Engine pinging under load

[jovial_cynic]

I've been driving my L/Z hybrid motor (around 9.6:1 CR) around the block, and I notice that the engine is pinging on acceleration (ie., not when parked/idle -- only when accelerating).

 

What are all the possible causes, and what's the order you go about ruling things out?

[ggzilla]

Don't overthink it, you just need to adjust the timing. Rotate the distributor back 2 degrees and see if it goes away. If not, rotate it back some more.

[banzai510(hainz)]

BUy the best HIGH octance gas first then do as Zilla said

 

unless your dizzy is off a tooth or something.

what the intial timming setting?

[datzenmike]

Expect to run3-5 degrees, maybe less? All engines are different.

[420n620]

I had a pinging in my 92 Toyota 4x4 because I was trying to save money by buying the cheap gas.

A buddy of mine told me to start running the Chevron w/ tetralean (spl) additive. Within a month the Toyota quit pinging.

you can also find the tetralean additive in stores like Cosco, Auto Zone, Oh Shucks and so on that you dump into your gas take when filling up.

it helps clean up your pistons, valves, spark plugs, carb/ fuel injectors..

that stuff really works and well worth the $$$.

[jovial_cynic]

I stuck my timing light on it, and couldn't find the timing mark. I did some hunting around the crank pulley and found the timing marks on the opposite side of the pulley.

 

Are there L-series or Z-series crank pulleys designed with the timing marks on the opposite side? My stock pulley lined up on the driver's side, but I threw a new pulley on the engine with a double-grove (for running AC or some other accessorY). I'm used to seeing them on the driver's side, but I think I've seen a timing indicator tab on the passenger side of a Z24 engine that was running AC, since the AC unit was in the way of the standard location for the timing indicator tab.

 

I'll have to yank the pulley to see what's really going on. Can I just relocate the timing indicator tab to the passenger side, or will I need a different one entirely?

 

I'll see if I can rule out a timing issue first, and then I'll get some higher octane gas or gas additive.

[banzai510(hainz)]

later L18 and alot of l20 there was 2 types of SAWTOOTH timming marks.

So your pully will be match wit one or the other.

So you need the appriate Sawtooth timming plate. Unless this pull is set up for a L16 pointer type.

 

Be honest how you find TDC ??

Unless you put the chain ON using the Bright links on the Dimples ,you could be off a tooth. Using thr Brite link on the Dimple on the cam sprocket and crank sprocket SELF lines it up for you. So no need to worry if off a tooth then.

 

best deal is just run good gas and turn the dizzy for now.

 

U could find TDC by pulling the spark plug and see close to TDC and using a ink pen on the carnk and front cover as a general base for ZERO. and WING IT from there.

[jovial_cynic]

So, right before I had to head to work, I ran into my garage and found some more pulleys to verify, and sure enough, the double-pulleys have the timing marks on the opposite side, and are meant to be timed on the passenger side. So... (before I saw your post, Hainz) I went to swap the timing indicator to the other side. However, as it turns out, the problem is that the the indicator that sits on the driver side is bolted up with two 10mm bolts. On the passenger side, the available spot uses one 10mm and on 12mm, which means that my timing indicator won't even fit.

 

Hainz - how different are the two indicators? Is it just a matter of the bolt-holes not being sized properly, or are the marks not even in the same place? Do you have a couple you could take pictures of and post?

 

Regarding how I set TDC in the first place, I actually built up the engine by following every step-by-step guide in all of my datsun 510 books. So yeah - bright links on dimples, matched to cam sprocket, etc., etc. I am fairly certain that I'm not off a tooth on the chain.

 

Since I had to pull the front cover off to address an oil leak, I did end up accidentally dropping the oil sprocket from the distributor (since you have to pull the oil pump to take off the front cover), and I didn't think to mark the distributor. I had to pull spark plug #1 and eyeball it to make sure the oil sprocket was matched up to the distributor properly. I simply turned the rotor until it pointed to plug #1 when I found TDC, and put the oil sprocket back in. Is it possible that I'm off a bit on the oil sprocket?

[banzai510(hainz)]

Hainz - how different are the two indicators? Is it just a matter of the bolt-holes not being sized properly, or are the marks not even in the same place? Do you have a couple you could take pictures of and post?

 

 

I never noticed the hole size differnce the 10mm 12mm I have to look at the front covers but assume your correct.. and dont have photos to post. But I do have those Timming plates both types.

 

 

maybe DatszenMike or somebody else can help on this as I use the L16 pully and just the one pointer that sticks out.

 

 

all I can say is put the piston looking inside the spark plug hole till it looks like its at it Most top of the cylinder and then look at the dizzy drive and see if its 11.28 as in this photo. then install the dizzy and should be pretty muck in #1 plug wire and should both back and fwd movement on the timming plate.

 

But let not overreat here just try the better gas and turn the dizzy first.Yhen run it hard and see if it pings.

 

No need to break things open if its not needed.

[jovial_cynic]

Yup - that's where my distributor sits. So that pretty well rules out the oil sprocket. Good.

 

Ok - so apparently, this is the timing indicator that I need:

 

 

I'll hunt around in my box o' parts to see if I have one that I overlooked. If not, I can probably grab one for $5 or so at the local JY. There was a truck I was wrenching on (I wanted to yank the AC unit...) that had the timing indicator on it... but I didn't know I needed it.

