Hello, working on my '76 tuning in my holley 650 DP, been having some idling issues, really hard to keep running on start up needs a lot of choke. And then once warmed up it'll idle fine, then if you go down the road and back the idle will be way up around 1500-2000. So one thing i did was got a fuel gauge installed and i have a solid 7 psi. The other thing i did was bought a vacuum gauge to adjust my idle mixture screws.

When i hooked up the vacuum gauge i disconnected the outlet for the headlights that right on the intake manifold. But when warmed up and idling around 650-700, i have less then 5 inch on my vacuum gauge. So i moved it around to different ports, less than 5 everywhere. When i rev the engine up, the gauge does go up, around 15 at 2000. My manual that came with the gauge says the manifold vacuum should be around 15-20 at idle. It does take forever for my headlights to pop up and go back down.

So i plugged all the carburetor ports and left my gauge on the intake manifold port, still less than 5. The carburetor base gasket is brand new a few months ago. So i'm not sure what to make of this. Maybe i have a bad gauge? I'd try it on one of my newer cars but i'm a little cautious about unhooking the wrong thing. What do you guys think?

Also, when is it going to warm up? I'm tired of being cold...

 

I would pull the carb off and check your blades in relation to the transition slots ecthttp://members.tccoa.com/392bird/tuning.htm

 

If it were me, I'd check timing first. Use the timing sticky for complete instructions on checking base timing and advance. If you don't have a timing light, you can use your vacuum gauge. Once your timing is right, if you're still having a problem with idle speed, then go into the carb.

Pete

 

1)Is the cam stock? 2)Is the gauge solid at 5" or is it erratic? 3)If so how erratic? 4)Have you ran a compression test, if an intake valve was mis adjusted or stuck open it might show on a compression test. 5)Have you tried the propane torch with no flame around carb base and the interface between the intake and head? 6)What do the plugs look like? 7)What's the timing set at?

 

When I started this morning I went to loosen the distributor bolt, and with the weight of my arm on the distributor something snapped down, like the cap wasn't on right. So I started it and it fired in a half crank and idled right out perfectly, I must have been not hitting on one cylinder or something? But I still don't have any vacuum, the gauge bounces from 3-5" vigorously. When I open the throttle it goes up and stays solid.

The cam is not stock, other than knowing its a comp cam I don't know any more about it.

When running I tried adjusting the distributor and it did nothing to vacuum. I'll have to get a timing light, I've been borrowing one, I'll see if I can just get one bought maybe today yet. I'll have to retime it now anyway since I messed with it. I think I was running at 12/36°.

When I get back outside I'll try testing with the propane and I'll pull some spark plugs.

Also today after having the distributor pop in, the exhaust reaks baaaad, I'd don't know what's up with that either. Almost like a sulfery smell, almost like the gas is bad maybe, don't know why so bad today and not yesterday.

 

Try this also:

If the car has power brakes, remove the vacuum hose from the rear base of the carb and plug the open port on the carb...

Do not drive the car/you won't have any braking ability!



Start the engine and bring it to operating temperature...readjust the distributor timing AND idle rpm to 900 rpm if needed so the engine will idle smoothly because of the different cam.

If the vacuum increases while idling, the brake booster diaphragm may be punctured.

Also check the PVC valve to make sure that it rattles when you shake it the way you would shake a can of spraypaint (it can get stuck in the open position causing a loss of vacuum)

Also check the distributor vacuum advance unit...with the engine running disconnect the vacuum line that is connect to the carb...then, either use a hand-held vacuum pump (Mighty Vac) or you can just suck strongly on the end of the vacuum hose--the engine should idle faster if the advance is not damaged....reconnect the vacuum line after the test is done.

Reconnect the vacuum line to the brake booster after the testing is finished.

Does the car have a catalytic converter....it could be going bad/stopping up the exhaust which would cause vacuum problems/stinky exhaust smell.

