Pinking when hot

[woodslat]

I'm leaning toward two possible causes... What 009 is it? One of the new Chinese ones? Brazilian? German? I've read articles that have tested the different manufacturers of 009 distributors and found them all (when compared to a German built one) to have a few degrees of error in the advance curve, usually advancing too fast. Maybe it's set correctly but the faster advance is making for some pinging?

I'm interested in finding out more about the heads, if they were new it still doesn't account for how many times the case was decked, increasing compression. Your local mechanic should have done a deck height measurement on the pistons and a CC measurement on the head to calculate the correct compression ratio before bolting the heads on. If the heads are rebuilt instead of new, I guarantee that shims at the base of the cylinders would be necessary and the heads would have been resurfaced at the mating surface where it meets the cylinder sleeve.

I have a 1600 TP with a 100 grind on the cam to help with the flat spot normally associated with the 34 PICT/009 combination. My timing is set at 30 degrees at full advance. My compression ration is around 7.8:1 I asked the builder for lower compression to run cheap fuel. The only time my poor crew cab ever pinged was going through the mountains in 45 degree weather here in Northern California, I just backed off the throttle a bit and took it easy.

One more thing, Trikky is absolutely right about the pulley markings, the later TP years had different notches all over the place, for Auto Stick, Full Automatic on the Type 3's etc. THey could have 1, 2, or 3 notches! I set my timing with an aluminum degree pulley first so I know which pulley I have.

 

[67panel]

yes check timing marks,check advance with strobe.as for vac module when i was at collage we were taught that it was a fuel saving device cause it only advances the ignition under high vac conditions,ie foot of gas ,part throttle as the engine is not under load and will stand more advance so gives more power therefore less throtle needed in cruise conditions,then you have the early dizzys that have no mecanical advance at all only vac,but it depends where the vac port is taken from and the operating vac needed to work it.this threads going to run :msn4:

 

[six]

Second that on timing. I had my DVDs set at 30 it pinker got a doc from oldvolkshome I think where they tested Max advanced to 28.5. I wound mine back lil by lil till it didn't low behold didn't pink at 28.5

Oh also don't trust degree pulley. Mine at least was a degree out makes all the diff

Sent from my GT-I9000 using Tapatalk

 

[jimbope]

hey guys - thanks so much for your input....a quick update.
I have just returned from a 360 mile round trip over weekend. I ran the flaps fully open, time was set conservatily (checked 28 deg with strobe). Van seems to run very well - its just those dreaded motorway hills - as you put your foot down to keep up momentum the dreaded pinking occurs. Managed to sit in a horrendous queue on A46 for about 50mins - engine seemed quite happy in that. Temps were 22-24 deg which is not hot for sure!
Think ive made up my mind - after whitenoise im gonna drop engine, pull heads and work out compression ratio. Will also jet carb as recomended by 67panel and try and get hold of a sva dizzy.
@woodenslat - the heads are from vw heritage. They are remanufactured units. They werent much help technically when questioned about need for shims. My engine guy only ever fitted new heads back in the day so i guess shims are a bit of a novelty to him!!

The muir book has a good section on cc ing the heads and checking deck height- i will then be able to work out thickness shim reqd.

Whilst engine is out Trikky i will also change the stat rod as i think it is binding where is passes thru the head.

Ref the sva dizzy - has any one got any thoughts on the powerpark one on ebay? Supposedly a 034 spec c/w electronic ignition? Or am i better off getting a good 2nd hand unit?

Again many thanks for your efforts.....

 

[alikat]

Just out of interest there is a WR6 BC plug we call a BMW plug (I assume early BMW issue, now numbered 7993) that is slightly longer than a stock bug one, but is the usual 14mm thread. Good for cleaning up a slightly rich condition, but needs to be run hard as it is a cold running plug and short runs with choke on will soon foul it otherwise. It does not hit the piston, but being slightly further into the chamber it gives a better fuel burn. I run them in my '71 with 1600SP, Kadrons, 009 and head-work. The bus runs very well and I have no problems on the smaller hills around here.

