what am I missing?

[jjdart71]

I have a 71 318 that spark knocks under hard acceleration. I have so far replaced the points with accel point eleminator and matching coil . it has new holly 650 with weiand intake exhaust is open . distributor is new . pulls close to 18 on vac gauge at idle . i have tried all different timing seems to like 10-btdc the best. the book called for autolite 66 plugs at 35 gap it still would ping and it seem not to clean itself which to me seems like it was to cold a heat range for the set up. the also is no flutter on vac at idle so im thinking valves are still ok . mid range is fine vac advance is ok it works . no vac leaks . i have been putting same gas in 91 octane pure gas . should i switch to high e-gas to make it take longer to burn ? im sure im missing something any help would b greatly appreciated . thx jfj:banghead:

 

[67Dart273]

You have any idea what the total timing is?

Have you checked the timing marks are correct?

A 318 should not ping with the worst gas you can throw at it

I assume? you are using typically U.S. alcoholized fuel, IE 10-15% ?

 

[jjdart71]

total timing is at 32, marks are right , gas is 100% 91 octane, i can back it down to 8 btdc and ping goes away but its super sluggish

 

[moper]

Did you alter the springs in the distributor? What ignition do you run? Did you tune the Holley? Set the floats, get a vacuum reading at idle but in gear? If the exhaust is open how do you know it's pinging?

 

[67Dart273]

total timing is at 32, marks are right , gas is 100% 91 octane, i can back it down to 8 btdc and ping goes away but its super sluggish

Do you know for certain what the compression ration is? pistons, milled heads, etc? I'd be checkin' cam timing if it were me Engine temps?

The teen I had before I tore mine down was a stock 70's smogger. I put a Performer on it and a 340-ish cam. Ran 15-17 initial, abotu 36 total. Cheapest pump gas I could get. Never made a sound

 

[jjdart71]

numbers matching 71 motor temp is fine it has 3 core aluminum rad two fans never gets above 195 sitting in traffic . no headers but from manifolds back it has 2-1/4 pipe flow master 40 series it seems to breath well headers will come shortly. it has accel points eliminator and matching 8140c coil . it reads a constant 16 on vac gauge . the dial in timing ligh shows mech. advance is working fine it has a new vac advance with no leaks it drives fine with no noise only ping under hard acceleration.i put new timing chain and gears all lined up well no problems . sombody had been into motor b 4 i got car it acts like it has a mild cam .

 

[jjdart71]

the carb is as it came from holley with only minor adjust ments to idle its a 650 street avenger sitting on a staeth weiand intake

 

[jjdart71]

i got the car a little over a year ago and it had not been run in ten plus years . when i got it i took off oil pan cleaned pump and screen checked for damage . cleaned entire fuel system . evicted the family of mice from inside as well as out of the car replaced and repaired the wiring . everthing works including trunk light and light buzzer it had a bad distributor and a mallory points coil . it was worse with the pinging but i have made it better just not all fixed . could my plugs need a different gap or heat range? it runs really well no sputter no hesitation .drive line is all rebuit trans and rear what am i missing?

 

[OldmanRick]

I'm at a loss at this point. Nothing I'm seeing done so far would make a low comp teen ping. I even doubt a big carbon build up could do it on one of those engines? A compression test might rule out that issue? The 8*/10* difference is intriguing though.

It comes down to high combustion chamber temperatures, for whatever reason.....

Or, is there any chance it's a exhaust leak making the noise?

 

[jerry6]

Could the heads of been cut down enough to bring up compression enough to make it ping , that or pistons were been changed ?

 

[crackedback]

Did you pick an RPM number to see where total was or did you actually rev it until it stopped advancing.

Picking an RPM to observe will get you in trouble, especially with a distributor dating from about 1969 and up.

 

[moper]

Did you pick an RPM number to see where total was or did you actually rev it until it stopped advancing. Picking an RPM to observe will get you in trouble, especially with a distributor dating from about 1969 and up.

What he said. You haven't said what rpm does the advance start to advance, what rpm the total is at, was the carb tuned (I mean changing jets, power valve, rebuilt, etc) at any point. Is this car a manual transmission?

 

[magnumdart]

If it sat for ten years maybe some of the cooling passages have been comprimised. Under heavy acceleration upper cylinder temps could rise quickly and cause a ping. If the cooling passages are only somewhat blocked, when you let of it could cool back down fairly quick.

 

[fishy68]

Is ALL the fuel in it fresh? I say all because I see guys dump 10 gal of fresh fuel in 5 gallons of old crap thinking it will be fine and it rarely is

 

[jjdart71]

the fuel is fresh as the car is all i own and its my daily driver. i believe the carb is jetted at a 65 , the engine i flushed out really well numerous times and put new water pump, rad ,hoses, when i replaced intake i flushed from there as well seemed to flow good , the old coolant was surprising green and intact, i have two gauges both on intake and am not seeing high temps , im not thinking any thing is stopped up but as your right it is something to consider. when i put the timing light on it and adjust the setting i can see the mark move to where it supposed to b , to me it seems right i am thinking that what was meant by rpm was checking mech adv. for operation? it starts to advance right away and it dosent seem to move after it hit about 5,000 rpm . i want to thank everyone for the replys .

