66 Coupe Progress Thread

DTCRAWLEY · Apr 19, 2026

New guy from Sunset Beach NC. I have a 66 coupe I purchased about 3 years ago and have lots of questions about certain things. The one I'm dealing with right now is tuning the carb . The car has a 289 that was built in 2018 and worked on by previous owners. A mild cam (dont know anything about that), AC, PS, 4 wheel disc brakes, and had it rewired with AAW harness. It had an edelbrock 850 (?) when I bought it but that was too much and never really had any pep. I had a Holley 590 com installed a while ago but it was running really rich. What Ive done is check compression(135-140 on all cylinders) cleaned the plugs, new distributer, coil, wires. I have the float levels just below 1/2 on the sight glass(es). about 1 3/4 turns on the adj. screws. Seems better but still has a hesitation if I stomp on it. Is that inherent or could it be (should it be ) fine tuned. No tach so dont know what the idle is but its not stalling when I put it in gear. After this is figured out i have a cooling issue question as well

General karthief · Apr 19, 2026

Well a carb is just a mechanical computer and require things to happen so other things can happen, I've fiddled with carbs and a holley carb are the easiest, first try getting that fuel level just tickling the bottom of that site glass, make sure car is level.
Also, vacuum advance working?
Mechanical advance working?
I mention the advance because it could have been adjusted/removed to make the big honkin carb work.
What ignition you gots?

DTCRAWLEY · Apr 20, 2026

Hey thanks for the response. Advances seem to work as they are supposed to . Timing light indicates that. Blueprint engines ready to run distributer and pertronix coil. I forgot to mention that i used a vac gauge to set the fuel mixture on the carb to the best of my ability. they leveled out at about 14hg. also have an external vac pump for disc brakes so that port on the carb is plugged.

General karthief · Apr 20, 2026

DTCRAWLEY said:
Advances seem to work as they are supposed to .

'Seem to work' is not 'functioning correctly '
Remember garbage in, garbage out.. the power valve may be 'functioning ' at the wrong time ie: too early or too late, are the squirters adjusted correctly?
You got how much total advance and when does it 'come in'?
Hit the David Frieburger channel on the UTube, he explains holley carb stuff really well.
Does the distributor have mechanical and vacuum advace?
Some have and adjustable vacuum can but done start fiddling with that yet.
Did you drop the fuel level and test drive?

DTCRAWLEY · Apr 21, 2026

going to drop fuel level to just above bottom of sight glass and adjust fuel mixture . Then test drive. Still learning about vacuum advance stuff but it looks to be at about 10 degrees and revving it moves up to 25. Not sure of the lingo yet on how to describe it properly, that's why I'm asking.

Mcmahst · Apr 21, 2026

I wonder if the vacuum reading at idle (14) you cited isn’t pointing to a vacuum leak? You say it has a mild cam, but also a vacuum pump for what I assume is the brake booster. A mild camed 289 shouldn’t need a vacuum pump for the brakes; at least I’ve had a few that didn’t. Others more knowledgeable will chime in, I’m sure. Good luck.

DTCRAWLEY · Apr 21, 2026

what should a good vacuum level be at idle? if there is a leak could it be in the ports in the manifold and how would I check them? The external vac pump is for the brake booster.

AeroCoupe · Apr 21, 2026

I say this will all kinds of "be very careful" but typically on a carbureted setup I check the intake for vacuum leaks with carb cleaner but if the motor is painted this is not the way to go. In the case of a really nice motor (paint, chrome, polished aluminum, etc) you can use propane in lieu of the carb cleaner. I would think a hand held propane torch with just the propane coming out (ignitor disabled) would work very well. DYI propane leak detector here:

View: https://youtu.be/LTLM8ZYM85Y?si=YzhwHooBmGuq1Cbi

DTCRAWLEY · Apr 21, 2026

DTCRAWLEY said:
what should a good vacuum level be at idle? if there is a leak could it be in the ports in the manifold and how would I check them? The external vac pump is for the brake booster.

