flyway190

My engine has had this really annoying ping ever since I put it in. It will do it when the car is warm and only at part throttle. The warmer the car is, the more pronounced the ping will get. WOT seems fine, I ran a 15.3 which isn't bad for what the engine has in it (or doesn't have in it), and I don't notice anything strange. Idle isn't too bad, though it will kick around a little bit every once in a while and isn't perfect in closed loop. Idle is smooth in open loop. Also I would like to add that I know of another person who has done a very similar engine swap and is having the same problem.

The carburetor is the stock CCC quadrajet, and I have not made any modifications to it other than changing the secondary metering rods. I do not know what the lean stop screw is set at, but the rich stop screw is all the way in the air horn. There aren't any vacuum leaks that I can find, and I've checked them all. I hooked up a dwell meter today and drove with the rich stop screw all the way in like it has been as long as I've had the car, one turn out, and two turns out, but I did not notice a difference in the pinging behaviors or anything significant with the dwell. I set the idle air bleed screw at the point indicated by the gauge, then set the idle mixture screws to 8 turns out. I did not change the IAB when I adjusted the rich stop screw, I didn't think it would make a difference. Since I put the engine in I have added a one inch 4-hole carb spacer. I have run an open-element for at least 6 months before I put the engine in.

EDIT: I forgot to mention that the dwell is right around 30-degrees at part throttle when it's pinging.

I started with the factory computer and chip, then switched to an '87 Caprice computer and chip, and now I have the '87 computer and ZZ4 chip. With the previous 2 chips, the oxygen sensor would read very low, between 0.050 and 0.200. With the ZZ4 chip, it now varies evenly between 0.050 and 0.700 (which seems to be the way it should be). The knock sensor and module are also the ones that came with the ZZ4 chip in the 350HO conversion kit.

The timing is set at 8-degrees, and I am running 93 octane gas. The pinging seems to lighten up as the octane of the fuel increases. It seems to ping much more with 87 octane. With the ZZ4 chip it knocks a little with 89 octane, with the computer responding by retarding the timing as indicated by the decreased rpms. The coil, wires, and ignition module have been interchanged with the stock units, with no effect. Since putting in the engine I have changed from champion spark plugs to ac delcos with no noticeable effects. Plugs are gapped at 0.035, and the cap and rotor look fine.

The fuel pressure is a little over 6 psi, and seems to be consistent. I finally moved the pump near the gas tank and fuel supply or pressure does not seem to be a problem.

I have completely blocked off the EGR valve with a plate with no noticeable effect on the pinging. I even replaced the valve and solenoid with no noticeable effect.

The MAP sensor tests ok, the oxygen sensor seems to be working but has almost been on there for a year, but was installed only 3 months before I put the engine in. The coolant temperature sensor is several months old, and the TPS seemed to be fine last time I checked. The MCS also seems to be working fine.

Does anyone have any tips or suggestions as to what might be causing this? Sorry for the length of the post, but I wanted to get as much info in as I could.

305sbc

iTrader: (3)

Take a close look at all your sparkplugs again. You might have one or two lean cylinders.

later:
okay I tried looking around your site and I may be more confused now, so I have questions.
Are you running an Edelbrock performer intake manifold?
If so the #4 and #6 cylinders sometimes run lean with sbc dual planes like that.
Did you say that this engine burns oil too? Are the valve seals good? If one or two cylinders are pulling in more oil than the others, that can sometimes cause pinging too.

flyway190

The manifold is currently an Edelbrock Performer, but I didn't get that until 2 or 3 months after I put the engine in. Before that I was using the stock manifold and it was pinging just the same. I'll check on the distribution next time i get a chance though.

As far as I know this engine doesn't burn any oil, it was my old one that did. It has a few slow external leaks, but nothing to worry about.

F-BIRD'88

Hook up the EGR and make sure it is working.
Should flow ex gas at part throttle.
This goes a long way to reducing ping at part throttle.
What is the compression ratio on this motor? What cam?.
Pull one spark plug wires at a time and fine the cylinder that is pinging.
That's the one that is too lean.

flyway190

Compression is 9.6:1
Cam is 0.360 intake, 0.385 exhaust, 110-degree lobe separation, and I don't know the duration but it's probably similar to the LO3 cam.

flyway190

I took it out to check each cylinder by unplugging wires one at a time. To test it, I would pull the wire for the cylinder I was testing at a gas station then take it down the service road of a highway that has a 20 ft. high concrete wall on the highway side, then made a u-turn under a concrete bridge and back to the gas station to try the next one. I didn't notice much difference between the cylinders. Afterwards I realized that I hadn't hooked the EGR back up, so I hooked it straight into the ported vacuum port and ran it with all cylinders down the same test, and it sounded the same. I also made a run with the MCS unplugged, which seemed to make a slight difference. I tried that with and without the EGR and noticed no difference.

