Problems with the 408 in summer racing.

[SteveSS]

We don't race much but this happens every time. In our '71 Challenger we have a Blueprint Engines stroker 408. If the runs are separated by enough time things are great. But as soon as we run two in a row. The engine cuts out. I was riding with my son this time and it's like he lifted the throttle. It must be heat related. we've tried wrapping the fuel lines with insulation. Some one suggested a carb spacer but I'd like a more definitive answer.

 

[Bird 426]

Almost sounds like vapor lock.

 

[33 IMP]

Have you got a fuel pressure gauge you can see?
Fuel tank vent?

 

[RemCharger]

Sound like a mechanical fuel heater issue

 

[SteveSS]

What is a mechanical fuel heater?

 

[RemCharger]

What is a mechanical fuel heater?

Actually, it's multi- use. Pumps fuel to the carb  while making the fuel too hot for relible racing performance.
An electric pump removes the heat issue.

 

[kiwigtx]

We don't race much but this happens every time. In our '71 Challenger we have a Blueprint Engines stroker 408. If the runs are separated by enough time things are great. But as soon as we run two in a row. The engine cuts out. I was riding with my son this time and it's like he lifted the throttle. It must be heat related. we've tried wrapping the fuel lines with insulation. Some one suggested a carb spacer but I'd like a more definitive answer.

What sizes are your supply and return lines?
Have you checked down the throats to see all injectors are operating?

Is the return line dedicated straight to the tank, or are you running a Dead-head pressure valve?
Altitude must be at play here also..... has this been tuned at all for your higher elevation?

Also....breather on the tank? You might be sucking so hard that the time taken to "re-inflate" the fuel tank is not long enough.

 

[dvw]

Make sure the tank is well vented. My mild 360 Challenger runs the stock fuel system with the exception a bolt together mechanical fuel pump. Has run 12.70@107 in street trim. Never an issue with fuel delivery in any temperature. Same combo 21 years.
Doug

 

[oldbee]

What about adding a ‘cool can’ before the carb. Fill with ice while racing.

 

[DanielSlocum]

If your carb feels very hot to the touch.....you need an insulated spacer underneath.

 

[autoxcuda]

What sizes are your supply and return lines?
Have you checked down the throats to see all injectors are operating?

Is the return line dedicated straight to the tank, or are you running a Dead-head pressure valve?
Altitude must be at play here also..... has this been tuned at all for your higher elevation?

Also....breather on the tank? You might be sucking so hard that the time taken to "re-inflate" the fuel tank is not long enough.

Sounds like the OP is running a carb.

 

[autoxcuda]

What is a mechanical fuel heater?

Actually, it's multi- use. Pumps fuel to the carb  while making the fuel too hot for relible racing performance.
An electric pump removes the heat issue.

I believe RemCharger is talking about a typical mechanical fuel pump. ... just being tongue-in-check about it.

 

[RemCharger]

I believe RemCharger is talking about a typical mechanical fuel pump. ... just being tongue-in-check about it.

Yes. If you're serious about racing in the heat, a mechanical pump is not the way to go.

 

[autoxcuda]

Nascar short track racer run in plenty of heat. They run mechanical

I've done 15 min on track sessions, 15 min break. And on track again in the middle of the desert, Palmdale/Willow Springs. I've never had issues. I drive in 90-100 stop and go traffic with no issues too.

I run: fully covered fuel lines, no 90 degree fittings In or Out of pump, fuel lines routed away motor heat and in air flow stream, heat crossovers blocked, M1 single plane with air flow underneath, good cooling system.

I do understand an electric on more serious drag car. But I think the OP's son's Challenger is more a street car with 375-465 HP or so.

 

[autoxcuda]

Just wonder if there is something obvious and simple... A carb spacer wouldn't be the end or world. Float setting? fuel line routing.

 

[Lefty71]

You might be sucking so hard that the.............

This is exactly how I talk to myself at the dragstrip lol.

 

[Lefty71]

The engine cuts out.

How hot outside? When and how does it cut out?? You mean hard to restart, or it stalls on the line??

 

[DanielSlocum]

Does the carb get hot to the touch after running some time with the hood closed or not?