428 heat related issue

[drafterman]

Folks this is my first post which is actually to ask for advice on how to diagnose and proceed with an issue I am having.  I have been around SBF's a lot, but this is only my second FE.  I have a few old Ford muscle cars in my collection, but the one in question today embarrassed me today as it let me down right in front of a car show!

I have a 67 Fairlane with a 428 (I did this one for my wife).  I built the engine about 6 years ago (but only 4000 miles).  It is a .030 over 428 with CJ heads, a CC XE 274 hydraulic flat tappet, roller valvetrain , headers, and a Demon carb.  Nothing radial, but it has been a good runner on the street for sure.  Lately the engine will shut off when coming to a stop and will not start (but it will crank over just fine) although it will backfire while attempting to start.  The H2O gauge reads about 190 deg when this happens; so not extremely hot.  I am positive it is not a vapor lock or percolation issue as there is an electric fuel pump on a bypass regulator system.  I can see fuel in the bowls via the sight gauge glass and everything looks great there.  No fuel is dripping from the boosters and the carb and fuel lines are NOT hot at all.  The car pulls hard (rubber coming out of 3rd gear) when cool, but give it about six or seven miles and it feels like I am driving a model A Ford. 
Today, I had the car in the shop to check timing, etc.  While idling at 800 RPM (after about 8 to 10 minutes) the engine started faltering, stumbling, and it shut itself off within a minute of doing this.  I tried this again after it cooled and with a vac gauge and I read about 10 in-Hg and right before it stalled out it was fluctuating between 8 to 10 in-Hg.  The ignition does not seem at fault (about 12 deg initial) on a Pertronix billet distributor and a remote mounted coil.  I yanked the Motorcraft plugs and they appear to show a lean condition and while they were out I checked compression and all cylinders were around 115 PSI with the carb removed.  Also, since the carb was already off I quickly swapped on a Holley 750 DP from my Mustang and it gave the exact same results as the previous combo (which would seem to rule out any carb issues).  This issue is very repeatable as you can let it cool just a few degrees  and everything is good, but it always quickly returns with heat.
So, I am leaning towards a vac leak caused from a poor gasket seal or an intake crack (Edelbrock Performer manifold) that shows itself with heat, but I would rather obtain some advice or another opinion before I dig into this; since as you know this is more involved on an FE than other Fords like I am used to.  Perhaps with your experience you have ran into something like this before?

Sorry for the long post...I hope my future posts are less needy.  I like to figure things out for myself so that I can learn from it, but this one has me stumped.

[Joe-JDC]

Do you have a vented gas tank cap?  Or is it old?  Does the electric pump actually still pump fuel on shutdown?  I had a vehicle that would shut down after a short drive, but start and idle OK.  It had a fuel filter that had sediment in it that would pull up against the element and block it off after a couple of minutes and stall the engine.  It would then settle level, and the car would start, and repeat the same issue.  I had to change the filter a couple of times fairly close together, but that cleared up the problem after all the trash was captured in the filters.  Joe-JDC

[winr1]

Have had more than a few coils do odd things when they got hot

One more thing to rule out perhaps


EDIT:

What Joe said, Pod restored a 66 F100... except the fuel tank
Every time we went for a cruise, was not long before the mill would stumble and go dead


The fuel filter was stopped up, he replaced a ton of them before the tank was clean

Would not pull the for fear of risking the paint .. ^_^



Ricky.

[drafterman]

Joe-JDC:  Thank you...I still have the factory 67 tank vent tube that exits the top rear of the tank and routes to below the passenger quarter panel. It is not plugged.  The cap is the sealed unit, no vent due to the alternate tank vent.   The fuel pump still runs even after shutdown.  There is no longer a fuel screen (sock) on the in tank fuel pickup tube, but the fuel pump inlet filter is clear.  I checked the inline fuel filter to the carb and it all looks good.  There is still fuel visible in the bowls via the sight glass, so it still has fuel when it dies.

winr1:  I can sure try a coil...pretty easy compared to my diagnosis.

[jayb]

Couple of thoughts.  On the fuel system, glad to see you are running an electric pump with a return style regulator, that is the way to go with today's fuel.  Do you have a fuel pressure gauge at the regulator?  If so, I assume it is still reading good pressure when you have this issue?  I've had an electric pump vapor lock at the inlet because it got hot and was heating the fuel right at the pump inlet, and you could diagnose this by looking at the fuel pressure gauge at the regulator.  Also, sounds like you are sure it is not fuel percolating in the carb, so I assume you are looking at the carb when the problem appears?  If not, try that because the fuel percolation problem, where fuel spits out of the vents and floods the engine, disappears pretty quickly once the engine stops.

If you are sure its not the fuel system, I'd be looking at ignition.  Swap in a coil as Ricky suggested, and then try a different distributor.  I've had a Pertronix go bad before.  Does your distributor have vacuum advance?  If there is a problem with the distributor that could be the source of the vacuum readings.

Rule out fuel and ignition before you start tearing into the engine.  Doesn't really sound like a vacuum leak issue to me. 

[427LX]

115 psi seems quite low on cranking compression.

