Heat Soak and Flooding

quote:

Originally posted by MARLIN JACK:
Those Heads are 800-900 Degrees F! Perhaps even Higher! Anybody have a IR Thermometer, who can verify this?

The last time I point an IR meter, shooting the back of the steel heads I had at the time, they were around 190-195 degrees F(but this was with the engine running).

...You know what solved the 'Hot Soak', Hard Starting; for Me, Forever??

I got rid of the Ignition Switch, wired in a 'Continous Duty' Solenoid Controlled By a 'Round Key' 3 Position Switch (OFF-Accessories-Unilite Brain 12 Volts(On a 270 OHM Resister to supply 7.5 Volts to the Brain Only)). Then a 'Push-Button' Starter Switch Off the Acc.! But, like the Racers; I also wired the Hot 12 Volts + side of the Coil through a 40 Amp Relay, contolled by a seperate Toggle Switch!

Yes! It takes Both hands to Start My Engine, But instead of It Trying to Start Slowly, 'Fighting' against Itself...It Spins Over at High Rpm, a Split Second Later, I Hit the Toggle Switch, Turning ON the Spark, and the Explosions Begin! Absolutely Perfect and FailSafe!! And Another Great 'Theft Deterrent', except, Now, I've told all of You!

As far as My Carbs. I have NO Fuel Issues!! With Dual Quads, I can shut the Engine Off and I defy anyone to even get a whif of Gasoline! NO Noises, Nothing! Maybe a slight tick from the Exhaust Pipes Cooling Down!

quote:

Originally posted by LIV1S:

quote:

Originally posted by MARLIN JACK:
Those Heads are 800-900 Degrees F! Perhaps even Higher! Anybody have a IR Thermometer, who can verify this?

The last time I point an IR meter, shooting the back of the steel heads I had at the time, they were around 190-195 degrees F(but this was with the engine running).

...I really Do find that hard to Believe! Your telling Me that Your heads are at the same Temperature as the Coolant!? That would mean a 100% Heat exchange! Impossible! I'll Have to verify that for myself. But Thanks!

quote:

Shut the Engine off when Hot, right after a LONG Drive; and go back there and try to wrap Your hand around that Can Filter;

No ... as important as 'hands-on' learning is, I think I'll take you at your word that it is hot and badly placed ... I've felt the rubber hose, it's hot enough your point is well taken

We've got the Phenolic spacer along with new braided lines (plus extra insulated wrap) that will sit 3" higher above the intake - rather than meandering around the engine bay - a new and smaller fuel filter that will also sit much higher along with the smaller diameter but taller air filter and a variety of heat shields and spacers to make my back pocket lighter - I don't think it's going to win any beauty awards, but if this stops the fuel from boiling, then that's one major gremlin eliminated.

Inspecting the carb more closely, it looks like the fuel was shooting out of the bleeds so high that while most of it was dropping into the bowls, some of it fell forward and collected along the edge of air filter pan and seeped down the outside of the carb onto the intake on the passenger side as well as on the drivers side ... the internal flooding was then causing the slow trickle through the secondary throttle shaft ... it's a theory - the analysis continues.

[/QUOTE]
...I really Do find that hard to Believe! Your telling Me that Your heads are at the same Temperature as the Coolant!? That would mean a 100% Heat exchange! Impossible! I'll Have to verify that for myself. But Thanks![/QUOTE]

Uhhhhmm! Okay.... As a disclaimer - I never checked what my temp gauge showed when I was playing with my highly accurate, super duper, handy dandy, Harbor Freight purchased 'Cen-Tech' IR meter (read 'cheap'). Your results may vary. I doubt the heads will read 800 to 900 degrees F though. I'll try to do a test next week when I get a chance.

Picture of my highly accurate meter (LOL).

Sounds to me like it's not about heat or worn axles, simply a fuel leak. I'd pop in new hi-perf (they have another material or size of the tip) fuel needle and seat. If they work properly and there's no dirt in them (do you have a good fuel filter?), fuel won't flow out anywhere regardless of how hot it gets...

A very powerful fuel pump may overcome any marginal needle and seat, so a fuel pressure regulator might be a good idea.

The highest temperature I've seen on an air-cooled cylinder head (Lycoming IO-540) is 450 degrees F. This was on a VERY hot day on climb-out. I would think that air-cooled cylinders would reach much higher temperatures than liquid cooled.

