I am working on a 73 1.7

Valves adjusted to spec
Points set using dwell
Timing on the nose at 27' @ 3500 rpm (vac lines plugged)

She runs fairly well. had lots of ping on a up hill.
I could rev through it ... More ping as revs drop under load.

Today I put in fresh 91 octane and 16oz of seafoam, took a nice drive up a mountain.
Almost all the ping is gone.

Should I retard the timing just a bit ?
Or other suggestions / input much appreciated.

Fuel injected or carbs?

Any idea of the compression ratio? Yes retard the timing.

pinging under load is too much advance, stock dist.?
make sure weights are free and the advance curve is correct.
for the fi you are running.

More Sea Foam or try squirting some water in the TB at 2000rpm. It will bog down a little.

Thank you for input.
It is stock FI (D jet)

I have not done a compression check . So do understand that is an unknown .

I will try seafoam again next tank .
& have used water years ago with other vehicles , may try that to help clean .

Next would be to then check the dizzy out

Now at least I have some ideas and a few things to try.

Make sure the distributor plate in the distributor is moving smoothly and not sticking.

Click to view attachment

An extreme technique,filling each cylinder with Berryman's™ carb cleaner in turn,to the top.
Using the 50/50 acetone/trans fluid mix,pre-soak the plugs and exhaust studs.
Remove the plugs,disconnect the bat,rotate the crank to tdc and fill the cylinder with the Berryman's.
Let that soak for 2 hrs,while you gently attempt to loosen the exhaust studs without damage.
The exhaust can now be repaired and or maintained to perfect condition.
Discovering the solvent leaking past the exhaust valve will determine the seat condition.
A poor seal will mean a poor guide,so,drain and strain the oil,pull the valve cover,inspect the valve guides.
Use a syringe to suck the solvent out of the cylinder,and swab them out with long Q-tips,the industrial kind.
Rinse again and reswab,do [not] lose any swabs downhole,roll the crank slightly and repeat until relatively gritless.
Repeat the process for each cylinder for carbon free chambers and valves.
Give each hole a spray of light oil and roll the crank 720 minimum.
Use a borescope to inspect the now clean cylinders,most have record functions,looking for scratched bores.
Gap your plugs,and give each thd a lick of high temp copper anti-seize.Roll the engine to #1 tdc.
Marking and labeling each new plug ht and distributor,remove and repair/maintain,replacing the points.
Check the distributor shaft and bushings for damage and wear,the plates move freely and the vacuum canister functions.
Lube the plates,springs and centrifugal weights with a light coat of lithium grease.
Inspect the cap for carbon tracks and burned anodes,rotor for the same.
Insert the dizzy and set statically,refill the oil and start,setting the advance with the light.
Use a spray carb cleaner a few times to blow the loose carbon out.
A decent assessment of the cylinders and valves can be had without disassembly.

/

I agree with other to focus on the distributor. If a spring is broken it will advance early.
How long has it done this? I would pull the distributor and take it apart. Take pictures of the orientation of the top plate to the body. Note that the screws are different lengths and installed wrong will lock it up.

Also verify fuel pressure, MPS operation, and absence of vacuum leaks. Could be going lean under part load conditions.

Lots of carbon build up in the combustion chamber will create detonation because of random hot spots. One way to get rid of that a bit is to use water to steam clean the cylinders. Dribble it in via the distributor intake hose and a ketchup squirt bottle. Do it outdoors because it will blow a ton of black smoke out if you do it right. Car is running while you do this

Try running Premium fuel .

He is, 91 octane is the highest grade we can get at the pumps in California.

1. get a normal sized bottle of water. Distilled is even better.
2. Get a long piece of vacuum hose.
3. Hook the vacuum hose to the intake.
4. Start the car.
5. Hold the throttle at 3,000 RPM
6. Put the vacuum line in the bottle of water.


The water will be sucked into the engine, steam cleaning the combustion chambers and the tops f the pistons. You will get clouds of white smoke out the tail pipe. But it will clean all the crud off the insides of the heads. IF it dies, you will have a tough time getting it to re-fire, so make sure you keep the rpms up.

if you think a de-coking is nessesary, i like the idea of sea foam on a vacuum line rather water. also add sea foam to the gas. still think you must verify correct operation of distributor advance and correct timing.

Hello.
I rigged a spray bottle the kind you would use for bug or week spray in the TB. .
Sprayed while running at about 2500 RPM .

Huge clouds of BLACK smoke !.
Then went for a run with sprayer still attached and sprayed while driving had one more puff of black smoke .

I did take a couple of degrees advance away as well.

Runs great . NO ping while climbing hills .


Thanks all !

Sprayed while driving deserves a picture of the contraption

Actually premium fuel has more additives, burns slower, and causes more carbon build up in the combustion chamber. BG makes a combustion chamber cleaning fuel additive that works very well. Always use the lowest octane fuel possible, without detonation.