# pinging issues, please help



## Iraq 69 (May 4, 2013)

Hey all,
Thanks in advance for your input.
1970 GTO 455HO with GM HEI dist. Don't think the engine has been apart but the timing chain cover has been off. First long drive over the weekend and had some pinging issues under load. Checked the timing today and when I went to loosen the dist hold down, it was loose and the dist turned freely. I set the base timing at 9 deg and at 2800 or so rpm dialed in another 18 deg of advance. Took it for a drive and the pinging was better. Took another 2 deg out for a base timing of 7 deg. The test drive was better but still some pinging under load. Got home and took another 2 degrees out for a base of 5 deg. The advance at 2500 or so was 15 more degrees for a total of 20 degrees. The vac was off the canister and plugged during the timing checks. I don't know what it had for fuel but at 1/2 tank, I filled with 91 octane.
It sure sounds like I am well into the "not enough timing" area but it sure runs well.
What do you guys think? Am I ok with this little bit of timing?

Marc:cheers


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## geeteeohguy (Feb 2, 2008)

Specified base timing on my '65 and '67 GTO's is 6 degrees BTDC. As long as you don't get too much timing at the wrong time, and it has good power and does not overheat or ping, you are good to go. I have a different issue with my '65...likes to detonate at light load/cruise due to too little octane. The fix for me is race gas. (until I fix the problem with some Edelbrock heads!!)


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## InjunRAIV (Aug 21, 2013)

One problem I've heard of is the balancer could have gone bad. The rubber sandwich deteriorates and the outer ring could shift and show you an incorrect timing measurement. The only fix for that is a new balancer though.

Not likely, but something to consider if all else isn't helping.


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## InjunRAIV (Aug 21, 2013)

Also, are the mechanical advances working? I can't remember the base specs so I can't tell from your post, but 18 degrees seems a little stingy?


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## Iraq 69 (May 4, 2013)

Hey Guys,
Thanks for the reply. I will check the mech/vac advance and weights for free movement. 

I found a fairly close gas station that has 93 octane fuel. I siphoned all the 91 octane out and will add about 15 gal of 93 octane tomorrow. I hope that will help my issues.
Someplace in this forum, I saw that you could add a couple gallons of E-85 to your tank to raise the octane a few points....I cannot find it again. What do you guys think of that?
Marc:cheers


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## geeteeohguy (Feb 2, 2008)

Nix on the E-85. It will eat up your carb and fuel lines, etc. If you want to raise the octane, use real race gas, TEL-130 booster, or Touluene. Do a google search for these three, and you'll learn a lot.


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## chuckha62 (Apr 5, 2010)

I was getting on the freeway the other day and a guy decided he didn't want to let me in... I jumped on it and forced the issue a bit and she pinged like crazy. Here's what I did... 110 Octane Sunoco leaded. I mixed 1 gallon to ten gallons of 91 octane and just took her out. Niiiiccce!

This stuff isn't cheap @ $11/gal., but it is out there. As GTOGuy says... Toluene works great to boost octane, too.


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## Iraq 69 (May 4, 2013)

Thanks for the extra info. I live in a very rural area and was lucky to find 93 octane here. There are no Sunoco stations and the next closed town of any size is 1 hour drive. There is a small airfield near here, I'll give them a call about buying a can of it.
I am hoping that the 93 octane will solve the issue. Does 2 points on the octane really make a differance?
Thanks,
Marc:cheers


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## geeteeohguy (Feb 2, 2008)

2 points of octane can make or break an engine. You can mix 100LL aviation gas, and it'll work, but it's formulated differently than automotive fuels, and less stable. It's not the ideal solution. Race gas is. Where I am, there are a handful of distributors that sell it by the jug or barrel (if you're feeling rich!).


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## chuckha62 (Apr 5, 2010)

Iraq 69 said:


> Thanks for the extra info. I live in a very rural area and was lucky to find 93 octane here. There are no Sunoco stations and the next closed town of any size is 1 hour drive. There is a small airfield near here, I'll give them a call about buying a can of it.
> I am hoping that the 93 octane will solve the issue. Does 2 points on the octane really make a differance?
> Thanks,
> Marc:cheers


We don't have a Sunoco station anywhere in the state as far as I know. There are many independent fuel companies around the US which cater to corporate and farm accounts. Many offer specialty fuels out of 55 gallon drums from their warehouses. Take a look in your yellow pages and see what's offered near you. I'll bet you'll be surprised. 

Yes, it will be expensive, but an additional ~$20.00 per tankful to raise your octane is going to be worth it down the road.