Dupli-Color® Engine Enamel w/ Ceramic Resists temperatures up to 500 degrees F. One would think that if the cylinder-heads reached 800 to 900 F the paint would burn off pretty quickly.

AutoMeter cylinder head gauges for liquid cooled engines top out at 340 F., however, VDO has some that go up to 600 F. for Air Cooled engines.

I just can't see a liquid cooled cylinder head reaching 800-900 F or higher on shutdown.

Well, I won't have any updates until after the weekend now :-(

Parts were in late yesterday, so they didn't really get into it until today hopefully everything will be buttoned up early Monday and ready for a road test.

For everyone else, you've got the weekend to enjoy your cats, get out there and have some fun!

quote:

Originally posted by 1973 Pantera:
The highest temperature I've seen on an air-cooled cylinder head (Lycoming IO-540) is 450 degrees F. This was on a VERY hot day on climb-out. I would think that air-cooled cylinders would reach much higher temperatures than liquid cooled.
Dupli-Color® Engine Enamel w/ Ceramic Resists temperatures up to 500 degrees F. One would think that if the cylinder-heads reached 800 to 900 F the paint would burn off pretty quickly.
AutoMeter cylinder head gauges for liquid cooled engines top out at 340 F., however, VDO has some that go up to 600 F. for Air Cooled engines.
I just can't see a liquid cooled cylinder head reaching 800-900 F or higher on shutdown.

Agreed. For instance, oil combusts at a lower temperature, and valve stem seals melt (teflon at only 250F). On air-cooled aluminum-head Corvairs, the stock cylinder head temp gauge once showed 510F after a broken fan belt on the road. On teardown a week later, valve seats were beginning to move and the cylinder to barrel register surface had softened & receded, slacking off the head torque so a gasket was ready to blow...

Tentatively ALL BETTER!

Aluminum heat shield, 1" phenolic spacer, braided line and insulated wrap (running along the top of the valve cover with a bracket to hold it up and away from some of the heat), new oval air cleaner since the increase in height puts it slightly above the height of the deck, new plugs, timing adjusted, and new heater hose.

She was warm when I picked her up but no problem starting. Took her for a good run in mixed traffic (a fair bit stop and go) and the temp guage was steady at 180. When I parked, I pulled the air cleaner and not a drop of fuel came out of the bleeders, she just sat there quietly. I grabbed the IR gun and the top of the carb read 130, the heads were 220, the secondary temperature gauge crept up slowly toward 200 as the block cooled down, no fuel leaking from anywhere on the carb.

She'll need a few more good runs, but based on what I've seen so far, it looks like she may be fixed.

Great news!

My car operates in hot Atlanta without any of the stuff you did and works fine. Expect the root case was related to the float needle valves. I’m running a Holley 650 that replaced a 600 that also worked fine in the extreme Atlanta heat.

Mike

Unfortunately I don't have a break down of what he did with the carb. the next time I talk with him I'll get further into it, but I only had a few minutes to talk, pay the bill and get the car home today.

I have to say thanks to everyone for their input again, plugging the cross-over and doing the ugly fuel line routing that he had originally suggested were obviously not necessary, and would have been a waste of time, money and in the case of the cross-over, negatively impacted the handling of the car. Glad I put this out there for y'all to comment and keep me on the straight and narrow!

I'm bringing this thread back because it has become particularly relevant for me as I'm entering the first warm season with my Pantera.

Yesterday I took the car out in the warmest weather we've seen since it came into my possession. We topped out in the high 70s, a far cry from the 100+ days to come.

I ran some errands around town with no problems. Then left the car parked for an hour before heading home. On the way I bogged and nearly killed it a few times with acceleration. Just as I was cornerning to enter the neighborhood it died on me. I had to put the pedal to the floor and crank for a while before it would start. Once started I would have to keep the revs up to keep it from dying and even then I'd get about 100 feet before it died. Repeated this process about 10 times to make my way to the house and into my garage.

It would get harder and harder to start each time and would only do so if the pedal was on the floor. I had several large puffs of exhaust when it would finally start.

I could hear the fuel boiling before I stepped out of the car. I pulled the air cleaner to find dense vapor billowing from the vent tubes and an intermittent spray from the squirters. The liquid fuel as vaporizing as it hit the inside walls. I actuated the throttle and got the squirt I expected but then it continued to squirt after I let off the throttle.

