[Chevrolet 38]

I don't know if I flooded or even if it's possible to flood it while driving and engine up to temp, could someone help me to understand? Or might there be a hidden issue somewhere?

So, I have SBC 327, on Holley 1850-2 which is std 600CFM on single plane intake, mild cam, double hump iron heads, I suspect compression is fairly high as it likes (98 Octane / 93 RON - for the US) petrol. I have MSD 6AL on Mallory unlite (I suspect on points) on 4sp saganaw

It drives fine for 15 minutes, motor is starting to warm, defn not overheating, outside temp is nice 25C = 77F - perfect condition for a drive outside

I have being revving it to 4k ~ 5k fine, really fun, no problems. Driving up and down slight hills around my area. Very good.

When it came to a bit of a straight I thought I can test how it feels by going to 5.5k

I put my foot down to open throttle
The engine bogged, no bangs or hiss
Where I expected power it didn't come
So, natural instinct is I feathered the gas (which I think pumps in more petrol)
Then engine shut off

I thought to myself, kinda feels like I have flooded the engine .. but while driving for 15mins ???
Cranked, didn't fire up
I rested for 10 minutes while checking, no leaks, no overheating

I thought, might treat this as a flood as I was going to call a tow truck anyway

Couple of attempts, gas to the floor
She came back to life normal, and I drove it home.

Has anyone experienced this and or can share any insight?

I do feel my spark plugs do look like I am running rich, using NGK BP5S and in the process of getting new plugs.

Thanks very much for the forum's help, I have learnt a lot and so much more to learn.

 

[Chevrolet 38]

I think I have a theory ....
The only thing I changed on the car was I wanted to see the MSD 6AL rev limiter working

I have read this MSD 6AL rev limiter is not very accurate and the way it works is it will cut the spark first time it reach the limit and fire the 2nd time .. etc designed not to flood the engine.

So .. it was set at 5.5K .. and I never ever have rev this high
So .. I changed it to 4.5k, wanting to see the effect

could I have rev it to somewhere near 4k .. entirely possible .., and the rev limiter kicked in and flooded the engine ???

.... because after I cleared the flood, I drove home without any issues.

 

[RWENUTS]

It’s not the Msd.
likely just float level too high.
pull the sight plug off the bowl.
if set right the fuel should just trickle out of the hole when you lean on the fender.

 

[lmsport]

I would take the fuel bowels off and check for any debris in there that might have held the needle valve open when you stomped on the throttle. Holleys do this.

 

[2old2fast]

If the carb backfired & this is an older carb without power valve protection , you may have blown the PV diaphragm , leading to an overly rich carb . debris in the fuel is not a holley specific problem . Is this something that has been running for a while , or a new setup ?

 

[gregaba]

You might check your chock and make sure it isn't closing when you floor it.
Greg

 

[Watercooled]

I don't know if I flooded or even if it's possible to flood it while driving and engine up to temp, could someone help me to understand? Or might there be a hidden issue somewhere?

So, I have SBC 327, on Holley 1850-2 which is std 600CFM on single plane intake, mild cam, double hump iron heads, I suspect compression is fairly high as it likes (98 Octane / 93 RON - for the US) petrol. I have MSD 6AL on Mallory unlite (I suspect on points) on 4sp saganaw

It drives fine for 15 minutes, motor is starting to warm, defn not overheating, outside temp is nice 25C = 77F - perfect condition for a drive outside

I have being revving it to 4k ~ 5k fine, really fun, no problems. Driving up and down slight hills around my area. Very good.

When it came to a bit of a straight I thought I can test how it feels by going to 5.5k

I put my foot down to open throttle
The engine bogged, no bangs or hiss
Where I expected power it didn't come
So, natural instinct is I feathered the gas (which I think pumps in more petrol)
Then engine shut off

I thought to myself, kinda feels like I have flooded the engine .. but while driving for 15mins ???
Cranked, didn't fire up
I rested for 10 minutes while checking, no leaks, no overheating

I thought, might treat this as a flood as I was going to call a tow truck anyway

Couple of attempts, gas to the floor
She came back to life normal, and I drove it home.

Has anyone experienced this and or can share any insight?

I do feel my spark plugs do look like I am running rich, using NGK BP5S and in the process of getting new plugs.

Thanks very much for the forum's help, I have learnt a lot and so much more to learn.

I had the same problem in my 34 coupe. SBC with 1850 carb, edelbrock turquer, headers. It would run fine and then stop as if you turned off the key. Let sit and fire back up.
It turned out to be the carb. Took it apart and cleaned it out, and replaced the cheap fuel filter with a filter for an 86 mustang 2 that came with FI. No more problems.
Hope the info helps
WC

 

[BogiesAnnex1]

I expect that your actions flooded the engine but that the Root Cause is the Unilite. These use an optical trigger to a switching module. They have a long history of temperature related issues. This being at normal engine operating temps they quit till things cool off a few degrees then work again. This intermittent failure related to temp comes and goes till eventually it comes and stays. This has been a long time known failure, it doesn’t affect all Unilite’s but it is fairly common.

