Help with dialing in points ignition and carb
 

Hi guys,

Spring is almost here, so it's time to dial in the 70 Trans Am for it's first car season since it's multi year restoration. I have a few questions about timing and carb settings, and a fuel cap question. Probably gonna be long winded here, sorry lol

First off, I noticed a small fuel puddle on the intake manifold, next to the base of the carb. I pulled the carb off to give it a quick once over, and noticed there was pressure in the fuel lines going into the carb. Very strange for a Q-Jet that's been sitting months since running.

That's when I remembered the reproduction fuel tank doesn't seem to accept 1970 style vented fuel caps. I was speaking with Ames about this in the fall, and we didn't really come up with anything. Non-vented caps fit, so that's what I stuck on the tank just to keep moisture out over the winter. I only put it on after shutting the car off, but it seemed to pull a vacuum and completely fill the engine with fuel. It was so full of fuel I had to pull the plugs and spin the engine over, which soaked several towels in the engine bay.

Does anyone have a source for a vented cap that had longer prongs, like the later caps? I took a pic of what I have, with the sand blasted cap being original, the two in the middle being Ames attempt at finding something that fits, and the last being the cap off my 71 that fits perfectly but doesn't vent.

https://pixvid.org/images/2026/03/12/W2WuY.jpg


https://pixvid.org/images/2026/03/12/W2Wzl.jpg




Next up is timing. The car tends to start hard, almost as if it's too advanced, but retarding it slightly makes it not want to fire at all.

I've never messed with points much. I'm an HEI guy. Is dialing in a points setup roughly the same process? Pull the vacuum advance, set the initial, check the mechanical advance, then check the vacuum advance? What about the dwell? I dont have a dwell meter, should I get one?

I have some questions about dialing in the choke, but I dont want to flood you guys with questions.

Thanks fellas

Yes get a dwell meter but make sure not to lean on the fender with a sweaty arm while adjusting the points. It stings a little if you hit the wrong thing. LOL
As for the cap. If nothing else can you drill a small hole it? Where did you get the tank from? I found this on Ames site and it says it fits repro tanks.
https://www.amesperf.com/parts/35314/

Before adjusting timing the points dwell has to be adjusted (from the Shop Manual):

Does your tank not have vents?

70 A-body tanks actually have 2 vents (one in the front and one in the neck) so do not rely on the cap.

???

I agree it is unexpected to find pressure in the fuel line after sitting for extended time. Even with pressure, there shouldn't be a leak into the manifold. What's your thought on why this is happening?

What is the fuel pump?

If you don't want to buy a dwell meter, bump the engine so it stops on the high spot on the distributor cam. (points open) Set the point gap at .017" with small feeler gauge set. That will get your dwell at 30 degrees +- 1 degree. As mentioned, do this before setting the timing. Not sure about your venting situation.

The old rule of thumb was a matchbook was .016 and if you were stuck on the side of a road you could set your points with a matchbook and get home.
Now, matchbooks themselves are a thing of the past. Good to have in your glovebox anyways.

Setting the choke goes like this.
Hit the gas pedal half way and the choke should close off all the way if the motor is cold.

Once the motor fires over it should open 1/8”.

You can use a drill bit as a gauge.

This is a starting point and the motor may want a bigger choke opening then 1/8”.

You can play around with that by hand.
If after 40 seconds or so of running you open up the choke some and the rpm picks up then leave the choke set that way and drop the motor in gear if it’s a auto and that choke setting should be good.

On the other hand if it’s manual and it wants more choke opening bend the rod to give it some.

On my everyday car I had a winter and Summer setting I used on mine if you want to get nuts with it.

Don't forget to grease the points fiber rubbing block and distributor cam lobes. Points sets used to come with a small capsule of grease for this purpose.

I believe that's the one they supplied me with the 2nd go around, although it doesn't have the lettering stamped in it. I got the tank, sending unit, and straps from Ames as a kit.

I took my 71 cap and blasted a hole thru it for the time being lol


It's a 70 non emissions car, so no vents.

I'm wondering if the float sunk, and combined with the pressure built up it just kept draining into the engine. The fuel pump is a reproduction mechanical pump from Ames.




I'll be working on the car later today. I'll fiddle around with it some and report back. I'll also grab a dwell meter and check that.

I pulled the carb apart to check the float. I started thinking it might have sunk, based on the amount of fuel dumped into the engine. I pulled the float and dunk it in some water, and it seems to float fine.

I did notice it doesn't have the little wire/spring thing that attaches the needle to the float. I flipped thru the 1970 assembly manual, but didn't see it in there. Should a 70 RAIII carb have one?

Everything seems clean otherwise

https://pixvid.org/images/2026/03/13/WBlgj.jpg https://pixvid.org/images/2026/03/13/WBlVI.jpg

Yes, every late production 1967 or later Quadrajet made had the float needle pull clip #7033751 from factory.
1965 to early 1967 had a different clip due to the diaphragm type float needle and seat.

BTW, the float hinge pin open end should be towards drivers side for stability.

And for best performance and durability i would use an original style nitrophyl float because the brass float has less buoyancy and puts less pressure on the float needle.

Make sure that the U shaped wire rod that the float hangs off of is bent up high enough such that the air horn when on pins it down tight .

I'll make sure the float is set up how you guys are saying when I put it back together. I'll also check the float height.

Side note incase you guys were curious, I drained about 15 quarts of oil mixed with fuel.

Yikes

Lack of issue with the float cannot be reassuring.

Probably worth verifying your float, needle, and seat will hold pressure. Do you have a way to do this?

I don't have any idea how much could build up inside your tank if it wasn't vented but I'm skeptical it could be enough to cause what you found.. would have to be from heating and would probably have to build over 10 psi, which seems very unlikely. IMO, there is a bigger risk for the tank collapsing than for the pressure building enough to push quarts of fuel past the needle and seat. ????

There are reports of mechanical pumps delivering pressure higher than expected, but again, doesn't seem to fit with pushing large volumes of gas into your engine ???? I expect that would only happen with the engine off, which means the pump isn't pumping....

Something isn't making sense to me on this one.

Mike

It is strange.

Fresh restoration, everything is new. Had the car running with the fuel cap off the tank, backed it into the spot it has sat all winter, and put a non vented cap on the tank to help keep moisture out.

Went to mess with it this week as we had a few warm days, and I'm sick of working on other cars. Every cylinder was full of fuel, with pressure in the steel line leading to the carb.

Here's what I'm working with:


https://pixvid.org/images/2026/03/13/WBYff.jpg

Not sure whats going on, but I have clicked on 2 of your pics today to zoom in and take a closer look and came up with some not so good pop ups.
First one was some kind of porn and now a warning that my phone has been comprimised.
Need to take a look for the safety of any body here.

Me too... the "Pixvid" site that you link to your photos is filled with malicious popups and misleading links....

Unfortunately, the photos you post are too large to view on my PC so I'm basically unable to see them.

Is it possible to load these same photos directly to the PY site?

It’s easy enough to check how the float and needle are doing once the air horn is held on by even just a few of the screws.

Screw a nipple into the carb then flip it upside down and blow into it.

You should hear no air getting into the carb, and yes your lugs can put out more then 7 psi to make this test valid.

Unfortunately if the motor was run for even 1 minute with just a half a qt of gas mixed into the oil it’s going to be time to rebuilt it .

I've done the old blow into the upside-down carb trick before. It seems to be holding back the pressure now that I've reassembled it.

Engine was not ran.

Never had issues with Pixvid, but here's the pics hosted thru this site. Unfortunately this site knocks the file size down so much, they become blurry.