Jump to content

No Tappet Clearance


Recommended Posts

Hey Guys wander if you can help me.

 

New rebuilt engine, 89mm, fast road cam, ported head etc. I did about 25 trouble free low rev miles and it was running really well.

 

Day 2 no power pulling away in any gear and needed revving to 1500 rpm to pull away then ok.

 

Engine sounded tappety so I checked clearances (we set to .010 when built) and I find that 2 of the valves have no clearance

and I cant get a feeler gauge under them at all. I put a straight edge on the top of the valves and the 4 inlet valves are higher by

about 1.5mm?

 

I then pulled the rocker shaft and now it wont go back down fully onto the head with a 2mm gap because the push rods

stop it even when undoing the tappet heads fully and moving the car in gear to get them roughly level. Whats going on?

Presumably valves are sticking open so loss of power. One of the push rods now has a burr on its edge. I was going to shim the

pedestal but this is a plaster not a proper fix.

 

Why would I be able to set the tappets before and not now? I used the rule of 9 method in pairs.

 

I have since realised the fast road cam should be set to .022 but I cant even get .010 under some of the valves.

 

Any help would be appreciated. Feeling fed up, wanted the car done in June and its just running on and on.

 

Colt

Link to post
Share on other sites

Hi Colt, when the cylinder head is reconditioned, it's not unusual to sound tappety even after a proper initial clearance adjustment. The reason is that you need time for the parts to bed-in properly. On my last recon, it was very tappety from the onset and i left it alone until I re-torqued the head after 800 miles. Then adjusted the clearance again and since then no problem.

 

There might be several problems:

1/ If the head has been skimmed, which is likely, you'll loose clearance and the head gasket starting bedding in will compound the problem as you use the car;

2/ If the head has been ported then it is likely that the inlet valve seats have been reground hence further compounding the problem and causing your inlet valves stems to stick out of alignment;

3/ For valve adjustment I always use the following method:

Balance valves cyl 1 adjust clearance cyl 4

Balance 2 adjust 3

Balance 3 adjust 2

Balance 4 adjust 1

One of the solutions is to add shims under the rocker arm pedestals

 

Hope this helps

Edited by Geko
Link to post
Share on other sites

I have since realised the fast road cam should be set to .022 but I cant even get .010 under some of the valves.

 

Not saying you are wrong - but be careful. Some fast

road cams need that clearance, but many others do not.

 

Although - that would not explain the problem of valve

clearances closing up and probems after just 25 miles.

 

It sounds like you did the engine rebuild yourself?

How did you lubricate the cam lobes and what was your

initial firing-up procedure?

Only thing I can think of that could cause the symptoms

you describe is knackered cam followers. This can happen

extremely quickly if the start-up procedure is wrong.

 

AlanR

Link to post
Share on other sites

 

Only thing I can think of that could cause the symptoms

you describe is knackered cam followers. This can happen

extremely quickly if the start-up procedure is wrong.

 

AlanR

Which would cause too much clearance, not too little

Link to post
Share on other sites

This is weird. I can only guess that the offending valves were stuck slightly open when you originally set the clearances. That would explain the loss of power but not why it ran well for 25 miles. If all the valves have now seated properly and you can't locate the rocker shaft either the valves have receded radically, which doesn't seem likely as they're inlets, or the head has had a big skim or the pushrods are wrong. Too many conflicting symptoms for my brain. Head off I'm afraid.

Edited by peejay4A
Link to post
Share on other sites

Hi Colt,

I can offer a possibility for the small rocker gap but not the other problems.

 

A couple of years ago (2010) I popped my 4A into a garage in readiness for the Club TRiumph RBRR. They reported back that the rocker gaps were only 0.004" instead of 0.010"

 

My millimeter feeler gauges refer to 0.1mm (0.04") as '10' so I interpretted 10 as 0.010".

The car ran very well. I'm sure I adjusted down to the 0.004" setting after it had run for quite a while so any teething problmes were gone.

 

For the non-fitting rocker shaft have you completely unwound the rocker adjusters.

 

Roger

Link to post
Share on other sites

Guys thanks so much for the detailed replies, awesome.