The optical sensor is also given to a sensitivity to dirt, moisture and oil contamination. Working is a typical automotive dirty, damp and oily environment it is more problematic that magnetic sensing whether Hall or induction.

The Unilite is not designed for 12 volt operation, it must have either the factory resistive wire or an external resistor typical of points type ignition systems for about 9 volts operating.

It also needs resistive or spiral wound high voltage wires not solid metallic core plug wires.

Bogie

 

[95 Truck]

We used to have this problem all the time with older used holleys. You stand on them, open everything up, floats would drop and stick, when we got off the gas car would flood out and stall.

We keep a screw driver in car, we would tap on float bowls to unstick the floats. then stick screw driver in the card to hold the butterflies open. Turn the key and let is clear the fuel, car would start, pull screw driver out, let it idle put air cleaner back on and drive home.

This was when we did not have money to get a rebuild kit or a new carb, everything was hand me downs.

 

[Chevrolet 38]

I expect that your actions flooded the engine but that the Root Cause is the Unilite. These use an optical trigger to a switching module. They have a long history of temperature related issues. This being at normal engine operating temps they quit till things cool off a few degrees then work again. This intermittent failure related to temp comes and goes till eventually it comes and stays. This has been a long time known failure, it doesn’t affect all Unilite’s but it is fairly common.

The optical sensor is also given to a sensitivity to dirt, moisture and oil contamination. Working is a typical automotive dirty, damp and oily environment it is more problematic that magnetic sensing whether Hall or induction.

The Unilite is not designed for 12 volt operation, it must have either the factory resistive wire or an external resistor typical of points type ignition systems for about 9 volts operating.

It also needs resistive or spiral wound high voltage wires not solid metallic core plug wires.

Bogie

Thanks Bogie, what are your thoughts on a good dizzy to go with MSD 6AL ??? I can't work out if I should change from points or go pertronix for my next dizzy, it but if this unilite is gonna haunt me, I will just replace the unilte 9000.

 

[Chevrolet 38]

We used to have this problem all the time with older used holleys. You stand on them, open everything up, floats would drop and stick, when we got off the gas car would flood out and stall.

We keep a screw driver in car, we would tap on float bowls to unstick the floats. then stick screw driver in the card to hold the butterflies open. Turn the key and let is clear the fuel, car would start, pull screw driver out, let it idle put air cleaner back on and drive home.

This was when we did not have money to get a rebuild kit or a new carb, everything was hand me downs.

Does that mean the float level was too low ???

 

[Chevrolet 38]

You might check your chock and make sure it isn't closing when you floor it.
Greg

No choke in this

 

[Chevrolet 38]

It’s not the Msd.
likely just float level too high.
pull the sight plug off the bowl.
if set right the fuel should just trickle out of the hole when you lean on the fender.

Thanks a lot ... I checked the sight plugs and I don't think I am that far off it .. I do think the carb is running rich so I will lower the float level a bit to try, thanks

 

[Chevrolet 38]

I expect that your actions flooded the engine but that the Root Cause is the Unilite. These use an optical trigger to a switching module. They have a long history of temperature related issues. This being at normal engine operating temps they quit till things cool off a few degrees then work again. This intermittent failure related to temp comes and goes till eventually it comes and stays. This has been a long time known failure, it doesn’t affect all Unilite’s but it is fairly common.

The optical sensor is also given to a sensitivity to dirt, moisture and oil contamination. Working is a typical automotive dirty, damp and oily environment it is more problematic that magnetic sensing whether Hall or induction.

The Unilite is not designed for 12 volt operation, it must have either the factory resistive wire or an external resistor typical of points type ignition systems for about 9 volts operating.

It also needs resistive or spiral wound high voltage wires not solid metallic core plug wires.

Bogie

Ooooops, I really got myself confused, I don't have a unilite .. i actually have a Mallory Comp 9000 ... pretty sure it's on points on how it's connected to the MSD 6AL .... is that a good dizzy to keep ?????

 

[BogiesAnnex1]

The Comp 9000 is all electronic. As with other Unilite distributors it uses an optical sensor instead of Hall or magnetic sensor, there are no points.

The shutter wheel interrupts a light beam triggering a voltage break. This is sent to a module with an amp to boost the signal and a switching FET transistor that then shuts off the voltage to the coil, this switch is on the coil’s ground side. This causes the collapsing primary side electro magnet to cause the secondary side electro magnet to generate a high voltage.

