In need of carb help

I have a 79 gts and was wondering if any of you out there have a break down of how the carbs go together so i can rejet them and also what jet set up to go with when putting an after market exhaust on my car?

Nick

 

find "BIRDMAN" s post on carb tutorial. it has EVERYTHING with pics. i printed the thread its that good.

 

Pierce Manifolds has a parts diagram on their website.

However, you don't have to take anything apart to rejet them. Well, OK, you do have to remove the air cleaner, which means the little velocity stacks have to come off. The main/emulsion tube/air corrector assembly comes right out the top, the idles come out the side. Wouldn't hurt to have new O-rings for the idles.

 

Let me know what jets you are interested in. I have extra sets of various sizes. A couple are brand new. I purchased a few sizes to try to find the right configuration. Have a few sets of idles and and extra set of mains. I will sell for 50% of Pierce's price. That is where I purchased them.
Will check but I think I have:
135 mains
40, 50 & 55 idles

 

sounds good! What Jet combo did you end up using and what mods do you have? This info should give me an idea of where to start. Your help is ver much appreciated.

Nick

 

I believe the 79 cars are fitted with 40DCOE/72/73/74/75 carbs. Stock they are fitted with:

.55 mm idle jets
1.25 mm main jets
2.00 mm air correctors
F36 emulsion tubes

To go richer you could try

.57 or .60 mm idle jets (higher are richer) which affects most of your driving

1.30, 1.35, 1.40, 1.45, 1.50 main jets (higher are richer) effectively raises the air/fuel curve

1.90, 2.10, 2.20 air correctors (higher is leaner) effectively changes the slope of the air/fuel curve. Air correctors mainly effect the top end.

If you don't have to worry about emissions I'd try:

.60 idle jets
1.35 main jets

Then see how that feels.

 

Thanks guys

 

Just as a point of referrence, I had a 78 308 which has the identical stock jetting. The only major mods were cat test pipes, K&N air filter and Crane electronic ignition (oh and NGK platinum EVX plugs). After several dyno runs the tech ended up with 140 main jets, with all the other jets kept the same. Car ran much better, esp. at higher rpms. Though I was running NGK 6 heat range, the plugs seemed to be loading up (fouling some) in city driving, and heat range 5 plugs may have been in order. The car was in an accident, so I was never able to experiment with that.

135 mains would be a good starting point.

Dave