My '66 Dart recently developed a slight miss while idling, the idle quality has been becoming worse also. I figured it was about time for a valve lash adjustment but that didn't do the trick.

So I set about adjusting my idle mixture and speed screws. What I found is that my idle speed screw wasn't even seated on the stop bolt (BBS) so the throttle was completely closed and it was still idling around 730RPM. The idle mixture seems about right and I can only increase my idle speed. Right now I have 7 degrees of initial advance. Wires and only a couple months old and the cap, rotor and plugs are no more than a year old.

The carburetor is a NOS BBS that I picked up a few months back, rebuilt it and its been great. I did notice that some of the bolts were rather loose so I tightened those a bit (there was some gas leaking out of the float bowl). Not sure if that is reason enough to rebuild again so soon, but figured I should mention it.

I'll take a look at the cap and rotor tomorrow. But any other suggestions and hunting down the cause for my rough idle and slight miss? Also I should mention that it misses warm or cold (although I do know the choke pull-off needs to be adjusted, although that shouldn't affect idle while warm).

_________________
'66 Dodge Dart

Check for vacuum leaks.

_________________
Joshua

Disconnect your transmission kickdown rod -- push the top of the rod rearward towards the firewall so it snaps off its ball on the bellcrank at the firewall end of the throttle rod -- and take a look and see if your "all the way closed" throttle actually wasn't. It's fairly common for the geometry to get thrown off if the kickdown has been misadjusted to compensate for some other fault, or if a thicker-than-original gasket has been installed between the carb and the intake -- which it usually is, because the pre-'68 cars had a thin gasket rather than the more desirable thick heat-insulating one, and which often necessitates a kickdown linkage adjustment (longer/unscrew the rod top several turns before snapping it back onto the ball) which is usually not done.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

What lash are you running on the valves?

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Doh! Ok, any tips for one new to hunting down vacuum leaks? Also would this include leaks in the exhaust (because I do have a backyard bent exhaust, courtesy of the previous owner)?

Dan, I was actually thinking that on the way home from work. I'm going to do that as soon as the engine cools a bit.
A tight 0.11 on the intakes, a loose 0.21 on the exhausts. Adjusted good-n-warm, of course. Normally it really likes the setting.

I noticed something else today, the engine seems to be running a bit warmer than normal, although it could just be heat and humidity of Washington summers (I'm still new to this part of the country).

_________________
'66 Dodge Dart

The kickdown linkage is pretty much right on. I readjusted per FSM instructions just to be sure.

I also checked the cap and rotor on the dizzy. I'm running the Echilin MO-3000 rotor with a blue streak cap. Both the cap and rotor contacts are worn. All the contacts on the cap have spark bursts (not sure what to call them, looks like they arched really far and got melted a bit), but only on the leading edge of the posts. The rotor has similar looking markings on the trailing edge. Is this normal cap/rotor wear or could it be caused by too much advance?

_________________
'66 Dodge Dart

Sounds like your timing needs to be checked out more closely. What does the timing set look like? A bad distributor stab with the cam out of time, or the bottom adjuster whacked out can put you in a position that will cause the firing point to be incorrect for the distributor.

Check the chain for slop, replace as needed, get the timing where it's on the post, and make sure you lash is appropriate. Sometimes looser is better. Adjust out till it gets loud, then close it up a couple thousandths.

2¢

CJ

_________________
Part of Tyrde-Browne Racing

I very well may have put the distributor in incorrectly (if so it wasn't in correctly before either). My understanding is that the bottom adjuster is pretty much just like the other adjuster, if not someone please educate me.

Also is there any way to measure timing chain stretch without removing pulleys and replacing gaskets... seems like a lot of work for something that may not even be the issue

_________________
'66 Dodge Dart

The quick way is to pull the cap, have a friend watch where the rotor is pointing.

Remove the plugs to make this easier.

Battery disconnected, rotate the engine forward and mark the balancer, doesn't matter where. Have your buddy watch the rotor. Rotate the engine in the opposite direction. When the rotor starts to move backward, stop.

Mark the balancer again. measure how many degrees the crank moves prior to moving the rotor.

Report back. Anything more than negligible is to much.

CJ

_________________
Part of Tyrde-Browne Racing

Well that fixed that... Despite my best efforts to keep the carb securely fastened to the intake the bolts had come very loose. In fact when I went to put a wrench on them they spun freely.

Which brings up another question, how do you prevent this from happening? I know the BBSs are known to warp badly, especially when really torquing on the threw bolts that hold the body together. Does this apply to the throttle plate and the bolts that hold it to the intake? I didn't see any kind of torque specs for these in the FSM. So what do you guys do to keep your carbs secure, and any tips on getting at the bolt on the driver's side (open end wrenches only go so far in that small area).

I'm still going to check for timing chain stretch, but I won't have an assistent till later in the week.

_________________
'66 Dodge Dart

Been there! It's very easy for this to happen, especially with variants of the BBS that leave very little room to get a good grip and swing on the nut with a wrench.
Nylon-insert locking nuts.
They're through-bolts (actually through-screws) unless you "threw" them up against a wall in frustration.
No, but don't get ridiculous with torque.
Use a different box-end wrench!

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

So my carb is held to the manifold with two bolts, and it would be impossible to get nuts on the other side of them since the other end is inside the manifold. So this leads me to believe that the previous owner used the incorrect bolts...

So, Dan, can you explain how the correct bolts would fit in the manifold and what size and where to get them? The bolt holes in my manifold are straight through the intake so I don't see a good way to insert a headless bolt. Thoughts suggestions?

With the bolts I've got on there, there is no way any of my box-ends will fit in the space

_________________
'66 Dodge Dart

Ah! There's the issue. Those're supposed to be double-ended threaded studs. Use removable Loctite on the end that goes into the manifold, and nylon-locking nuts on the (fine-thread) end that sticks through the carb flange.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Agreed! the manifold is suppose to have studs in it. You can get them from the Dorman selection at most auto parts. Ny-locks are nice, if you don't have any handy a star washer will help or a lock washer.

Not sure if you have a problem with heat soak in the summer on your car, or like to keep the intake warmer during the winter months.....I feel the heat deflector can really help improve overall mileage.
When installing a carb heat deflector I like to install longer studs to make room for the two thick gaskets above and below the aluminum sheet stock used for the deflector.

Click on the red link below my name to view pictures of a simple aluminum heat deflector.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

So anybody have a part number for the correct studs, or any info on what kind of thread should be on either side? Or specs on how long they ought to be and thread count on either end?

_________________
'66 Dodge Dart