[drafterman]

jayb- the fuel gauge at the reg reads 7 PSI and it reads this right up to the time that the engine shuts off.  No fuel pours from the bowl vents at all.  No vac advance at all...all mechanical in the dizzy.  The coil swap is next on the list.  I may have the old point distributor laying around, so I can try that as well.

427LX, I thought the pressures seemed low as well compared to my small blocks.  I have an ancient compression tester with the rubber boot that you have to hold in the plug hole while you crank.  I usually crank it over about three compression cycles to get the reading, but I am never confident that I am getting a perfect seal and thus an accurate reading.  What numbers would you expect?  I am running L-2303NF Sealed Power pistons with the CJ heads on a stock crank setup.

[427LX]

jayb- the fuel gauge at the reg reads 7 PSI and it reads this right up to the time that the engine shuts off.  No fuel pours from the bowl vents at all.  No vac advance at all...all mechanical in the dizzy.  The coil swap is next on the list.  I may have the old point distributor laying around, so I can try that as well.

427LX, I thought the pressures seemed low as well compared to my small blocks.  I have an ancient compression tester with the rubber boot that you have to hold in the plug hole while you crank.  I usually crank it over about three compression cycles to get the reading, but I am never confident that I am getting a perfect seal and thus an accurate reading.  What numbers would you expect?  I am running L-2303NF Sealed Power pistons with the CJ heads on a stock crank setup.

What is the calculated compression? 
With 10-10.5 you should be in the 185-200 range.

[drafterman]

I had a chance to install a different coil today.  I also left the gas cap off just to satisfy the previous post about tank venting.   It ran longer today (about 20 min), the ambient temp is way down; however the same result.  Right before it died it started to diesel.  Mind you, all of this is just setting in the shop idling, no road tests as I am tired of towing it home. I did notice that once the stumble started that the idle improved if I turned the idle mixture screws almosjt all the way in.

[GerryP]

If you hadn't written that you have headers, I would have said your heat riser is stuck.  But that doesn't mean you don't have a hot intake.  If you have a restriction in one side of the exhaust, the gasses will still pass through the heat riser.  The time component is what is leading me to this suspicion.  What you can do is to unbolt the exhaust from the collector and do your test to see if it makes a difference.

[drafterman]

That actually makes a lot of sense GerryP.  I don’t know if I should have done this or not, but when I built the engine I put heat riser block-offs in (something I always have done on Fords).  So any hot exhaust gasses should not be able to pass through the intake.  I don’t know about any restrictions in the exhaust, but I can sure respect your opinion.  I have the FPA tri-y’s going into 2.5” exhaust through dual 40 series Flows.  Is there a chance I mismatched something on the head gaskets related to coolant passages?  I would have thought any issues would have popped up before now.  When the motor was fresh, we used to drive the car to a lot of shows with no issues.

[66FAIRLANE]

Thought this was a clue
 "I did notice that once the stumble started that the idle improved if I turned the idle mixture screws almosjt all the way in."
until I saw you swapped on a known good carb.
I would also try it with fuel pressure down a bit (4psi) and see what happens.

[My427stang]

These are tough, but the thing that you will need to determine is if it is ignition or fuel

Some thoughts

Fuel related is logical, because heat with todays gas (more easily evaporated because made for higher pressure EFI), you can lose control of the idle circuit pretty easily as it sits there and chugs away.  The question I would ask is, does it do it when the engine is cooler, after it needs no choke and just sits there idling, or only when it gets heat soaked.

Ignition is logical too, and a Pertonix can do funny things when failing, as can a coil, but adjusting the carb should have little benefit. 

How does the carb adjust before it gets hot and funky?  Is it at 1 1/8 to 1 1/2 out from bottoming the screws? 

[GerryP]

It certainly seems to be a heat related issue.  Do you have a good engine-to-chassis ground where the cable size is sufficient and the electrical contact is clean?  I can see a scenario where the circuits (including the pickup and module in the distributor) are just sufficient when things are cooler but degrade one they take on some heat.

[drafterman]

My427Stang-It will start great cold, I just set the choke (electric) and turn of the key and it usually fires right off.  It will settle out after the choke opens and run great at idle or down the road, but let it get to about 180-190 degree water temp and you had better find a spot to pull off the road.  So the problem is only heat soak.  The carb usually likes about 1 1/4 turns out on all four corners, but when it starts to get hot, I can only keep it running by moving them in to about half that.  Seems like that should mean something, right? 

66FAIRLANE- no change with lower fuel pressure.

GerryP- I have a ground strap between the starter and the subframe, but I will have to check how good it is.  It is one of those bare wire braided ground straps.

Tonight I had the timing light on as it started to die just to monitor the spark and it flashed right up to the end.  I know that is not a good measure of the ignition, but it would indicate spark on the secondary.  Also, before I started tonight, I pulled the carb off and reset the throttle plates per the Speed Demon manual..after that I felt like It lost my quick cold start settings, but I got it tuned back...I feel like the Idle-Eaze circuit on Demons is never helpful for any of my engines; does anyone have a comment on that?