Alright I don't know how many of yous know about carbs... but here's the situation.

Lately my car has been running funny. Like just the past week or so. It all started when I had trouble firing it up the other day. It didn't want to stay running (seemed like it was on 1 rotor), so I gave it a little gas, revved it probably higher than I should've cold (6500 or so). It cleared up and ran "normal" after that. It's happened before, and a quick rev usually cleared it right up, but this time was worse than usual.

But the other day, getting on the freeway, I gave her hell... but she started cutting out ~4500 or so, and snapped, crackled and popped all the way to redline (it also has acted the same every day since). It seems like the car is hesitating now too on regular acceleration, and seems slightly down on power.

The car has always ran a little on the rich side as far as I could tell. I probably need to get rid of the old disty and swap in a DFLDIS, which I plan on doing soon. I'm sure I could use new plugs too (any recommendations? where I can find them?).

Oddly as well, my car seems to be having no problems starting. Ever since that day, I haven't had a single time where the car didn't want to fire right up. It also has quit backfiring after I shut it off hot. I'd usually get a "pop" after I shut it off, but this also has gone away since.

Am I imagining things, or is my 12a on it's last legs?

EDIT: Forgot to mention: 12a stock port, Holley 600cfm on RB Holley manifold. No rats nest. Later style ignition. RB header + custom exhaust.

 

do you have a fpr?

 

Change your fuel filter

 

And your spark plugs...

 

im my experience, mr project, most 'carburator' problems end up being something else. for the most part the carb is just a piece of metal with holes in it....

first two things to look at for 'carb' problems, are vacuum leaks, and ignition problems.

also since these cars are old, fuel filter is also good to replace (they are like $2 even from the dealer!).

if that doesnt fix anything, might be time to test the fuel pump. ive been testing mine, and sometimes it doesnt work right....

 

look at the coils and make sure all the wires are tight. also make sure your ingnitors (SP)..are plunged in tight

 

well i would start by popping off the air cleaner, after look down the primary's while u give it some gas and see if your accelerator pump streams are half decent.. they shoot out the two nossles on top of the air horn... next start it, and check if when u give it gas, the primary venturis have good even streams of gas coming out through the rpm's... if that seems all good but still acts up. change the fuel filter and if you can pop off the air horn to check for debris in the bowls you can get an idea of how things are in the carb. things to consider. have you changed anything or worked on anything lately?

 

I used to get the same backfire while shutting the engine off hot too. I retarded the timing a couple of degrees and it seemed to help. I would check your fuel pressure. Holleys require quite a bit of fuel pressure. You need to have a good strong Holley pump with a Holley regulator and gauge set at 6 PSI. You could have a clog in you secondaries. Remove them and clean them out. Check your spark plugs. They will foul out over time, especially when using such a huge carburetor.

BTW... A Holley 600 is extreme overkill on a stock port. The motor can only flow 313 CFM at capacity. It may increase bottom end I guess, but it probably kills velocity at mid to high end. I'm running a Sterling 465 and it makes PLENTY of power. It still flows more than what the engine needs.

You may need to sell the 600 and pick up a 465 unless you plan on giving it a big port. Just a thought.

 

You have that backwards. Smaller carb means higher velocity all around. Higher velocity at low end is where big carb are lacking.
A carb should only meet your engine intake requirements. Exceeding those requirements simply lessens the performance in the low end.

 

I was going to check the secondaries out, that was one of the things I had thought as well.

I'll also check the fuel filter for sure, this car sat for a while, so who knows what kind of goop is in that thing.

It's just odd that this has only recently started happening. I used to be able to take it to 7500 with not so much as a hiccup from the engine.

As for the huge carb, I do plan on building a large-port 13b sometime in the near future, as soon as my budget allows. I figured I was going to need the bigger carb sooner, but the slowdown at work has prevented me from building my larger motor. I've gotten pretty good with the throttle however, so I can drive it as is without any hiccups (until recently). When I bought the car, the Nikki was junk, and I wasn't about to blow money on parts I didn't plan on using very long.

