Valve timing

[swapped]

I took a deep breath and plunged into my first attempt at adjusting valve-clearances on Saturday - not just my first time on the 914, but my first time ever (the only other car I've ever had without hydraulic tappets was when I was 17 and I just paid someone else to make the clattering stop).

Finding TDC was HARD! - no marks on the fan at all - nothing...nada...diddly-squat. I had to find the timing mark on the flywheel by sticking a finger in the hole at the top of the tranmission while on my back, turning a wheel with my free hand and a knee. Found it though, and it's all marked-up now at TDC and 180 degrees opposite TDC, so future repeats should be minus the 1.5 hours THAT took me

Setting the clearances, however, was easy - and the car now sounds like a lightly-pedalled sewing machine (well, sort-of).

I do have a couple of questions now:

1. do clearances on type 4s tend to tighten-up over time? - the valves were probably equally divided between being set ok, gaping like a (insert metaphor for big wide gaping thing here) and tight as a (ditto metaphor for very tight thing). it didn't occur to me at the time, but i'm wondering now if there was a pattern to the gaps that suggested they had been set to different inlet and exhaust specifications by whoever was in there last. to be fair, i think it has just been a long time since they were done at all.

2. are the valve-covers interchangeable between type 4s and type 1s? I see lots of replacements available, but will 'beetle' ones fit? - the reason i ask is that one of mine has rotted a hole through - not terminal yet, as it's at the top, and is where the cork gasket sits, so the hole is blocked. Can I convert to the kind that bolts on instead of using the big spring-clip?

thanks,

Carl

[Nige]

No real need to find TDC when checking valve clearances, just flip the dizzy cap and rotate the engine until the rotor arm points to the notch in the dizzy body or to the no1 cylinder plug terminal. Then turn the engine until the rotor moves 90 degs for the next cylinder. I mark the dizzy body with a permanent pen at 90 deg intervals, makes it easier, then pop your head underneath to check the rockers are loose for whatever cylinder you are doing.

Covers are not interchangeable between t1 and t4. I have a pair somewhere in my shed if you want them, not rusty but could probably benefit from some new paint. Bolt on one can leak just as bad or worse, though I always stick abit of blue hylomar on the gasket and they never leak.

Suppose the gap could decrease/tighten if the valve sten stretches or the seat wears/recession.

Best time to do valve clearances is on a stone cold engine, I would park mine up on a Friday night in position for Saturday morning so that I didn't have to start the engine to move the car.

[Nige]

actually just remember, the covers I have are powder coated and are like new. Forgot I had them done then added a breather kit that came with tapped covers.

[swapped]

Hi Nige - didn't recognise you at first with the new avatar.

No real need to find TDC when checking valve clearances, just flip the dizzy cap and rotate the engine until the rotor arm points to the notch in the dizzy body or to the no1 cylinder plug terminal. Then turn the engine until the rotor moves 90 degs for the next cylinder.

I thought about that at the time, but couldn't find a straight-forward confirmation that it was OK, so I set about finding TDC to re-assure myself, as much as anything.

Covers are not interchangeable between t1 and t4. I have a pair somewhere in my shed if you want them, not rusty but could probably benefit from some new paint. Bolt on one can leak just as bad or worse, though I always stick abit of blue hylomar on the gasket and they never leak.

Ahh.
Well, yes - that would be great, thank you!
I forgot to ask WHY the bolt-on ones exist TBH - mine aren't leaking, but the hole is there and I thought there might be some cooling advantage from cast fins - to change to bolt-on seems a bit pointless for me, then.

Suppose the gap could decrease/tighten if the valve sten stretches or the seat wears/recession.

The plan now, of course is to keep a regular eye on things and then I'll grow to know what tends to happen on my car...

Best time to do valve clearances is on a stone cold engine, I would park mine up on a Friday night in position for Saturday morning so that I didn't have to start the engine to move the car.

That much, I knew - the car wasn't quite where I needed it, but it was only a matter of pushing it a couple of metres forward - and it doesn't weigh as much as my Saab, so it felt quite light.

Can I take you up on the covers?

I'll PM you.

Thanks,

Carl

[swapped]

actually just remember, the covers I have are powder coated and are like new. Forgot I had them done then added a breather kit that came with tapped covers.

Ooh - does that change their availability?

How much do they owe you?

Are they pretty?

Carl

[Barry]

My '14 had tightened one of it's clearances so much when I got it, it had started to loose compression on one cylinder.

After I adjusted it, it was fine thereafter. I gather, however, that some of the really cheap valves can stretch through the stem just prior to the heads falling off ( ). My personal feeling is that just so long as you keep an eye on clearances you'll probably be fine.

BTW, the easiest and most accurate way of finding TDC is with an adapted spark plug:

Step 1: Break off both electrodes from a spark plug, and remove the inner ceramic: important, make sure there are no loose bits left.
2) Find a bit of round bar that is a tight fit in the centre of the plug, and tap into the newly formed hole.
3) Cut the bar off so that is sticking out of the plug by 1 1/2 or 2 inches (Not critical).
4) Get number one on compression stroke (look at dizzy or rockers).
5) Now insert adapted plug into number one plug hole.
6) Carefully and slowly wind engine up towards TDC until the piston touches the adapted plug. Mark engine pulley at this point.
7) Wind engine backwards until the piston again comes up against the adapted plug. Mark pulley again.
8 ) Remove plug, measure between both marks: the point exactly between then is spot-on TDC, irrespective of pulley's in wrong place, missing timing marks, incorrect pulleys etc etc.

This method is very accurate, and the ideal is the the crank should be stopped rotating by the adapted plug somewhere around 90 degrees from TDC: i.e piston half way up the barrel.

Obviously for valve gaps its not that critical, but for checking ignition and valve timing, it's a different matter.

BTW, My '14 was 20 degrees out on ignition timing when it arrived: amazing it didn't destroy itself . Still, it went rather well after that .

[swapped]

While I was scratching my head on Saturday morning, looking for a mark on the fan, I recall wishing I knew a method for finding physically where TDC was, but my imaginings consisted mostly of sticking a bit of welding rod down a spark plug hole and noting where is was at its shortest - your approach is much more thorough!

I'll be checking my ignition timing next, then!

Carl

[fourteener]

- and the car now sounds like a lightly-pedalled sewing machine (well, sort-of).

Now all you need to do is fit some 911 elephant-feet swivel adjusters ......

[swapped]

- and the car now sounds like a lightly-pedalled sewing machine (well, sort-of).

Now all you need to do is fit some 911 elephant-feet swivel adjusters ......

What them then?

[fourteener]

On my 4 cylinder I had my rockers machined 1/8" to clear the 911 swivel feet. They are quieter than the standard adjusters....others say they're more precise and create less wear. You can make up your own mind. I just thought it was a good concept

[swapped]

I see.

I tell you what - those things look like elephant's feet!

[fourteener]

Yes I think the Pachyderm reference so you're not confused with the cheap type one swivel feet.