance is lost when I snug everything down by tightening the outer nut (0.006"), add this to my desired valve lash, and set them by hand to this. Well, I tightened the set screw with the Allen wrench to this spec. Tightening the outer nut by wrench brought them right to final spec, every time. All 8 valves, exact lash, first time. Much less frustrating than the trial-and-error method, and a lot quicker.

Once again, my engine makes that beautiful "clack clack clack" that sounds like a 5.8 liter sewing machine and I'm a happy camper.

gt5s_1985

Original Poster:

703 posts

224 months

Thursday 23rd October 2003
quotequote all
Mr2Mike said:

gt5s_1985 said:
I think that the setup is the same one you are familiar with and describe. There is an allen set screw in the middle that tightens down the roller rocker, and the lash is set by the outer nut.



This dosen's sound like any setup I have ever seen. Generaly the screw is used to set the clearance(lash), and the outer nut is used to lock the screw in place. If this is the case then you ned to understand how tightening the locknut affects the clearance. Normaly as you tighten the locknut, the clearance increases slightly as the screw is forced hard against it's threads. In order to get the correct clearance after tighening the lock nut, you need to set it very slightly tight.

gt5s_1985

Original Poster:

703 posts

224 months

Thursday 23rd October 2003
quotequote all
Mr2Mike said:

gt5s_1985 said:
I think that the setup is the same one you are familiar with and describe. There is an allen set screw in the middle that tightens down the roller rocker, and the lash is set by the outer nut.



This dosen's sound like any setup I have ever seen. Generaly the screw is used to set the clearance(lash), and the outer nut is used to lock the screw in place. If this is the case then you ned to understand how tightening the locknut affects the clearance. Normaly as you tighten the locknut, the clearance increases slightly as the screw is forced hard against it's threads. In order to get the correct clearance after tighening the lock nut, you need to set it very slightly tight.


That's how valves are adjusted on at least Ford V-8s, dont' know about other US engines... I've had two different brands of roller rockers, and they both function like this.

You turn the outer nut which increases or decreases valve lash, and the inner set screw holds it in that setting.

The snag is that you can't snug down the set screw sufficiently just using an Allen wrench - you need to tighten the outer nut which also tightens the inner nut, but since the outer nut controls lash, you change the setting when you tighten it. The trick is to make sure that when you tighten it down, you end up with the lash you want.

sheepy

3,164 posts

217 months

Thursday 23rd October 2003
quotequote all
gt5s_1985 said:
Thanks for the suggestions... For posterity, I think I found an easier method when I set the other half last night.

I determined how much clearance is lost when I snug everything down by tightening the outer nut


That's exactly what I do by adding a bit to the clearance before tightening. Your explaination is much clearer than my attempt!

Sheepy