What spark plugs do you guys reccomend, and where can I purchase them? Whenever I go to anywhere local, all they have is Autolite garbage.

Another thing I'll be checking is my ignition timing. I suppose somehow my disty may have loosened up and retarded the timing. We never really set the timing right, since my main pulley is rusty, and we cannot find the timing marks. But again, I haven't had any problems until just now. A local rotary guy "set" my timing, and disconnected my vacuum advance.

So I'll be doing a little searching, looking for answers to my two main questions-
What spark plugs should I get, and where can I find them?
Where should I set my ignition timing?

 

Just get the factory 8 heat NGKs. Autozone or even ebay has them. If you go 2gdfis (2nd gen leading coil) I would use BUR7EQP leading and 8 heat stock NGKs for trailing. You can line up your pulley by looking through the flywheel inspection plate to the rear of the exhaust manifold. Search on what to line up (a couple notches on the flywheel must line up to the engine somewhere). I have perfect pulley marks so I've never had to do this. If your engine runs halfway decent at all it should not be off that much. It only takes a gear tooth or two to make the engine run so bad it won't even start.

For factory timing you want to set your timing at 0 degrees TDC for leading and 20 degrees TDC for trailing. It's on a sticker under your hood. You can adjust the timing by tweaking with the rotation of the dizzy on the 10mm nut for leading/trailing combined. Left is retarding, right is advancing. Trailing can be independently tweaked by loosening the phillips screw on the vacuum unit closest to the driver side. Sliding it towards the front retards it. Sliding it to the rear advances.

You can connect your vacuum advance if if you run it from a vacuum source thats used only between certain RPM. I'm not sure the actual RPM number as I have mine hooked up properly on a Nikki. Nor am I familiar with the vacuum routing on Holleys, but I thought Racing Beat had this solved on their manifold?

 

Well I had 2/3 of the equation correct

 

Well I've got is all but figured out.

It has to be a "fuel system not able to keep up with demand" issue, and here's how I came to that conclusion. Today, getting on the freeway, I took it up to 6500 or so, at part throttle, and didn't have any sort of breaking up at all. If it was ignition problems, it would've had problems at high rpm regardless of throttle position.

So now comes my soloution- change and upgrade everything. Time to change the fuel filter, and upgrade to a better fuel pump and FPR. I'll be sure to check out all things with the carb as well, but I'm thinking it's more of an issue that the fuel filter is probably clogged up (especially since the car sat for a long time, and lately I've been driving it a LOT more frequently), and the pump was probably struggling to keep up with my monster carb anyway, so now it just can't keep up.

I'll still be doing the DFLDIS with the GM ignitors (not the 2gdfis) since I already have a pair of MSD Blaser 2's that I got solely for that purpose. I'll also be sure to change the spark plugs.

 

i agree with your conclusion, but the ignition working/misfiring is load dependent too.

with the stock distributor ignition, i like the stock GSL-SE spark plugs, same as the 12a, but they are colder.

with MSD's and things, then basically any plug is fine

 

ALRIGHT update...

I have new evidence that this is in fact some sort of an electrical / ignition issue and NOT a fuel issue.

The other day, driving my girlfriend home with the headlights on, it started acting even worse. Every time I'd be at idle, the car would start sputtering and seemed to be running on 1 rotor, and then I'd have to rev it up to "clean it out" and then it would run a little better. It spat and sputtered all through the RPM range, but seemed to be not as bad at midrange RPM (3-4k). I didn't bother revving it out very high, but I took it to about 5k, and it didn't have a problem.

I do not believe this is caused by the alternator, as my voltage gauge was reading ~12.5v the whole time (13-14v right after startup). I don't have an amperage gauge, however I wasn't running anything unusual, just the lights (which I kinda unusual for me, I don't drive at night very often, especially since my car is loud and I am not an *******). However, my ignition system does not have a relay in it, and my power is drawn direct from the ignition switch (original harness was kinda messed up, so I made it work). The small electrical draw from the lighting relay may have been just enough to cause issues.

