Bad day with cam install... think I found the reason.... FIXED & RUNNING.

[Jim 1]

Hi guys...

 

Well got stuck in today with changing the tappets and injectors on my VR today. We eventually got everything apart and replaced the tappets (which I had soaked in oil for 24 hours) but upon installation of the cams, starting with the exhaust cam and tightening down the inner bearing caps (as per the workshop manual) the cam snapped around the area of the journal of cap number 3.

 

****.

 

We assumed it was a fault in the cam (which were some second hand OE ones I'd bought a while back) and just put it down to bad luck and set about reinstalling my original Schimmel cams instead.

 

To our horror the exact same thing happened - so I've basically wrecked two cams and now have a dead and unmovable car in my garage :( Not a good day. We're trying to work out what we did wrong. What the hell did I do wrong? My only doubt is around having had the cams actually in the correct positions prior to trying to tighten them down... is that the most likely thing?

 

Pretty gutted especially as it means my Corrado is now in my 'home' garage and stuck until I can get it reassembled again and my normal car is going to have to live out on the street until I can get it sorted again.

 

Cheers.

[robrado974 1]

so the cam was gently tightened all the way along the shaft . Then each one was torqued in sequence ? . When I was an apprentice years ago . My boss always said forget the manual . Gently tighten down each one along the cam , keep doing this back an forth with a socket , looking to see everything is seated evenly . Tighten again back and forth . Only then follow the sequence to the factory torque . Bad day for you Jim . I hate it when things happen like this . It puts you on a real downer .

[Harrier 1]

Are you sure the tappets are moving freely and not jamming ?

[Dox 22]

Nightmare :(

 

If a valve has gone solid against a piston as you suggest then there's a possibility the valve itself is also bent, after you install the next set of cams you might want to compression test the engine before you rebuild it completely. Fingers crossed for you.

[Jim 1]

Thanks for the replies guys. Feeling pretty hacked off. It's not been a good year or so with this car but this is the biggest set back in quite a while.

 

We don't know for sure if the tappets are feeling moving, but they are a brand new set of INA's so I'd hope they were correct.

 

I did soak the tappets overnight in oil for 24 hours - was that the right thing to do? Should I have waited a few hours before trying to tighten down?

[Harrier 1]

What Dox said is a possibility , if the cam was in the wrong position when tightening down ?

[Jim 1]

That is my only thought - I have a feeling we didn't have them in the correct position prior to tightening down. It's the only logical explanation. Just hope it hasn't damaged a valve into the bargain if so.

[Portent 0]

Gah. Sorry to hear this :(

[lilfuzzer 1]

Unfortunately jim I agree with the above of mis positioned cam.

 

Sorry to hear buddy hopefully will come good

[bruny 0]

Hi Jim,

Sorry to hear of your plight. When we installed new INA cam followers we compressed each one in the vice before hand. I know this isn't generally advised but at least two from the set were unbelievably tight. The amount of pressure required to release them surprised me. It may not be the main reason for your problem but would advise releasing pressure prior to assembly. They will re-prime. Good luck with the rebuild.

[Yandards 0]

Unfortunately jim I agree with the above of mis positioned cam.

 

Sorry to hear buddy hopefully will come good

 

It wasn't Jim didn't look at it but both Eric and I did on both occasions.

[Dox 22]

So you had the engine set to number 1 TDC and the cam with the off centre slot horizontal and uppermost?

 

Did you progressively nip the cam cap bolts or just torque up the first nut you put on the cam caps?

 

Cams are made of cast iron and cast doesn't like to bend, the best way to nip down the caps it to see which lobes are touching the tappets and tighten those progressively a turn at a time.

 

If you tighten one with the base of the cam nearest the tappet (so its hollow or gapped) first you're trying to bend the cam.

 

If you can secure the upper chain from jamming you can use a spanner on the crank pulley bolt and put your thumb over each sparkplug hole in turn to see if there's compression.

[Yandards 0]

So you had the engine set to number 1 TDC and the cam with the off centre slot horizontal and uppermost?

 

Did you progressively nip the cam cap bolts or just torque up the first nut you put on the cam caps?

 

Cams are made of cast iron and cast doesn't like to bend, the best way to nip down the caps it to see which lobes are touching the tappets and tighten those progressively a turn at a time.

 

If you tighten one with the base of the cam nearest the tappet (so its hollow or gapped) first you're trying to bend the cam.

 

If you can secure the upper chain from jamming you can use a spanner on the crank pulley bolt and put your thumb over each sparkplug hole in turn to see if there's compression.

 

Centre bearing caps fitted first as per the workshop manual for fitment sequence of bearing caps, finger tight initially and then 1/4 per nut in a diagonal sequence as per the workshop manual.

 

Just to clear this one up everything was setup correctly in terms of No.1 at TDC, correct orientation of cams and correct bearing cap fitment sequence and subsequent tightening down onto the head as per the VW workshop manual.

 

Looking at the VR6 self study guide there is a valve in the oil system that is there to prevent oil draining from the cylinder head oil paths - if there is too much oil in the tappets its got nowhere to go when you start to tighten the bearing caps down. This seems to have resulted in a hydraulic lock on either no 1 or 2 exhaust cam tappet being fully pumped up, although I would guess its no 1, and the camshaft snapping at the load point of the bearing cap.

 

Interestingly the first break was to the left of the bearing cap under load and the second was to the right of it - which is odd when you consider the caps run down true to the cylinder head.

 

Aside from what Brunny mentioned on the bottom of the last page to ensure the tappets are free to move and fully compressed prior to fitment there is not a lot else in the system that could cause it as everything was setup correctly for the task.

[Dox 22]

Are you 100% sure the bottom of the engine didn't move between removal and refitting? If the car was in gear and moved slightly the engine would have rotated also.

 

Before fitting the next set of cams I'd move the tappets front to back and vise versa as at least you have a few spare inlet cams now (not meant as a joke)

 

Really bad luck

[Dox 22]

You could also temporarily refit the old tappets and torque down to prove its a tappet issue at maybe at the expense of another broken (inlet) cam though on refitting the new ones.

 

Once the engine is back together I'd use a spanner on the crank pulley to rotate the engine gently several rotation to ensure there's going to be no valve / piston contact on start up.

[Yandards 0]

Are you 100% sure the bottom of the engine didn't move between removal and refitting? If the car was in gear and moved slightly the engine would have rotated also.

 

Before fitting the next set of cams I'd move the tappets front to back and vise versa as at least you have a few spare inlet cams now (not meant as a joke)

 

Really bad luck

 

Yes as engine was hand cranked to No 1 TDC, not in gear and handbrake applied.

 

Regardless of where No 1 piston is with the cam lobes at a position where they will not be opening the valves then you won't get contact between the valve and the top of the piston.

[Dox 22]

Yes as engine was hand cranked to No 1 TDC, not in gear and handbrake applied.

 

Regardless of where No 1 piston is with the cam lobes at a position where they will not be opening the valves then you won't get contact between the valve and the top of the piston.

 

Yes, but what about the other 5 pistons and there respective valves?

[Jim 1]

Hi Jim,

Sorry to hear of your plight. When we installed new INA cam followers we compressed each one in the vice before hand. I know this isn't generally advised but at least two from the set were unbelievably tight. The amount of pressure required to release them surprised me. It may not be the main reason for your problem but would advise releasing pressure prior to assembly. They will re-prime. Good luck with the rebuild.

 

Hi Dave - thought this was an interesting idea that I will look to follow too. Just wondered how much travel you expect on the 'compressible' part of the tappet (no idea what the technical name is) - are we literally talking a few mm? Don't want to risk over tightening them and ruining them if I can help it!

[Supercharged 2]

Hi Dave - thought this was an interesting idea that I will look to follow too. Just wondered how much travel you expect on the 'compressible' part of the tappet (no idea what the technical name is) - are we literally talking a few mm? Don't want to risk over tightening them and ruining them if I can help it!

 

Jim, take it you have the old tappets you can practice on?

[Jim 1]

Yes mate. Did try on one or two of them earlier and found there's very little movement - could get them to squeeze in (as oil came out of the little oil hole) but it was a minuscule amount of travel.

[Jim Bowen 1]

When I've done mine in the past i remember having to push the cams down by hand to get the caps on. Meaning it was pushing down on some of the valves.

 

I had to have a mate hold the cam down while i got the cap and nuts on.

[davidwort 0]

...

Looking at the VR6 self study guide there is a valve in the oil system that is there to prevent oil draining from the cylinder head oil paths - if there is too much oil in the tappets its got nowhere to go when you start to tighten the bearing caps down. This seems to have resulted in a hydraulic lock on either no 1 or 2 exhaust cam tappet being fully pumped up, although I would guess its no 1, and the camshaft snapping at the load point of the bearing cap.

 

...

 

oh spit, what a downer, so what's wrong with fitting tappets without any oil in them? I've never soaked tappets and they seem to pump up within a few seconds of the engine running.

[Kevin Bacon 5]

No me neither. I thought pre-soaking in oil was a legacy of leather oil seals from 50s Jaguars?

 

I've never seen a cam snap on a VR before! I'm surprised there's enough pull down strength from a couple of 10mm bolts in ally threads to snap a cam like that! I would have put money on the threads stripping first, but stranger things have happened! As Dox said, the cam must have had excessive bending going on.

 

Strange! Hope you get it sorted.

[g0ldf1ng3r 13]

oh dear, I feel your pain Jim :(

 

not once but twice, I can only imagine your heart sank!

 

I have a set of standard VR cams which were removed around 150k when I had my stealth head rebuild done. I was planning to make some book ends or something with them but if you need them pls let me know - though they are very heavy indeed as you know

 

I know it is nothing to do with them but have you tried calling vince to ask if he could shed light on what is going wrong? 5 mins with him & all could be explained

[Yandards 0]

No me neither. I thought pre-soaking in oil was a legacy of leather oil seals from 50s Jaguars?

 

I've never seen a cam snap on a VR before! I'm surprised there's enough pull down strength from a couple of 10mm bolts in ally threads to snap a cam like that! I would have put money on the threads stripping first, but stranger things have happened! As Dox said, the cam must have had excessive bending going on.

 

Strange! Hope you get it sorted.

 

First one went that well it jumped out of the engine bay, missed the wing completely and hit the floor.

 

Second time was just a ting as I got Jim to stick the outer pair of bearing caps on and follow the cam down with finger tightening the nuts.

 

It is a very odd scenario, having done the 16v earlier this year that's a much trickier bugger as there are more tappets over a shorter run per cam and I needed to lean on the cam whilst trying to get enough threads engaged on the cover caps to stop them stripping.

 

There's seems to be plenty of internet based info ref soaking them in oil first but neither the workshop manual or the crappy install sheet from INA have anything like that there; seems like a pile of crapola and something you shouldn't be doing instead.