pinging on an hill?

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63dartman

63dartman

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I was coming up a hill today and put the pedal to the floor at around 35mph. It kicked down a gear and took off. My problem is it started pinging pretty bad. I am running 12* advanced initial and 35* total with no vac advance. I am running a holley 670 avenger out of the box. 360 10:1 compression, lunati cam with 1.6 clearwater magnum heads. lift is about 490 duration is pretty mild just a street cam. I did notice that my plugs are VERY clean. I can't tell if I'm lean because there is nothing at all on the plugs. Should I try going up two jet sizes at a time on the primary and secondaries?
 
yes, you need to tune the carb. Start with the power valve. So use a vcuum gage to see where you are driving around town. Then go to jetting.
 
if your timming is off it will ping not carb it's kinda hard to exsplain to you some times a timming light will work but the ear works better or put fuel additive in for more octane rating maybe your not going high enough with your % of octain
 
I only run premium in my car and here in NM that is a 91 octane rating. I buy my gas at a Shell down the street. I thought they had pretty good gas anyone hear different? My timing is good unless 12 and 35 are too much. Moper, I'm new to the holley carbs. I don't get any pinging unless I'm under a heavy load......all other times I get no pinging. Why the power valve first? I don't know the fuel circuits on the holley but, I would think that under heavy load it would be the secondaries that are too lean, help me out moper:)
 
If all else fails as mentioned above try another gas station. The stations tanks may contain more moisture then some others. My old Dart will ping using a couple of the local stations in my area and not a problem with my fuel injection cars due to the FI computer adjusting!
 
I would start by jetting up the secondaries first for the test. If the plugs are THAT clean it could be lean. If secondaries does not resolve it, I would back off timing.

From your combo description, it sounds like a pretty efficient package, but the 10. to 1 compression ratio, with cast iron heads (even if they flow well, they retain heat in cylinders), is pretty agressive on pump gas, not to mention the cam.

Sounds to me like the combo of compression, heads, WOT, and the load of the hill was just a bit much for the pump gas to handle, so it started to pre-ignite, or detonate. If adding a little more fuel doesn't solve the ping, it is now a situation of too much timing for the given load and situation. Back it off 2-3 degrees and you will probably be ok.
 
63dartman said:
I was coming up a hill today and put the pedal to the floor at around 35mph. It kicked down a gear and took off. My problem is it started pinging pretty bad. I am running 12* advanced initial and 35* total with no vac advance. I am running a holley 670 avenger out of the box. 360 10:1 compression, lunati cam with 1.6 clearwater magnum heads. lift is about 490 duration is pretty mild just a street cam. I did notice that my plugs are VERY clean. I can't tell if I'm lean because there is nothing at all on the plugs. Should I try going up two jet sizes at a time on the primary and secondaries?
Click to expand...

Magnum heads require less total advance than open chamber heads. Try setting the total to 32-34. Also, how quick is the timing coming in? You want to use springs that have it all in around 2500 rpm.

I am running a 670 on a 360 with magnum heads and 10.6:1 compression. The stock jetting on my set up is as close to ideal as I am going to get without an air/fuel meter. With today's gas if you can see a distinct tan color on the center insulator you are to rich.
 
well, I didn't do anything except back off the timing to 9* initial and I came up the same hill today and I got no pinging......I still think I may be under jetted or power valved. I think I am going to get me some jets and play with it a little. Also I need a good recommendation for a distributor. The one I'm running now is a stock unit with the vacuum plate locked down and the advance removed. It looks like With just the initial and mechanical I am coming up short on the 35* total that is recommended. I think I am getting about 29-30* total.
 
The Mopar Perfromance distributor is a good value. It has a fully adjustable mechnical and vacuum advance.

By pulling the initial back to 9 degrees you are right where you need to be (32 degrees) for total on a sb with magnum heads. As I stated before the magnum head is more efficient of a design than the old LA open chamber head so it does not require as much total timing. The new LS engines for GM are running less than 30 degrees total.

Before mucking with the carb you need to get the timing dialed in. Depending on your cam you could need as much as 20 degrees initial for clean idle and crisp throttle reponse on the bottom end. This will require an adjustable distributor or a lot of trial an error welding slots in a factory one.

Unless you have very low vacuum it is very seldom that the power valve needs to be changed. FWIW, the PV rating doesn't change the amount of fuel it changes when it opens.
 
If you spark plugs are that "Clean" they may be running too hot. Try a colder plug.

If the plug is too hot it will cause ping also.
 
try the external carb stuff first. the 670 holley has a 6.5 valve that should be good for that motor setup. you might want to play with the secondary spring and check the float setting first. it sounds like your timing adjustment cleared up your problem though. :cheers:
 
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