Airports may sell you fuel in gas cans, but keep in mind fuel is color coded so that the feds know that appropriate "road" taxes have been paid. Most airports these days don't want to be caught selling an off highway fuel to a guy who's going to put it in his car. If you can get the 100LL, get a bottle of lead additive to put in with it.



Good luck!

Chuck


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## PontiacJim (Dec 29, 2012)

In the days of leaded gas, I used to run the cheaper regular. I did not use a timing light as you have, but just would take the car out on the road and keep retarding the timing until there was no ping, then tighten the distributor down. The drop in power is not really noticeable in my opinion. You may also want to check your spark plugs for the correct heat range, might have incorrect plugs. If correct, you can try a colder set of plugs which may help the pinging. If your carb is running a bit lean, this can create a problem. Good high flow air cleaner? Check the PCV valve? Distributor vacuum line connected to the correct ported outlet on the carb?

Other considerations. How hot does your engine run? Might try a 160 degree thermostat. Does it look like the water pump was removed or replaced? A couple of baffles in there that are important for coolant circulation to the heads. They have a nifty hand held digital heat sensor available at the parts stores that can be used to see if you have any hot spots in your radiator/cooling system/heads etc..

Just try one thing at a time to narrow it down. Not sure if the higher octane will be the cure, but it can't help. The compression for that engine is listed as 10.25. Might want to do a compression test. The engine is supposed to have the factory "067" cam for the automatic and "068" for the manual. If a different cam has been installed in the engine at some time (does the intake look like its been off? this with the timing cover may mean a cam change), it could be aggravating the situation with a 10.25 compression ratio. Just my opinion on all this and a few things to consider.


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## Iraq 69 (May 4, 2013)

Hey Pontiacjim,
Thanks for the help. I have been busy and will look at some of your ideas when I have time. I have checked the temps with the laser and they are good. 180 degree thermostat and the head temps on the front are about 15 to 20 degrees hotter than that. Intake temps are about 190. The intake does not look like it has been off. I'll replace the pvc and the car does need cap and rotor. I will change plugs then and look at the old ones.
There are several things I can check pretty easy.
Thanks again,
Marc:cheers


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## chuckha62 (Apr 5, 2010)

FYI... A cooler thermostat doesn't mean your car will run cooler. A cooler stat will only open earlier, i.e. 160 degrees instead of 180 degrees.


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## geeteeohguy (Feb 2, 2008)

And, the real issue is that the car needs 100 octane fuel. It was designed for it and should have it to run properly. So, race gas added to the mix or lower the compression. Band aids don't work...not if you drive the car day to day.


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## PontiacJim (Dec 29, 2012)

chuckha62 said:


> FYI... A cooler thermostat doesn't mean your car will run cooler. A cooler stat will only open earlier, i.e. 160 degrees instead of 180 degrees.


You are correct about opening temp. differences, however, I have a different opinion on operating temps. and have witnessed the difference first hand in cars I owned.

A thermostat regulates the engine's coolant temp by controlling the rate of coolant flow through the engine. A lower temp stat will begin to open at a lower temp, thus lowering the engine's operating temp IF the radiator has sufficient heat rejection capacity. You need a radiator that has sufficient capacity to maintain below 180 degrees at cruise. At low road speeds, there is less airflow and thus the coolant temp creeps up. (thus the need for a fan)
In heavy traffic, the temp rises until the rejection of heat by the radiator equals the heat supplied by the engine. This rise can be slowed, or halted under some conditions, by increasing airflow with the fan. With a 160 STAT, the cruise temp will be about 180 degrees, but will rise as high as a car with an OEM stat in heavy traffic- it will just take longer to get there. Having a sufficient capacity radiator with a good fan will slow the rise even more, or even lower the max temp under some conditions. And high engine heat can add to a pinging problem.

I like a 4 core radiator, big flex fan, and radiator shroud. The newer aluminum radiators are said to run cooler, but have not used one, yet -upcoming build. It is also possible that the 455CI has a factory clutch fan and these can go bad and air flow is suffering, so this could be checked.

If the engine is original, how about the timing chain? Pontiac chains are known for stretch and this will change the relationship to cam opening and distributor firing, yes? You can check this by popping your dist. cap and leave the rotor button in place. Use a breaker bar/ratchet with socket and insert onto the big bolt that holds the harmonic balancer/hub on. Rotate until you see the rotor move. Put a mark on your pulley for reference. Now go back the other way with the crank until you see how far it rotates before the rotor button moves again. If the chain is loose/sloppy, you will get a good amount of crankshaft rotation. If excessive, the chain is loose, and could be affecting spark timing. And if its that loose, you need to change it before it breaks or slips -which is typically in my experience with original nylon gear/timing chains around 80,000 miles.

