Petro Points

Hello everybody. New member, new boat guy. I bought myself a fixeruper last year and have been and finally put it in the water this past weekend. The boat is an 89 Pachanga 32 with twin 454s. I have named it Petro Points. The port engine is having some issues that I have (maybe) narrowed down to an ignition issue. I have been combing though all the posts on problems with the Thunderbolt IV system and have found a lot of clues but nothing that addresses all the issues specifically. Hopefully someone can shed some additional light on the issues I am having.

Here is the story line.

- took the boat out for its first rip
- starboard enging ran like a champ
- port engine backfires through carb and runs horrible
- pulled the plug wires while running and found that #5 was dead
- plug fell apart when I removed it
- replaced the plug and took the boat out again
- huge improvement until 3000 rpm were the engine just kind of said no and bogged out
- checked that all cyliders were firing and they were this time
- thought I might have damaged the carb (quadrajet) with the backfires and might not be getting fuel to the secondaries
- was set to swap the carb out but thought I would check the timing as the idle was irreguar.....and here is where my questions about the Thunderbolt IV begin.

The engine timing sits at 8 deg a few seconds after coming down to an idle but then bounces between 8 and 6 for a second or two and then goes down to 0 deg. The timing does advance significantly when the rpms are increased so the ignition module is definitely doing something. I have heard that these modules (mine's a V822) either work or they don't work but I don't know if thats true. Asumming it is, am I wrong in thinking that the only way the timing could go down to 0 deg would the base timing actually being set to 0 deg instead of 8? Maybe the previous owner had it idling to high when setting it? Is it possible that the ignition sensor is missing someing at idle? Would that cause the timing to go down to 0 deg?

I guess my over all question is...... is there anything in the Thunderbold IV system that would cause a properly set timing to drop down to 0 deg?

Thanks in advance for your help. Been learning tons already from the other threats on this subject.

Chris

Ryanw10

Have you checked fuel pressure while running?

Petro Points

Fuel supply is on my list of things to check/address and would definitely answer to the not running over 3000 rpm issue. Will be checking that as well before I take it out again. Any thoughts on what would cause the timing at idle to go from 8 deg down to 0 deg?

Ryanw10

I would focus more on the fuel pressure first. For ignition I would start with the basics, all new plugs, wires, cap, rotor.

Brad Christy

Petro,

Inspect the check valve at the origin of the fuel supply lines on top of the tank. These can get full of crud and corrosion and choke out the supply. It will run fine up to a certain RPM, then will sag. Wouldn't hurt to replace them both anyhow (assuming there are two).

Thanks. Brad.

Wally

I usually set the timing at 3400rpm. since you have a V822 then its giving 22 deg of total advance. So the 8 deg of base timing and the 22 from the module give you a total of 30* at 3400rpm. If you have a timing gun with a dial its much easier...set the dial to 30* and rev the motor till the timing mark is at 0 on the balancer and your set. Should be good to go.

SB

V8 -22 advance curve:

Petro Points

Thanks for the suggestions so far. Will definitely investigate and address any potential fuel issues.

The reason I am digging into the ignition side of things first is that I know for sure that something is off. Either the base timing wasn't set right (easy fix) or something wonky is going on that is knocking the base 8 deg at idle down to 0 deg.

I will try setting the timing to 30 deg at 3500 rpm as Wally suggested, hopefully without loosing a finger. If the timing turns out to be where it should be at 3500 rpm then I guess I'm looking at a faulty something or other. Ignition sensor maybe?