Pinking when hot

[jimbope]

Hi guys - I have a problem with my 1600 SP motor then I had refreshed last year - I THINK I know whats wrong with it but thought I would run it past the experts first....

Basically I bought my van as an "unfinished project" - basically the engine was sick - it would only ever run on 2 or 3 cylinders so I pulled it out and stripped it - the heads were cracked.

I had a local guy check the engine over - he is totally reliable as he used to run his own VW garage and is a fountain of knowledge - like he straight away told me I needed special oil seals for the oil cooler for instance.....The bottom end seemed fine - P+B also fine. I bought new heads from VW heritage and he re assembled it all for me and it runs like a dream - not even a leak from a push rod tube!

Now this was at the end of last year....I use the van quite a lot - It was used when it was -9 last november - always started on the button.

The problems start when it gets above about 22 deg ambient temp.....It starts to pink in 4th when climbing a slight hill when warmed up. 1st noticed it on the long gradients on the A14 on way to Stamford Hall. (The air pick up from warm air pipe is pulling from the engine bay not the head.)

Now am I right in thinking that Im going to have to pull the engine and put some shims under the barrels to decrease compression ratio? I have set the timing from 28 deg to 32 deg dynamically and it appears to make no difference. I have tried Super Unleaded, Octane boost in Unleaded or Super but if the day is warm I get pinking which is obviously not good on an aircooled engine.

I have checked the thermostat and it opens/closes and seems to operate the flaps Ok.

I have a long run down to wales next weekend am a bit nervous if its a hot weekend. I know these engines run OK in hot weather as I owned an 69 Bay in Western Austraila and have cruised around in 38deg C heat no bother before!!

Anyone any ideas before I strip the engine - which I am reluctant to do as it runs soooo sweet. My engine guy reckons he has never had to shim a stock engine in all his 40 years of experiance.

Any input greatly apreciated!!

 

[67panel]

WELL COULD BE A NUMBER OF THINGS,whats your dizzy,single vac or 009? you just advanced the timing ,wrong way to stop pinking retard it a bit,what plugs and gaps ?and carb whats size is your main jet coz could be running lean,or a mix of all these :shock:

 

[jimbope]

Cheers for quick reply.

I'm currently running a 009 dizzy - I started off with 32 deg max advance - this equated to about 7 or 8 degrees BTDC at idle. I backed the timing off to try and reduce the pinking. This appeared to not have helped much.

The plugs as far as I know are correct spec and gap - they were new at engine rebuild time.

I do not have a clue what main jet I am runnig - which jet should I have for a 1600cc? Are they marked up so I can identify what I have? I rebuilt the carb when I did the engine but TBH just blew through the jets.

I guess if I take a plug out I should be able to tell.....

 

[jimbope]

I have a 30 Pict 2 carb on this engine which I overhauled when doing the engine - at the time I didnt take much notice of Jets etc - just made sure they are clean....

Now Ive read a bit about these carbs also being used on 1300/1500cc lumps - Im wondering whether mine has the wrong jets for a 1600cc.

Does anyone have the Main jet sizes etc for the different CC engines?

I think I can buy them from Gower and Lee. Just need to know what to change to.

Many thanks.

 

[Trikky2]

Yes the 1600 has different jets to the 15/1300. Its best to jet it to the 1600 beetle twin port specs (early 1600 campers were under jetted).

If you are worried your compression ratio is too high then I would suggest doing a compression test before taking the engine out and seeing if the readings are within normal tolerances. If your compression is too high you will get readings noticeably higher than stock.

 

[jimbope]

Just noticed 2nite that i dont have the front bell housing to firewall engine tin! Wasnt there when i took engine out so didnt notice its absense when putting it back it ( i know- stupid mistake!)
gonna fit one and hopefully it will let the engine run cooler-the fan was obviously drawing in hot air from heat exchanger area rather than from ducts thus cooking engine!

Will report back - hopefully no need 2 pull + strip engine!!

 

[BJ1]

Yes the 1600 has different jets to the 15/1300. Its best to jet it to the 1600 beetle twin port specs (early 1600 campers were under jetted).

Quite right! The carb is a tad too small for a 1600 engine. Read this for jet sizes
http://www.vw-resource.com/carb.html#brosol

 

[jimbope]

the story continues....

Fitted my modified beetle front tin.looks pretty good to be honest. Drove home 12 miles. By mile 8 the van pinks in 4th gear. Doh!

On way in to work when temp in low teens there is no issue. So tonight i have disconnected thermostat and pushed and pulled the rod. It seems stiff. Also should it spring back up when pulled down? If so mine does not. There is a lever on the front of the fan housing that rotates to the right when you push the rod up to open flaps. When the rod is up i reached around the back and im sure i managed to shift the flap bar over a bit more. Im now thinking that maybe my stat isnt opening the flaps fully.

Will see how i get on tomorrow with flaps permanently in open position. At least that will get me on holiday sat! Will sort out linkage when engine is next out.

 

[Trikky2]

There should be a spring on the back of the fan housing that pulls the flap operating bar across to the flaps open position.

Did you do a compression test yet? (to see if your earlier theory was right or not?)

