Tune-up question

-
dartnlo

dartnlo

Has Dart Fever
FABO Gold Member
Joined
Sep 5, 2018
Messages
541
Reaction score
502
Location
Lawrence, Kansas
Stats:
318 108k
2 barrel chinese carter bbd clone
Pertronix Ignitor II with coil, I haven't bypassed the resistor yet.
New Plugs
New vacuum advance
Stock single 1.75" exhaust
16.8 MPG on the last 100 mile highway trip driving between 60-70.

My tachometer turns out to be a piece of HF crap and I just tried to set the speed and idle mixture by ear. Set timing with vacuum advance plugged off. The car's spec tag said timing TDC with no number so I set it at idle at 0. I have been chasing a severe miss/cough and die on hard acceleration. It hasn't really improved. It feels flooded a lot of the time, accelerating in neutral seems to clear it out and make it idle better.

I originally decided that the vac advance was the problem, and it was definitely not working, the diaphragm leaked badly and the advance plate was sticky. I fixed that and verified that the advance was working.

I've read through several posts to get an idea of what I'm doing but I ended up being unsure of what I'm doing wrong.

I'm thinking it might be the crappy chinese knock-off carb. it only has 2 vacuum inputs. A pvc on the throttle plate and the other one on the carb body passenger side. That is hooked up to the vac advance.

I know I still need to do a compression test, I failed to do so while changing the spark plugs.

It does the miss/die under load for take off, but it also does it in park. I don't have an air fuel mixture tester but the tailpipe doesn't burn my eyes as much as it used to.

I have a carb kit for the old carter but I snapped one of the idle mixture screws off while getting it ready for the ultrasonic cleaner. I think the throttle plate off of the chinese carb will fit it, I just need to try it.

If you are still reading this, and reading it on Christmas day, Merry Christmas and thanks for any helpful advice you have to offer!
 
Last edited:
I should add that it cruises down the highway at 70 just fine and has good acceleration and power once it is going, it's just the initial take-off acceleration that bogs down and kills it.
 
My 318 2bbl in my dodge truck did something very similar to that it wound up being a bad carb. I striped it and cleaned it and it ran like a champ again. I believe mine was due to setting because there was alot of gooey varnish looking crap in the carb when I took it apart. I still have that same carb. I ended up replacing it with a new one a few years later.
 
dartfreak75 said:
My 318 2bbl in my dodge truck did something very similar to that it wound up being a bad carb. I striped it and cleaned it and it ran like a champ again. I believe mine was due to setting because there was alot of gooey varnish looking crap in the carb when I took it apart. I still have that same carb. I ended up replacing it with a new one a few years later.
Click to expand...

I'm leaning toward the crappy cheap carb. It was 59.99 from Amazon. It doesn't have near the correct vacuum ports which I would like to hookup. The float that came in it failed in just over 500 miles.
It is clean though. I have the kit, I'll plan on rebuilding the original one with the throttle plate from the cheap one.

Is there something about the throttle shaft leaking vacuum? Is that a thing?

Also this warning was on the item page from Amazon:
"The oil channels of carburetors will be blocked without cleaning.Please clean up the oil channels and air filters as well as use the clean fuel before installing the carburetors"
 
First thing I would do based on running the Petronix is bypass the ballast. All you need to do is unplug the single wire and tie it to the double wire. Done.

Your never going to fix your problem running 10v to the Petronix. Start there.
 
Do the by-pass as stated above ^^^.Bump up the timing from 0 to 5 or 8*. This may take away the off idle stumble. Also depending on the altitude where you live it may even like more. I run 14* in my 318 truck @ 2600 altitude. Just a thought.
 
I've been sick with malaria or something since Christmas evening. I had to go to the pharmacy today. I had enough energy to make a jumper wire and eliminate the ballast resistor. It made a world of difference. It still fell over on itself but not nearly as bad I managed to do a one-leg chirp on accident when I accelerated the first time I took off out of my driveway. I think adding timing to it should fix it the rest of the way. I'll take care of that when it gets above freezing.

Weird side note: My gas gauge started working. I changed the gas tank and sender about 2 months ago. I ran out of gas at 11 pm on Christmas night about 3 miles from a gas station. I pushed it for 1/2 mile until someone stopped to help. So a gas gauge is fun to have now!
 
So I took the BBD clone out and pieced together parts from the original and the carb rebuild kit. It has been flooding on cold starts since I got it so I figure it was time. I found out a few interesting things:

The float had no pivot pin.
Both balls were not installed.
The choke vacuum diaphragm was leaking.

I got it all back together. Set the float height to 1/4" It definitely took care of all of the hesitation, the throttle response is very good.

But... now it idles fast and rough. At idle I can watch gas slobbering out of the venturi cluster. The idle smooths out and gets even faster if I choke the carb a bit. I have all of the vacuum ports plugged. It also has a new sound which I'm guessing are the balls rattling around. It's supposed to be warmer tomorrow, I'll hang a tach, vac gauge, and timing light on it and hopefully get it idling smoothly without losing my new found throttle response.
 
