Hot starting problem.

[Daytona Dek]

Sorry if this is a bit of a numpty question but my Daytona fitted with a 302 and Edelbrock Thunder 1805 carb is difficult to start when it’s still hot. I think it’s due to fuel evaporation not heat soak on the starter. It will start eventually but after an embarrassing amount of churning. Is there a technique I can adopt to improve things like opening the throttle wide but don’t know the exact details?

[Unique427]

Originally Posted by Daytona Dek

Sorry if this is a bit of a numpty question but my Daytona fitted with a 302 and Edelbrock Thunder 1805 carb is difficult to start when it’s still hot. I think it’s due to fuel evaporation not heat soak on the starter. It will start eventually but after an embarrassing amount of churning. Is there a technique I can adopt to improve things like opening the throttle wide but don’t know the exact details?

If you think fuel evaporation due to heat soak is the issue,
lifting the hood after shutdown helps. Of course in a Daytona
that's also a PITA.

Check that fuel lines are not making contact with the engine.
Insulate fuel lines near engine.
Install a heat shield kit around carb.

If all else fails you can also try...........
Using non-ethanol fuel mixed with unleaded racing gas.
Race gas has a lower RVP (Reid Vapor Pressure) rating
for the specific purpose of better starting characteristics
of heat soaked engines. Downside is you may need to
adjust/tune for it. Sunoco 260 GTX is non-oxygenated
unleaded 98 octane. 91 octane non-ethanol mixed
50/50 with 260 GTX is confirmed to work well for hot
starts and reduced vapor lock tendencies.

[patrickt]

Next time you park it hot... give it 15 minutes with the hood down and then take the air cleaner off and look at the top of the butterflies for puddled gas. Watch for drips of gas from the boosters. look for suspicious wet spots or brown stains on the outside of the carb at the downside (meaning the direction that a drip would go if it was running off your butterflies) especially on the butterfly shaft. Any of those will tip you that you have a percolation problem. If you see none of that, with your hand on the carb linkage give it a good "push to the floor" and watch for accelerator pump to see if it will squirt gas out in two nice strong streams. Those two tests will put you down the road to success. Personally, I'm betting on percolation.

[HighPlainsDrifter]

https://www.summitracing.com/parts/edl-9265
I use this, works good.
Perry

[mrmustang]

Originally Posted by HighPlainsDrifter

https://www.summitracing.com/parts/edl-9265
I use this, works good.
Perry

For all of my race cars, I prefer the Mr Gasket kit, part # 3710 , as it gives more options. You only need one heat shield, and two gaskets, and do not have to use the whole kit.


Dozens upon dozens of cars I've dealt with, and this fixes any carb percolation issues I've run across.





Bill S.

[saltshaker]

do you have a electric fuel pump? You can put one in line with a check valve Turn it on to fill the bowls before starting … solved it for me
jom

[Daytona Dek]

Originally Posted by HighPlainsDrifter

https://www.summitracing.com/parts/edl-9265
I use this, works good.
Perry

I think phenolic spacers do work but unfortunately there is very little space between the air cleaner and bonnet to increase the height of the carb.

[HighPlainsDrifter]

https://www.summitracing.com/parts/edl-9265
I use this, works good.
Perry

[Daytona Dek]

Originally Posted by patrickt

Next time you park it hot... give it 15 minutes with the hood down and then take the air cleaner off and look at the top of the butterflies for puddled gas. Watch for drips of gas from the boosters. look for suspicious wet spots or brown stains on the outside of the carb at the downside (meaning the direction that a drip would go if it was running off your butterflies) especially on the butterfly shaft. Any of those will tip you that you have a percolation problem. If you see none of that, with your hand on the carb linkage give it a good "push to the floor" and watch for accelerator pump to see if it will squirt gas out in two nice strong streams. Those two tests will put you down the road to success. Personally, I'm betting on percolation.

Thanks Patrick I will follow your tips next time I have it out. I should have added that once started it runs fine.

