Chris J

my 400 with aluminum heads, headers, QFT carb, HEI and TH 400 starts when it is cold and runs and shifts as it should. when it reaches operating of about 190 or so if I shut the car off it is very hard to start and will often sound as though it is trying to run on three or four cylinders once I get it started and shift to reverse or drive it dies as soon as it goes in gear. I have new fuel lines front to back running a mechanical fuel pump with an inline filter before the pump. It has to have something to do with heat as the car runs perfect until hot then goes bad unless I put a lot of fuel to it. I want to start driving my 442 as the weather is getting good but I cant figure this out any help is as always much appreciated. This is a freshly rebuilt motor and everything is new.

billmerbach

Smell your oil for gas sounds similar to something that happened to me not to sure but its a starting point. When you give it gas does it sound like its sucking air?

MDchanic

Start with the basics: Fuel and Spark.

Warm it up and see if it starts easier with a spray of ether. If so, then it's a fuel issue.

Also check the spark warm - should be fat and hot. If it's weak, yellow, or orange, you've got a problem. First place to look is the HEI module. If the temperature problem is consistent, you can warm it up, remove the cap, and give the module a good spray with Dust-Off or similar freon spray from an upside-down can to cool it off, then try starting right away. If it runs well with the module cold, then there's your problem.

- Eric

73aussie455

running cold but not hot, runs when you give it a boot full openning up the butterflies to let in more air, running too rich and stumbling at idle when restarted hot.
sounds too obvious but is the choke staying on or stuck on?

billmerbach

Aussie that's what I'm thinking sort of it sounds like it runs great when the choke is on because the bowl is filled with gas but as soon as the choke opens up it dies. It sounds real similar to what happened to my dads apparently it had something to do with a blown needle seat or something in the carb. I guess my question to the OP is is this a new, used, or rebuilt carb?

fbonanno

You say all fuel lines are new. Make sure the line from the carb to the pump isn't too close to a heat source. Meaning you need air space around the line. Otherwise you may be experiencing vapor lock.

oldcutlass

Idle rpm too high, timing a bit too advanced, possibly running rich, float set too high?

rjohnson442

flodded! needle or float adjustment. stuck choke for starters

73aussie455

You mentioned everything new. Some QFT carbs have an electric choke, has it been set up for the correct adjustment?
If its a mechanical choke and you have ally heads without exhaust crossover and an ally manifold maybe the bi-metalic coil isnt getting hot enough to shut off the choke when the engine heats up?

Certainly sounds like a carb issue, some good suggestions here already just pick one and start there. Check and trial one thing at a time until you find the problem.

I have waay too much time to think about this at the moment as I ruptured my ACL in my knee motocycle racing 2 weeks ago...

dmullin

Another possibility,
Shutting down engine at operating temp. After 30 seconds restarting causes no problems.
Shutting down engine at operating temperature then restarting after 5-15 minutes it is hard to start, runs like crap unless throttle is put down.
If these statements apply, you may be suffering from fuel perk and fuel is dumping into intake after shutdown. Aluminum heads and intakes transfer heat to the carb fast, especially with the fan off and no airflow from travel.
The fix for this is phenelic carb spacer. 1/2 inch or 1 inch if you have clearance.
OR a choke problem...

Chris J

WOW thank you all for your great advice! I cant spend a lot of time on this until Sunday my next day off. I can rule out the choke, it is electric but not hooked but yet. I am going to start with fuel, specifically the line from the pump to the carb it is very close to the block, alternator and intake and I'm hoping its that easy! I was also thinking I would change the metal inline filter to a glass one so I could see what was going on with the fuel and move it further away from the header at the same time. I will update as I work through this thanks again for all the help!

MDchanic

What position is the butterfly in?

- Eric

m371961

I'm with MD. If you have not adjusted choke to stay open, it must have voltage to open as engine warms up. I sure would look there first.

Chris J

I'll go ahead and hook up up the choke and that will determine if that is the cause, if it is that would be awesome I think I can do that tonight. I will let you know as soon as give it a try.

MDchanic

Why don't you go ahead and look at the position of the butterfly?

- Eric

Chris J

Ok the butterfly is open and the fuel line from the pump to the carb has plenty of air around it it isn't close to any heat source.

MDchanic

Is the butterfly firmly open, or does it flap around?

- Eric

73aussie455

Float level too high or jets too large giving it a rich condition/choke effect when cold, but way too rich when hot?

Chris J

yes it is firmly open it doesn't flop around at all

MDchanic

Good.

We've just excluded one possible problem.

Now we can tackle the others one at a time.

- Eric

Chris J

Yes I'm going to check the float level next and adjust if needed. I will update after I have finished that.
Chris

MDchanic

I would still recommend checking the simple things first.

Check to see whether there is fuel in the carb when it starts to stall.

Check for spark.

THEN start taking things apart.

- Eric

Chris J

Made some progress today, car is running much better. Started with the timing it was to advanced corrected that, checked the float level, it was to high so I adjusted that. Drove the car starts and shifts much better when at temp. I need to finish adjusting the air mix and tweek the timing a bit more as it is a little lean now but much better and going in the right direction. I will update again when I get everything dialed in.
Chris