I am not saying you do not need higher octane gas, you may indeed need it for your engine. I think it does not hurt to check a few things first that you might want to check anyway. If everything comes up roses, then higher octane it is. I am no expert and my knowledge of cars may be clouded by my age and skewed by my romanticism of owning several GTO's and other older Pontiac vehicles over the past 35 years. Just throwing out some considerations that I would check out if it were my car as many of the cars I had were already wrung out, filled with problems, and I had to learn on my own how to repair them -usually after they broke 'cause I didn't have the money to fix 'em right before they broke. Funny how that worked. Now I have the money and find it so much easier to wait until it breaks so I know exactly what it is -and just ante up and pay for it. HaHaha.


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## PontiacJim (Dec 29, 2012)

Another Consideration. Looked up the Emissions Controls in a Chilton's repair book for the 1968-1973 Tempest, GTO & Lemans. Seems 1970 had engine emissions controls, and one that may be of interest.

"The more stringent 1970 laws required tighter controls of emissions. These included the Positive Crankcase Ventilation (PVC valve), the Controlled Combustion System used for exhaust emissions in conjunction with the "new" Transmission Controlled Spark System."

Ah ha. Transmission Controlled Spark System -a transmission switch, a solenoid valve, and temperature switch. Under normal conditions, the system permits the vacuum distributor (spark) advance to operate only in high gear and reverse (on both auto and manual cars). The trans switch on the trans senses when the trans is in one of the lower gears. When in the lower gears, the switch activates the vacuum solenoid valve. this valve is located in the vacuum line that runs from the carb to the distributor and shuts off vacuum to the dist. advance when its activated. There is also an engine-temp sensing switch which overrides the trans switch. It will allow vacuum advance in the lower gears when engine temp is below 85 degrees, or above 220 degrees. There is always vacuum advance in high gear and reverse.

So, if your car has this system, which it should according to this book, it could still be a timing issue at the distributor if perhaps some/all of this system is not working properly. Again, no expert here, but it may be worth looking into as well.


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## Iraq 69 (May 4, 2013)

Hey Guys,
Thanks soooo much for all the input. I have installed a new fan clutch and thermostat. It has a new timing chain in the last year or so. The cap and rotor had carbon build up on the brass parts that I have cleaned off. These along with the plugs will get replaced soon. There is a weird switch like deal in front of the distributor that has a pointy end(like a vacuum hose would fit on) and an electrical connector with several wires on the other. There is no hose and I don't know where the electric wires go to. The vacuum advance is hooked to a fitting on the intake at the back of the carb(Rochester q-jet) and when taking it off the dist to plug it and check timing, changes the way the engine runs.
Thanks again, I have been so busy at work, I have not had time to work on the car for a week or so. I hope to have time off next week.
your input is valued very much as I am learning.
Marc:cheers:cheers


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## PontiacJim (Dec 29, 2012)

You may want to locate a 1970 Chassis book which may have the emissions control devices I mentioned in my last post. That may be that thing on the front of the distributor. 

Do a compression test to see what type of compression pressure you have. It is possible that your timing could be off a tad if the chain was replaced and somehow misaligned causing too high a compression. You may want to retard the timing with a different lower sprocket or keyway at the crank. Found a pretty good page that details all this on a web page. Type in Dave Miranda in your search engine. Look for the site titled "Hot Rods/Pontiac - Dave Miranda" and click on it. Then enjoy the article. it may help a bit, I found it interesting.


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## BearGFR (Aug 25, 2008)

Don't discount the idea that the balancer marks could be off, especially if it has some age on it. When I put my engine together I used a *brand new* SFI-rated balancer, but when I verified it against the timing marks using a degree wheel and a piston stop (the heads were off), I discovered the marks on it were off by about 4 degrees. A timing tape fixed that little problem right up....

It's worth going to the trouble of making SURE the marks are right, otherwise you'll never know for certain exactly "where you're at".

Bear


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## PontiacJim (Dec 29, 2012)

BearGFR said:


> Don't discount the idea that the balancer marks could be off, especially if it has some age on it. When I put my engine together I used a *brand new* SFI-rated balancer, but when I verified it against the timing marks using a degree wheel and a piston stop (the heads were off), I discovered the marks on it were off by about 4 degrees. A timing tape fixed that little problem right up....
> 
> It's worth going to the trouble of making SURE the marks are right, otherwise you'll never know for certain exactly "where you're at".
> 
> Bear



Yep, I second that, another good point to look into.


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