Your case is a little more complicated with the MSD box as the Unilite is switching the MSD box which basically is a bunch of high power capacitors which then discharge into the coil. This hits the coil with say about 50 volts instead of the typical 9 to 12. This makes a very high voltage discharge at very low amps in a very short time period compared to not using the MSD box. The problem this creates is at low RPM and thready, thin mixtures it frequently miss fires. The answer to this is another circuit that in milli-seconds hits the coil with several strikes causing the plug to fire several times as in 2 to 4 times so it rather simulates the long duration spark of a conventional induction ignition whether triggered by points or transistor switching on 9 or 12 volts. The multiple sparks go away as RPM gets around 2 to 3 thousand as time to recharge the capacitors gets to short to rebuild and collapse the coil‘s magnetic field.

These systems are easy to flood so messing with the throttle can easily put enough fuel into the cylinders to short the plugs. The same can be said for too much choke or some defective event in carb or fuel pump.
But keep in mind the old saying that most carburetor problems are electrical. Given carburetors don’t typically use electricity that brings you to the ignition system.

In your case you have a pretty complicated ignition system where there are a lot of opportunities for component and process failures.

The whole point of capacitive discharge versus simple inductive ignition is really event time. In the case of old fashion induction especially where one coil is supporting 8 cylinders or more is that as engine RPM increases the coil runs out of magnet saturation time so as engine speed increases the spark gets weaker While the forces of pressure and temperature the spark has to force its way through get stronger. Capacitive discharge is nothing more than hitting the coil with a higher voltage to force a stronger spark as time shrinks at high RPM which lowers magnetic saturation time. Not a lot unlike like wearing gloves because your pen leaks ink.

Obvoisly the modern ignition system using a coil per plug switched electronically thus eliminating the distributor allows more time to build magnetic saturation as each coil has the time it takes for the crankshaft to rotate 720 degrees since it’s last discharge instead of having to pull the rabbit out of the hat trick every 90 degrees of crank rotation as a distributor with one coil is demanded to perform.

Still check out your fuel system to be sure its clean and properly tuned but don’t forget the old adage I earlier included.

Bogie

 

[2old2fast]

I expect that your actions flooded the engine but that the Root Cause is the Unilite. These use an optical trigger to a switching module. They have a long history of temperature related issues. This being at normal engine operating temps they quit till things cool off a few degrees then work again. This intermittent failure related to temp comes and goes till eventually it comes and stays. This has been a long time known failure, it doesn’t affect all Unilite’s but it is fairly common.

The optical sensor is also given to a sensitivity to dirt, moisture and oil contamination. Working is a typical automotive dirty, damp and oily environment it is more problematic that magnetic sensing whether Hall or induction.

The Unilite is not designed for 12 volt operation, it must have either the factory resistive wire or an external resistor typical of points type ignition systems for about 9 volts operating.

It also needs resistive or spiral wound high voltage wires not solid metallic core plug wires.

Bogie

The unilite will operate fine on 12V . The unilite can be run off a ballast resistor , " Dirty electrical systems , jumping / charging the battery & welding on the vehicle without unplugging the module may kill the module . My unilite went in service in 1984 , it has been in 5 engines ,I would guess 250k miles , my unilite has the original module in it ! Unilite got a bad wrap from people who wouldn't read directions &/ or had/ have inadequate , poorly done wiring . replacement modules are far less than a new unit . Like a GM HEI module I carry a spare in the car . And please tell me who , in 2023 uses solid core plug wires ???

 

[95 Truck]

Does that mean the float level was too low ???

No float was not to low, these were just old used carbs that needed to be rebuilt.

 

[55_327]

I put my foot down to open throttle
The engine bogged, no bangs or hiss
Where I expected power it didn't come

You said the engine bogged. That typically means not enough fuel, not flooding. Many years ago I had a daily driver beater 65 Olds that would run OK for awhile, but then start bogging when I rolled on the throttle, even slightly. If I let it sit and idle for a couple minutes it would run fine again for another few miles. Turned out to be a partially clogged fuel filter that was limiting how fast the float bowl could fill.

 

[Chevrolet 38]

Thanks everyone for their help, it has given me lots of reading and learning to do. I will change my fuel filter and lower the bowl level a little bit and pull the cap off the distro .... as I thought the comp 9000 was on points ......

 

[BogiesAnnex1]

View attachment 628551
Thanks everyone for their help, it has given me lots of reading and learning to do. I will change my fuel filter and lower the bowl level a little bit and pull the cap off the distro .... as I thought the comp 9000 was on points ......

Your right, I was thinking what would be 9148202 which is electronic.

I‘m not so sure that a 6AL box needs dual points. I haven’t tried that but when considering the dual point is intended to add dwell time to the coil and the 6AL is not sensitive to dwell it’s only looking for a on off switch. So I don’t know what the 6AL thinks of this?

Bogie