Sircajun

Hi guys.
So my engine has a lot of pinging.
Story is: 1970 Cutlass with a ´69 400cui out of a 442. Only changes are: Edelbrock performer intake, Edelbrock carb 1910 (850cfm), Points replaced by a Crane Cams XRi module but otherwise original style distributor.
Car has been runing with no issues. The other day under acceleration in 1. gear it suddenly started pinging. So something is out of "line" or broken.
My mechanic friend and I have gotten so far:
Fueled it up with 99 octane fuel, this gave minimal changes. Disconnected the vacuum advance, this also gave a minimal improvement.
Timing was checked at idle, it read 0 degrees with VA disconnected. At 2800 rpm 13 degrees.
We have tried to change the springs in the distributor to some not so hard and the pinging got worse. Had none that was harder but we put some cable ties on it so it will not advance and the pinging is almost gone. Only when hard on the accelerator you can still make it ping. But I do not want to run it without any mechanical advance.
So what are our choices on things to check up on?
I think I´m runing a bit lean but it has been runing with this carb setting with no issues.
This weekend I wil get hold of a complete distributor setup to try in the car.
But what else?
There is no hesitation to start, it fires up on cranking, no problem. Runing good on all cylinders.
It´s no running hot either. Any comments or ideas?
Thanks for your help.

tru-blue 442

What spark plugs?
I dropped to 44 from 45's
with A/C Delco's.
A little colder plug makes a
world of difference. Performance
pretty much the same without the pinging.

pogo69

for a start i believe your timing should be at around 10 at idle not 0
so its a hei i thought points...did you put the timing from 10 to 0
?

oldcutlass

It's a points replacement module. Actually with points I think it's 2 with a manual trans, 8 with an automatic. It's the 13 @ 2800 I'm concerned about. I think the advance plate is binding.

442rocketdave

I think Eric has the right idea on this, when everything was running fine and it started pinging I would first say fuel because we often get bad fuel but your replaced it and checked your vacuum lines and you have a good carb so like Eric said look at that distributor!! Good luck!

Sircajun

It's an automatic transmission, sorry for not stating that.
As mentioned the pinging started during a cruise under acceleration. So it isn't bad fuel or spark plugs.
Those 0 to 8 degree difference what would be the first effect on start up? I have no problem getting it running and 8 degrees sound like a lot. Also, what is timing supposed to be @2800 or @ 3000 rpm?
Thank you for replies, they are appreciated.

MDchanic

Do you not have a Chassis Service Manual?

Page 6C-12:

Base Timing for 400 with automatic transmission: 8°BTDC @ 850 RPM


Page 6C-13:

Vacuum Advance - Start @ 8"-10"Hg, 12° @ 18½"-20½"Hg,
Centrifugal advance - 0.4°-2.4° @ 500 RPM, 8-10° @ 900 RPM, 10°-12° @ 2,000 RPM


Also, if you are using European 99RON gasoline in a 10.5:1 442 engine, it should ping - it needs 102-103 RON octane.

- Eric

edit: I believe that all of these timing numbers are in distributor degrees, so double them if you are measuring them at the crank.

MDchanic

Oh, and I should also say that I agree with Eric:
In the event of a sudden change in timing, you need to check the vacuum and mechanical advance mechanisms for smooth function without binding, including the condition of the vacuum hoses.

In your case, the points plate binding would be a good reason for your problem.

Finally, don't forget that in any car, an exhaust manifold leak can sound just like pinging under the right circumstances, and really drive you crazy.

- Eric

Sircajun

My CSM only covers 1970, I have unfortunately not yet gotten a ´69 CSM.
Thanks for the numbers on the timing. I have been runing 95 octane with no pinging, only filled it up with 99 octane due to it suddenly started pinging.
What I gathered so far is: we will need to check the timing mark in relation to TDC, to know if we can rely on this measurement. Seff on this board is also bringing me a complette setup for me to try (great many thanks to him )
If another distributor works I´ll see if I can have my distributor fixed or if a replacement is needed.
Also check up on the exhaust

Could there be anything in conjunction with the front timing chain, worn out or moved a tooth or two?