[banzai510(hainz)]

you can dial moto up to Zero and get a ink pen and generally imposed the timming marks on the front Cover(clean it good) for now

[jovial_cynic]

I'll do that as soon as I get home. Thanks!

[jovial_cynic]

So, I have now verified that my spark timing is correct. At least, the distributor shaft is pointing at 11:30 with piston #1 at TDC. I've also marked a spot on my front cover to check for timing while the engine is running, and with the distributor backed off as far as possible, my timing mark is at around 5 BTDC. When I rev the engine with the timing light, the timing mark scoots back a bit to around 15 BTDC.

 

I cut out a spot in my exhaust (right about where the transmission is), and welded in an O2 bung, threw in a 1-wire O2 sensor, and have wired in an O2 gauge, and from what I can tell, I'm running a bit lean when I slam on the gas. But only while under load. I can rev all day in my driveway, and my O2 gauge reads just fine (I've got it running a little rich, just in case). When I drive around, if I accelerate slowly, no ping. But when I hit the accelerator hard, my gauge pegs lean and it pings.

 

I don't imagine that running higher octane will have much to do with running so lean when I slam on the pedal.

 

I've got dual SUs feeding my engine.

 

Any ideas?

[72240z]

Have you considered you may have gotten a bad batch of gas? In Jersey its not common at all but from what I read/hear it seems pretty prevalent in a lot of places.

 

Without a wide band its kind of impossible to tune, Idk if that's what you have in there or not. Did you check for leaks?

[dgi]

So, you've confirmed you are going instant lean when you dump the throttle open. Your timing is close and you are running SUs

 

None or too light oil in dashpot? That lets the slides open too fast when you dump the throttle open, it leans out, and you get spark knock.

 

When not under load, just idling, if you dump the throttle and you get a momentary lag, then you have confirmed it.

 

If you are gentle with the throttle under load and O2 readings are good, then your needles must be pretty close.

[datzenmike]

A leaner engine will run hotter, producing 'hot spots' that can cause pre-ignition. The proper fuel ratio, even a bit rich when under load will help cool the cylinder and reduce ping.

 

Some use ATF in the dash pots. Maybe too thin too.

[jovial_cynic]

So, you've confirmed you are going instant lean when you dump the throttle open. Your timing is close and you are running SUs

 

None or too light oil in dashpot? That lets the slides open too fast when you dump the throttle open, it leans out, and you get spark knock.

 

When not under load, just idling, if you dump the throttle and you get a momentary lag, then you have confirmed it.

 

If you are gentle with the throttle under load and O2 readings are good, then your needles must be pretty close.

 

What do you mean that my needles "must be pretty close?" I'm not familiar with that term.

 

Also, no -- I don't get a momentary lag when I dump the throttle at idle.

[ggzilla]

Fix that leaning out first.

 

Did you fit a 195-degree thermostat? Put in a 180 and the pinging may stop.

I don't want to buy PREM so I set my timing for regular. Yes I know I might get better mileage with PREM and make up the difference in cost. Pay now or pay later.

[jovial_cynic]

Fix that leaning out first.

 

Did you fit a 195-degree thermostat? Put in a 180 and the pinging may stop.

I don't want to buy PREM so I set my timing for regular. Yes I know I might get better mileage with PREM and make up the difference in cost. Pay now or pay later.

 

It's a 180 degree thermostat, and with the electric fan I just wired in today, it stays reasonably cool.

 

I'll get some higher end gas, and I'll check the pots for oil on the SUs. Any other ideas? I keep reading online that a faulty EGR valve will cause pinging. Any way to diagnose that?

[jovial_cynic]

Per the bluebird mailing list, dgi, and datzenmike, it appears the lack of oil in the dashpots was the issue:

 

SUs get thier acceleration mixture enritchment from the dampeners. Using thicker oil in the dampeners will slow the rise of the SU fuel needle pistons, creating a temporarily ritcher mixture until the piston reaches its new higher equilibrium point. Too much dampening will over ritchen and hurt the throttle respose by also restricting air.

 

Being unfamiliar with SUs until recently, I never even thought to check the oil dampener levels, since the engine always seemed to run just fine sitting in my driveway. After this explanation of how the dampeners work, it seems to pretty accurately describe what my engine is doing under acceleration. I checked the oil level, and it was pretty much empty, so I added some 20wt oil (per this link: http://www.jetlink.net/~okayfine/su/damper.html), drove it around, and it's not pinging at all.

 

At the moment, I've got the carbs tuned rather rich (since I was trying to prevent yesterday's pinging), so I'm going to lean it back a little (hooray, O2 gauge) until I'm closer to where I need to be.

[dgi]

Happy to hear you've eliminated the pinging. Glad I could help.

 

When you said you are running SUs, I was pretty certain what was happening.

 

I'm in NC, so my ambient temperatures are a bit different probably. I run 10-30W because it is really difficult to find 20 or 30 weight oil around here. The 10-30W is a little light until the engine is warmed up, but at normal operating temps it seems about perfect. You may find you need to change weights to match seasonal temperatures.

 

Since you've linked the tech pages about SUs, I imagine you know by now what I was referring to about your needles being "pretty close". If not, read those pages about needles, their tapers, and thier effect on tuning.