TR2/3/3A the value of experience when setting timing on a modified engine

[GTP1960]

"The problem with being ignorant, is your to stupid to know your ignorant" (anonymous )

after several months of continually re-setting the timing & re-tuning my 3A.
Never completely correcting the missing, backfiring, low power condition that I created.
I threw in the towel & trailered my car 120 miles to Charleston Import Automotive. ( highly recommend if you ever need service in Charleston SC, BTW).

Darrel, the owner, turned it over, warmed it up, listened to it run & said " timings way off".
Now I had targeted the OEM spec , ranging between 3-6 degrees before TDC, but because the engine had been modified with an improved cam & over bored cylinders, Those # were out the window.

in short order they found the sweet spot (by ear), then reset valves & carbs accordingly & in that order. He put a timing light on it, just to see where it fell......a surprising 28 degrees before TDC.
He reminded me if you tweak anything in the ignition chain, you must tweak everything & in the proper order. Which of course I wasn't doing.
So the chances of me accurately tuning my car were nil........but of course I was too ignorant to know that.

 

[3798j]

Good to hear you've got it straightened out. It's nice to have that "go to" guy when stumped.

 

[TR3driver]

If it runs OK, I guess that's good.

But 28 degrees of initial timing seems way too high to me, even with a 'performance' camshaft and oversize liners. I think there must still be something else wrong, like the timing mark is not accurate or the cam timing is off or the advance mechanism isn't working right. The stock advance mechanism should be doing an additional 26 degrees of advance at redline; giving a total around 54!

 

[GTP1960]

If it runs OK, I guess that's good.

But 28 degrees of initial timing seems way too high to me, even with a 'performance' camshaft and oversize liners. I think there must still be something else wrong, like the timing mark is not accurate or the cam timing is off or the advance mechanism isn't working right. The stock advance mechanism should be doing an additional 26 degrees of advance at redline; giving a total around 54!

I wondered about that, not that I really understood what I was wondering about,(high tech is a relative thing).
perhaps I misunderstood him.
in any case, she runs better than ever! Wish I would have taken her in sooner.

thx

 

[sp53]

That just sounds like way too much, but if it runs good, then good. Just curious, I wonder if you were a full tooth off on the distributor installation, but sounds like they would have caught that. Again just curious, where your vacuum advancement line fitting is? Is it almost parallel with the engine or way out by the fender or way into the block? Maybe a picture of the distributor wires and advancement for my mental records in case I put a big cam in.

 

[Frank_D]

If the timing was checked with a timing light at 2500 RPM then the total advance would be what is measured and that should be about 32 degrees give of take. I cannot imagine that the shop was setting a static timing at 28 degrees BTDC. My fresh engine has a more aggressive cam and 89 mm pistons in a balanced engine. The total advance at 2500 RPM is at 30 degrees give or take 1. You are in good order and if the car is running well at all engine speeds that should also be your good feedback.

Frank D.......

 

[GTP1960]

That just sounds like way too much, but if it runs good, then good. Just curious, I wonder if you were a full tooth off on the distributor installation, but sounds like they would have caught that. Again just curious, where your vacuum advancement line fitting is? Is it almost parallel with the engine or way out by the fender or way into the block? Maybe a picture of the distributor wires and advancement for my mental records in case I put a big cam in.

SP53,
The vac advance line is close to parallel with the engine, slightly toed out.(I had it pretty heavy toed in before)
the mechanic didn't mention repositioning the distributor, so I don't think he did.
i'll take a pic & send it.

It is running good.......for 45 minute (+\-); then it starts missing at speed.
im going to run it hard tomorrow until it misses, then get a temp. reading on the float bowels & elec. fuel pump to see if it's vapor lock.

thanks for asking.

 

[GTP1960]

My fresh engine has a more aggressive cam and 89 mm pistons in a balanced engine. The total advance at 2500 RPM is at 30 degrees give or take 1. You are in good order and if the car is running well at all engine speeds that should also be your good feedback.

thanks Frank,
are you running electronic ignition?
also interested in what idle is working best for you.
i don't know for sure what mods were done to mine, as there was no paper trail when I purchased.
So I'm just going by what two mechanics have guessed at.

 

[No Jump Seat]

I wonder if the camshaft timing gears are degreed than from factory specs, thus making the timing to "appear" too "Advanced".

"1" would agree that 54 degrees of total timing is WAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAY too MUCH!!!

Would be difficult if not impossible to get an engine to fire up with 28 degrees of initial timing!

 

[LarryK]

Lots of high HP engines run at idle with 35 deg settings. Maybe chain and crank are set to specs but cam was not set for extra timing. Mod cams are clocked then timing would appear way off.

 

[Frank_D]

Frank Here. I have Pertronix points but a conventional distributor that has been rebuilt and calibrated. Idle can be an issue sometimes. I am sitting at 1100 for idle which works well for me. A vernier cam gear was installed with the new cam to assist in setting it up. My mechanic tells me it was worth the small extra cost. Hope it all works out for you.

Frank D........