As stated previously, checking your compression ratio before final assembly is critical, especially on older re-worked heads & cases, as is timing to avoid pinking. Your motor should NEVER pink - it is really destructive to your motor.

 

[moler]

Are you absolutely sure it's 'pinking' and not just misfiring?

 

[jimbope]

monday update...

After work 2nite....engine out and on the bench. Rh head off. as expected very little deck height - o.o38''. Cc chambers ad done the maths. CR of 8.8:1! Worked out i need a 90 thou shim 2 give me 7.28 to 1 ratio. That would be the cause of pinking i reckon! The plugs and valves are reddish brown.

 

[Trikky2]

monday update...

After work 2nite....engine out and on the bench. Rh head off. as expected very little deck height - o.o38''. Cc chambers ad done the maths. CR of 8.8:1! Worked out i need a 90 thou shim 2 give me 7.28 to 1 ratio. That would be the cause of pinking i reckon! The plugs and valves are reddish brown.

Interesting. Obviously you need to get both sides the same but isn't 7.28 a bit low?

I'm currently running 8.4 on a +2 liter without any pinking issues - though it does run better on 98 rather than 95.

I think if it were my 1600 I would go for something between 7.5 and 8 to get the benefit of a bit more efficiency eg. power/mpg.

 

[jimbope]

Hi Trikky, Many thanks for your comments regarding CR. TBH I was going with 7.28:1 as I had found that on BoB Hoover blog...which incidently where I found some great info - A story of a guy who had virtually the same issue as me - couldnt stop pinking - except he continued to drive and holes 2 pistons. His rebuilt heads had been flycut giving him too high compression.
My heads have have a capacity of 46cc - which isnt too bad apparently. The problem I have is the piston almost comes to the top of the barrel i.e too low a deck height. I dont know why this may be occuring - its as iyf the barrels have been machined off the case end.

I have 40, 60 and 90 thou shims coming - the choice is between the 60 and the 90 really. Think because of my recent probs I am erring on the side of caution with the 90s!!!

 

[67panel]

yes but when you tried it on super unleaded it should have stoped it pinking,our drag beetle runs fly cut 1300 cylinder heads on 1679 barrels and when it was still road legal it pinked unless on super ,but it didnt pink that much,and on a rough work out recon its 10 to 1 cr!! so i think your still running lean ,what size main jet and air correcter have you got,and forgot to say running 36 deg advance

 

[jimbope]

I have 125 Main Jet. The air correction jet says 125Z on it I think. I will try and get a 130 Main jet - they seem pretty hard to get hold of!!

The engine pinked no matter what fuel I used.Or what advance I set dizzy at. The probs definately temp related. On a cold winters day no prob, 22 deg ambient and problems start.

Regarding running lean the plugs and chambers were a reddish brown. Surely lean running would result in a whiter colour?

Cheers for you ideas though 67 panel!

 

[Trikky2]

I have 125 Main Jet. The air correction jet says 125Z on it I think. I will try and get a 130 Main jet - they seem pretty hard to get hold of!!

The engine pinked no matter what fuel I used.Or what advance I set dizzy at. The probs definately temp related. On a cold winters day no prob, 22 deg ambient and problems start.

Regarding running lean the plugs and chambers were a reddish brown. Surely lean running would result in a whiter colour?

Cheers for you ideas though 67 panel!

You might be on to something re the mixture. In a VW aircooled, if you make the main jet too small, the car runs lean and this makes the engine run hotter. Because the aircooled engine runs hot anyway, the smaller jet in the carburettor can make too much heat and burn the exhaust valves. You can also get detonation (pinging/knocking) if the engine gets too hot.


the 1600 is usually jetted with a X127.5 main jet, and 100Z -120Z air correction jet. the main jet is sized to the engine capacity, rather than the carburetor size, and X127.5 is the usual minimum for the 1600cc engine. That said I often ran a 130 main. 125 is too small IMO. Did your carb maybe come off a Beetle?

