Help with Compression Readings...

[Molmeister]

Afternoon

Anyone can give me some advice I'd appreciate it....for several months my bus has lacked power, to the point I didn't think I was going to get up the hill up to the Balloon pub outside Malvern...so, I've rolled up my sleeves again to find out what's going on......

Using my compression tool. and having removed all the spark plugs and noted the following readings....

Cylinder 4 - 125 psi (8.8 kg/cm2)

Cylinder 3 - 140 psi (9.6 kg/cm2)

Cylinder 1 - No pressure

Cylinder 2 - No pressure


OK - I appreciate the obvious response it, screw it in tighter on 1&2 but however many times I screw the compression tube in, no joy, no reading at all on Cylinders 1 and 2..I've reviewed the manuals and about from a cylinder head there doesn't appear to be any commonality between these cylinders..

I can sense a Winter project coming on :lol:

Engine is a stock 1600 on a 72 Bay, no modifications (ie Single carb)

Any help/comments/advice would be apprecaited - Thanks

 

[Trikky2]

Have you checked the valve cleances? eg. are the valves closed and the tappets loose when the cylinder is at tdc?

If they are definitely closed then you probably have burnt valves (or a loose head?). I say this because if it were the rings or pistons the engine would smoke - a lot of blue smoke.

A way to double check it is to turn the engine over by hand (spark plugs in). You should be able to feel each cylinder compressing - four compressions in two turns of the crank.

Dodgy valves/head would mean you could feel little/no resistance on those two cylinders and probably hear the air blowing by.

 

[67panel]

Check the valve clearances first either that or 2 burnt out valves :roll:

 

[Molmeister]

Many thanks...

Just back to see if there's anymore comments - plus i'm cold and a bit wet!

Since the last post..and taking on board whats been said ....weve ...

Removed the rocket cover and rocker arm, torqued up four cylinder hut bolts/nuts and reset valve clearances and re-assembled...Result......

Cylinder 2 - 50 psi

Cylinder 1 - 120 psi

Question - Looking at my Haynes manual there are EIGHT cylinder head bolts and yet only FOUR seem accessible.....so how do you access the FOUR cylinder head bolts OUTIDE/ABOVE the rocker cover.....


Many thanks for comments -really do appreciate it...

 

[67panel]

THERE UNDER THE COOLING TIN,need to take the engine out to strip of tin wear :roll: but I would say you need to remove head and check cos if its come loose its been OVERHEATED and will be damaged where it seals on barrells and rest of motor could do with a check over ,usualy rear main seal fails if its been that hot.

 

[Doris]

Just to add,for correct reading,open the butterfly in the carb whilst doing a compression test.just in case you didn't know ;-) (I didn't )

 

[Molmeister]

Just to add,for correct reading,open the butterfly in the carb whilst doing a compression test.just in case you didn't know ;-) (I didn't )

er....never knew that ..learn something new every day...

....as for engine out job, worried someone was going to say that...might be a few weeks before that job starts...thanks for your messages....

 

[Doris]

Just to add,for correct reading,open the butterfly in the carb whilst doing a compression test.just in case you didn't know ;-) (I didn't )

er....never knew that ..learn something new every day...

....as for engine out job, worried someone was going to say that...might be a few weeks before that job starts...thanks for your messages....

I was worried about my readings,then found out about opening the throttle for un restricting the inlet and my readings were much higher.

 

[Trikky2]

You cannot just tighten up the head nuts and most definitely not just the lower ones. Distortion and damage WILL happen.

You need to get yourself a workshop manual. There is a specific sequence of tightening down the head nuts.

They are torqued down in two hits and the sequence is different.

These engines are not great lumps of cast iron like many other engines and the torques and sequences are critical.

If you do it wrong it will come back and bite you.

 

[jonboylaw]

Also, if you are doing a leakdown compression test (where you fill the cylinder with compressed air) it will give you a much better feeling for the problem. You will hear the air leaking from the head (loose head), via the inlet or exhaust (valve problems) or via the crank case (rings/piston/cylinder problems). You do not need the throttle wide open for a leakdown, but you do need to lock the van in gear and have a decent handbrake to stop it moving forward

 

[BJ1]

Just to back up what Trikky2 said - you MUST pull the engine and strip down that side to sort the heads and studs. It's really not a big deal - takes me about an hour to get the engine out by myself and about 30 minutes to strip the engine to the heads, but I've been doing it for 40 years :roll: If you run an engine that has had a loose head and only the bottom four nuts tightened you will seriously screw it up so spend a day or so saving it.

Before you sort the loose head issue you will want to replace the exhaust valves. I do this routinely if I have a head off. You will also want to check the timing (30 degrees at 3500rpm - don't time it statically), carb settings, cooling system etc so you can be sure it runs nice and cool.

 

[Molmeister]

People of the Forum (Ladies and Gents - not sure which way you bat)...

Many thanks - great advice.

I need to tidy out the garage and then just crack on...hoping there's no serious damage done. Going to be a little time before I can start....

So meantime Appreciate all your comments...

Being a Cross Over (72) BUT still a Low light (just for the record ), I don't have the luxury of the rear cross member to remove so engines coming out via the bottom....should be... :shock: ..interesting...

 

[BJ1]

Just pull the engine back with the van on the ground then jack it up over the engine - just like a beetle but higher and heavier.

 

[Molmeister]

Afternoon

Katy's a 72 crossover so my "end" is probably from a late Bay - as there is no cross memeber to remove. So I assume it's height on the rear end and drop the engine out the bottom?

Don't chuck me off the forum - I couldn't afford a proper "Early" :lol: