Ok so I posted about this a little while ago, thought I had fixed it but it is still a problem...here is the deal with my 345.

Started suddenly, when I am on the gas under load...and hit 2500 rpms it starts to shudder and I get a soft thud or popping out the exhaust. Felt like a fuel deal, so I changed all the filters and bypassed both pumps (seperately) no change. I am running a new edelbrock q-jet. So I figure it must be spark. Here is what I have:
MSD 6 new
Pertronix flamethrower coil < 6months old
Helicore wires Put on at same time as coil
Plugs gapped to .050 and clean
Ignitor PO installed don't know how old.
New cap and rotor.
Double checked timing.
I have been through all of it and the only thing I am unsure of is the ignitor?

So I thought maybe I had a cylinder down..did a dry compression test and high was 145 low was 120 or ~83% which is fine.

So I am running out of suspects?? If it had a timing chain I would think it had slipped a tooth, that would explain the exhaust and the backfiring out the carb(only happened twice). But I doubt that the gears slipped?? Could be the ignitor, new one is one the way.
I also noticed that my exhaust flange is leaking, could it be building up back pressure in the exhaust at higher rpms?? I am supposed to leave for Moab tomorrow after work...ideas?? wild guesses??





:confused: :confused:

You didn’t mention you vac advance... do you know if its working? You bought a new carb…why?.. don’t know how they work?.

It’s a 100 plus year old invention:rolleyes:

I’m not being a dick, but the info you have supplied isn’t enough. it could be anything.

When does your advance kick in??


:D

plug gap seems a little to much....good luck

What’s the diz hooked to


ported or manifold
:question: :zzz: :rasta: :flipoff2:

I have not checked the advance yet...good suggestion.

As for the carb, do you mean the shiney thing on top?? :flipoff2:

l bought a junker to rebuild when this deal came by for about the price of a rebuild kit....but feel free to give me more details in the history of carbs :flipoff2: it really is facinating :rolleyes: And I realize you are not going to diagnose the problem on the web just looking for suggestions as to what to check next??

Wiped camshaft:flipoff2: