Hey i just swapped in a 383 in my car is the exhaust stinks the 350 i had in before the 305 did the same and both are cammed. My question is after i took out the 305 i had to change the vacuum lines due to not having an egr anymore i had two plugged off from the charcoal canister. I looked today one line is a bigger one and it looks to be the purge line the other was from the egr. Could this cause this problem? The 383 was a used motor and the plugs were a tan colour but after idling it there all black. Just trying to narrow it down.

 

Wow, take a breath, and punctuation is your friend, I had a hard time following your thoughts.

What does it smell like? Do you have a cat? Is the cat working? Do you have an o2 sensor?

Black plugs are fouled. Your motor needs a tune up at the least.

 

Motor doesn't need a tune up since everything is new I wouldn't bother to put in a new motor and not do that. I found the problem thanks for your input hope you could follow this.

 

Glad you found the problem! That's the important part.

 

The main problem is getting engines with big cams dialed in right. The charcoal canister will not make a big diff in it.

It's setting of the timing curve, carb idle mixture screws, power valve/metering rod step up springs that will change/cure this prob.

With bigger cams you need to take a vac reading at idle. Adjust idle mixture screws 1 at a time to get highest vac reading.

Add in more timing at idle, use vac advance hooked to a full vac source.
Most performance engines likes/needs 14 to 18 degrees BTDC timing w/o vac advanced, then add in the vac advance and limit it to add 10-14* more.

Limit mech. advance to give you a total of 34 to 38* total and set the springs to have all your timing fully in by 3000-3200 rpm.

Install a power valve or step up springs that's rated at half of what your engine's idle vac is. (if you have 12" HG vac at idle, install a 6.0 power valve)