318 tuning help please. multiple issues..

[Agent_Orange]

Hey everyone, thanks in advance for your help. ​

First off lets get the basics out of the way. I have a 1974 318, basically stock as far as I know. It does have a very mild cam, but I have NO other information on duration or lift. heck i don't even know the brand. :banghead: Behind the 318 is a TCI streetfighter 727 and I don't know the TQ size or brand. The engine has a Edelbrock Preformer 4 barrel carb with electric choke, I believe it has electronic ignition and it does have a vacuum advance on the carb. Currently the vaccum advance is plumbed into the manifold and not the carb. With a vacuum gauge also on manifold vac, i'm pulling 14-15 lbs at idle in park. It does have a steady, fast flutter of around 1-2 lbs. Also, I running full tubed headers into 2 1/2 exhaust out the back

When it comes to engines, i probably know just about enough to get myself into trouble. SO, hopefully you guys will allow me to lean on ya here to help me troubleshoot issues.

With no further to do: The first issue I have is with the idle of my car. I don't have a tach so i cant give exact numbers, but in order to keep the car from dying when put in gear, the idle at park/neutral is easily 500 to 1000 rpm higher than it is in gear. So as you can imagine, when i put my car in gear you can definitly feel and see it.

Another issue, or maybe another symptom of the first O is the speed my car idles at. Where i work there is a qt mile, flat concrete drive from the road. The speed limit on this road is 15 mph. In order for me to maintain 15mph, i litterally have to ride the brake. If i let the car idle at it's own pace, it easilly passes 20 mph. I'm pretty sure this is screwed up, right? It might just be an adjustment on my carb but i don't like messing with things without knowing what will happen first.

Third Issue. I know my car is a v8 without overdrive, but i'm pretty sure my engine is running really rich. The car has a very strong smell of unburnt gas out the tailpipe. That, and from what i've read, a 318 should be putting down somewhere around 20 mpg. Not the 12-14 mpg that i'm currently reading. It should also be noted that i have .223 gears and 245/60/r15 tires.

:cheers:Thanks agian everyone. ANY advice to help point me in the right direction would be greatly appriciated. :cheers:​

 

[crackedback]

Plug installed in the rear of carb? Throttle carb has some slack in it?

Sounds like a huge vacuum leak.

I'd disconnect EVERYTHING vacuum related fromt he manifold/carb. Isolate the intake tract and see if it clears up. A stock engine should idle easily with minimal RPM drop when in gear.

Any fuel dripping in the carb at idle? There should be none.

Sometimes the carbs do not seat on the intake properly. Make sure there is no interference with lnkage and intake manifold.

 

[TrailBeast]

Plug installed in the rear of carb?

Sounds like a huge vacuum leak.

Or a valve problem or 2 and a high idle to make up for it. (Vac jumps around a little)
But that could also be caused by cam overlap.

What would be really nice is to see a couple of plugs (a couple if they all look the same that is)

Rob I know you know this, I was trying to add some next things to look at for the OP.

 

[Mopar Tim]

Without knowing cam profile and what stallspeed conveter you have hard to say. Heck you could have a high stallspeed converter needed because of a long duration cam! That would explain most of the issues you have. MT

 

[Agent_Orange]

I wish I had time tonight to take a look at the car, but it may have to wait until this weekend. Both of you guys are kind of on track with what I was thinking though. My first assumption was a vacuum leak. I have bought all new vacuum line, but havent had time to swap them over, although the lines look okay. I have already replaced (hopefully) all the vacuum system plugs, a couple did look dry rotted, but no change in the vacuum guage. A couple days ago, I shot some carb cleaner around the carb base gasket while it was running and I thought I heard her rev up just a touch, but i'm not 100% sure if it's because the base gasket is leaking or if the the motor fan whipped the spray around enough for some to go into the air cleaner. My other thought was a bad valve or valve guide. But wouldn't a bad valve only show a vacuum sputter when the associated cylinder fires? i'm not sure. I wish i knew what cam was in this thing so i could tell if there was a valve overlap.

I'm a bit younger than some of the other members on here. Me being 30, I feel like there is so much I need to learn from you guys. I grew up with computers and efi. lol

 

[RustyRatRod]

Close the choke blade. If you have a vacuum leak t will keep right on running. Report back.

 

[Agent_Orange]

Without knowing cam profile and what stallspeed conveter you have hard to say. Heck you could have a high stallspeed converter needed because of a long duration cam! That would explain most of the issues you have. MT

That makes 2 of us!

Like I said, I don't have a tach in the car yet, so I can't tell you RPM. But I can say using my butt and doing a slow brake torque, It's a rather light TQ, probably around 2500


Another thing i thought it could possible be is a timing issue. Riddle me this guys, If the engine fire too much into the down stroke, wouldn't that cause what feels like a lack of power, and the exhaust having a strong gas sent? if the engine is firing late, would that allow the exhaust valve on the previous cylinder to suck out a touch of fresh gas before it closes? or am i off my rocker

 

[Agent_Orange]

Close the choke blade. If you have a vacuum leak t will keep right on running. Report back.

Okay i let the car warm up to where the electronic choke disengaged. closed the choke blades and the car started running really poor, but it kept running. Let me rephrase. i used the stopwatch on my phone and it sputtered for 30 seconds, and then it finally did die.

 

[Louie70Dart]

If its running rich, the exhaust smoke will be black from unburned gas. Burning oil is blue. Or pull a plug and see if its black. Plus, aren't distributor advance hooked to the carb and not the intake?

 

[threewood]

A_O, make any headway on your idle issues? Older thread but I like closure lol

 

[318willrun]

Just a minute! You stated in your opening that you have the vacuum advance plugged into the intake, and not the carb?? Am I getting this right: you have the vacuum advance hose from your distributor going to the intake? IF so, that is way wrong! It has to go to the vacuum advance spout on your carb. If it's going to the intake, your pulling a lot of timing which will rev it up, and cause some funny idling problems. The advance needs to pull vacuum at part throttle, not idle.

Just realized, Old Thread...... Never mind