 

The bad exhaust smell is from unburned hydrocarbons in the exhaust. Apparently the catalytic convertor converts them to something that smells like that. It should improve once you get the engine running properly.

 

I just put on two new catalytic converters a month or so ago, there had been some smell but not that bad. I ran the car again and it has seems to be better, maybe just getting some crap out of the one cylinder that wasn't doing anything...

Testing for intake leaks with propane doesn't work to well, my engine fan just blows it away. I'm not to keen on spraying the thing with carb cleaner, my intake is painted and I don't want to strip it off.

The spark plugs are what I'd call a 'dry black'. Not wet with extra gas or scorched white.

I won't rule out an accessory causing my problem, but I did plug all ports on my carb and still got nothing. I know a guy that's got a hand vacuum pump, I'm going to check this gauge against his just to be sure. I looked under the hood of my 2012 ford to look for a vacuum line to check and just laughed and closed the hood.

 

Can you post a video of the needle on the gauge? What rpm does she idle at?

 

I didn't think about the fan and propane, try carb cleaner.

 

Disconnect every vac connection to the carb and intake . Plug them off .. Start car see what vac is at, if it is still really low it is a gasket issue , if it is good then 1 by one reconnect all vac hoses until you drop vac . presto ya will have found it.

 

gauge is good, checked against another gauge. I've troubleshooted one by one already, and nothing. The PCV valve does rattle. I won't rule out a gasket issue despite being brand new so i'll check it out. I haven't had one of these carburetors apart yet, could there be something internal of the carb that could cause this?

 

Bingo.

Start with timing - always. You've stated you have a "little bit of a cam." If you have your timing set to the stock recommended initial timing, and the vacuum advance disabled or hooked up to ported vacuum, you are grossly retarded, and you'll pull lousy intake vacuum. Set your total timing to 36-38 degrees, and then make sure you have initial timing in the 18-degree range. Install an AR31 (VC1862) vacuum advance control unit and hook it up to a manifold vacuum port. This will allow the engine to idle at just over 30 degrees of timing, and it will give you very good intake manifold vacuum and idle quality. Once you have this all taken care of, you can balance out your primary/secondary idle speeds and tune the carb for best performance. Doing any carb work before you straighten out the timing issues is a waste of time.

Lars

 

The one thing I would add is do a compression test or leak down test to make sure you have a healthy engine. If the compression is way low or leak down is way high, you are beating your head against the wall.

 

I'll get me a timing light rounded up and get that distributor set to your specs. All i know is when i turned that distributor advanced or retard i got zero change in vacuum. I have a vacuum advance control on my distributor, not sure on the number, was on the car when i bought it, it looks just like the VC1862 you've suggested.

v2racing i'm defiantly beating my head against the wall just kind of made more work for myself. Probably should let this one go down the road and get a C5 .

 

That's the easy way out. Your car will fetch a lot more money if it runs sweetly and has plenty of power.

Pete

 

Alright, found a major problem. I went to start pulling spark plugs to check compression and noticed some liquid on my intake manifold, lots of gas. Pulled the carb only to find my gaskets soaked with gas. I'll post some pictures when I can, my internet is being pathetic today. After looking at the impressions on my gasket set, I think the problem lies in the transition between my edelbrock performer intake and my Holley 4150 dp. I have a 1/2" spacer between to two that I need, and two gaskets. I'll try and get the pictures uploaded and you guys can tell me if I'm set up right.

 

I hope this works, with the way websites are built now-a-days you know how hard it is got get anything done when your internet is stuck in dial-up speed .

Anyway, i had this set up the square gasket on bottom, spacer, round gasket, carb.

 

There's nothing in your gasket setup that will produce the low manifold vacuum problem you're experiencing unless you actually have evidence of a massive leak, which I doubt. Of concern is that you stated that the vacuum reading remains unchanged regardless of timing setting... that's a problem...

 

I agree completely with Pete. If you wanted a c5 you would have went that direction. I take it that the spacer is needed for the accelerator pump to clear the intake?