Thanks

MDchanic

A slipping timing chain will cause your timing to be retarded

And big thanks to Seff! He'll help you figure it out.

- Eric

cutlassefi

What?
It'll retard it a few degrees, that's it.
I'm guessing your octane rating over there is RON only?
Yes your balancer could be wrong as well. It's always a good idea to verify tdc first.

MDchanic

Yes, but my point was that IF his timing changed at all, it advanced, so the timing chain can't possibly be the cause, and he needs to look elsewhere.

- Eric

droptopron

Soren, I always had initial timing around 8 degrees. Start with that and it should advance more than 13 degrees like others have suggested. Maybe the advance unit crapped out.

PS - glad you are getting to drive it.

Sircajun

I really appreciate all your help and advice.

bkeese

I'm confused. Every recommendation has been to fix/free up the advance so that the distributor can add advance to the total timing. I agree that the timing has a problem, but there isn't enough timing and adding more is likely to ping worse. So I don't think that is the problem. Pinging can be caused by carbon buildup in the combustion chamber, hot spots on the head or piston or even a cracked piston. Basically, something must be acting like a glow plug in a model airplane engine or diesel for that matter. You could try to de-carbon the engine with Sea Foam or AT fluid mixed with water down to carb (steam clean), becareful here not to hydrolock the engine. I've seen this cure engine run-on after turned off. Basically, if you have no advance in the distributor (completely locked up) you could set the distributor initial timing way ahead and it will run good, but start hard hot, or you could leave the timing alone and it will start easy and run like crap top end, but not cause pinging, in humble opinion.

PS, I have jumped a tooth on the timing chain and the engine barely ran. To get the engine to run reasonably well I had to put a good twist on the distributor, I think more than a few degrees. After the second time, 2 weeks later, another good twist. After the third time, a week later, it barely made it home.

Look elsewhere!

MDchanic

Not at all.

If the points plate is binding, it might be pulled into the full advance position at cruise and then fail to snap back when the vacuum drops with acceleration.

- Eric

cutlassefi

I agree with most everything above except the cracked piston comment. That won't make it ping, it's typically the result of excessive pinging.

As stated, check the validity of your balancer first. Then do as above with water, ATF or whatever.
And also as mentioned, make sure it isn't an exhaust leak. That would show up when you pour ATF in it as well. That might be a good test to do first.

droptopron

True but OP said it was fine one day and bad the next. That points to some sort of mechanical failure and not something built up over time.

Sircajun

Ok, so I had a day off today since I went to a Metallica concert last night ;-) and that gave me the opportunity to look a little more on this problem.

Seff provided me with another distributor setup, so...

A good friend of mine and I started of by making sure the harmonic balancer was in the correct place and the marks line up. Everything is fine, we measured the TDC on no. 1 cylinder.
Changed the distributor, fired it up and went for a drive, almost no pinging, only when really hard on the gas. "Cool" where our thoughts...
Came b ack, setup the initial advance to 8 degrees BTDC, no vacuum advance hooked up. Test drive, and massive pinging was there again.
These are the numbers for machanical advance, no vacuum.

Rpm: degres

700 (idle) 5
1000 9
1500 15
2000 19
2500 22
3000 26
3500 30
4000 32

The above gives massive pinging on even just a little load /accelaration.

So we turned it back and retarded the timing aprox. 5 degres AFTER TDC

Car starts with no problem, runs great and only pinging under heavy accelaration.

I´m puzzled, what is going on here?????????

IF we hook up vacuum advance the numbers are even higher. We can have as much as 60 degres advance @ 3000 rpm.

What I am thinking is, set timing to 8 degres initial advance ang look for the culprit else where or do you guys think that the advance curve is off?

Thanks

oldcutlass

Here are a couple of articles to read:


http://www.angelfire.com/on/geebjen/timing.txt


http://www.lbfun.com/warehouse/tech_...101Article.pdf

MDchanic

You may have already mentioned this elsewhere, but what is your compression ratio, and what octane gasoline are you using?

- Eric

oldcutlass

Are you running points or the electronic ignition with the new dist?

Sircajun

Thanks for the articles Eric.
I'm running 99 octane (=us 95)
CR 10.50:1
No points, the "new" distributor has a Petronix electronic ignition.

