can't stop this pinging,.....

[merrill]

well, I am out of ideas,
66 230 sl rebuilt motor etc, new ign parts, inj pump and injectors etc....

when I first put the car back together it ran great, no pinging.
torqued the head, adjusted the valves, adjusted the inj pump via the richness test, now it pings during acceleration.


the distro is the 051 with vacuum retard, all seems to work ok.
I have actually backed the timing off, so now it is at 26 deg btcd at 3000 rpm.

Hans at H&R is out of ideas as am I.

Thoughts, Ideas?

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[seattle_Jerry]

I gotta ask:

Did you check compression to see if one or more cylinders is too high?

Did you use the same crank? Was it checked for tolerances?

How about cooling? Are you running hot? Could you do something to run cooler?

Have you tried a cooler spark plug?

How is the intake manifold gasket? leaking?

1967 230SL Havana Brown Auto with A/C

[Shvegel]

A couple of things come to mind.

Cutting the head on these older high compression engines can raise the compression enough to make it unrunnable on available fuel. I know some people on this board will think less of me but when I rebuilt my head I didn't let my machinist even measure it for warp because I refused to cut it below stock. I figured it was sealed when it came off and the cam didn't bind so I decided to leave it as is.

It could be that when you leaned it down you might have raised combustion temperature enough to start the pinging. If you have not tried Sunoco 94 and it's available in your area try it. I find it the most consistent of all the fuels I have tried. If not try some octane booster.

I find wild variations in octane from fuels that are supposedly the same octane. I tuned my car to run on Sunoco 94 and it pings on anything less. A few times after buying "93" octane along the interstate the quality was so low I have had to pull over retime my engine to not ping.

When an engine "pings" it disturbs the airflow across the piston and more importantly the boundary layer or thin layer of air that adheres to the piston top.  What this all boils down to is that the temperature of the piston top can soar to three times normal. So in short PING = BAD.  

If all else fails keep dialing the timing back until it no longer pings.

[merrill]

guys
thanks for the replies,

regarding cutting the head, metric motors rebuilt the entire motor
the head had a minimal cut when resurfacing.  

distro has been backed off to 26 btcd at 3000, s/b 30 deg at 3000

I did add some octane boost which did not make any difference

compression - I have not checked since the rebuild
used original crank - metric did the rebuild assume it was checked
temp is solid at 80 c
tried 2 different sets of plugs ngk bp6e's and bosch wrd9's
last time i checked the for leaks I did not find any leaks



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Shvegel]

Try locating TDC by some other means(dowel in the spark plug hole and GENTLY turning it to find where the piston travel is at the top) and compare it against what the timing marks are telling you where TDC is. I don't remember how the front hub is keyed to the crank but something could have slipped.

In other words what you see on the marks may not be right.

[graphic66]

Time it by feel, turn the dist. until it runs good. Do some zero to 60 performance runs ans compare. Some engines just don't time well with a timing light.

[al_lieffring]

Matt

it is possible that one of the springs has fallen off of the centrifugal advance weights. this will casue the timing to advance too early in the rpm range.

I know that Benz Dr. Dan will cringe at this, but when I rebuild these distributors I cut one coil off of the springs to increase the tension and slow down the advance curve.

I have never needed to use any fuel other than regular.

Good Luck


Al Lieffring
66 230Sl
New blue top just arrived
new gas tank on order

[TheEngineer]

My compression is 195 psi and i'm running regular Costco gas. Timing is set to the book but I have reworked the stops on the distributor flyweights to give me 33 degree of advance @ 3,000 rpm. No change to the springs. Pistons are Mahle and flat. Flush with the deck. Head is new and not machined. Cam is 08 with 09 waiting to be installed. The small space under the intake valves promotes even combustion without pre-detonation. Honda did a lot of research about that. Pinging is very bad! Don't drive it! Inspect ignition timing at 3,000 rpm and verify that it comes up gradually from idle. Check plugs for heat range. check valve timing & compression. Check intake valve clearance at 5 deg btdc. Look at the book for that procedure. Don't assume that the engine has been properly rebuilt.

'69 280SL,Signal Red,Automatic,retired engineer, West-Seattle,WA

[merrill]

all
so how would I inspect the distro weight springs?

the engineer,
this is a new issue.  I put 600 km on the car with out pinging.
something has changed.  

Plugs are new, same type as the ones I started with.
the only real change is torque hear and adjust valves (snug)
leaned out inj pump via the richness test.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Benz Dr.]

I agree that you not run this engine if it pings. You could ruin it very quickly.
If a spring broke inside the distributor it would advance too quickly. I've seen this a few times but it's rare. It should be 30 degrees at or before 3,000 RPM. The actual spot can vary somewhat but most engines will reach max advance before 3,000 so I can't imagine it's a problem with fuel or too high compression ratio. My engine is around 180 PSI and it seems to run fine on anything but regular. I can run it on 91 but it has more power using 94.
So, it would seem to me that you should look closely at the distributor advance. An engine is most likely to ping ( where you can really hear it ) if you have too much timing advance.



Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[TheEngineer]

When you put the engine together,did you tighten the clamp that keeps the distributor from turning? Get a timing light and verify the timing: At idle, it should be about 3 deg. after top dead center and as you speed up the engine, (have a person on the throttle & read the rpm's)the timing should advance smoothly to about 30 deg before top center at about 3000 rpm. This test is with vacuum connected. It is much easier to see when you remove the hood. Test the vacuum advance mechanism: Using a vacuum tester, pull a vacuum on the retard mechanism and observe rotation of the distributor plate clockwise. There should be no vacuum leak. If you can, exchange distributors.

[Shvegel]

Any carbon in the combustion chambers can raise the compression ratio. Any chance that the rich mixture may have built up some carbon?

[graphic66]

I use decarbonizing aerosol in my engine at each oil change. You get it at a marine dealer, OMC makes one, Yamaha makes one, these are primarily for outboard boat engines. The stuff cleans carbon like nothing else. I spray it in the intake then into each spark plug hole and let it sit overnight. Run the engine, then change the oil. There is also a fuel additive I use every so often to help with decarbonizing made by OMC. The aerosol is great for parts cleaning also. This may not help the pinging, but it is great regular maintenance. I use it in all my gas engines. In the early 80's the fuel companies took the dispersants out of fuel and this resulted in older engines getting carbon buildup, thus the advent of the 2 stroke TCW-3 oil, it has the dispersants in it. The end result if not used in high performance 2 strokes is a ring of carbon on the head and the top piston ring and cracks the rings, a condition called ring jacking.

[merrill]

so, here is an update and a correction.

I have the 009 distro not the 051, I know the 009 replaced the 051

I checked the retard vacuum at idle, hooked up a vacuum gage in line so I could check it live.  At idle there was at least 10 hg/mm then when I inceased rpms the vacuum dropped to zero.

I re installed the old condenser I had
Set the timing at exactly 30 deg btdc at 3000 rpm
at idle the timing is about 3 atdc

car started right up, got the idle rpm's set to 850 rpm
did the richness test, seems ok
took it for a drive, still seemed to ping a little, just a tad.

? are the points for the 051 and 009 the same?

shoud I check the valves?  Since I set them snug maybe set them not as snug?

thanks for the feedback

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Naj ✝︎]

Matt,

 

quote:? are the points for the 051 and 009 the same?

No, Have a look here under Maintenance, Service parts table:

http://www.sl113.org/wiki/pmwiki.php?n=Electrical.Distributor

naj

68 280SL

[TheEngineer]

No, the points for the 009 are different:For the 051 it's Bosch P/N 1 237 013 027 for the 009 it's 1 237 013 112. The 009 has an alu housing and replaces the 051

[merrill]

well, that is not it,  I have the correct points installed.

I may check the valve adjustment, I did make them snug last time.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[TheEngineer]

What do you mean by "snug" ? You ever heard of "specifications" There's a reason why things have to be adjusted to "specifications" Such as pinging which will destroy your engine.

[seattle_Jerry]

I'd make sure the engine is stone cold and readjust the valves. I've never done my SL's But on my Triumph you had to use a feeler gage to get the right distance. Torque wrenches are great too.

1967 230SL Havana Brown Auto with A/C

[Benz Dr.]

Why would anyone think valve adjustment has anything to do with an engine that pings? It doesn't.
However, set the valves because it can't hurt to have them right.

Look at timing.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[seattle_Jerry]

As far as I know the main causes for pinging are too much heat or too much compression (for the octane rating).

contributing factors to these include:

too-lean fuel/air mixture (not enough gas for the air present)
incorrect valve timing
engine cooling system inadequacy
faulty exhaust gas recirculation (EGR) valve
high intake-air temperature
excessive carbon deposits
poor combustion chamber design/shape
wrong spark plug


But if the valves were adjusted wrong, it couldn't hurt to get them right.



1967 230SL Havana Brown Auto with A/C

[seattle_Jerry]

I was thinking about valve clearences today and if there was a way they could contribute to pinging (contrary to Benz Doc's opinion).
I know it can make a car run hotter. I dug around the internet for corraboration. I found this on a valve company's website.

"Too little valve clearance throws valves out of time. Valves open too early and close too late. This causes the valves to overheat due to hot combustion gases rushing past valves when out of time. Overheating lengthens valve stems which prevents proper seating of valves. The valves seat so briefly or poorly that normal heat transfer into the cooling system does not have time to take place, causing burned valves and low power."

As I was saying in an earlier post. One of the things that can cause ping is excess heat. The question is if the hot valve would be enough of a hot spot to create a secondary ignition.

Knocking and pinging result when the fuel/air mixture self-ignites somewhere else in the cylinder, away from the spark plug. In these cases, the combustion from each source burns toward the other until their leading edges — called the flame fronts — literally collide, causing the ping or knock sound.

1967 230SL Havana Brown Auto with A/C

[merrill]

well, checked the valves today and most were tight, so I ended up doing the valves.

checked the dwell and timing which were spot on
did a richness test, the car barely increased in idle, so I increased the mixture x2 clicks.

took the car for a drive, I could still hear something but maybe not pinging any more.

I have a local indy I am going to take the car to. maybe they can figure it out.

matt

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Benz Dr.]

I had an engine that lost compression and was smoking a little bit. After I took it apart I found two cylinders slightly scored and one piston and its rings slightly scuffed.
Unpon further inspection I found a loose valve guide and some worn valves which were letting engine oil get into the cylinders. In this case the extra oil getting into the cylinders was causing the engine to run hot similar to a lean condition. The carbs were working properly ( 190SL engine ) and the coolant temps never went above 180F. I heard no pinging during driving yet it was still gamaged. Engine used a liter of oil in about 400 miles.

Is your engine smoking or using oil? Does it ping when cold or only when hot? Does it ping under light throttle up or heavy?
Adjusting the valves will make it run better but I still don't think that's the main problem. What is your compression readings?



Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[merrill]

Dan,

the motor is only 800km since a rebuild at metric motors

1. exhaust does not smoke
2. I notice the pinging sound when cold and hot
3. it only seems to ping when under heavy load, once I get up to 60 mph I have a hard time hearing the sound.
4. I have not verified the compression since the motor is new



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230