ptlmveng

Looking for some advise on a minor issue I have. I have a 454 gen IV with holley carb (no choke) and mechanical fuel pump. When I start it when cold I pump the throttle a few times and it fires right up, but after a few seconds it will die if I don't keep on the throttle. It'll usually do this until its warmed up. Once warmed up the idle rpm's fluctuate up and down a few hundred rpm's. Seems like its not getting enough fuel when cold or at idle, only burning whats in carb from couple pumps. Runs smooth other than this. Was thinking about putting an electric fuel pump on just for starting and idleing, and using mechanical for normal operation. Any suggestions would be great.


Thanks!

Budz Motorsports

Sounds like a carb issue! If you have the cash I would get a new carb. If the idle is up and down, could be a vacuum leak. You could try to rebuild the carb, but I suggest a new one!

Rebel_Heart

I have a problem with one engine if it hasn't been started for a week. It takes forever for it to warm up. Once it does, it runs fine. Just thought it was something that I had to deal with because it was a carb.

ptlmveng

Yeah thats what I thought also. Just figured since it was a carb with no choke thats how it should be. But I'm seeing more and more boats with similar setup not having this problem. I'd hate to go buy a new carb and still have the same problem.

spazboz

iTrader: (2)

With the Holley's, you'll never get rid of the "cold-bloodedness" completely. What you describe sounds about natural. As for the flucuations when warm, that sounds like a problem. I worked on a 420 that was doing this last year. Problem was a vacuum leak. One new $4.00 gasket under the carb, and we were good to go. That may explain your issue with cold running also. This would create a lean condition and make the engine run worse when cold. Just a simple thought.

SB

iTrader: (1)

Cold motor needs much richer A/F to run because everything is cold not letting fuel vaporize. Fuel collects on cold metal.

It's the nature of the beast, however, if you really tune your idle well on the carb and bump base timing (not total) up, the motors will run much better cold and start to idle smooth faster.

===============

As far as the fluctuation - hard to tell what's going on by that description. May be normal when cold but may not be. Definately shouldn't be when warm.

ptlmveng

The cold starting issue I'll just deal with. It's a little annoying, but doesn't bother me that much cause with a little play on the throttle I can keep it going. After sitting all winter, three pumps on the throttle and turning over for 3-5 seconds it fired right up. Likewise everytime I run it. But I would like to figure the idle problem so that I can turn the idle down a little bit to get that real nice sound, plus a little less strain on drive going in and out of gear. This may be a dumb question, but where do I start with checking for a vacuum leak, aside from any hoses?

The only other thing that I can add to maybe help is that when I first get into the throttle it does hesitate a little. It is very brief. Almost seems like too much fuel, but like I said it is very brief. Probably around 1200-1500 rpms, but is very responsive past that.

spazboz

iTrader: (2)

Yeah the cold thing is just the nature of the beast. As for the hesitation, it may not be a bad thing to overhaul your carb. Sounds like it may be time to do some PM and a tune-up. I don't know what model BBC you have, but normally there are very few places where a vacuum leak could occur. Heres how I found the carb base gasket was bad on that 420. While the engine was idleing, I sprayed carb cleaner on the base gasket of the carb., and the engine picked up about 350 rpm. Stop spraying, the engine would settle. When I removed the carb, it was very obvious where the gasket was tore. But if you have poor performance and hesitation, it may be time to rebuild the carb.

Griff

The hestitation could probably be cured with a larger accelerator pump.

As far as being cold blooded, thats the nature of the beast with a carb and no choke. You can try to richen it up with the 4 corner adjustment a little. It will help, but its hard to get a happy medium between rich enough at when cold and being too rich when warmed up.

ptlmveng

How tuff is it to rebuild the carb? I'm no motorhead, but I can do a little bit of wrenchin. Never rebuilt a carb though.

Could the idle be affected by a poor seal between flame arrester and carb? Or the float posiibly need to be adjusted?