 

The bottom end was rebuilt by a well know TR garage and seems ok. The head is skimmed a fair bit and ported as per Vizards

approach.

 

I read through your replies and decided to go back to the start.

 

The head bolts had loosened a bit and I re-torqued them back to 105.

 

The rocker shaft didn't touch the cylinder head when initially placed back (do any?) I needed to bolt it down and the springs compressed, I was worried the push rods were going to be forced so was hesitant but it bolted down ok. I do currently have 1.2mm shims under the pedestals and tomorrow I will redo everything again without them.

 

I reset the clearances to .022 (Exhaust are meant to be .024 on a Moss Fast Road Cam but I'm advised .022 good for all)

 

Its possible I may have done a tappet clearance wrong somehow and this caused the lack of clearance? this time instead of doing in pairs I simply did the rule of 9 from front to back which we did the first time at .010.

 

The timing was quite far out (it had been done before) so I redid this.

 

The car ran well and I did 80 miles, the power was back immediately, so a combination of all the above I think was the problem. The engine still sounds very tappety all the time but as Geko says this is normal? I need a new push rod.

 

I have some running on which comes and goes a bit and I'm playing with the advance / retard / timing to help this.

 

Can you advise regarding running in a new engine please -

 

How many miles do I need to drive under 2500 rpm?

How often would you normally check the timing?

How often would you normally check the tappet clearances?

 

Anything else?

 

Many thanks

 

Colt

Edited by Britishbest
Link to post
Share on other sites

The engine still sounds very tappety all the time but as Geko says this is normal? I need a new push rod.

 

Anything else?

 

Many thanks

 

Colt

Out of interest, did you initially use the rule of 9 following -blindly- the Haynes Manual? If so, there's a mistake in it (p 48 - Valve 7 open, adjust Valve 2, not 8 as indicated). Did you adjust the valves cold as in "stone cold" as per the book? I do it hot with the engine running and only that stops the tappet noise once for all (kidding).

Edited by Geko
Link to post
Share on other sites

If the head has been skimmed to any degree, the push rods will need to be shortened in order to maintain the correct geometry for the rockers.

Kastner's manual explains why and how to do this.

Jacking up the pedestals with shims is but a short-term fix because the geometry will be wrong.

Ian Cornish

Link to post
Share on other sites

Running on often associated with lower octane pump fuel: try a tank of 98 super

You will find it doesn't run on

In fact it is probably worth using better fuel all the time - especially if you don't do high mileage

Michael

Link to post
Share on other sites

Geko I followed a print out I got from somewhere that says to do the clearances in pairs as 2 valves are always down. I think i will scrap it. Valves were done on a hot engine which i thought was correct? Interesting about the Haynes manual.

 

Pete the pedestal shims weren't on there before I decided to fit them today as I had quite a gap under the pedestals. I may come to find that not using them is a problem which them proves Ians point about needing shorter rods. Can they be bought? I am still unclear why I had the power loss.

 

Michael my local garage has 97 as it's premium grade which I used. I have some castrol valvemaster which I will try after experimenting. I also read on here advancing the engine helps, I thought retarding was correct?

Link to post
Share on other sites

Geko is quite right that Haynes TR2/3 manual has had that error for ever...

 

The factory method of adjusting in pairs is much more satisfactory and also results in less crankshaft rotation being required, only two revolutions to do all 8 valves.

 

Iain

Link to post
Share on other sites

Hi Colt,

the slightly loosened head nuts would not caus ethe gaps to close - open more likely.

 

When you went to replace the rocker gear onto their studs and found that the pedestals had a gap underneath is was probably

because one or more rocker arms were contacting the closed valves - this is normal. No need for shims unless the geometry is all to pot.

 

Do not forget to retorque the head after the next 500 miles. Crack the nuts open a half turn then torque to correct figure.

 

Roger

Link to post
Share on other sites

You might not cure run on even if you can find 98 or 99 octane even with an additive especially with the skim your head has had. You'll find plenty of potential solutions if you search the forum. Cooler plugs, slow tick over, retard ignition a bit, improve cooling. For my own part I have two aro valves and I don't have the idle speed too slow so that on shut down plenty of air is drawn in to suppress run on. Seems to be working.