The flaps should not be stiff to operate. There could be mis alignment or corrosion causing them to be stiff but the most common cause is the rod going up from the thermostat is bent and catching where it goes up through the head. (this is most commonly caused when re-fitting the fan shroud - the rod is quite thin and has to be carefully threaded through its small channel so it doesent get bent).

 

[jimbope]

Hey Trikky,

No I havent done a compression test yet - I was just trying to sort out the simple things 1st! Driving to work this morning I have still had pinking even with flaps fully open. The spring on the back of the fan housing looks worn and the mechanism is stiff. When i pull the stat down in the housing (unbolted) it doesnt "spring" back up like its supposed too.

I think I have a chicken and egg situation - is it the pinking causing the heat or is the heat causing the pinking!

The thing is this morning I could take the dipstick out and hold it quite compfortably after the blast to work at 55-60mph for 12 miles. It still pinks if you floor the pedal in 4th or if you have to climb a hill.

Gonna check valves again tonight and double check the timing tonight. Will try and get hold of compression tester too.

Cheers for your help - this is driving me mad!!

 

[Trikky2]

Ok. Just one other thing - when you re-check the ignition timing, also check the timing mark on the pulley is correct. I mention this because I have come across a few engines where the timing marks were wrong. Either because the pulley came from another engine or because a new pulley had been fitted and wrongly filed/marked (replacements came with no marks other than an approximate dimple at tdc).

 

[moler]

I always time a 009 to 28°btdc, and this usually settles to about 7°btdc, is this wrong? as I very often see figures of 32°btdc quoted :?

Isn't checking plugs, points, tappets, etc the fundimental start for any fault finding?

 

[67panel]

well tbh unless valves have no clearance cant see that making it pink ,proper pinking is pre ignition caused by something firing the fuel mix to soon .on water cooled moters have found fire ring from head gasket sticking into combustion chamber ,it acts like a glow plug.so does large build ups of carbon.wrong grade spark plugs running to hot,lean mixture will make plugs ect to hot.do you have a flat spot on acceleraton that will be lean and a 009 needs a richer mixture,read the link to carb jets ,very informative.also try some NGK plugs cos the bosh ones are made in china :roll:

 

[moler]

well tbh unless valves have no clearance cant see that making it pink ,proper pinking is pre ignition caused by something firing the fuel mix to soon .on water cooled moters have found fire ring from head gasket sticking into combustion chamber ,it acts like a glow plug.so does large build ups of carbon.wrong grade spark plugs running to hot,lean mixture will make plugs ect to hot.do you have a flat spot on acceleraton that will be lean and a 009 needs a richer mixture,read the link to carb jets ,very informative.also try some NGK plugs cos the bosh ones are made in china :roll:

Wouldn't the timing being to advanced cause the engine to run hotter?

Why does a 009 need a richer mixture?

 

[robjarman]

I just bought a new Vege 1600 and was told to fit long reach plugs to their new heads - i.e. W7CC - if you have fitted new heads might this make a diff?
Rob

 

[67panel]

the 009 dissy advance curve is totally differant to a vac (sva)dissy it advances much sooner and therefor the engine needs more fuel to keep the air fuel ratio correct,basicly the 009 is for a tuned engine ie race where you want full advance quicker.dont think they made single port heads with long reach plugs ,worth checking though.have you read the link to carb jetting?dont take this the wrong way but how much do you understand how an engine works?read the link it repeats itself a bit but it will help.

 

[Trikky2]

I always time a 009 to 28°btdc, and this usually settles to about 7°btdc, is this wrong? as I very often see figures of 32°btdc quoted :?

Isn't checking plugs, points, tappets, etc the fundimental start for any fault finding?

No its not wrong. The figures quoted should be 28 to 32 eg. max min

 

[Trikky2]

Wouldn't the timing being to advanced cause the engine to run hotter?

Why does a 009 need a richer mixture?

Yes both over advanced and under advanced timing will cause the engine to run hotter (for slightly different reasons)

The richer mixture advocated for 009's is to overcome the inherent fault of the 009 compared to the SVDA dissy. The 009 does not supply the small kick of advance as you open the throttle such as when you pull away from standstill and this can cause a hesitation or flat spot. By making the mixture richer it smoothes this out by making the combustion "softer" but it does mean you use more fuel.

 

[Trikky2]

I just bought a new Vege 1600 and was told to fit long reach plugs to their new heads - i.e. W7CC - if you have fitted new heads might this make a diff?
Rob

Longer reach plugs are for engines using the thicker, later Mexican heads. If you fit long reach into stock heads, designed for short reach plugs, they will hit the piston at tdc.

 

[Trikky2]

the 009 dissy advance curve is totally differant to a vac (sva)dissy it advances much sooner and therefor the engine needs more fuel to keep the air fuel ratio correct,basicly the 009 is for a tuned engine ie race where you want full advance quicker.

You have that back to front. The 009 has no vac advance and therefore will not advance the ignition until the revs rise - thats why they can cause flat spots which can be improved (though not eliminated) by running a richer mixture.

Far from being made for a performance engine the 009 was designed for and used on industrial engines such as those used for pumping and generating electricity. These engines run on steady throttle settings at constant RPM and hence have no need for a vac advance system.