are fumes normal?

[rd100]

I just tuned up the engine, used a dwell meter and vacuum gauge for the first time.

Seems to be running ok.

I was hoping this would reduce some of the fumes. It's not smoking or anything visible, it's just if the truck idles for a small bit it's surrounded by fumes. Is this just how a 1970 engine design is, or do I need to work on something more?

[fordman]

how are the eahaust leaks? where does the exhaust dump out at? if it doesnt dump out from under the side of the truck it will stay more around the truck. if it dumps under the truck and not out to the side.

[rd100]

Yeah I've got exhaust leaks near the engine, that's the next step in fixing stuff.

But I mean like 15 feet away from the truck you'll be hit by fumes, will a proper exhaust system help with that?

[ximy]

there shouldn't be any fumes.. it could be as simple as adjusting the carburetor mixture screws

[rd100]

I'll hook up the tach and try adjusting the carb mixture tomorrow.

[fomocoguy]

Exhaust leaks and carb adjustment could definetly be contributing, but keep in mind that if you are comparing the exhaust smell of your truck to your newer vehicles, the truck was built when there were no emissions regulations and has almost zero emissions control equipment so it will "smell" a bit in comparison. When you adjust on the carb, make sure that when the truck is hot that the "flap" on the air cleaner where the heat riser attaches opens up completely. If it stays shut that could be making it run slightly rich. Also make sure the choke is opening all the way. That being said, if you are smelling it strongly from 15 feet away and everything looks good then I would say you definetly need to adjust or possibly rebuild that carb.

[rd100]

I just rebuilt the carb so that's ok. The mixture is probably the issue. When you say the flap on the air cleaner where the heat riser is should be open. Do you mean it should be laying flat allowing all of the air to come in? The choke seems to be fine.

The fumes I'm talking about aren't gas smells but a combustion process smell so hopefully the carb adjustment will help out.

[MotorDog]

It's entirely possible your PCV valve is not working and you are smelling the "blow by" smell of the engine at work. It might not even have one attached to it as some I have seen have been removed. It could be that your engine is in need for a rebuild soon. Crankcase blow by will smell bad but doesn't necessarily leave a "cloud" of smoke you can see.........

[rd100]

The carb was lean. Using the tach I adjusted the mixture screws to obtain max RPM and re-adjusted the idle back to normal.

There is marked reduction in exhaust smell.

[ximy]

The carb was lean. Using the tach I adjusted the mixture screws to obtain max RPM and re-adjusted the idle back to normal.

There is marked reduction in exhaust smell.

Great!... congrats...

[rd100]

Yes this site is great.

In the past week, having never done it before, I've:

rebuilt the 2100 carb
replaced points
used a dwell/tach meter
used a timing light and adjusted the timing.

I'm now really good at taking the distributor cap off and tweaking the points gap, it's amazing how super hair fine an adjustment can make to the dwell angle.

After the points were in, my timing on the 302, which is supposed to be 6B was around 20B before adjustment.

The timing really smoothed things out, before that it was stumbling as it revved.

[fomocoguy]

Congrats! It's a great feeling when you learn how to tune that engine in exactly how it's supposed to be and it makes such an improvement, isn't it? Now you can brag to your buddies about how smooth your 40 year old truck runs!

BTW, the flap on the air intake should lay flat after the engine is good and hot, allowing fresh unobstructed air to enter from the engine compartment.