 

[sp53]

It sounds like the distributor is correct; the way I do it is to set the carbs last, so if dwell, timing, valve lash is good, I would be prone towards fuel problem, maybe the coil is arcing off also. I keep a known good coil and put that in sometimes when trying to find a tough problem. I use a stock distributor so I have no advice on the electronic stuff; you will find it your close.

 

[GTP1960]

It sounds like the distributor is correct; the way I do it is to set the carbs last, so if dwell, timing, valve lash is good, I would be prone towards fuel problem, maybe the coil is arcing off also. I keep a known good coil and put that in sometimes when trying to find a tough problem. I use a stock distributor so I have no advice on the electronic stuff; you will find it your close.

The shop put in Bosch platinum plugs.( im not a fan of) I found the front two were fouled & had a coat of black powdery carbon, the back two seemed fine.

therefore I'm thinking the front carb mix might be to rich. I've leaned it out (3 flats) and advanced the vacuum timing a little & will try it again tomorrow. Also ordered the old champion L87yC's.

here's a pic of the distributor alignment.

thanks for the help!

 

[AltaKnight]

The mechanic probably meant the timing at full advance is 28 deg, probably at about 3000rpm.
mine is about 32deg total advance at that rpm and I have a non-stock camshaft

 

[TR3driver]

The shop put in Bosch platinum plugs.( im not a fan of)

I used to be really fond of them, as they seem to last almost forever.

Then I had one where the gap mysteriously disappeared, and discovered that the other 3 all had the center electrode moving out of the insulator.

On the black plugs, it might be worth trying a "plug cut" to see what they look like at speed. Not unusual for those old carbs to go rich at idle (for various reasons), which will turn the plugs black if you've let the engine idle. But, since the mixture adjustment affects the entire range, leaning out the idle mixture can cause the cruise mixture to go too lean, leading to poor performance and overheating.

A "plug cut" is where you run the engine under the conditions of interest (eg fully warm cruising at highway speed), then flip the ignition off while you shift to neutral and coast to a stop where you can pull the plugs. That way, the plug reading is not contaminated by what is happening at idle.

 

[GTP1960]

n the black plugs, it might be worth trying a "plug cut" to see what they look like at speed. Not unusual for those old carbs to go rich at idle (for various reasons), which will turn the plugs black if you've let the engine idle. But, since the mixture adjustment affects the entire range, leaning out the idle mixture can cause the cruise mixture to go too lean, leading to poor performance and overheating.

I will try plug cut, just to get a S.P. reading. But I think I'll wait until my replacement plugs arrive.
I can't even see the electrode on those bosch. it looks like a ceramic cone.

Interesting thing is, is that it started missing and cutting out after it's completely warmed up and running along at a good speed in 4th.
I pulled the plugs and torched the carbon, brushed and replaced. adjusted the mix (2 flats) and it ran fine for about 20 minutes, then intermittent cut-outs.
I pulled the front two plugs again, they were not as black, but not grey either, and re-cleaned. plugs 3 & 4 look good, so i keep thinking my problem is with the front carb..........but maybe it's something else.

 

[GTP1960]

The mechanic probably meant the timing at full advance is 28 deg, probably at about 3000rpm.
mine is about 32deg total advance at that rpm and I have a non-stock camshaft

Thanks Alta,

you are probably right. I'm going to have him clarify, especially since it's not running as well as it was from just a few days ago, when I left the shop.

 

[TR3driver]

I can't even see the electrode on those bosch. it looks like a ceramic cone.

Normally that's right. The center electrode is entirely inside the ceramic insulator, and is very thin (like a thin mechanical pencil lead). But on these plugs, it had somehow come loose up inside the plug and extended out of the insulator towards the ground electrode.

The front plugs being black does sound like a mixture problem, but I doubt that is the cause for the intermittent cutting out. Generally once a plug is too carbon-fouled to run, it just quits working altogether. I'm thinking you're more likely to have a problem on the low-tension side, like maybe a ground or point lead that is broken internally. (Assuming I recall correctly that you've tried different points, condenser, coil, cap & wires without changing the problem.) The backfiring also indicates something worse than just timing or mixture.

 

[CJD]

Something else to consider when working with "initial" timing settings is that many owners are idling much higher than the factory recommended setting. If you are setting the initial on a running, idling engine, that idles at 1100 rpm, it will be into the advance curve quite a bit compared to one idling at 500 rpm.

 

[GTP1960]

I'm thinking you're more likely to have a problem on the low-tension side, like maybe a ground or point lead that is broken internally. (Assuming I recall correctly that you've tried different points, condenser, coil, cap & wires without changing the problem.) The backfiring also indicates something worse than just timing or mixture.

ill ck the ohms on my S.P. Lines.
im using pertronix flame thrower,III & new 43k v coil.: but I should try a different coil.

If you are setting the initial on a running, idling engine, that idles at 1100 rpm, it will be into the advance curve quite a bit compared to one idling at 500 rpm.

i am running the idle at around 1100. Do you think i need to advance the ignition timing to compensate?