engine knock/ping, retard ignition doesn't help

[recordsj]

I have a 1500 midget, pertronix ignition, weber 32/36 carb.
I have an issue of engine knock/ping. It is more noticable at idle and lower revs (<3000 rpm). I replaced the spark plugs and wires, which didn't help. The timing is set 10 BTDC. I tried retarding the ignition, but the knock/ping is still there. Any ideas?

 

[JPSmit]

I'm not near my manual right now but I am pretty sure that 10deg BTDC is for 1275's and 1500's are actually 2 deg ATDC - I'll check when I'm in the garage to confirm

 

[64rocksprite]

Another possibility:
Coil perhaps? not getting sufficient spark?

 

[recordsj]

I have a new pertronix coil (the issue was still there with the old coil).

 

[Jim_Gruber]

PRemium Gas please not 87 octane

 

[JPSmit]

PRemium Gas please not 87 octane

even for a low compression 1500?


BTW, just checked Bentley and for 1975, 1976, 1977 all US models except 1977 California is 2 deg ATDC

 

[recordsj]

From the Haynes manual it says the following for igition timing:
1500, except USA: 10deg BTDC @ 680 RPM
1500, '75-78, USA: 2deg ATDC @ 800 RPM
1500, '78 and on, USA & Canada: 10deg BTDC @ 800 rpm
1500, '78 and on, California: 2deg ATDC @ 800 rpm

 

[tosoutherncars]

Vacuum advance connected & working? 10 BTDC set static, or at idle?

 

[bigjones]

Hi there,

I have a 1500, Pertronix and ZS carb.

The only time I had a knock it was the rod bearings.
They can be replaced from under the car - messy and claustrophobic but I would do it again. Probably best to also replace main bearing while you are there.

I use 87 gas (the cheapest) with no problem.

Cheers,
Adrian

 

[Jim_Gruber]

Didn'rt read that this was a 1500. With Bugsy a '68 Sprite with 66 vintage 1098 anything less than Sunoco 240 = dieseling on shutdown.

 

[Morris]

If you are getting "knocking" at idle, it seems unlikely that the noise you are hearing is spark related. Spark knock almost always occurs when the engine is under load.

If you can recreate the noise in your driveway, I would probe around with a stethoscope (a piece of vacuum tube in the ear works if you don't have a stethoscope) and isolate the source of the noise.

Given the 1500's reputation, it's very likely you have worn rod bearings or a dropped thrust washer.

 

[recordsj]

timing set at idle.
vacuum advance is connected and working.
the ping/knock is not noticable under load (like going up a decent hill in 4th), but noticable at idle and at <2000 rpms

 

[recordsj]

what do you mean by rod bearing and thrust washer (where in the engine are you talking about?)?

 

[JPSmit]

Crankshaft - The weak point of 1500's is the thrust bearings that have an annoying habit of dropping out.

In the attached diagram, it is actually mislabeled as a "key" you are looking for the piece labeled #23 near the flywheel - it is "C" shaped

 

[tosoutherncars]

J, here's how you can check...

With a crowbar or similar, push backward on your main pulley (#24 above) to make sure it's fully back. Then, while watching it closely (or even better, with a dial indicator zeroed against it) have someone depress the clutch fully. If your thrust washer has worn or fallen out, it will allow the whole crank to 'walk' forward, and you will see movement at the pulley end. Really, any movement is too much - I think endfloat is supposed to be 0.001-0.003 or something, hopefully someone will correct me. Excess movement throws everything offline, causing strange noises, problems with main & rod bearings, and (eventually) engine failure.

Hopefully your problem is something less serious... but as mentioned above, the thrust washer and rod bearings can all be replaced with the engine in the car. Messy, but doable in the driveway. (Did mine a few weeks ago.)

-Duncan

 

[recordsj]

can you give me some basic instruction on how replace the rod bearings and main bearing with the engine still in the car? Would it be quicker (maybe at least easier) to remove the engine?

 

[recordsj]

thanks for the info, I will check that out to see what I get.

 

[tosoutherncars]

Mains can't be done with the engine in the car. Rods are fairly easy for someone mechanical. See if the crank's loose, first...

 

[Morris]

I respectfully disagree. Mains CAN be done with the engine in the car. But it is probably easier to pull the motor. At the least it's 6 one half a dozen the other.

The only real problem with pulling the motor is it could unearth or create other problems. And there are always the dreaded might as wells. Ask Tony about those. 6 months ago he pulled the motor in his '62 to replace the clutch and now he has a (almost) completely restored car.

 

[recordsj]

when the clutch pedal is pressed the crankshaft pulley moves forward, is this what I am supposed to be looking for if there are issues with the thrust washer and rod bearing?
how long did it take you to replace the rod bearings and thrust washers while the engine was still in the car?