Tuning engine, what to do/how to know when you're done?

SadbutTrue · May 23, 2004

My car is getting horrible (more horrible than it should) gas mileage and I was going to tune it up anyway, so tomorrow seems like a good day. First, I thinkt he carburetors probably the culprit... I was going to adjust the idle speed and air/fuel screw. What rpm should my engine (details below) be idling at, and how do I know when the air/fuel screw is at the right place? Should it just sound right?

I was also planning on playing witht timing some, my car is pinging a good bit with 89 octane, which is weird considering that my car has a stock compression ratio and should be able to run on 87.

Again, same deal, when do I know when I have the timing where I want it? Vacuum test? Sound?

Also, I'm going to reset my plug gap. Never done this before, but when I installed my MSD it told me to reset hte plug gap and I never got around to it, so I figure nows a good time.

Thanks for any help one could provide...

pabear89 · May 23, 2004

Start with plug gap before making any adjustments, Or you may have to redo them.

I set the timing with a light and vac guage and my ear for pinging on road test. to find where it runs the best and highest setting.

Carb settings are done with eng at operating temp for smoothest running and idle speed.
Idle speed I use for auto's is 600-650 in drive.

mixture setting are done by many by preference.
Old school Holley trick, Move choke plate to set fast idle cam.
I have mine set between 1000 and 1200, this will keep it drawing from idle mixture.
turn mixture screws till highest rpm with smoothest running.
Release choke cam and reset idle speed.

PB

Hack · May 23, 2004

You also may have some carbon deposits causing some of the pinging. Run a can of Sea Foam through to clean them up. That may help some.

351w_swap · May 23, 2004

Question for Sadbut True

I don't mean to get off topic, but I have a 65 coupe w/ 351w and heddman swap hedders. They hit on the shock towers, and get in the way of the steering. Did you have any of these problems, and how did you fix them? Thanks for any help

SadbutTrue · May 23, 2004

351w_swap said:
I don't mean to get off topic, but I have a 65 coupe w/ 351w and heddman swap hedders. They hit on the shock towers, and get in the way of the steering. Did you have any of these problems, and how did you fix them? Thanks for any help

As far as that goes... we didn't have any fitment issues, and I have power steering as well. They're a real tight fit but they have a few millimeters on each side and haven't bumped em. Sorry. I know motor mounts on 65s and 66s are different, perhaps that might be an issue.

Hack - you mean just use that Sea Foam stuff to clean the carb?

Also, what are the signs of a car running lean or rich? Smell, sound, performance etc..

calpolymustang · May 24, 2004

lots of people agree with my setup, so hopefully it will work for you:
msd 6a, autolite plugs --> .045 gap
15* initial timing
38* total timing
dont forget to plug the hose that goes to the distributor
run around town and get it warm before adjusting mixture, turn them individually till the engine starts to slow down then turn out till it goes down, youll want to adjust the mixture knobs to near a spot inbetween the two spots where it goes down in rpm. it may help to switch back and forth between right bank and left bank
you want to get the rpm as high as possible with the mixture, then you set the idle speed
yeah, this is a complicated process im trying to condense, and lots or people will say it takes a trained ear and all, but this should help it get in reasonable tune
set the idle speed in gear with a friend pushing on the brake and emergency engaged
mine idles at 850 in gear, but it depends on your cam

BTW: whats your major over at Bezerkly?

SadbutTrue · May 24, 2004

mechanical engineering

hows cal poly... got a lot of friends there

Ronstang · May 24, 2004

The only way to properly set the mixture screws is by using a vacuum guage on the manifold and setting the mixture to achieve maximum vacuum. I usually set them to the leanest setting I can that yeilds the highest vacuum.

calpolymustang · May 24, 2004

yeah, a vacuum guage is a good investment

plus, when youre done tuning it, you cant put in in your dash and watch the negative boost go wild

and why cant they use the same units for boost AND vacuum? inches of mercury and then psi??????

