# strange noise when accelerating



## Chris-Austria (Dec 23, 2010)

Hi!

My 428cui makes a "pinging" noise since today. It starts while I'm driving and pushing the pedal so far, that the tri-power starts to work (outer carbs). Maybe it has nothing to do with the tri power. Also if I push the pedal while I'm not driving, there is NO strange noise coming from the engine, which makes it hard to locate where it comes from while driving.

While checking the engine I could see that one of the cables coming from the alternator has a little heat "damage", it touched the intake manifold exactly in the center of it. Can't see any real damage, but maybe this can cause the strange noise?!

I checked the ignition already, all wires are good and because the noise isn't there while I make something between 800 and 5000rpm in my garage I stopped searching for ignition problems.

I could imagine that the noise is caused by vibration, maybe something is touching the engine when it moves a little bit more because of full throttle?

Chris


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## Rukee (Feb 8, 2007)

Sounds like low octane and too much timing maybe? Take a few degrees out of the timing or add some race fuel to see if it stops. If it is pre ignition, you don't want it to make that noise!! I"ve seen a rash of bad gas issues going around, did it start shortly after getting some fuel?


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## Chris-Austria (Dec 23, 2010)

I always use the same fuel (100 octane). I filled up about 30 liters of fuel some days ago, but the noise started today.

I'll have my timing checked with a timing light soon. Ignition has been set up some months ago and always worked pretty good since that. (36° max)


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## geeteeohguy (Feb 2, 2008)

Sounds like detonation. Something has changed if it wasn't doing it before. Fuel, ambient air temperature, engine temperature, engine load, ignition timing, or fuel mixture. Too hot, too lean, too advanced or just plain too much compression will cause detonation....If you didn't change anything, I'd check for sticking advance weights in the distributor.....


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## Chris-Austria (Dec 23, 2010)

Didn't change anything.. temps are always the same as well.
Since it did start while I was driving, I'll see if it still "pings" with a cold engine tomorrow. I'll check the distributor, but weights and springs are pretty new. Funny that it doesn't make any strange noises if I push the pedal while the car is standing still.


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## Chris-Austria (Dec 23, 2010)

Update:
The noise only appears during hard acceleration on the road (under load).
My mechanic checked the timing.. starts at 18° and ends at 38°.. dropped it a litte after that but the noise is the same with 14,5° to 34,5°.

He also said he believes that the cylinder head gasket is bad and or a valve is damaged (he checked the compression and on the right side cylinder head #4 seems to blow into #6 he said)
He also removed the valve cover to check for bad lifters but underneath the cover everything looks great.

What do you think? Do I have to remove the cylinder heads? Can I get replacement parts if for example a valve is bad? (670 heads)


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## geeteeohguy (Feb 2, 2008)

Detonation can and will cause blown head gaskets. Yes, the head(s) need to come off. And,yes, parts are available. I seem to remember that a long time ago you had posted some information and it was determined that you were set on running very high compression on today's fuel....Euro 100 octane is nowhere near 100 US rated octane, JMHO......I would seek out another set of heads for that 428 of yours if I were you, with bigger chambers than 670's...or some aluminum 87cc Edelbrocks. You need to drop your compression down to about 9:1. You are well over 10:5 to 1 presently, if I remember correctly.....I broke several pistons in my own 428 back in the '80's from pinging/detonation.....and I never heard a sound. My bet is that yours was detonating for a while, if not always, and it finally "went". Keep us posted, and good luck on the re-do!


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## Chris-Austria (Dec 23, 2010)

I won't drive any more until the heads come off and I'll think of using other heads. I thought about it like you remember it, didn't hear anything until now, but maybe it's a bad idea to repair the 670's and have the same problem in 1-2 years again. 
If pistons were broken in my engine, the engine wouldn't run at all I guess? So maybe I can get away with "only" new heads. What do I have to know/order/use if I want to create a powerfull and reliable 428?

There are the Edelbrock EDL-61579 and the Edelbrock EDL-61575 available at Summitracing both with 87cc. I guess I need the D-Port style heads?
I'd really appreciate help on chosing the best heads (and if necessary other parts) for my engine. If I have to spend that much money, I want to create real power if possible


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## BearGFR (Aug 25, 2008)

All the symptoms you're mentioning do point to detonation issues - especially the fact that it only happens under heavy load.
At what RPM does it happen? Do I recall correctly that you have a manual transmission? Try shifting to a lower gear and see if that makes it stop. The "worst" conditions for detonation are low rpm under heavy load.

