Cracking and banging of of exhaust

[madmike]

yea I'm old skool for sure,,, The only problem these guys are having could be 'small motors' and a miss match carb,, I couldn't get enuff fuel into the sidedraft to work on my 2276cc , so swapped to the 4 barrels problem solved,, so if they build bigger motors and a good 4 barrel
or my suggestion small 4 barrel and a good RLR heated intake probably solve their issues or warm weather

[advinnie]

I thought I had it fixed but no today took it for a drive and the first five minutes was fine then I started to backfire through the exhaust but only on acceleration it slow got worse to the point that the engine just would not accelerate and every time I increased the pressure on the go pedal she would just continuously backfire out the exhaust. I have checked for air leaks and found none. I’ve tried increasing and decreasing timing but that makes no difference. I’m starting to think it’s missing any thoughts?

[falcor]

Weak coil so the extra fuel kills the spark?

[advinnie]

It’s definitely intermittent. Just been for a drive and at first all ways good then ten minutes later it was backfire like mad then it just stopped backfiring

[madmike]

That does sound like ignition or a slug of bad fuel what do the spark plugs look like? could be fouled (black)

[advinnie]

Spark plugs are always black on this draw through but just checked them in the machine at work and all four fire and all leads check out ok. But I’ve just plug my laptop into the CB performance black box to recheck the timing and something strange is going on, when at a stand still the CB performance program display on the laptop is working fine but when I start moving and going over bumps the CB performance program display starts flickering on and off ?

[buguy]

Sounds lean to me. You really need to get a working wideband. Ive been tuning in mine and I had it where it looked good on the gauge and sounded good sitting still. As soon as I took it for a drive it went mega lean almost everhwhere. On my Holley I went up 7 jet sizes and almost 10 sizes on the accelerator pump shot. It is still right on the edge of lean through most of the power band. I am constantly amazed at how much fuel it takes to make a draw through work.

[buguy]

I should mention that when I took mine on the first drive yesterday when it was real lean it acted like your describing. Popped and banged. Barely able to go.

[advinnie]

I hear what your saying I really do but I’ve just had a faultless 40 minuet drive taking her from idle to 5000rpm and 6psi boost. Then seconds from home she started backfiring again at random rpms and it was all of boost as soon as boost kicks in she seems to stop backfiring.

[Dan Dryden]

Because it drives ok to start with, I wonder if the problem is heat related (or lack of).
Could you be getting intake manifold freezing?
The weather here in the UK is pretty chilly at the moment.

[advinnie]

Now I have an idea, I don’t think it’s due to the engine going lean although my A/F sensor has packed up because I have now tried 45, 50,55 & 60 idle jets, 125,130,135,149,152 & 160 main jets, 50 & 70 pump jets and no matter what combo I do I still get random backfiring. I also do t think it has anything to do with my ignition table because I’ve now tried six different tables ranging from very retarded to very advance and still I get random backfiring. Now this may be a silly beginners mistake, from the position post on the ignition coil I have four auxiliary units running from it and they are
1- external oil cooler fan relay
2- manifold de-icing unit
3- cheers performance ignition unit
4- boost sensor
Now would/ could this be to much and taking to much power away from the coil?
Or am I thinking about this totally wrong?

[advinnie]

Because it drives ok to start with, I wonder if the problem is heat related (or lack of).
Could you be getting intake manifold freezing?
The weather here in the UK is pretty chilly at the moment.

I don’t think it’s icing problems now I’m hoping that’s all sorted. I have a manifold de-icing boot fitted now and also a 2” hose that is rammed up under the cylinders collecting all that nice hot air and the other end it routed up underneath the carb/manifold and after ten ish minutes of driving there is plenty of red hot air warming the manifold.

[Dan Dryden]

Now I have an idea, I don’t think it’s due to the engine going lean although my A/F sensor has packed up because I have now tried 45, 50,55 & 60 idle jets, 125,130,135,149,152 & 160 main jets, 50 & 70 pump jets and no matter what combo I do I still get random backfiring. I also do t think it has anything to do with my ignition table because I’ve now tried six different tables ranging from very retarded to very advance and still I get random backfiring. Now this may be a silly beginners mistake, from the position post on the ignition coil I have four auxiliary units running from it and they are
1- external oil cooler fan relay
2- manifold de-icing unit
3- cheers performance ignition unit
4- boost sensor
Now would/ could this be to much and taking to much power away from the coil?
Or am I thinking about this totally wrong?

I think you definitely need to have a look at that. I used to get a similar problem whenever I switched on my headlights.
Once I gave the coil its very own exclusive power feed it never happened again.
When I switched to EFI, the wiring instructions stipulated that the coil must have its very own feed directly from the battery. The ECU now controls when the coil pack gets power via a relay.

[buguy]

Oh! I didn't realize you were able to drive it that long without a problem

[advinnie]

Oh! I didn't realize you were able to drive it that long without a problem

yep it can happen within minutes or an hour into a drive. You don’t know when it’s going to happen but it will and it’s normally at the worst possible time like joining a motorway or at a T junction