Link to post
Share on other sites

Roger loosen the head nuts first before tightening?

 

How many running in miles do these rebuilt engines need?

 

Pete yes I turned the tick over down to 800. Cooling is best I can get with electric fan, ducting and coolant. Not seen anyone put vents in the bonnet but tempted. My temp gauge tends to read hot but it hasn't overheated.

 

Will get some more miles on today.

 

Thanks

Link to post
Share on other sites

The Rule of None has been mentioned, and then a table, that tells you which valve to adjust and when, which in some editions of the manual has an error.

The Rule of Nine is so simple, no table is required - you can do it in your head, or even just by eyeballing the engine.

 

The Rule of Nine.

Number the valves, front to back, 1-8

Turn the engine until two valves [any 2 valves] are open (down)

Subtract that valve's number from 9.

Adjust the valve with the number that results.

 

Alternatively, the Mirror Method (same as RoN, but visual, not arithmetical)

Imagine there is a mirror across the middle of the engine, dividing it into two, front and back.

As before, note the valves that are down.

Adjust the valves that mirror those.

(EG No.1 Cylinder inlet valve down - adjust No.4 Inlet vave)

 

 

So, no need for tables! Some can't face a sums. I'm lucky, I can, unless there is a £/$ sign in front, when my mind goes all goey and I panic.

JOhn

Edited by john.r.davies
Link to post
Share on other sites

You could also try this method, courtesy of Macy's Garage. For each cylinder in turn, when the exhaust valve just begins to open, adjust the inlet clearance. When the inlet valve just begins to close, adjust the exhaust clearance.

Link to post
Share on other sites

Hi Colt,

 

Sorry late on the thread, Seems you've about bottomed it but just to advise on your last two questions the second first.

 

As Roger says the engines require a retorque, on a standard build engine as per the book at about 500 miles, under mileage is ok over mileage only leads to heartache if it blows the gasket, don't do it. In fact on my race engines I retorque at about 200 miles, whatever movement is going to happen has happened by then.

 

The head nuts need slackening off first to avoid "stiction" (sticking friction) corrupting the torque figure, so first drop the water below the cylinder head level to avoid any seepage or your bad thoughts that it may happen, save it you can drop it back in afterwards. Then undo the nuts about 1 flat in head torqueing sequence and the retorque again back up to 105 in sequence, don't be surprised if you find it going past 1 flat by maybe the same amount again. Then refill the water.

 

Mick Richards

Edited by Motorsport Mickey
Link to post
Share on other sites

Perfect thanks Mick.

 

Is 500 miles the running in period or longer, no one has answered this.

 

Its frustrating sticking below 2500 rpm which equates to 50mph in my car but

Gotta be careful to do so.

 

Goings for a drive now.

I think anywhere between 500 and 1000 miles is alright for re-torquing which marks the end of the running-in period and that's the rule of thumb as far as i know but I may stand corrected of course. You need not "plateau" at 2500 rpm (where's that coming from ?), just drive it normally like around 3-3500 rpm with short runs peaking at 4500 rpm even 5000 rpm since you have a fast road cam, towards the end of the running-in period. What matters is that all moving parts bed-in properly across the rev range. Just avoid extended rides in the vicinity of the red zone. I believe the manual doesn't give specific instructions beyond the later.

Edited by Geko
Link to post
Share on other sites

I remember your senior moment on clearances Roger. At the time I was surprised that the 4 thou feeler didn't seem a bit thin to you. I would also have thought that the unusually low level of tappet noise for a TRactor engine would have given the game away!

 

Tim

Link to post
Share on other sites

Hi Tim,

when you want and expect a certain result (just like Gov't surveys etc) then anything can happen to make it so.

 

Yes the feeler would have been seriously too thin for my experienced fingers and the noise far too quiet for a TRactor but that is what I wanted and so, got it.

 

Management ploy - go do an unbiased survey, but this would be a nice result. You can guess the result.

British Airways lost a great deal of money with stupid twisted surveys.

 

Roger

Edited by RogerH
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.