The carb was junk, ended up buying another carter clone, the correct one this time, until I can get a four barrel setup. Runs great for now.
 
Unless you have to pass smog... throw the factory timing specs in the garbage.

Tune the engine to what the engine tells you it wants. It takes some work to get it right. You'll end up with a better performing engine in every range that way.

@dartnlo
 
crackedback said:
Unless you have to pass smog... throw the factory timing specs in the garbage.

Tune the engine to what the engine tells you it wants. It takes some work to get it right. You'll end up with a better performing engine in every range that way.

@dartnlo
Click to expand...

I'm trying a different tune today.

I think my carb still might be junk. One idle mixture screw likes to be almost about a half turn out and the other about 1.5 turns out. My warm idle sits about 950 with 11.5 degrees initial timing. Vacuum and centrifugal are working but I don't have an easy way to see what it is. My timing mark is dead steady at 11.5 and the idle is smooth. The throttle isn't quite as snappy as when I give the curb idle screw a little more or put a little more initial timing.

My manifold vacuum is sitting steady at 23.
New vacuum advance and the dist has been cleaned and lubricated.
The car stays cool at 185 even sitting running during testing.
I've replaced all of the vacuum lines and ECS.
At higher RPMs I can hear a little ticking but I can't tell if it is a lifter/valve or an exhaust leak.
It has a new pertronix ignition with matching coil.
Spark plugs are new as well.
New gas tank and filter.

This could be a transmission issue as well, as it does slip just a tad shifting into Drive. Next up is to replace the rear axle bearings as it makes a little noise in the city, probably highway as well but I can't hear it. Not a grinding noise, doesn't change with cornering or braking.

I'm going to give it another road test today at 55 mph and see what I get.
 
Just in case anybody stumbles upon this thread in the future hoping for answers I want to give details what I've figured out.

The Carted BBD clones are not very good. It is prone to plugging the idle circuit if it sits for any decent length of time. I just worked through this issue again. I spent a couple of days tuning and trying to get the idle set. I was starting to think I had no idea what I was doing. These are very easy to set the idle on and are fairly forgiving. I would get the idle set perfectly and it would purr just fine at 750 RPM but as soon as I would drive it it would die at stops, neutral was fine but in gear it would die. Sometimes it would even seem to be ok at a higher idle for a few hours but then it would sit overnight and in the morning it was back to not idling in gear.

I knew from past experience that if I could get carb cleaner sprayed into the mixture screw holes it would fix it but this time it didn't. It had sat for almost 10 weeks while I worked on the front end/suspension rebuild. I finally took the carb off and doused it with carb cleaner down through the metering jets, the idle ports, and through the venturi cluster. Then I used compressed air in the same spots, then carb cleaner again. Reassembled and installed. The idle was set easily and perfectly in about 3 minutes.

One thing I noticed while having trouble setting the idle was a whistling or air whine when it would get close to being right. I could make it stop this by either setting the idle speed higher opening the throttle plate, or by opening either of the idle mixtures. The problem was: doing this would make the idle wrong. When I got the idle circuit cleaned out it didn't do this. I surmise that the whistling was from the idle circuit pulling air through the venturi cluster because the fuel channel was plugged or partially plugged to the idle port.

This may be a well known thing to most people but I just wanted to complete this thread for any carb novices like me.
 
if your car routinely sits for a fairly long period, I would either put a shutoff in the fuel line, or go to an electric pump, run off the key, and through a switch and relay. That way you can shut the fuel off and run the carb dry

Likely not related to your miss, but learn to check total timing and check your advance, both vacuum and mechanical. you can usually bump the timing from TDC to about 5 with no changes, but you really need to consider recurving the dist. mechanical advance. The 70's advance curves were very slow and very long. "For smog." Don't discount "simple" stuff like deteriorated coil wire or plug wire, or dirty cap and rotor. Worn distributor. Poor spark voltage caused by a number of things
 
67Dart273 said:
if your car routinely sits for a fairly long period, I would either put a shutoff in the fuel line, or go to an electric pump, run off the key, and through a switch and relay. That way you can shut the fuel off and run the carb dry

Likely not related to your miss, but learn to check total timing and check your advance, both vacuum and mechanical. you can usually bump the timing from TDC to about 5 with no changes, but you really need to consider recurving the dist. mechanical advance. The 70's advance curves were very slow and very long. "For smog." Don't discount "simple" stuff like deteriorated coil wire or plug wire, or dirty cap and rotor. Worn distributor. Poor spark voltage caused by a number of things
Click to expand...

I'm running about 18 initial at idle (I made a 20^ mark on my balancer) with the vac advance plugged. It seems to like it there. The only miss i have is from a 95 psi #7. An overhaul is in my future but it runs good enough for now when the carb isn't plugged up. Next time It has to sit for more than a month I'll just unhook the fuel line. It still managed a 17.6 last week at the test and tune, easing into the first 40 feet to avoid spinning my 185 70 14s I thought that was respectable for a 318 2 barrel auto with a 2.76 ratio.
 
You must log in or register to reply here.
-

Back
Top