A little help with 427 timing marks please.

[cleandan]

Good day everyone.
I am working on a 1967 427 street cobra and I am having a brain fart remembering the 427 timing marker meanings.
This engine has the calibrated tab/pointer with no indications on any portion of the balancer and just two indents on the outer lip of the single pulley.

I seem to remember the first mark is initial timing setting and the second mark is the total timing mark...but I am not certain. I checked my 1966 shop manual and it does not directly address this timing set up other than to mention setting it at 8 BTDC initial. The manual has images and directions for many 1966 options, just not this timing marker set up.

My main goal is I am trying to figure out a slow overheating issue and I am discovering things as I go.

The internals of this 427 are unknown to me, but I suspect it is 1967 stock with the exception of a Pertronix in the distributor.
It starts and runs well enough, idles fine with what sounds like a stockish cam, but it has a slight surge at steady cruise and eventually loses control of the coolant temps if the ambient temps are above 80*F. and the cruise speed are below 40 mph.

I was looking to see if the timing curve was bouncing at the lower cruise rpms, causing the surge. When I tried to verify timing I discovered the curve is quite slow, and not all in until about 4,400 rpm...which seems very high for this vehicle.

My theory is the carb is running a little bit lean causing the cruise surge (because the timing curve, although very slow, is very steady across the rpm range) and the timing is good at idle, but runs retarded through the 2,200-5,000 rpm range due to the slow, tight curve, thus causing the slow overheat condition.

Today I will verify TDC to see if the markers have slipped...which I kind of think they have, but I will verify.

Just to give some info about what I have verified.
The carb is a Holley LIST 3255 (C5AF-9510-BE) which was redone and looks perfect, but I have not verified any internals. I have only snugged up a few things to stop weeping fuel.
I have vacuum gauge tuned the idle screws, which are currently 1-1/4 turns out, and the engine likes it there.
I have played with the inital timing by finding the range between where the engine is hard to start (cranks hard when hot) and where it is lazy to start. Currently initial is set higher than stock and it is ever so slightly hard to crank when fully warm, but the total is 37* at 4,300 rpm.

I installed a 180* T-stat thinking the 160* that was in there may be holding open and not allowing the radiator enough time to cool effectively. This helped, but did not cure the heating issue.
I can see the waterpump is moving the coolant a good amount through the expansion tank.
All the cooling system components look to be in great condition and hould be up to this task with ease

Do I have the timing markers correct? (one is initial, the other is total?)
Am I on a good track to finding the overheat issue? (likely due to slow timing curve)
Any ideas are appreciated.
Thanks and have a great day.

[My427stang]

I tend to start at the basics with timing and never trust marks until I check them.   Thread a piston stop, or make one out of a plug, and find true TDC.  If you can put a timing tape on after that, or verify the TDC mark, you can do the rest.  Even just having TDC allows a dial back light

Then I set total to 38-40 for a bone stocker, 38 is fine, and see where initial lands.

The other thing you can do, knowing the timing is slow, is pull the top plate now, and see what the slot says, or measures.  You can lube the advance, swap a spring if they are real tight, and then mathematically calculate total and just set initial

I will say, if initial is too early, and rate is that slow, it'd make some heat.  It'd be money well spent to find out exactly what the marks are

[cleandan]

I have now verified TDC and it is correct at 0 on the marker....Which is good.
The initial advance springs were waaaaaay too strong.

I used my trigger pull gauge to measure them and they pulled 30oz at the point of first expansion! They pulled a LOT more when at the resting installed length. Strong springs indeed.
I have never seen, or used, advance springs this strong.

I installed medium weight springs.
The reluctor is on the 10* slot.
Everything moves freely.

I set the timing at 35* total for now.
I can not measure the initial because the pointer only goes to 12* but it does look to be in the 14*-15* area if the pointer was marked that far.

Hot cranking (engine at full temp for at least 20 minutes) is a tiny bit hard for the very first turn and then it seems to crank easier and starts right up...I think it can take a bit more initial.
Cold crank goes without issue and fires right off.

The best part is my cooling abilities are greatly improved.
Driving around casually in town, on the highway, or whatever, the temps are under control as long as I am moving (todays temps are in the high 80's)

Unfortunately when standing still, idling, elec fan on, it will slowly creep up and eventually overheat, but it takes a lot longer than it did before.

A few more degrees timing and things may be good.

I am not able to hear any detonation, but the exhaust is pretty loud so it drowns out those subtle sounds....I'll check the plugs after things cool down some more.

[My427stang]

You are on the right track, but 35 is still light for an iron head FE.  If it can't handle 16-18 initial, may want to consider swapping slots, even 36 is late for full power.

You mentioned electric fan, it takes a heck of a fan to keep them cool at idle.  If unable to run a fixed blade, may want to see if there is a better fan available.  May be the whole issue in a nutshell

[GerryP]

...
Unfortunately when standing still, idling, elec fan on, it will slowly creep up and eventually overheat, but it takes a lot longer than it did before.

A few more degrees timing and things may be good.

...

Ford -and other manufacturers- had a very simple way of dealing with engines overheating in traffic.  They used a thermostatic switch that was plumbed with vacuum advance from both a ported and manifold vacuum source.  When the engine was operating cool enough, the switch used ported vacuum to the distributor.  When the engine began overheating, the thermostat switched to manifold vacuum to increase timing to make the mixture burn in the cylinder rather than the exhaust port.  This switch to manifold vacuum also increased the idle speed, which ran the coolant through the engine faster.

[cleandan]

Thanks for the input.
I am now certain my overheat issues were caused by the very retarded timing and super slow curve.
The cooling issues just get better and better the more timing I put into this engine.

I will be tuning to run pump premium, non-oxy gas, so I can reliably get gas wherever I am driving rather than being limited to a driving range of 1/2 a fuel tank so I can get to my barrel of race fuel.

I am curious what others have found to be a good timing curve, especially in the 2,200-3,100 rpm range where I am cruising down the highway.

[427John]

...
Unfortunately when standing still, idling, elec fan on, it will slowly creep up and eventually overheat, but it takes a lot longer than it did before.

A few more degrees timing and things may be good.

...

Ford -and other manufacturers- had a very simple way of dealing with engines overheating in traffic.  They used a thermostatic switch that was plumbed with vacuum advance from both a ported and manifold vacuum source.  When the engine was operating cool enough, the switch used ported vacuum to the distributor.  When the engine began overheating, the thermostat switched to manifold vacuum to increase timing to make the mixture burn in the cylinder rather than the exhaust port.  This switch to manifold vacuum also increased the idle speed, which ran the coolant through the engine faster.

Like

[My427stang]

Thanks for the input.
I am now certain my overheat issues were caused by the very retarded timing and super slow curve.
The cooling issues just get better and better the more timing I put into this engine.

I will be tuning to run pump premium, non-oxy gas, so I can reliably get gas wherever I am driving rather than being limited to a driving range of 1/2 a fuel tank so I can get to my barrel of race fuel.

I am curious what others have found to be a good timing curve, especially in the 2,200-3,100 rpm range where I am cruising down the highway.

Light 4 speed car, good gear, in the 10:1 range with iron heads, good quench, 14-16 initial, 38 degrees all in by 2700-2800. Add weight, compression, less gear, more quench, slow it down a little.   You could also play around with manifold vacuum to the vac advance, but man I don't like doing that, seems to make idle and low rpm wonky for me.