Carb tuning eh?

[vtwinsport]

Hey all,
Got a question. Here's some background;
1. rebuilt 350 in in a 76 C10, th350 trans, edelbrock 2101 intake, edelbrock 1406 car, hedmann headers into new duals and pipes, msd streetfire diz with vac.
2. been tuning the carb, timing, and vac (ported and manifol) for months now.
3. have had timing as high as 14 down to 2 and was most recent at 12 btdc, at 12 and anything above 6, exhaust spits out water on ground and plugs read tan and clean, with vac at manifold and mileage is about 6-7 mpg
5. now is set at best operation with timing 4 btdc, vac at ported oulet and water from exhaust has stopped, plugs read mildly sooty but performance is all round better including pickup and mpg is closer to 10-12

First question, was that fuel coming out my exhaust? it didn't smell really gas like.

Second question, better mpg with mildly sooty plugs? Is that possible? Isn't it running richer with the soot?

Thanks in advance for all comments.
greg

[Damien]

Water is a byproduct of the combustion of gasoline and oxygen, so that is fine. There is also some condensation in the exhaust due to temperature fluctuations.

With having the truck run a little rich, you are making more power as you stated. With the more power, you do not need as much throttle so you are saving gas. If you run the engine lean and it is struggling, you are going to need more throttle to get up to speed, and therefore need more fuel.

[ChevLoRay]

On my '69, there was a 1406 (manual choke, right?) atop an adapter on the OEM Q-Jet manifold. It had Hooker headers and an HEI with an RV camshaft. Beyond that....nothing out of the ordinary.

But, it ran rich....rich enough to bring tears to your eyes/nose if you were standing in the exhaust stream. Nr. 1 plug would gas-foul every few weeks. The oil was diluted from the the excess gasoline washing through the cylinders. Timing was set at 10BTDC, I believe. I did have to replace the vacuum advance because the old one wasn't working (used one intended for a Vette that was recommended in a magazine I read).

I finally bought an Edelbrock 2101 Performer intake and an Edelbrock Q-Jet. I had to add a heat shield to the starter because the new intake/carb ran so much leaner that the heat soak from the headers made hot starts a problem.

In my opinion, if you have it tuned and running like you like, it starts easily and gets decent mileage w/o oil dilution, you should be good to go. As for the liquid you see/saw from your exhaust system...it's condensation. As far as the exhaust system color goes, we used the term "chalkin' the pipes" to indicate a good, lean-running engine. It wasn't something you saw if you were driving in town, but would be apparent after some highway running.

www.edelbrock.com should have tuning technical help available if you have any questions.

[spinem]

vacc leak.

[vtwinsport]

Damien, I understand the water as a bypoduct of combustion but wouldn't there still be water out the exhaust even if it was richer?

Chevloray, yeah I have had to install a spacer to stop the heat soak and was replacing plugs regularly every two weeks due to white ash buildup on the plugs. May have a mild intake leak. Oil seems fine so yeah, I may leave it as is until spring.

Spinem, how do you think a vac leak is affecting things?
I do have some problems with idle tuning that make me think of a vac leak. For instance, when setting idle, has to be around 850 to keep from stalling in gear.
I was thinking this might be transmission vac modulator or torque converter issue or the possible intake leak I mentioned above, as I have checked for leaks in every other hose including brake booster.

thx