Also, remove the spark plugs and look at them closely - use a magnifier if you need to. See if you can find any 'shiny specks' on the ceramic around the center electrode. If you find it, that's cause for concern and more evidence of detonation - what you're seeing are flecks of aluminum that's coming off the pistons - which are disintegrating.

Bear


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## Rukee (Feb 8, 2007)

It will run with broken pistons, mine had a broken piston when I bought it. It was broke between the top ring and the second ring, so it would pass a compression test. Still have that piston too.


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## Chris-Austria (Dec 23, 2010)

I had the spark plugs removed and they look fine (a little brown with a little white). No shiny specks visible...
The car has a 4 speed manual, that's correct. It happens if I for example drive in 2nd gear at 20mph and push the pedal to the floor.. if I drive along with 4500rpm in 2nd gear everything sounds great (at lower rpm as well).
If there is a detonation issue, why is it hearable now? I didn't change anything and the ignition (distributor) works like before (has been tested today).
If I push the pedal to the floor while the car is standing still, everything seems fine, no strange sounds... if other things like pistons, valves... would be bad, would it be possible to not hear anything under these conditions? I remember a bad bmw engine.. it sounded really bad with piston problems.. everytime!


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## BearGFR (Aug 25, 2008)

It's not guaranteed to be "the ugly D-word" - we're all just guessing at what's likely. Something else you could try would be to find a nice long uphill grade, leave the car in high gear, and "play" with the throttle going up the hill. If you can make the sound come and go at will with your right foot, that will be more evidence.

Bear


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## Chris-Austria (Dec 23, 2010)

I can surely try that, but I don't want to make it worse. I can drive high speeds with high rpm and no strange noises.. only if I push the pedal at low rpm it starts doing that. If I only cruise around there is no noise that doesn't belong there.
Can a bad valve like my mechanic is guessing cause this? Or could there be 2 different problems? And if the head gasekt isn't in good condition (it doesn't leak or use water) can this cause a sound like it has "D"?


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## Chris-Austria (Dec 23, 2010)

I drove uphill in 3rd and 4th gear. As soon as I push the pedal a little harder the strange noise appears. As soon as I stop pushing the pedal it stops. If I drive a little faster uphill in 3rd gear with 3500rpm everything sounds great as well as soon as I push it to the floor, this will make the strange noise appear once again. It's pretty the same if I drive uphill or not.

I checked the ignition once again and cleaned the contacts (cap and rotor). No difference at all.

Thinking of the compression test which showed a leak and that my mechanic said he can hear a valve blowing (I can't hear that)... What do you say Bear? Where could my problem be located?


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## BearGFR (Aug 25, 2008)

Man, Chris, everything you're describing sure sounds like a detonation problem - including the head gasket. Note that it's possible for an engine to be detonating without you being able to hear it. That could have led to the head gasket failure and now the leak between cylinders is making it 'worse' - causing you to be able to hear it now. You might be able to hear the valve leak if you remove the air cleaner and listen to it idle. Listen carefullly near both exhaust pipes and also near the carburetor ( again, air cleaner removed) for a short, faint "hiss" that seems to happen "in time" with the engine. Hearing it at the exhaust indicates a leaky exhaust valve, at the carb - an intake valve. (More likely to be an exhaust valve). 

Considering that you're running 670's on a 428 --- if all the dimensions are "factory nominal" you're already over 10.5:1, higher if the block has been bored and/or zero-decked. That's pretty far into the 'danger zone' with iron heads even with a pretty nasty cam.

Bear


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## Chris-Austria (Dec 23, 2010)

So probably a valve (or more) has been destroyed because of the enginge detonating for some time, which I couldn't hear until now? All I'm sure is that there are no shiny things on the spark plugs, so maybe I can get away with a bad cylinder head and not with bad pistons.. as well?! I guess it's hard to say until the heads have been removed.

My mechanic said he can hear the bad valve on idle when he listened at the middle carb while he pulled the gas a little.

I don't know which cam I have now, but if I need to replace the heads, a new cam and lifter set would be recommended? Maybe you can tell me something to the parts I have found from Edelbrock in my other thread. I have calculated and would be able to afford the new heads (d-port?) and the cam-lifter set if I need to. The heads with 87cc would make something below 10:1 I guess, even if my block has been bored and zero-decked?!
Maybe this would be the cheapest way to get back on the street and building a real powerfull engine must wait until I can afford it (I checked the parts you told me.. looks very nice but as you mentioned.. they are not cheap). I'm so glad you can tell me these things. Nobody near me has the experience with these engines and I don't really trust in what some guys say who drive Fiats and VW's if we talk about 45 year old Pontiac engines


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