Hi. I just got my car back from the shop. They rebuilt my tranny. I have a 70 mustang.. Anyways, now its running really lean. I recently had the top half of my engine upgraded to mild cam, aluminum intake, edelbrock aluminum heads etc. I literally havent driven this car all summer because of all the work I had put into it. Needless to say, I would really love to take it for a cruise before the summers over. But, with the lean running, I cant do that. Can someone please give me some ideas on why this is happening? Also, I noticed a small puddle on the timing cover. Thanks,

 

how do you know its lean? A small puddle of what on the timing cover? Oil? water? Fuel?

-Gun

 

I started pulling the spark plugs on the passenger side bank and they were almost pure white. I have a 600 holley. Is there anything I should be looking for on the carb?
A small puddle of oil... thanks

 

The puddle of oil can be considered typical. It leaks from the intake to block/head union caused by not using enough permatex "right stuff" or using cork gaskets. Not a real big deal as long as it does not get worse.

As for the lean issue:
1) how many miles are on the plugs?
2) does the car run fine under wide open throttle?
3) does the car run fine at cruise speed (50 -80 mph)?
4) does the car transition between cruise and WOT fine?

-Gun

 

it seems to run pretty consistent,although the kickdown needs to be ajdusted.i think it should have a little more torque out of the box.i think maybe the secondaries aren't opening causing lean conditions?also,plugs are new.

 

There is a simple way to check to see if your vacuum operated secondaries are working.

At the base of the vacuum mechanism you'll notice an actuator rod that moves up into the vac housing as the 2nds start to open.

take the air cleaner off and move that rod up until the 2nds are fully open make a mark on the rod at the base of the vac housing so you'll have a reference point that says "this is fully open"

next cut a notch all they way to the center of some stiff card stock like a piece of business card. The notch should be cut so it hold the card onto that actuator rod with just enough force so it wont slide down with the engine running.

Place the card on the actuator rod at the base of the vac housing so its at the top of the rod touching the base of the housing with the 2nds closed normally just like they sit with the car off.

Now replace the air cleaner and go for a dive...Open her up like in 1st gear locked down until you reach an aggressive shift RPM. As the vacuum pulls the 2nds open it will push that card stock down the actuator rod. Take a look and see if the card made it to that reference point.

That's about the best test for checking vac 2nds that I can think of. Just make sure that the card stock for some reason dont fit so tight that it stops the rod from advancing into the vac housing...effectively jamming the 2nds closed

-Gun

P.S I would gather new plugs make for a poor a/f reference...Dont know how many miles it would take for a new set of plugs to make good judges of your current a/f ratio...but I would guess a fair amount.

 

Thanks Gunjam! You sure know your stuff! Ill keep posted on the progress..

 

honestly I think its okay...if the 2nds check out and it runs smooth under full power you should probably just go about your business.

maybe someone who knows more about tuning a holly could provide some tricks to check a/f ratio. Im more into the carter AFB/edelbrock side of things.

I cheat and use a wide band A/F gauge along with vac and tac it really puts foot to ***. if dialing in your A/F dead on like the holly will allow you to do is something you want to tackle the wideband a/f gauge is a must. Its also a great way to keep an eye on the cab and lets you know when something is doing bad (is is flooding or is it starving)