The main jet feeds fuel, so larger numbers mean richer mixtures, but air correction jets feed AIR, so larger numbers mean leaner mixtures. (The optimal stiochiometric (balanced) ratio is 14.5:1 -- that is, 14.5 parts air to one part fuel. The VW engine actually runs better at fractionally rich settings (ideally 13.8:1 rather than 14.5:1 according to Bob Hoover).

As for the colour you mention - how do the plugs look? The center electrode should look quite clean and grey/white. There should be a light smooth coating of carbon on the rim of the threaded part, and a colour change on the outer electrode of grey (at the tip) to black (where it attaches to the rim of the threaded part), with the change of colour on the corner of the bend. All this indicates a good mixture. A brown deposit all over the combustion chamber is rather strange. Normally they would be mostly grey/black.

 

[jimbope]

Hey Trikky,

I would describe the combustion chambers and plugs to be a "rust" colour.................Heat? Lean mixture?Result of excessive pinking?

I have worked out my compression ratios - Im going for the 60 thou shims rather that 90. This should give me 7.6:1 (rather than 7.281which I believe to be about right.

From the chambers I have measured at 46CC - this would indicate a 50thou flycut over standard. This along with minimal deck height is giving me a very high CR.

I am also on the hunt for a 130 main jet as 67panel has suggested - pretty much from the start of this thread. They seem quite hard to pick up - Were the transporters jetted down a size from the bugs originally?? I thought I had read that somewhere.....Maybe I can pick up a jet at a show - sooner rather than later.

I want to cover all bases here! With correct CR and a slightly richer mixture then fingers crossed all should be good. I will build the engine up again tonight/tomorrow night and put it in saturday and report back. I also have a new thermostat rod - They actually were not closing before so all the above should result in a much sweeter engine!!! Fingers crossed!!

 

[Trikky2]

Solex jets should be available from most carb specialists - like this one maybe? http://www.gowerlee.dircon.co.uk/" onclick="window.open(this.href);return false;

Yes early bays had a smaller main and idle jet than the 1303S beetle - used to be common practice to re jet them to beetle spec at the time.

 

[alikat]

yes but when you tried it on super unleaded it should have stoped it pinking,our drag beetle runs fly cut 1300 cylinder heads on 1679 barrels and when it was still road legal it pinked unless on super ,but it didnt pink that much,and on a rough work out recon its 10 to 1 cr!! so i think your still running lean ,what size main jet and air correcter have you got,and forgot to say running 36 deg advance

I am assuming you were running dual carbs on this motor. The efficiency of dual carbs/FI allow higher CR's to be run - Mexican FI bugs can run on 86 octane without problem. Again, NO pinking is acceptable if you want your motor to live a long happy life. A 130 main will liven your motor up a little also.

 

[woodslat]

Hi Trikky, Many thanks for your comments regarding CR. TBH I was going with 7.28:1 as I had found that on BoB Hoover blog...which incidently where I found some great info - A story of a guy who had virtually the same issue as me - couldnt stop pinking - except he continued to drive and holes 2 pistons. His rebuilt heads had been flycut giving him too high compression.
My heads have have a capacity of 46cc - which isnt too bad apparently. The problem I have is the piston almost comes to the top of the barrel i.e too low a deck height. I dont know why this may be occuring - its as iyf the barrels have been machined off the case end.

I have 40, 60 and 90 thou shims coming - the choice is between the 60 and the 90 really. Think because of my recent probs I am erring on the side of caution with the 90s!!!

I think 7.6:1 will be great, you'll definitely ditch the pinging then! I was pretty sure the heads were suspect. If I were in the business of selling used rebuilt heads I would mark the cc for each cylinder in pen right on the box.

 

[jimbope]

well. Engine in yesterday am. 150 mile round trip 2day to whitenoise...(which was a great show by the way!) and guess what.....van runs like a dream. Can know keep momentum up the hills without any worries of pinking....got so used to driving around the problem i.e asing off the gas when the pinking occured....know we can charge up hills! (so to speak!)
many thanks to everybodies input!!!