Ronstang · May 24, 2004

They do make guages that are vacuum when less than zero and boost when more than zero....where have you been?....hehehehe, but the kind of vacuum guage I'm talking about is the diagnostic type and you can get one at Sears for not much money.

calpolymustang · May 24, 2004

no, i meant units of measurement for the same guage, mine shows psi on the boost side (above 0) and inches of mercury on the vaccum side (below 0). its just the standard i guess

Ronstang · May 24, 2004

Yeah...standards are hard to get over.

Hack · May 24, 2004

SadbutTrue said:
As far as that goes... we didn't have any fitment issues, and I have power steering as well. They're a real tight fit but they have a few millimeters on each side and haven't bumped em. Sorry. I know motor mounts on 65s and 66s are different, perhaps that might be an issue.

Hack - you mean just use that Sea Foam stuff to clean the carb?

Also, what are the signs of a car running lean or rich? Smell, sound, performance etc..

Well, I was thinking you could pour a can of Sea Foam in the tank. It will clean the carb, valves, combustion chamber. Pinging can be caused by deposits in the combustion chamber. There's a more radical method (instructions on the can) where you use a vacuum line to draw the Sea Foam directly into the motor, I guess you could try that. It can knock big hunks loose, which doesn't seem the best to me. However, auto shops do this all the time, so I guess it's ok.

A lean condition can cause pinging.

Too rich, carbon build up on the plugs or dark smoke out the pipes. I'm no expert, but I've heard that reading spark plugs isn't a bad idea. Chilton's or Haynes manuals show pictures for various maladies. Since you're going to pull the plugs to gap them anyway, have a look at them.

SadbutTrue · May 26, 2004

Okay, well I pulled the plugs, none were fouled or anything and all had a light goldish/tan color to them. I'll look it up later in my shop manual to see if thats good or not, but I'm pretty sure it is. I opened them all up to about .045 and cleaned em up (though they weren't really all that dirty).

My dad was very convinced that it was running rich, but the plugs showed no indication of that. So... I turned both mixture screws about a quarter turn in the lean direction, if it continues pinging i'll turn them back and then some.

Hack... I was thinkign that might have been what you meant, but I didn't want to dump stuff in the tank unless you really meant it.

We have a vacuum gauge, I was planning on using it for the mixture too though. The changes I've made were really minor (quarter screw in on both screws).

I'm gonna go time it now, be back in a bit heh.

SadbutTrue · May 26, 2004

Well, I got the timing to 14 degrees BTDC, and it seems pretty happy there (vacuum wise). The engine still pings a lot though, I'm thinking it might still have to do with the A/F mix, but when I tried editing that, I could turn the screws (I would turn them roughly the same... such as half a turn on one, half a turn on the other, and so on) pretty far without changing vacuum more than a point or so. So I'm open to suggestions there.

10secgoal · May 26, 2004

Ronstang said:
The only way to properly set the mixture screws is by using a vacuum guage on the manifold and setting the mixture to achieve maximum vacuum. I usually set them to the leanest setting I can that yeilds the highest vacuum.

That's how set them!
As far as your plugs, that is a good color for idle, and maybe a light cruise. Tan is actually rich. But that is needed at the lower RPM's.
And for the ping, you really shouldn't get that unless the car is under a load.When is it actually pinging ? The screws are also only for the idle of the car. So if it is actually rich any other time than idle, you will have to rejet, or other changes.
I would also do Hacks recomendation. Now matter how you set the fuel,timing...if you have a huge carbon depesit, it will detonate. That carbon build up just gets hotter and hotter, acting like another spark plugs.

oldmustangjunki · May 26, 2004

Where can I purchase Sea Foam?
Thanks,
Bryan

Hack · May 26, 2004

oldmustangjunki said:
Where can I purchase Sea Foam?
Thanks,
Bryan

Around here, any auto parts store. I favor a Bumper to Bumper warehouse store near my house.

Tuning engine, what to do/how to know when you're done?

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