Tunnel ram problems

Guys,My tunnel ram on my car is giving me fits.The engine is .030 over sbc with 12.1 compression,306 dur,510 lift solid cam.I've checked everything I know to do.The damn thing will start,run awhile,then loads up and dies.Restart,then it backfires and flames up.The carbs are the 450 holleys for a tunnel ram.Any suggestions.I'm not going change the tunnel ram.Thanks,FALFA

 

How much fuel pressure are you running ? Have you checked for va***e leaks around the carbs and where the T Ram top mates to the bottom ?

 

Weak spark, bad power valves, floats not set properly, internal flooding ................................

 

It's the carbs. They need to be tuned for the dual carb setup. The idle is too rich, the low airflow at idle causes rich mixture to worsen and engine loads up and dies.

The relationship between the idle restrictors in the metering body, position of idle screws and how much of the idle transition slot is uncovered at idle has to be correct.

Try putting a small piece of wire in each primary idle restiction and go from there. Don't drill the idle air restrictors up top unless you are really sure what will happen.

 

I would say that after the first backfire the power valves are toast,, no pun intended.

 

Your right ,cant believe i didnt think about that.I have blown Power valves on Holleys in the past .It wont idle for **** afterwards ,and the va***e will be all over the place .It doesnt take much of a backfire out of the carbs to do it either .If those check out okay ,i would make sure that you dont have too much fuel pressure (over powering the needle and seats) ,or the float levels set too high ...

 

If they are the 450's I think, they have side hung floats. I have never had any luck with them. They will be fine one minute then flood over the next. In a nutshell, I hate them! I like the Carter/Edelbrock style carbs. Just my 2 cents.

 

I went though that , not to long ago.

 

Thanks Guys.Your probably right about the power valves,I'll check those. I know the floats are right,checked and rechecked. I'll try that thing with the piece of wire next.Fuel pressure is ok,around 3 to 4 lbs.FALFA

 

Setting up my first dual quad I struggled ALOT - my first major issue was getting a HOT enough spark to allow me time to diagnose the issues. Running a "standard" points & coil couldn't keep the plugs fired over enough time to figure things out. Plugs would foul - run liek **** then I had a different problem to diagnose. Switching over to a MSD allowed it to run (rich) long enough to give me time to try things without stumbling over fouled plugs.

Now don't get me wrong - the Hotter spark doesn't "fix" anything - it merely helps mask the problem long enough to figure it out.

I ran dual 450's - I restricted the idle ports as well. One way to decide whether or not you need to consider that is to determine if they "work" at the moment. In my case twisting the idle screws did nothing. First clue something was amiss.

Also as you already know - be sure those PV's are ok. Again here's where the hot spark helped. As I fouled plugs it'd backfire and cough - again causing issues - hot spark prevented that.

EDIT: I second the comment about checking throttle plate positioning/transfer slot exposure. I also recall having to drill some small holes in my throttle plates to get them into the right position in relation to the transfer slots.

 

If yer carbs are newer, they may have power valve protectors. You could check the base plate to see... you may be able to survive a backfire. Check your idle vacuum. Make sure you have power valves sized so that they are not open at idle!

 

This is only a hunch without really diagnosing your situation up close, but I just had the exact same thing going on with mine. I run a SBC 10.5 to 1 with two Holley 450's on a Edlebrock TR1. I messed with the timining the fuel mixture, everything possible.
Try taking a plug out and grounding it to see what kind of spark you are getting. If it has a slight orange glow rather than a blue white color it may very well be your coil.
An old timer was telling me this and I was like "My coil going bad?" "Yeah right."
Did the test and that was the problem. It fires right up and runs like a champ now with a new coil.
Overall it sounds like you have a poor spark or need a stronger output coil.

 

If those carbs truely are tunnel ram carbs, they will have a check to eliminate the chance of backfires taking out the power valves, If they do not have checks, the whomever you bought them from or built them for you missed it. Any true tunnel ram prepped/built carb will have them.

I'd say also make sure your ignition is up to par, as already stated.

When it is running, can you hold the rpms up a little to keep it running or does it die no matter what?

How easy does it start back up once it dies, or will it not start at all just backfire?

What do you have to do to get it to start once it dies?

Does it ever backfire when you first start cold?

One more thing, is this the first you have tried to run the tunnel ram or has it been on and running fine, now giving you fits?

 

The backfire on restart is probably the result of it dyeing rich. Start it up with no aircleaners and let it run looking down in the carb's and see if one is going rich. Determine which carb it is. You should be able to see which one is dumping excess fuel at idle.I doubt if both carbs are screwing up at once. Report back.

 

Not a good idea at all unless you like the smell of burning hair!

 

I didn't say look down in the carbs while STARTING it!!

 

And theres a good example of what could happen to ya!