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  #1 (permalink)  
Old 02-11-2018, 07:53 AM
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Default Fixing one thing leads to another...

So reading all the literature about how the oil Temp should really be run above waters' boiling point so as to burn off condensation, and acids formed by it and combustion products sneaking by the rings, made lots of sense to me. So a canton Oil thermostat was installed and is working as it should; oil running about 220 rock solid.

Problem now is that the motor is HOT, which results in summer like fuel percolation and vapor lock problems. After shutting down the heat soak causes the accelerator pump blocks under the carb to get hot enough to start burping fuel through the nozzles, of course flooding the motor...carb spacers won't do anything for this, nor will float levels? The needles are in there, seems to be prevailing on the primary side.

Carb is a Holley 750xp on a super Vic manifold with a turkey pan cool carbs spacer hvh 1/2" out 1/2" in contour spacer: 427 ford racing 535 horse crate motor...

Ideas?

Thanks

Steve H
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Last edited by tortuga; 02-11-2018 at 07:55 AM..
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Old 02-11-2018, 08:13 AM
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Do you have a return line on the carbs that returns excessive fuel pressure to bleed back into the tank?
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Old 02-11-2018, 09:13 AM
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Quote:
Originally Posted by tortuga View Post
So reading all the literature about how the oil Temp should really be run above waters' boiling point so as to burn off condensation, and acids formed by it and combustion products sneaking by the rings, made lots of sense to me.
The SAE literature, and the engine engineering literature, does NOT say you have to have your oil temperature gauge up over 212 degrees to burn off moisture and contaminants. The only people that write that are forum guys that don't realize that the temperature of the oil on the back of your piston is a couple of hundred degrees higher than what your oil gauge is showing. To lower the wear on your engine, the literature is clear -- have everything run at around 185 degrees or so. If you drive your Cobra for an hour, and the engine coolant gauge and the oil temperature gauge both read 185, then that's about as perfect as you're going to get. And if you have any doubts at all, use a vacuum pump and pull a sample of oil out of your pan and ship it off to the oil lab for an analysis. An analysis will tell you if you have any moisture or contaminants in there.
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Old 02-11-2018, 10:32 AM
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Default Return line

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Originally Posted by t walgamuth View Post
Do you have a return line on the carbs that returns excessive fuel pressure to bleed back into the tank?
No it's a dead head system: thought about that too, however to be really effective I would think you would want to return the fuel over the engine (ideally in the bowls) but don't see any system that does that. With proper port FI all the fuel is moving, it's just when the injectors fire when some of it goes Ito the motor.

With the return regulators I've looked at it seems you still have static fuel from the reg to the motor but are recirculating the fuel to the reg which isn't where the problem Is?

Seems like recircing from the other end of the fuel log would be close to ideal?

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Old 02-11-2018, 10:36 AM
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What Patrickt said. You don't need to run oil that hot.
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Old 02-11-2018, 10:36 AM
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Default Hmmm

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Originally Posted by patrickt View Post
The SAE literature, and the engine engineering literature, does NOT say you have to have your oil temperature gauge up over 212 degrees to burn off moisture and contaminants. The only people that write that are forum guys that don't realize that the temperature of the oil on the back of your piston is a couple of hundred degrees higher than what your oil gauge is showing. To lower the wear on your engine, the literature is clear -- have everything run at around 185 degrees or so. If you drive your Cobra for an hour, and the engine coolant gauge and the oil temperature gauge both read 185, then that's about as perfect as you're going to get. And if you have any doubts at all, use a vacuum pump and pull a sample of oil out of your pan and ship it off to the oil lab for an analysis. An analysis will tell you if you have any moisture or contaminants in there.
Thanks for your response.

She's running about 180 coolant and as stated about 220 after warming up, weather it's 35F or 75F best ambient this year so far...

Before the t stat it would over cool and never reach more than about 140-150F...

I wonder if the guts in the canton Tstat are adjustable or replaceable?

Steve H
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Old 02-11-2018, 01:00 PM
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Quote:
Originally Posted by tortuga View Post
No it's a dead head system: thought about that too, however to be really effective I would think you would want to return the fuel over the engine (ideally in the bowls) but don't see any system that does that. With proper port FI all the fuel is moving, it's just when the injectors fire when some of it goes Ito the motor.

With the return regulators I've looked at it seems you still have static fuel from the reg to the motor but are recirculating the fuel to the reg which isn't where the problem Is?

Seems like recircing from the other end of the fuel log would be close to ideal?

Steve H
SPF 1764
I have an old carb somewhere around that has a second nipple on the top of the carb and a reed valve IIRC which allows fuel to bleed back to the tank if its all not being used by the engine. This keeps it from vapor locking I suppose. I would think such a device could be added to the system somewhere without too much ado.
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Old 02-11-2018, 02:33 PM
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I think the time at temperature, say 90C, for the oil is important for both condensation in oil and exhaust systems. I suspect it is more important than the actual temperature.
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Old 02-11-2018, 04:06 PM
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I have a 17 Mustang GT350 with the 8200 redline Voodoo motor and Ford has put a lot of engineering into the oiling system and has digital temperature readouts on nearly everything you can imagine. Ford even requires their own Motorcraft oil for it that is some weird formulation that isn't sold by anyone else. It will not allow the computer to engage full power until the oil reaches 190 F. But like so many Cobras with the remote cooler, the cooler on the Mustang seldom allows the oil to get over 175 F on cooler days unless it's blocked off. Although you can't go full throttle/rpm in the winter, apparently Ford isn't too bothered by 175 F oil or they would have put a thermostat in the system.
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Old 02-11-2018, 04:58 PM
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Before you start chasing your tail any further remember that California is currently pumping their winter blend of gasoline which has a lower boiling/vaporization temp than summer grade gasoline does. And with the unusually hot temps we have been experiencing this winter it could be that the winter grade of gas and your increased engine temp have created the perfect storm to cause fuel percolation upon shutting down of your hot engine.
If it were me, and I think the oil thermostat is a good idea, I would install a 180 degree thermostat. These cars were designed in the 60ís, when fuel percolation wasnít a concern. And with the advent of highly pressurized fuel injection systems, calif can run their highly volatile blend without any problems.
But our cars canít handle the low boiling point.
You can wait till summer and your problem could go away. Summer blend is much more heat tolerant than winter blend. But then it may show up again as soon as we switch back to winter blend.
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Old 02-11-2018, 06:22 PM
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This does sound sorta hot. Aircraft recips are regulated to 200F but those are different animals.

