I have a 1976 Dodge Aspen with a 318, 4spd. Since the weather warmed up this week into the upper 80's I've been experiencing a light throttle ping when leaving a stop light. It gets progressively worse as under hood temp rise.
The EGR was deleted by a previous owner. Short of replacing the EGR system what are some tips and tricks to lower the intake air charge and Cyl temperature? Coolder plugs? Snorkel? (My car doesn't have a provision for the paper tube). More fuel from the accelerator pump?
I've checked the temperature at the Thermostat outlet (194°), water pump inlet (147°), Snorkel (130°), and EGR block off (230°). I have an electric fan which is running at idle and the center of the radiator is 115°.
Any ideas are appreciated. Thank you.
I know this is an old thread but I thought you guys would appreciate an update.
One thing that turned out to be a problem in the beginning was the Factory BBD carburetor. On the manual transmission cars they were tuned leaner than the automatic. I didn't want to modify the jets/rods and finding an assortment wasn't looking good. I found a Holley 4bbl (list 7002-1) for $25 and installed it on an old 4bbl intake I already had. That woke it up nicely and holley tuning parts are readily available. The carb and tuning helped some but it still had some pinging at WOT.
I did chart and dial the timing in but at first I couldn't have more than 6° or so of initial timing (I tried different spring tensions too) and I had 32-35° total using an FBO limiter plate.
Another issue was the oil consumption from failed valve stem seals. I replaced them and that helped some too. I also replaced the timing chain and gears to eliminate the possibility of the nylon gear failure. It was loose so that helped some also.
Having run a couple of compression tests the numbers came back on the high side for a stock 76 318, around 175-180 psi, (also cylinder 6 and 8 took several cycles to build pressure). I decided to take a peak in the cylinders with my bore scope. There was a lot of carbon build up. I used the water drip method to try and steam clean the cylinders and it worked OK. I could see some of the carbon was disappearing and some was much softer. At first it didn't seem to make much of a difference but I was able to add a degree or 2 of initial timing. I continued to do some more water cleaning procedures for a couple of weeks and when it didn't seem to improve anymore I decided to try a fuel additive. After trying a few brands Techron is what did the trick. The oil deposits from the bad valve stem seals are all gone now and whatever carbon was contributing to pinging is gone too.
I've been running 16° initial timing (still 34° total) for most of this summer without pinging while running 89 octane fuel. I ran a compression test this past weekend and all 8 cylinders were 155psi +/-2psi and they all hit 120psi on the first stroke. In the end it was a lot of factors but the biggest contributor to the pinging was years of oil deposits and carbon build up.