flyway190

BTW, I had my car tested for emissions a few weeks ago and here are the results:

High Speed Test (25 mph)
HC(ppm)....116
CO(%).......0.10
CO2(%).....14.7
O2(%)........0.3
Nox(ppm)...830
Dilution.......14.8

Low Speed Test (15 mph)
HC(ppm)....166
CO(%).......0.30
CO2(%).....14.4
O2(%)........0.5
Nox(ppm)...1104
Dilution.......14.7

flyway190

I pulled the spark plugs just now. All of them are black, but #8 seems slightly less charred than the rest of them. I also found the plugs I had in there before these, and one of them was obviously lighter than the others. Those seemed normally worn by the way. So I suppose the question now is why would #8 be getting a leaner mixture than the others?

F-BIRD'88

A vacuum leak

flyway190

Could there be a leak that would cause that anywhere besides where the intake manifold meets the head?

F-BIRD'88

The #8 intake runner on a performer manifold has a vacuum
fitting on it. what do you have connected to it?
Vacuum modulator?, PCV? power brakes? etc. That vacuum line may be leaking causing the lean cylinder on #8.

Just curious, how much cylinder pressure do you get on a compression test?

flyway190

You're right! It's a line that tees off into a hard hose going back along the firewall, and a hose that tees off into the cruise control that has never worked, and a big ball under the charcoal canister. I'll cap off the whole line as soon as I get my car running again (carb just started leaking gas and needs a rebuild).

F-BIRD'88

Vacuum leaks can be areal pain.. Start with new plugs too.
Good luck....

BLJ

I am the other person that flyway190 mentioned at the begining. I put this same engine in my 83 Malibu. I too have the gas ping at cruise. It goes away with any acceleration. I even bypassed the egr solenoid and ran the vac hose to the valve. I have noticed that when giving it the gas the egr valve pulsates very rapidly. Normal? I have replaced nearly everything. Carb (four times- other problems, now ok), wires, plugs, cap & rotor. New Be-Cool radiator, high flow water pump replaced about one year ago. I put the engine in Sept 02. 160 thermostat, 25% antifreeze and Red line wetter and synthetic oil. Everything possible to keep the temp as low as possible. If the temp is below 175 no ping. But running on the highway for 10 or more miles the temp will creep up to about 180 and stay there, and I get a light ping. Using AC plugs 42's (as cold as possible, I think what a 92 Caprice calls for). At 2000 or so rpm's I get 30 degrees total advance from the computer/distributor. Intial advance set at 3 ATDC. Less ping here. Has the original computer. No update found for the chip. No knock sensor ever on car. Have not changed the ignition module or pickup coil. By-the-way, I had the same problem with the original 305, but with premium gas it went away. Too much advance at cruise? I have thought about doing away with the computer system, but with Austin 2 years or less from emmision testing, that may not be a good idea. Barton

flyway190

I capped off that whole line, if it made any difference on the pinging it was slight. Any suggestions?

flyway190

I just noticed that one of my header bolts on #8 is gone. What effect might that have?

flyway190

I replaced the bolt and tightened the rest of them and it seemed to make a small difference. Still pings though. Also, I finally smoothed out my idle by tuning the carburetor just right. I plan on replacing all of my header gaskets and checking the compression of my engine sometime in the near future. BLJ, I don't suppose it's possible that you have an exhaust leak? I suspect that one of my collector's is leaking, though I can't see or hear anything on my driveway.

82camaro

Still pings, back the timing up a couple degrees at a time and see what happens. If it was me, I would convert to non-computer and run a regular HEI distributer with an adjustable vacuum advance. Why...you can then adjust the part throttle advance(vacuum advance) so it won't ping. If you can't convert to non-computer, just back the timing up until the ping is gone and/or run a custom chip that provides less part throttle advance. The pinging isn't good on things, and it hurts power.

BLJ

There is a slight leak on one the air pump tubes. The ping was there before the pinhole developed. The noise is not the leak but a ping that gets worse as the temp rises. I have thought about getting a non computer carb and dist but with Austin 2 years or less from emission testing I am not sure it is a good idea. And will it get rid of the ping?

83_1/2 L69

I've had a light throttle ping problem twice. It was due to a lean mixture. Replacing the O2 sensor fixed it both times . But looking at your smog test data, you are not running lean.