Help!! Idle problems.

[429Thunderbird]

The engine and c6 trans are originally from a '69 TBird. 10.5 comp, c9heads (72cc) 360hp. It's currently in a '78 TBird. Stock convertor (1,800?), 3.25 in the rear, car weighs about 4,100lbs.

It has some idle problems. I thought it could be carb. so I put a friends Holley 750 dp that works good, and it did not change the idle problems. I currently have a Holley 750 vac. sec. The engine does runs a little better once it's warmed up, but until then, I have to keep reving it past 1,500 or it stumbles and dies (like its choking). Once it's warmed up I keep idle at about 1,000rpm, and it still stalls when I put it into drive unless I keep giving it gas. Some say it might be the stock convertor that's too tight. I have adjust. rockers, and I think they may be too tight and not closing properly (runs better once warmed up). They don't tick or anything. Compression test showed 169 on all eight, what do you think? I plan on taking the valve covers off and readjusting them ( one rocker at a time just like Comp Cams web advice for cold valve adj.). Dist. Mallory unilte vac, and Holley Anihilator box are both new. Timing is about 14 init, and 34 total, carb rebuilt, no vac leaks, vac 10-12in. I can't think of anything else that can be wrong.

Look forward to any advice!!!!!

[Gearworks]

my friend you have a GIANT vaccuum leak in the intake system somewhere! Places to start looking would be:

1) Power Brake Booster line, and or the fitting in the booster itself

2) Possibly the main vaccuum feed for the headlight system. (however you would hear an audible hissing from under the dash)

3) Intake gaskets?

The leak you're looking for is on the manifold side of the vaccuum system. A carbureted side leak will not cause these problems. The way to tell which side the hose is on, is simple. A manifold vaccuum signal is a hose that is plugged into the carb BELOW the throttle blade centerline. (Ie. Power brake booster, PCV valve, etc.)A carb'd vaccuum signal comes from anything else ABOVE that centerline. (ie Distributor vaccuum advance, A/C dashpot, etc.)

You might find it easier by spraying carb cleaner around the areas in question. If the carb cleaner is Flammable the engine speed should pick up briefly, if it's non flammable the engine should slow briefly

Just check EVERYTHING with a vaccuum hose.
And please let me know what you find!

Paul
The Gearworks

[429Thunderbird]

Thanks for the info,

So you don't think it's carb vacuum problem but a mainifold (engine)vacuum leak?

Would it help if I plug all the vacuum ports, including brake booster, pvc etc., coming off the engine and see if runs any different? Should I also plug all the carb ports except the dist?

I do get a hissing sound under the dash, but it comes from the heater/AC controls. It hisses if the lever is in any other position other than the one with the "downward arrow" and that where I keep it.

As for intake gaskets, i replaced them three times with different style ones (baffle and strip) and it didn't make a difference.

Also, how much hp do you think my combo makes, and what kind of e.t. could I expect?

Thanks for the info!!!

[Gearworks]

it might help. you can even unplug the distributor if you dont raise the rpm above an idle.
the hissing under the dash is the rubber diaphragm in the airbox controller (the floor/defrost lever) unfortunately theres NO easy way to fix that, and i seriously DOUBT thats youre vaccuum leak.

As far as the power you MAY be around 400hp. remember these birds are HEAVY! usually around 4100 pounds in full trim! I had to damn near gut mine to get it to 3600!!!

As far as times its VERY hard to tell. That depends on youre prowess with the car. you MAY be able to pull off a low 11 with it.

WEIGHT is youre enemy! lose whatever you can. Ie. drop out the bumper liners (makes it neccessary to make youre own mounting brackets) but you'll lose 100 pounds right off the bat!

I gutted the entire air box and all related controls that was 150 pounds including the A/C pump. Power seats are about 100 pounds EACH... so you can see where they add up.

[429Thunderbird]

I'm still trying to solve this *#@% problem! (read the entire message for full details)

I put my Holley 750 vac back on yesterday and one again tried to get her running right. I disconnected and plugged all vacuum lines except brake booster and dist. I set init timing to 16deg which gives me about 36deg at idle. I pulled all spark plugs out and they looked good (greyish colour). Spark plugs are Motorcraft BSF42C. I regapped them all to .055. No difference. I did another compression test and came up with the following:

#1 - 230 #2 - 230 #3 - 235 #4 - 235
#5 - 235 #6 - 240 #7 - 230 #8 - 220

Much different then I previously reported. Can't explain why other than I was relying on memory before.

I sprayed carb cleaner all around the intake, carb, vacuum ports, and everywhere else and no change!

Also is it normal to have some vacuum vapour/mist coming out of the breather tube. The pvc valve was not connected at the time (checking for leaks). It was enough to that you could see it. I've never seen oil deposits in the air cleaner.

After all this the car runs the same. Get it to ide at 1000rpm nice and smooth then as soon as I put in D I chugs and sputters and stalls unless I give it more gas.

Any other suggestions? Am I missing something? Would changing the jets in my carb help?

JOE

[Gearworks]

hmm. interesting. i did have one years back that had that problem, and it ended up being a cracked distributor cap. on a weirder side note, are you sure its timed straight up? (At zero, on the chain assy.)
are you sure the idle screws are set correctly? (1 1/2 turns from bottom)

[ 05-03-2003: Message edited by: Gearworks ]