[Gaz64]

Open the throttle to about 1/3 initially.
If it struggles to start, at least you haven't flooded it worse.
While it is cranking, open the throttle wide.
As soon as it fires, back off and control the rpm as usual.
Add a heatsoak spacer or heatshield etc.
Gary

[DanEC]

What Gaz64 posted.

[Argess]

I had this problem and cured it with some silicone tubing over the fuel line as well as changing the line from copper to steel. Steel doesn't absorb heat like copper.

Here's a "before" pic:



Here's an "after" pic:



Here's the silicone tubing I used. It was 10mm ID and slid over the 3/8" fuel line. 3/8 ID silicone tubing would be too difficult to slide over the fuel line:

https://www.amazon.ca/gp/product/B073DXX9QB/

The steel line was just a piece of brake-line. Cut the flare off one end, cut to length, removed the fittings it came with, installed my own and the tubing, then re-flared the cut end.

Problem gone and has never come back.

[patrickt]

"Copper interferes significantly in the gum content of gasoline, because it is a catalyst of radicalar oxidation reactions and it accelerates peroxidation. Therefore, this metal must be avoided in any metal alloy that comes into contact with gasoline in the feeding system of engines."

Source: https://www.researchgate.net/publica...otive_Gasoline

[Daytona Dek]

Originally Posted by Argess

I had this problem and cured it with some silicone tubing over the fuel line as well as changing the line from copper to steel. Steel doesn't absorb heat like copper.

Here's a "before" pic:



Here's an "after" pic:



Here's the silicone tubing I used. It was 10mm ID and slid over the 3/8" fuel line. 3/8 ID silicone tubing would be too difficult to slide over the fuel line:

https://www.amazon.ca/gp/product/B073DXX9QB/

The steel line was just a piece of brake-line. Cut the flare off one end, cut to length, removed the fittings it came with, installed my own and the tubing, then re-flared the cut end.

Problem gone and has never come back.

Thanks John that’s a neat solution I wouldn’t have thought of. I’ll investigate my fuel lines.

[Argess]

Yes, I've heard that before. I used that copper line from when I first got the car on the road back in 1997 until I changed to steel line in 2018. I guess the reaction is slow.

[Tom Kirkham]

In addition to what others have recommended, look into a bypassing fuel pressure regulator. It works extremally in curing vapor lock.

[Daytona Dek]

Originally Posted by Tom Kirkham

In addition to what others have recommended, look into a bypassing fuel pressure regulator. It works extremally in curing vapor lock.

Thanks Tom. Excuse my ignorance but what do you mean by a “bypassing” fuel regulator and how exactly does it cure vapour lock? By increasing/decreasing fuel pressure?

[cycleguy55]

Originally Posted by Daytona Dek

Thanks Tom. Excuse my ignorance but what do you mean by a “bypassing” fuel regulator and how exactly does it cure vapour lock? By increasing/decreasing fuel pressure?

A 'bypassing' fuel regulator has a return line that carries the fuel back to the tank that's not needed by the carburetor. That maintains a flow of cool fuel, whereas a 'blocking' type regulator holds that fuel and releases to the carburetor only what it needs. By holding the fuel it provides greater time for the fuel to heat up.

More: https://helpcenter.jegs.com/hc/en-us...egulators-Work

[bkozlow]

SOME PICTURES WOULD BE NICE TO SEE WHAT YOU ARE WORKING WITH. If you haven't gone to an air box you should consider it as it will drop your carb temp that it maybe enough to solve your problem. Look at the air box in my album.

BillK

[Daytona Dek]

Originally Posted by bkozlow

SOME PICTURES WOULD BE NICE TO SEE WHAT YOU ARE WORKING WITH. If you haven't gone to an air box you should consider it as it will drop your carb temp that it maybe enough to solve your problem. Look at the air box in my album.

BillK

If it were easier to upload photos you might have them. I’ve got an oval Cobra air filter on top of an Edelbrock carb.