big block belches flame

First off thanks to everyone who replied to my last post. This is the same
engine as in my previous post (400 big block chrysler, not sure what
year). It has a non-stock cam (I don't know the specs, it was installed by
a previous owner and the guy I bought it from didn't know either), a
non-stock electronic ignition (once again previous owner)with no vaccuum
advance, and a non stock Holley 650 four barrel carb. The problem is that
it seems like there is more vibration than there should be at idle in gear
or in park, but it doesn't seem to be misfiring and the cylinder
compression is normal. When I hit the throttle hard enough for the
secondaries to open, it backfires and belches fire out of the carb, then
proceeds to have no guts whatsoever. I ran some lucas fuel system cleaner
through it and changed the oil and spark plugs, bought a Holley Trickit
for the carb and rebuilt it because the secondary float needle was
sticking and the secondaries are now operating normally and are getting
fuel. I checked the compression in all cylinders and it was normal. The
distributor cap and rotor are in good shape and I just set the air gap. I
checked the timing and it was set at more than 30 degrees (!) before top
dead center, so I advanced it to 7 1/2 degrees before top dead center, and
it behaved the same only ran worse, like that was too much advance. It has
fresh fuel in it also. Starting to run out of ideas. If anyone could steer
me in the right direction, I would be grateful!

Your total timing should be in the 36 to 38 range with a non vacuum set
up. That means bring the rpm up till it advances no more mechanically
and set it at 36 would be a good start. You divd not say if it was a DP
holley or a vacuum secondary! I'll assume it's a Double pumper
mechanical secondaries. I hope it is not a Vacuum someone has converted
to pull the secondaries open manually. (carb number please)
It sounds like a lean condition as the secondaries open. Could be the
squinter and accelerator pump are not functioning on the back barrels of
the carburetor. Front system may need attention to and condition could
be exasperated by too small of jets in the carb!
Dodegem

sackattack84 wrote:
> First off thanks to everyone who replied to my last post. This is the same
> engine as in my previous post (400 big block chrysler, not sure what
> year). It has a non-stock cam (I don't know the specs, it was installed by
> a previous owner and the guy I bought it from didn't know either), a
> non-stock electronic ignition (once again previous owner)with no vaccuum
> advance, and a non stock Holley 650 four barrel carb. The problem is that
> it seems like there is more vibration than there should be at idle in gear
> or in park, but it doesn't seem to be misfiring and the cylinder
> compression is normal. When I hit the throttle hard enough for the
> secondaries to open, it backfires and belches fire out of the carb, then
> proceeds to have no guts whatsoever. I ran some lucas fuel system cleaner
> through it and changed the oil and spark plugs, bought a Holley Trickit
> for the carb and rebuilt it because the secondary float needle was
> sticking and the secondaries are now operating normally and are getting
> fuel. I checked the compression in all cylinders and it was normal. The
> distributor cap and rotor are in good shape and I just set the air gap. I
> checked the timing and it was set at more than 30 degrees (!) before top
> dead center, so I advanced it to 7 1/2 degrees before top dead center, and
> it behaved the same only ran worse, like that was too much advance. It has
> fresh fuel in it also. Starting to run out of ideas. If anyone could steer
> me in the right direction, I would be grateful!
>

It is a vacuum secondary carburetor. The vacuum mechanism for the
secondaries seems to work just fine, though, and I can see the butterflies
open when I yank the throttle wide open(can't get too close, though, or I
might not have hair or eyebrows anymore!). What about the lack of a vacuum
advance on the distributor? Could the electronic ignition module possibly
play a part in causing the problem? Thanks for the advice!

Found the problem(s). The secondaries were not getting fuel; fixed that and
the problem persisted. Adjusted the timing back to 38 degrees before top
dead center, which smoothed the idle out enough for me to notice a misfire
in the engine. Upon investigation, I discovered that two of the plug wires
were switched. Switched them back and now it runs like a champ, although
now I'm going to have to readjust the carb and timing since it's firing on
all eight. Thanks for the advice!

Good and your welcome! which spark plug wires were switched 5 7 ?

sackattack84 wrote:
> Found the problem(s). The secondaries were not getting fuel; fixed that and
> the problem persisted. Adjusted the timing back to 38 degrees before top
> dead center, which smoothed the idle out enough for me to notice a misfire
> in the engine. Upon investigation, I discovered that two of the plug wires
> were switched. Switched them back and now it runs like a champ, although
> now I'm going to have to readjust the carb and timing since it's firing on
> all eight. Thanks for the advice!
>

Yeah, I think so. The rear two plugs on the driver's side cylinder bank

That's them 5 7! Real easy to mix up and they fire one after another
18436-57-2
Dodgem

sackattack84 wrote:
> Yeah, I think so. The rear two plugs on the driver's side cylinder bank
>