So I had to read up.

(100c) or 212F is the magic number from what most articles I read said oil should run at.
Probably why a lot of manufacturers use the radiator as a heat exchanger/oil cooler. Danger in that is when it leaks, water gets in your oil...(Happened on a Nissan I owned)

The top 3 (seems like they know what they're doing...)
What Is The Optimum Engine Oil Temperature? - Hot Rod Network
https://mobiloil.com/~/media/amer/us...duct-guide.pdf
https://www.cantonracingproducts.com...ion&key=22-480

The only thing I found which disagreed somewhat.
https://www.google.com/search?q=Engi...pPZJaTas0vZJM:

And Earls plumbing
https://www.holley.com/products/plum...t/parts/501ERL

The Earls part opens at 180F vs 215F as on the Canton part.
I might spring for the Earls unit as I'm changing out all my hoses anyways.


BTW Dan there is a recall on 15-17 GT350 for suspect oil lines, this is probably old news to you or may not apply.
https://ford.oemdtc.com/2472/16s40-e...g-gt350-gt350r
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Old 02-11-2018, 06:59 PM
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Default Done a few things that have improved the situation

I've converted to an all nylon braided hose fuel feed from my original big billet log and collection of an fittings to get it BELOW the turkey pan real close to the manifold; the hoses are all as high as possible up in the pan, both exiting at the back...I ran the forward hose as high as I could...in poking around it seems that the front of the manifold gets hotter than the back. Guessing that the coolant passages, the reservoir and generally less chance for air to circulate causes this?

The comment about the crappy CA winter fuel and the Wonderfully warm winter we've had is probably a very valid point.

Aside from the hot start problems, the motor seems really really happy running hotter.

Steve H
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Last edited by tortuga; 02-11-2018 at 07:26 PM..
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Old 02-11-2018, 07:01 PM
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Old 02-11-2018, 11:35 PM
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The trouble with late model Holleys now is they all run the more efficient umbrella inlet check valve in the pump cavity, but they all don't have a pump bleed back to the bowl, typically. 013, so when the pump chamber gets hot, it dribbles out the pump nozzle, flooding the engine.

You can drill a .013 hole outside the umbrella so the pump can bleed back.

Some guys machine a groove in the bottom of the bowl near the edge of where the umbrella seats.

Early bowls with their hung inlet check ball rarely suffer from this condition.

Gary
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Old 02-12-2018, 03:33 AM
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Just for what it is worth but both my small block and big block run the oil temps at around 240/250 and the water at 210/220. They were designed to run that way and if they don't get up to that temperature they don't run as well.

Ron
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Old 02-12-2018, 06:27 AM
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Just throwing this out there. Ford, back in the 60s, began installing 195 degree thermostats in most of their engines. Then began advertising longer oil change intervals and better fuel economy.
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Old 02-12-2018, 06:18 PM
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Default Great info

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The trouble with late model Holleys now is they all run the more efficient umbrella inlet check valve in the pump cavity, but they all don't have a pump bleed back to the bowl, typically. 013, so when the pump chamber gets hot, it dribbles out the pump nozzle, flooding the engine.

You can drill a .013 hole outside the umbrella so the pump can bleed back.

Some guys machine a groove in the bottom of the bowl near the edge of where the umbrella seats.

Early bowls with their hung inlet check ball rarely suffer from this condition.

Gary
I'm going web hunting for a how to on this!

Thanks!
Steve H
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Old 02-12-2018, 06:45 PM
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Quote:
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I'm going web hunting for a how to on this!

Thanks!
Steve H
It's a relatively obscure point; I've never had to do it myself. But you can read about it here: https://www.musclecardiy.com/perform...-pump-circuit/ Just skip down to the paragraph that starts with The accelerator pump system needs to counter the following two situations...
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Old 02-12-2018, 10:59 PM
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Here it is here:

The accelerator pump system needs to counter the following two situations. So as not to discharge fuel through the squirters when the throttle is opened slowly, in some systems there is a controlled bleed from the pump back into the fuel bowl. Older carbs have a check valve located within the pump. When the throttle opening rates exceed a certain amount, the check valve closes and the fuel is redirected solely to the squirters. Also worthy of note is that some aftermarket Holley specialists drill a small bleed-back hole through the pump roof/float bowl floor. This hole needs to be small (about 0.012 inch), but it can be used as a tuning aid for the pump system in much the same way as Weber pump jet float bowl bleed-backs.

Good to see this in black and white,.

Gary
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Old 02-13-2018, 04:30 AM
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I believe you changed to a Shaw Stat correct. If you are running a stat extension and did not take note of your clearance, you may have a flow issue, which I believe I cautioned about. More likely to cause a hot motor than the oil cooler stat. Check this out, you may have to have the ID of your stat extension bored, I know I did.
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