MDchanic

Since the engine was designed to run on 102 or 103 octane, I think we have at least a partial explanation.

- Eric

Sircajun

Well it has been runing us 91 octane wiht no problem and was runing on this when the pinging suddenly accured during an acceleration so I find it hard to believe that fuel is the culprit, then it would have started pinging the day it was was filled.

oldcutlass

It needs the highest octane rating fuel that you can get at the gas station.

Sircajun

And it has. Changed it to highest octane during first attempt to locate the fault.

MDchanic

I'm not certain what could have changed, but a 10.5:1 iron-headed Oldsmobile engine should not run on Regular with any normal timing setting without pinging.

The fact that it is doing this now is not surprising. The fact that it didn't do this before is.

- Eric

442rocketdave

X2 with what Eric said, the only thing I could think of is that your advance was stuck! before and now its working, back years ago in one of my 70 442s I had a true 10.5 to 1 compression and the W30 cam and the ONLY gas I could run was over 100 octane and it ran best on the Sunoco 105 what we called blue gas. anyway you cannot run it on regular and especially if it has ethanol in it even 10% which creates higher temperatures in the cylinders so it makes it worse!!! Check that your fuel is not an Ethanol blend! you need pure gas and high octane! Some of the gas we have here in the U.S. is really crappy!! I know in Europe when I lived there the gas was good I hope it still is.

Sircajun

Ok. I will get some octane booster set timing right and we'll see if you're right on it being an octane issue.

Anyone want to comment on the advance curves I put up?

oldcutlass

You need to limit your vacuum advance, I'd start with it limited around 48-50. I've found if it goes over 50 it will ping under light load.

cutlassefi

You're kidding right? It's pinging at 32, what makes you think he'll be able to take it to 50, even at light throttle?
And you won't normally hear pinging under light throttle, no matter what the timing is. However excessive advance even at a light load can still do damage.

Sircajun

Sadly higher octane fuel did not affect the pinging sound. So I took it another route. One after the other I pulled the spark plug boots with runing engine.
This suddenly gave me what I believe to be knocking sound from the low end.
At this point I have no doubt that I´m facing some kind of mechanical problem, just don´t know yet what it is. It has been behaving like detonation, @5* retarded timing it only accurs when hard on the accelerator.
Will be making plans for pulling the engine and tearing it apart.
Did anyone say 455 upgrade Only too bad parts, engines and such are so hard to come by in these parts of the world
I will be keeping you guys posted.

442rocketdave

If your engine is factory the knocking could be your ring lands breaking, I have had that happen on the factory cast pistons, or it could be a spun rod bearing. Contact Mark at CutlassEFI for Piston, pistons rings, cams and all the goodies he can help you out on the parts and what goes with what!! Good luck!

Sircajun

Today I tolk the first step towards pulling the engine. Had bought an engine stand loaded ny tools in the trunk and drove to my friends garage. We quickly realized thar something Washington not right Winther the flexplate. Pulled the trans and found the flexplate bolt all were not thightend. I could unscrew them with my fingers. We had little hope thai this would be the culprit behind the pinging sounds but put it all back together. The knocking sound is gone but I still have the pinging. So back to sqare 1.
Next step? I do not know yet.

442rocketdave

If the knock is gone at least you dont have to pull the motor and rebuild, so the pinging is one of two things the timing in the distributor/timing chain or the carb is way too lean but they are fixable and will just take some time and trial. Hopefully with little error. At least the big money is saved for now!

Sircajun

Carb will be the next thing. I had it torn apart and everything was nice. A replacement has to be tried out. Then timing chain check up.

Sircajun

So it has been a little time since last, and I have had the chance to try another carb. But that did not help me. I have come to the conclussion that I'm facing a mechanical problem that sounds and behaves like pinging / detonation.
Since summer lasted a bit longer than normal I will be tearing the engine down over winter to see what the problem is. I' ll keep you posted.

tru-blue 442

Out of curiosity, what spark plugs are you running?

64Rocket

Also may have a lot of carbon build up.
also what plugs are you using as already been ask?

Gene