Hi,

can i ask something about backfire in a carburator because of a high degree cam, my carburetor is holley 4150 street avenger hly-0-80770 and my manifold is edelbrock torker 2 intake manifold, my problem is my rpm dropped to 0.5k suddenly when i am stopped at the traffic and my airfilter started catch fire, i unfire it with a fire extinguisher quickly, now i am trying to understand why it catched fire, because of the distributor arrangement? All repairmen suggest me to change this high degree stage 4 cam to a performer cam and manifold, what do you suggest me? I dont want to lose power and voice, and also isolate the headers from headers to sidepipes starting point, i again dont want to lose voice, but this isolution makes better the heat isolution, should i turn to standart or performer cam, manifold and carburator from my modified ones or can these components arrange working ok with this situation, i am using it in street usage. What do you suggest me, what should i do?


68 model, 502 cui, can you tell me a suitable combination for 502, my carb which is 80770 is for 400+, 80870 is for 500+ , so my carb is less even for my stock 502, what do you say about this, if i demodify my cam and manifold, even my carb still less for this combination.


Should i change my carb from 80770 to 80870 in every condition.


it backfired, i am trying to understand why? Why rpm reduced from 1000 to 500 suddenly, is there a problem in distributor or it is because of my carb small for my 502?

we arranged valve timing, why it changing, what is the cause, can the arrangement on ignition and timing changing after a while, why the arrangement is changing by itself, its because of high degree cam, if we change the torker2 and high degree cam to the performer and less degree cam, if the problem is about timing and carburetor, it will backfire again,
i am trying to understand high degree cam broke the arrangement on carburetor and ignition and timing, the change is because of high degree cam?


Is my vacuum not enough for my distributer+westinghouse brakes+high degree cam ? But why yesterday make this problem i used this car till last september, only yesterday backfired, where is the problem and which component triggers the problem?


Is this distributors arrangement can change because of the motors vibration? Why my rpm dropped to the 500 suddenly, i only want to learn this questions answer?

Saturday 2 times it dropped to the 500 rpm, i hit the gas pedal and make it 1000 rpm again and sunday it dropped 500 and stopped and backfired from carburetor.

I red backfire from internet forums, My backfire causes because of wrong timing and ignition issues, is torker2 guilty in this situation? If i change it with performer, can i be more safe? I am trying to give decision between torker2 and performer, in internet in my searches, i red it on maliburacing forum, in this forum in a poll, %80 says performer better for street usage, %20 says torker2 better, someone says torker2 can be ok for street usage if the arrangements done correctly. Now i am thinking why my carb, ignition arrangements, timing started to work wrong, is this because of torker2 and high degree cam? Can you please help me, do i need to change my combination to a lower one, or it can work with correct arrangements for street usage?

 

Language issues make this hard, Serhan. While there may be a backfire (combustion in the intake manifold that comes up through the carburetor), the issue you're dealing with seems more like excess fuel in the intake. Your unstable idle (from 1000rpm down to 500rpm) and that your carburetor caught on fire leads me to believe you have an internal fuel leak. On a carburetor that isn't leaking fuel, a backfire will not set the carb on fire. It pops and that's it.

The easiest first check would be to make sure all of your vacuum lines are properly connected to the carburetor and intake and that none of them are leaking. If all of that looks good, move on to the fuel system.

First thing to do is remove the air cleaner, start the engine, and look down into the boosters and at the throttle plates. If you have fuel dripping from the boosters or the throttle plates are wet, you have too much fuel in the float bowls.

Now, with the engine not running, remove the float bowl sight plugs. Fuel should be at the very bottom of the plug hole. A very small amount (around 1cc) of fuel may run out of the plug hole. If there is more than that, you will have to adjust your float level. The WWW has a lot of information on checking and adjusting Holley floats. A high fuel level can be caused by maladjusted floats, leaking needle and seat, leaking needle and seat o-ring, or too high fuel pressure.

The next thing to check is to make sure previous backfires didn't damage your power valve (PV). Again, the WWW has a lot of information on how to check the PV. A ruptured PV diaphragm will leak fuel from the bottom of the carburetor into the intake.

You should check your ignition system to make sure the ignition timing is correct and all the plugs are firing.

I would not change any parts until you know why it's behaving this way.

 

First off, if you've backfired through the carb and your running a Holley, you've probably popped a power valve. Understand the power valve didn't CAUSE the problem but is common side effect from a carburetor backfire when a Holley is involved. Timing and firing order are the first things that come to mind when a big backfire is involved. That or your primary or secondary fuel bowls are incorrectly adjusted and literally dumping fuel .

 

thanks you for your help, we will check firstly what you said, timing, vacuuming, sparks, i dont want to change anything in the motor, i want a proper arrangement in my combination. Thanks.

 

thank you all of you for your help, the repairmen solved the problem, my distributor is an electronic distributor, but its installation was mecanic, they changed it to the electronic too, now i have more firing, timing and vacuuming, i have both brake and power now, also they open rear to power valves too they starting after 3000 like a turbo. thanks all of you for your help.