DTCRAWLEY said:
going to drop fuel level to just above bottom of sight glass and adjust fuel mixture . Then test drive. Still learning about vacuum advance stuff but it looks to be at about 10 degrees and revving it moves up to 25. Not sure of the lingo yet on how to describe it properly, that's why I'm asking.

ok so I lowered the fuel level in the sight gauges to just above bottom, adjusted the fuel mixture screws to 1 1/2 turns out to get steady vacuum of 13-14HG. when I throttle it, it jumps to 0 then up to +20Hg for the time its throttled. sprayed the manifold bolts with no idle change. Is that jump normal? curious that the temp gauge reads 190 in the car, fan comes on at 185 but never shuts off. is that caused by just sitting and idling for 15 mins? will take for a ride shortly.

Mcmahst · Apr 21, 2026

If you’re gonna take it back out again, do us a favor and record the best you can from your phone the experience. Lots of times people believe that their description is adequate for the problem, but hearing and seeing it will help some here who are very good at this.

DTCRAWLEY · Apr 21, 2026

Mcmahst said:
If you’re gonna take it back out again, do us a favor and record the best you can from your phone the experience. Lots of times people believe that their description is adequate for the problem, but hearing and seeing it will help some here who are very good at this.

will try to record vac gauge while in garage and manually throttling it. trying my best

AeroCoupe · Apr 21, 2026

So its not the bolts that I use the carb cleaner on. I spray it where the gasket is between the intake manifold and the heads and around where the base of the carburetor sits on the intake manifold. This will just find the big leaks. The absolute best way is a smoke machine of which you can search DIY smoke machine on YouTube and they are pretty cheap to build.

General karthief · Apr 21, 2026

10 * set and 25 all in is a little weak IMO, see if the vacuum rises at 12* idling.
Post a pic of the engine showing distributor and carb detail please.

DTCRAWLEY · Apr 22, 2026

AeroCoupe said:
So its not the bolts that I use the carb cleaner on. I spray it where the gasket is between the intake manifold and the heads and around where the base of the carburetor sits on the intake manifold. This will just find the big leaks. The absolute best way is a smoke machine of which you can search DIY smoke machine on YouTube and they are pretty cheap to build.

General karthief said:
10 * set and 25 all in is a little weak IMO, see if the vacuum rises at 12* idling.
Post a pic of the engine showing distributor and carb detail please.

I'll get more later. Temp gauge sensor in water neck bung. Fan on/off sensor behind distributer in manifold. Moved coil off of engine to the pass side shock tower. I will say that the carb is black from it running rich for so long.

DTCRAWLEY · Apr 22, 2026

can't seem to upload files

AeroCoupe · Apr 22, 2026

What type of file are you trying to upload and what size?

DTCRAWLEY · Apr 22, 2026

DTCRAWLEY said:
can't seem to upload files

AeroCoupe said:
What type of file are you trying to upload and what size?

8

DTCRAWLEY · Apr 22, 2026

DTCRAWLEY said:
From iPhone 14, 8 mb, 7 seconds. Trying to covert it

DTCRAWLEY · Apr 22, 2026

Just can’t get it to work

Mcmahst · Apr 22, 2026

You can try putting it on YouTube and then attach a link to a thread response.

66 Coupe Progress Thread

DTCRAWLEY

Member

General karthief

wonder how much it would cost to ship you a pair

DTCRAWLEY

Member

General karthief

wonder how much it would cost to ship you a pair

DTCRAWLEY

Member

Mcmahst

DTCRAWLEY

Member

AeroCoupe

lube between the nut and the face. I know my lubes

DTCRAWLEY

Member

Mcmahst

DTCRAWLEY

Member

AeroCoupe

lube between the nut and the face. I know my lubes

General karthief

wonder how much it would cost to ship you a pair

DTCRAWLEY

Member

Attachments

DTCRAWLEY

Member

AeroCoupe

lube between the nut and the face. I know my lubes

DTCRAWLEY

Member

DTCRAWLEY

Member

DTCRAWLEY

Member

Mcmahst

Similar threads

66 Coupe Progress Thread

Member

wonder how much it would cost to ship you a pair

Member

wonder how much it would cost to ship you a pair

Member

Member

lube between the nut and the face. I know my lubes

Member

Member

lube between the nut and the face. I know my lubes

wonder how much it would cost to ship you a pair

Member

Attachments

Member

lube between the nut and the face. I know my lubes

Member

Member

Member

Similar threads

Privacy & Transparency

Privacy & Transparency