 

[moper]

" i believe the carb is jetted at a 65 "
When was it last rebuilt? What power valve is in it? How far out are the mixture zscrews to get the highest and smoothest vacuum reading?
" when i put the timing light on it and adjust the setting i can see the mark move to where it supposed to b , to me it seems right i am thinking that what was meant by rpm was checking mech adv. for operation? it starts to advance right away and it dosent seem to move after it hit about 5,000 rpm ."
You check it at idle rpm, get a reading and write it down. BTW - what is your idle rpm? My light has the advance too, and I will advance it (the light) until the line is equal to the "0" mark on the cover. Then very slowly bring up the rpms and watch the mark, and the tach. Chances are it start moving around 1800 but jot down when it starts to move. Track the amount of degrees it advances as the rpms climb, and write down the amount for 250 rpm intervals. It helps to have a friend working the throttle on the carb while you do the light setting and note taking.

More than likely you will need to add the light advance weight springs, and take the dsitributor apart to weld up the mechanical advance losts to limit the centrifugal advance. I think it's a comdination of wrong advance curve, and power valve, possibly a carb that needs a rebuild if you don't know when the last time it happened.

 

[jjdart71]

the carb is new out of the box. i will try retiming with help . the screws adjustments that get the most vac at idle are about 2 turns out from seated pulls good vac at that point . someone suggested looking at vac when car is in gear , at that point the car idles at 600rpm its at 750 to 800 in park . it is all clean gas in fuel system as i dropped tank clean it blew through lines put new fuel pump ,sending unit ,filter etc. i put a new distributor on car and found the vac advanc wasnt working . the carb is ported but still a vac leak under light throttle so i repllaced that drivabily is good until you go hard on throttle it pulls good ,never skips just has that rattly ping on the top end . could it just b crappy gas from the pump. idk i have had many a 318 ,340,360, 383's never had this problem before . most 318's are bullet proof can just throw a tune up in their direction and their fine lol Everbody has had some good ideas and again many thanks for replys

 

[moper]

Ok - that was me that asked about the vacuum in gear. That's how you determine the right power valve required. You probably have a 6.5 in it, but you need something much higher number - like a 9.5 or 10.5. The wrong one (too high a rating) can run rich at idle, or (too low a rating) run lean during throttle tip in and cause pinging or detonation. I think 2 turns out might be excessive but if you're not running a higher initial timing setting that could be why it wants that much fuel.

 

[Rapid Robert]

What Moper said: the problem is in the too fast of curve (spring choice). (1) Set the initial to what it wants (2) weld/file (shorten) the slots to get 35 total & this is initial plus mech (slot) amount & can plugged (3) with 35 total then plug in the can. (4) start subbing in a slightly stronger spring for either of the current springs going stronger and stronger till the pinging just stops on accell on your hottest/driest (most likely to ping) day. since you have an aftermarket dist you do not have the OE (Mopar) heavy spring with the elongated loop on one end and with your "regular" springs they work together & advance in a linear fashion (straight line) so you can mix and match any combo to come in faster or slower (we need slower here). Short version: your springs are too light and it is advancing too fast/sub in a stronger one(s). EDIT the "mild cam" sound suspicious, I would confirm there is no vac leak & tho your vac is steady some gauges are extremely dampened

 

[jjdart71]

ty you for the tech advice it gives me a direction to go with . im going to adress the springs and the carb and see if that helps it seems to me that it will . I want to thank all who posted and helped . What a great group of people . jfj

 

[moparlover]

Or, is there any chance it's a exhaust leak making the noise?

try a set of percy's exhaust gaskets i bet it helps

 

[AJ/FormS]

Going back to what moper said;Once you get all those data points, you could plot them on some graphpaper. Use the horizontal axis for RPM, and the vertical for # of degrees. Now you have a nice visual depiction against which to plot future changes.For instance; you label this first cufve "A". then you make a change to the dist, plot a new curve on another graphpaper and call it "B".On each curve, you mark the rpm at which you first experience sparknock/pinging and at what throttle setting.Off to the side you can make notes such as "runs strong up to point of knock",etc. And also note what parts were used to achieve the curve.Using this method allows you to see trends in what works or doesnt and also you will easily be able to back-track when neccessary.
-btw, what diff gears are in there? The lower no. (highway)gears are sometimes harder to tune for.
-And in regards to your sparkplug questions; IIRC,those 318s run Champion RN14Ys, or equivalent,@.035gaps.With a good coil I like to run .045gaps.At this point,as long as she doesnt missfire the plugs are close and not likely to be the cause of your woes.

 

[Dezduster]

First thing I would do is install a cooler t stat to see if that does the job. Then I would add some jet to both ends to see if you can quench the knock with fuel if it goes fat and gets piggish before the S/K is gone go back. Then a new curve to the distributor curve until gone and power still there... Oh check your PCV valve oil mist in combustion cyl will cause detonation.

 

[AJ/FormS]

We still havent seen the compression test results.
-Also, you say it rattles at the top end. Do you have an RPM range for "top end"?
-I read that you cleaned the fuel system.But from experience I can attest, that if a fuel system was put away with fuel in it and parked for as little as 5 years, that there may be/are places you cant see or clean. When the fuel evaporates it leaves behind a varnish that I havent found a solvent for.It coats the pick-up sock and restricts the fuel line.I also didnt read that you replaced the soft lines. If the fuel bowls were running low it might be the cause of your top-end ping.
-So, I would also recommend a fuel delivery test.

 

[my5thmopar]

total timing is at 32, marks are right , gas is 100% 91 octane, i can back it down to 8 btdc and ping goes away but its super sluggish

What did you do to check the marks?

Did you check with a piston stop?

Maybe something is amiss with the cam, crank and timing chain. Someone may have degreed the cam incorrectly. My 2cents