I do believe I am getting a weak spark signal somewhere in the system. I checked my plug wires and they are all secure. The tach seemed to be working fine, so I doubt it is the magnetic pickups or the ignitors.

It's either my coils or my cap or rotor, or perhaps even my ignition timing is somehow way off all the sudden. When I do my DFLDIS upgrade this week (with MSD Blaster 2's, correct NGK plugs and GM ignitors), I'll be sure to check my mechanical advance and see if perhaps one of the weights is stuck.

Either way, the ruling has been appealed and this is definitely some sort of an electrical issue.

 

i'd check the charging system since its quick and easy, i'd check the voltage with the engine idling at the battery, and the coils. battery should be 13.5 or better, coils ideally would be also, but since there is some wire and a switch, there is a little drop.

 

Ignition breakup in the higher rpm range can be an indication of a cracked spark plug boot or coil tower bleeding off spark. Very easy to see in the dark and can often be heard if the exhaust isn't too loud.

 

Thanks guys.

I doubt it's a cracked boot on the plug wires, they're only a couple months old. I will be changing the coils with my DFLDIS so if that's the problem it'll be solved.

It has definitely gotten worse. Today I swapped the 7 for my Escort at my friend's storage lot (need a reliable ride to work!). I could barely keep it running at idle and it sputtered above 4000... it only ran good between like 2000-3500 RPM. Every time I stopped, it would go back into "run like **** mode"... and it seemed like it wasn't even running on 1 full rotor... it sounded like a Harley. But then when I'd get moving, it cleared up again, but still sputtered a little here and there.

Wednesday I'll do my DFLDIS and you guys will surely get another update.

 

I installed my DFLDIS today. It didn't fix the problem! So I checked compression. Well, I pulled the plugs out one at a time and cranked it over. That's not the problem.

I checked fuel again. Yep. Got fuel.

So I did something a little different... I installed my DFLDIS on the TRAILING side of the disty... and viola! It started running. It's not idling well, but any time I give it some gas, it runs good. So... I guess it's time for some new magnetic pickups on the leading side.

Is it possible to swap the disty pickups from the trailing to the leading? I really can't drop $140 on some new magnetic pickups right now.

 

You must have a bad igniter.

 

A bad ignitor would have zero effect on what I stated. I am not using the stock ignitors, nor the factory coils. The only factory part of my ignition system is the distributor itself. It is 100% the magnetic pickups in the distributor.

I have a DFLDIS setup. 2 GM ignitors, 2 MSD coils, leading ignition only. I hooked the DFLDIS up to the factory leading magnetic pickups (purple and green wires in the disty) and it would not run right- still ran like garbage, constant random misfires.

But when I hooked the DFLDIS up to the trailing magnetic pickups, it ran "ok". It still idled rough (probably because of the timing), but was good above idle. I adjusted the timing all the way to advance and it ran a little better, and is now "drivable" but not as good as it should be.

New magnetic pickups are the answer.

 

How do you know the GM igniter isn't going out? Just because it's not very old doesn't make it invincible. There's a reason they're so cheap in comparison to other igniters. Try running it back off of the leading side and unplug the leading igniter to see if it affects the way it runs. If it runs the same with the leading igniter unplugged then you need a new igniter. Even reverse the leading and trailing igniters.

On a stock or even 2gdfis you can run off of one igniter if it's in the leading side. It will idle poorly and rev up a little sluggish.

 

I am ONLY running leading ignition. BOTH GM ignitors are hooked to one magnetic pickup (now the trailing), and I am using wasted spark.

There is NO WAY it is an ignitor- if that was the case, one of my rotors would get no spark. I am running direct fire- 1 ignitor and 1 coil per rotor.

There is no "leading" or "trailing" ignitor in my setup. I am running 2 ignitors, yes, but BOTH are for the leading plugs, one for each.

Can anyone else explain this better than I can?

 

Question: What is the gap for the magnetic pickups supposed to be?

 

i think the pickups are the same L and T.

i'd have to look in the book to see what the gap should be, but its not a big number maybe .020-.040"?