I've got a Holman Moody intake with a Holley 750dp sitting right on top without a spacer. The fuel lines and filter have been run up along the firewall and there is some insulation between the rail and the intake where it meets the carburetor. I recently installed a Fluidyne aluminum radiator that by all accounts has been working well. No problems when I'm running around but I have noticed some 200+ temps when I'm idling or in stop and go traffic. My fans need upgrading but that's another issue. I had just come off the highway and my temp gauge had been a solid 170 the whole trip.

I've always suspected heat soak problems. My stepwise solution to the problem:

1. clean and/or replace needle and seat
2. add 1" phenolic spacer, this will require different air cleaner
3. rebuild carburetor if #1 and 2 don't fix, or
3a. replace with Demon 650

In my assessment I've got 1) a carburetor problem and 2) a heat problem and they need to be fixed in that order.

Does this sound like primarily a needle and seat issue? I'm planning on pulling them without removing the carb, any issues or concerns with that?

Any thoughts? Think I'm on the right track?

I would do the simple thing, pull the needle out, clean it, and your problems may be gone. I don't think heat has anything to do with it based on what you describe.

I'm lazy so I would never work on the carb while it was still on the engine in a Pantera, I'd take it out. Regardless:
-Hold adjusting nut with 5/8" and remove screw
-Note how high the needle is compared to the flat surface of the nut
-Use nut to unscrew needle
-Inspect and clean, replace if pitted or somethng
-Install with gaskets to same height with nut
-Install screw
-Adjust float level as usual
If it was just dirt, consider fuel filter...

Good luck

BTW, if you end up hating the Holley, I recommend a Summit carb. I've had problems with all Holleys I've owned, no problems with the two Summit carbs I've owned.

I really should have put in another update. After all that work I had done, it seemed to be running great for a while, then the problem came back in spades with it coughing and choking, billowing black smoke, and needing lots of revving to keep it alive after it had heated up.
After dropping the fuel bowls as a temporary way to get it to 'limp home' I replaced the needles and seats, brought the floats back up, and she's been running a lot better (I still haven't dialed in the idle to where it needs to be, I took it down a bit and now she is struggling with hot starts). I'll see what the new season brings when I get her out of storage in the next week or two - still waiting for the rain to wash all the salt off the roads.

If you have the brass floats, there could be a crack in one (or both) them. This will allow fuel to collect inside the float and cause the float to sink.

John

Mikael, you don't think heat is an issue even though fuel is clearly boiling in the bowls? Fuel should not be boiling and the fact that it is would imply that too much heat is being absorbed at the carb. Rebuilding or replacing the carb won't make it any cooler.

#5754, sorry to hear your problem has reared its head again. I'm interested in following your progress so keep us posted.

To address the heat I've ordered a 1" phenolic spacer from Summit and a 15" oval K&N air cleaner. My current round cleaner barely fits under the rear deck lid as it is so I'm going to have to go to an oval design to accommodate the additional height. I've also ordered a Holley rebuild kit.

Gonna start with cleaning the current needle and seat and checking the floats.

Could be boiling, it's just that overflow on a hot motor looks the same. And I've never seen fuel boil on a properly cooled engine.

Start with the simple inexpensive stuff, if that doesn't help, move on. $0.02

quote:

Originally posted by No Quarter:
Could be boiling, it's just that overflow on a hot motor looks the same...

Except that overflow doesn't pass through the bowls on my carb. I often hear sounds from the overflow but with this most recent episode I have absolutely confirmed that there is boiling occurring in the bowls.

Assuming the fuel is in fact boiling, couldn't the spewing and sputtering occur even with a properly functioning needle and seat? As the fuel boils off in the form of vapor or pressurized squirts the floats will drop and allow the passage of more fuel. So I'm thinking that even with a functioning N&S this problem isn't going away until I reduce transfer of heat to the carburetor?

Thoughts?

And, Mikael, I agree 100% that I should start with the simple inexpensive stuff. That's why I'm starting with N&S and spacer.

Hi
A few remedies found on the web:
-if you have too high fuel pressure, install regulator
-install spacer to lower carb temp
-make sure fuel lines are routed away from engine, exhaust, heater hoses
-make sure the heat riser in the manifold is blocked

I would add make sure your engine doesn't run too hot

Good luck