NLPerformance

iTrader: (2)

'85 12a with a weber 48, dual MSD 6AL and coils, new plugs

The car will idle strong and smooth after coming to a stop(around 800 rpms) stays there for a bit and then gradually gets lumpier and lumpier. Eventually it will get low enough that it dies. If I give it gas to hold it at 900 or 1000rpms, its fine and is smooth.

I stood behind the car and let it die, as it got worse, there was more and more white smoke coming out of the exhaust, however not nearly as much as a startup from overnight. Very small, very hazy puffs(hazy as in quite see-through). Smells a lot like oil.

Overactive OMP, weak msd/electrical?

FührerTüner

iTrader: (5)

Sounds like blown coolant seals...

t_g_farrell

iTrader: (1)

Blown coolant seals, really? Sounds like a fuel delivery issue or a vacuum leak. Rule out the fuel
issue by verifying that it can pump the gas to the carb sufficiently and that its at the right PSI for
a weber. Webers like 3-4 PSI, whereas Nikkis and Dellortos like about 2.5 PSI and Holleys like
around 6.

Next make sure you have no vacuum leaks, I bet you do.

NLPerformance

iTrader: (2)

I really do think it is a vacuum leak, coming from the carb gaskets, there's a lot of fuel around there and I'm not quite sure it was sealed properly when it was last taken off. PSI is around 3.5.

TimWilbers

iTrader: (1)

Symptoms sound similar to when my #2 Anti-Afterburn valve diaphragm dissolved and it was indeed a vacuum leak.

NLPerformance

iTrader: (2)

Your what what what hahaha.
I should also mention the car has no rats nest. But it does backfire quite a bit.....I'll have to find this diaphragm.

TimWilbers

iTrader: (1)

My bad. Wrong name, I replaced the coasting valve, aka Shutter Valve. (image)
But if your rats nest is gone, this valve may be gone with it.

NLPerformance

iTrader: (2)

Hmmm. I don't have one of those intake side, but I do have two near the distributor. But I don't think theyre hooked up to anything. Would the weber have something like this?

t_g_farrell

iTrader: (1)

You don't have a Nikki so what Tim Wilburs is mentioning doesn't really apply. I assume you have
a side draft DCOE 48 carburator on either a wrap around intake manifold like a lake cities or a
straight off the side over the headers manifold like the one from Atkins. Either way you have no
shutter or coasting valve.

The vacuum actuators on the dizzy are for leading and trailing vacuum advance which is normally
not hooked up when running nonstock carbs. You can hook them up to manifold vacuum but
then you will be advanced at idle. I used to have it hooked up for my Dell because other than
a lump idle it gave it much better performance in the low range.

I still think its a vacuum leak.

FührerTüner

iTrader: (5)

He said its blowin out white smoke. I dunno?

I also just realized this is the first gen section...

NLPerformance

iTrader: (2)

The white smoke is more of a mist of gasoline/oil. I resealed the connection between the carb and the intake manifold, down draft 48IDA. The problem is slightly better. And when I say slightly, I mean adding a second or two to the time that it takes to get lumpy. It takes about 12 seconds now for it to get lumpy and will die within 30/40. Should I mess with the idle mixture/speed?

t_g_farrell

iTrader: (1)

So did it ever run right or did you just get the car this way and trying to sort it out?

NLPerformance

iTrader: (2)

The car ran right when I got it. Then this and that happened. Could it be me changing the plugs to the BR8EQ? And something about not enough power at low rpms? I should also ask if it could be a bearing on the alt or oil pump or etc that is having a parasitic effect? I'm hearing a slight squeal above 5k rpms, only occasionally and only in second.

t_g_farrell

iTrader: (1)

More details on "this and that happened" please. The plugs shouldn't be too big an
issue but I'm not sure about what the difference with those would be. I run RX8
plugs and have great success with them so far.

The squealing is the belt probably. Do you have a dual sheave alternator pulley or
the stock single? Does your belt only drive the water pump and and alternator? That
setup usually needs dual belts to keep the squealing at bay.

NLPerformance

iTrader: (2)

Well, when I first got the car, one of the wires for the MSD burned through on the second time starting it(first was to move it from the side to the back driveway). Replaced the wire. Started driving the car and about a week later, the plugs fouled. Then two weeks after that the oil line burst in my driveway after starting. I shut the engine off within a tenth of a second and still had halfway on the dipstick after that happened.

I do have dual sheave on the crank and on the water pump, but not on the alt. And yes, those are the only two things being driven by it.

However, I have noticed that the OMP lever control on the carb isn't always square with the body. Could it be that? I.e. it is letting too much oil in at idle, I can line it up and it stays, but only if I don't go more than half throttle. I think I need to get a new nut.

Thanks for all your help so far.

diabolical1

iTrader: (3)

if the belt is loose enough for you to start losing power at idle, then yes, it could be problem or at least a part of it. if you're basically starting to lose fire, the chambers will start loading up with fuel until it dies. is it hard (or at least harder) to start after it dies?

1. check the fuel pressure.
2. check the timing.

you should also check the plugs the next time it does it. let it die and the pull the plugs and check if they are wet. what you described in your original post sounds like when i was trying to set the fuel pressure on my Dell'Orto.

NLPerformance

iTrader: (2)

I can pull the belt over without moving stuff. But it runs fine normally. Where's the tensioner on a 12a?
Ill check the plugs next time I happens. No, it's not harder to start at all.

t_g_farrell

iTrader: (1)

The alternator is the tensioner. Tensioners didn't come about until serpentine belts came into
use after the 80s.

NLPerformance

iTrader: (2)

Checked the belt again, it's snug and I can't slide it. I was remembering me turning the alt for when I had a bad ground.