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Push rod lengths


Iain T
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Bought an alloy rocker cover from the club shop but on looking at the rocker arms they are horizontal at valve closed. Should be pointing slightly up, it also makes the tappet adjustment screw hit the rocker cover when the valve is open. A fix seems to be shorter push rods? The head has had around 40 thou machined off and a corresponding pedestal shim under the rocker pedestals. I think about 3mm shorter rods would help. Are they available? 

Iain 

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Don't know what other mods you may have done, but, if you have fitted new valves, the stems may be different in length. Most surfaces will be hard, so be careful if you decide to shorten anything. On my motorcycles  there were different lengths of pushrods and valve stems available. The alloy rocker cover will be thicker than the steel one too. I would look at the adjusting screws to see if any metal could be removed from them.

Is it possible to fit a thicker rocker cover gasket?

Edited by Wagger
Correcton.
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1 minute ago, Wagger said:

Is it possible to fit a thicker rocker cover gasket?

I could use a cork and the thin gasket I bought with the alli cover. However that won't resolve the incorrect arm orientation. I do have a new billet cam (260 thou lift) from Newmans together with their followers and my original push rods. 

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7 minutes ago, KevinR said:

You should be able to correct the rocker geometry with a set of Pedestal shim

I do have 40 thou pedestal shims but it's the arm moving from horizontal to minus arc that I would like to fix. It should arc equally from horizontal. To achieve that the push rods need to be slightly shorter. I thought Triumph 6 pot rods come in varying lengths? 

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It's a Vitesse mk2 2 litre. The head has been fully ported, gas flowed etc and the compression is around 9.5/10:1 Using standard 150 CDS carbs but 6S needles. The valves are 'just' proud of the combustion chamber and are new. Before the old valves were very proud, around 2mm.

The engine runs fine its me being OCD! 

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There are different length push rods, but it may not help you,

2.5 S ones are longer, if you fit Vitesse ones to a 2.5 you end up with 150 thou gaps even at maximum adjustment, found that out when a mate asked me to look at his incredibly asthmatic Saloon. So 2.5 ones won't help.

Mk1 2000 ones may be slightly shorter than Mk2 2000 but are possibly a different size.

 

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I've just been looking at the exploded drawing and it looks like the adjusters are the pushrod end of the rockers. If I am correct, then removing the shims would change the angle to be more neutral. If I am wrong, then adding more shims may achieve what you want.

Early Vitesse had the ball and socket opposite way round. That will be no help either.

Check how hard the rods are. If they are are soft, just shorten them and re-profile if possible, but they have head and foot (Cup and socket) So a bit tricky. Luckily, my bike engines had soft rods with hardened ends that fitted over them, interference fit. That was easy. Depends how much suitable machinery you have access to. You could make these up.

Edited by Wagger
Correct dumb info
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Depending on the valve/rocker wipe I need to remove the pedestal shim which would raise the arm above horizontal, ideal, when the valve is closed. However I believe, according to the engine builder, there isn't any adjustment on the arm to achieve the correct tappet clearance. 

As I said, subject to the contact pattern, I think I need a slightly shorter push rod which would lower the tappet screw and give me clearance under the rocker cover and also give a more ideal rocker arm arc?

Iain 

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25 minutes ago, thescrapman said:

Just found the info.

When I take the rocker assembly off I'll measure the rod as installed. Most of our engines have had a checkered life with god knows what parts used! 

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I am obsessive too Iain. If possible, compare your cam followers with the old ones. Distance from cam to inside of socket. They are hard too. None of it is easy

There are different profile rockers too. Another bag of worms eh!

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I realise I may be wrong here, but if you have 40thou shims under the pedestals, removing them and having 40thou ground off the valve stem length (if they will stand it) should lower the whole?. Then it`s up to the adjuster?. 40thou is just a tad over 1mm?.

Do you still have the old valves?. If so, check the length from the valve face to the Collet notch, and the Overall Length, there could be an error there?.

Someone told me, that non o/e stuff, often is used in more than one engine?. With the same part number coming up on different marques?

Pete

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Wagger the old followers are in the bin. As you say it could be a combination of new cam which will give a maximum natural diameter as its not been reground, new Newmans followers and new renamed rocker assembly. 

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3 minutes ago, PeteH said:

realise I may be wrong here, but if you have 40thou shims under the pedestals, removing them and having 40thou ground off the valve stem length (if they will stand it) should lower the whole?. Then it`s up to the adjuster?. 40thou is just a tad over 1mm?

Pete, I'm not taking the head off! The old valves also went in the bin last year. 

Discounting the arm geometry it's the tappet screws that stop the Ali rocker cover from fitting. It just blossomed into me investigating why and as usual opening a can of worms! 

I've refitted the old pressed cover which if I just nip up the nuts just, sometimes, clears the tappet screws. 

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Ian,

Is the any mileage in just shortening the tappet screws. It`s 40+years since I went playing with a Vitesse Engine. But most have just a Square on the end for adjustment and a Lock screw, Careful work with a dremel or similar might reduce the clearance sufficiently?. OR thinking laterally, maybe there is enough thickness in the alloy Cover to do a little judicious fettling?. With the engine running satisfactorily as is, that too may be an option?.

Pete

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Pete, 

I thought the same about the screws but after doing some horizontal thinking in bed last night I'm going to try a cork gasket with the ali cover. I think I have enough clearance under the bonnet, I tested the pressed cover using some Blutack stuck to the front of the cover. I hope the extra few millimetres will clear the tappet screws. If I'm bored next week I'll take the rockers off and measure a push rod. 

Iain 

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There may be 'Tell-tale' marks on the inside of the ally cover. Careful use of dremmel will do the job, Otherwise, it's a case of removing all rocker screws to shave 2mm off all twelve.

After running for about 1000 miles, some bits may bed in. This could go either way, increasing or decreasing clearances. Your ears should tell you.

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37 minutes ago, Wagger said:

There may be 'Tell-tale' marks on the inside of the ally cover

I'll assemble with the cork gasket then turn over with the plug leads off and listen and check for any rub marks on the underside of the cover. 

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