Porsche Enthusiasts Club Forum

Hi

Hmmm interesting... that made me remember another couple of bits i forgot in my big post (age lol)

1, Forget the first turn of engine, you take the HIGHEST reading you can get after 4 or 5 or 6 or 7...turns....once the reading has STOPPED rising you STOP TURNING IT OVER lol

2, OIL .. a couple or maybe 3 squirts (usually from an old fashioned squirty type oil can) ,,,,NOT half a pint lol...the reason you dont use that much you already know lol.... your hose goes bang lol

What were the liners made of ?? Steel or Alusil ...

All the best Brett

Hi Again

Just read Chas post about his "Gunson" gauge lol...

He has a point though..what make is yours ?

Mine is Snap-on and good for 600 psi...

If you are anywhere near Bournemouth I would quite happily test yours with mine for free of course...

All the best Brett

Hi Brett,

Ah thanks for telling me that now lol TBH I didn't think I put that much in but I must have, oops. Would putting too much oil in also skew the reading?

When I did the first dry tests the other day, if I turned it over 7-10 times I could get all 4 up to 175psi, whereas 5 turns was between 160 and 170.

Liners are steel I believe, definitely not Alusil (was too costly and it would have taken an age to get it done).

Also running JE pistons and Pauter rods.

Thanks for the offer to test, that's very kind of you but unfortunately I'm in High Wycombe. Gauge (and hose) rated to 300psi (apparently).

Might just bite the bullet and do as Chas suggested and get a leak down tester.

Hi Mac

Yes a half pint of oil WOULD affect the test lol....think about it...with that much oil you are decreasing the amount of space in the cylinder at TDC and therefore the readings would be miles out...

Regarding the leak down tester, although a good idea in theory, you REALLY need to know how to use them and that usually means a qualified mechanic on YOUR type of engine....... a decent make compression gauge will tell you everything you need to know....

All the best Brett

Hi Brett,

It was no where near half a pint lol, maybe 30ml or so which still sounds too much but I understand what you're saying.

Hoping the overfill was the problem but will get another tester and retest.

Thanks for sticking with me! I will get it right next time

Hi Mac

Come back with a set of both dry and wet readings and we will figure it out.....

All the best Brett

Even if it took a decent mechanic to tell you what is wrong I would still trust one of those over a compression tester in being more conclusive. It will pinpoint the problem areas more conclusively with less guesswork.

Hi Chas,

Very true and if it was road legal or I had my own transport for it that's the first thing I would do but unfortunately I have to hire transport each time it's moved.

Thought I would try and do some initial diagnosis myself and if it turns out that there is a suspected issue then I can go from there.

Thanks

Hi Brett,

I've retested with a new compression tester.

Results:

Dry - 170, 172, 168, 174
Wet - 180, 190, 182, 190

Number 1 - I ended up putting slightly less oil in than others as I was paranoid about breaking the tester again. Number 4 - initial wet result was 200 but I ended up putting a bit more oil in than the others and so retested. In fact the number of pumps of oil from the can varied slightly between each cylinder.

I've also noticed that there's a chatty tappet, seems to be coming from intake side between 3 or 4. Engine has always been a bit chatty so maybe I'm just looking for problems where they don't exist but I've posted a video https://youtu.be/cDuBGqDs4cs

Thanks

Hi Mac

Hmmm they are not drastically low... its a BIG difference between cylinders which you would have to worry about, which you dont have....

I listened to the video and you are correct, there is a slight tappet chat, only on 1 cylinder i think....press a screwdriver against the bone in front of your ear, and press the sharp end on the cam cover working you way backwards...idle revs should do....you will easily find which cylinder it is.... I have a stethoscope for this but a long screwdriver will do....try not to touch a lead and get shocked lol...and mind the belt...

Anyway going from those figures I would think that although they COULD be higher, they are not bad, which would make me think >>>TOP END...

So if it was me I would pull the head only and have a very close look at valve seating and possibly cam wear...and work from there...

All the best Brett

Hi Brett,

It's the easier end to address at least!

Thanks for the heads up

I removed the cam cover to check overall condition inside, checked for any cracks, failed oil pipe etc and had a look at the cams. There is some slight wear but it's virtually the same as when it was rebuilt and there was no concern by the builder at the time so I THINK they are OK. The cams have had a minor reprofile which may explain why the engine is generally a bit chattier than stock but one now seems to be louder than others. I'll give the screw driver trick a go and track down where it is.

If the tappet was causing a problem would that have any effect on the compression results?

Would it be worth having the timing checked?

I'll take the head off and inspect further.

Thanks for all your help! Much appreciated!

Hi Mac

IF it was the tappet problem it would only cause a drop on ONE cylinder...

Timing...hmmm I assume you mean engine timing not cam timing ?

If engine, then yes IF its adjustable on your engine.... no if not although you CAN check it with a timing light...

The problem with cam reprofiling is that they often go too deep and grind through the case hardening, although if that was the problem you would see a LOT of wear on the lobes...

P.S ... Do ALL your other possible checks BEFORE you pull the head...just in case you dont have to...lol

All the best Brett

Hi Brett,

Although the cams only had a very mild reprofile there was a hardening procedure which was followed, involved high idle for about 20mins but I don't see any abnormal wear on the cams or tops of followers but I'll run a vernier over the cams and compare to profile spec to be sure.

The cam belt is tensioned with a non adjustable spring tensioner, although I've heard the springs can get tired and so loose some tension. Presumably if that was the case the belt wouldn't be as tight as it should be and therefore could put the engine timing out slightly which presumably would have a minor effect on compression? Maybe I'm clutching at straws but as you say it's worth making all the checks before removing the head.

Thanks