locating vacume leaks

[grumpyvette]

locating those intake manifold or other vacuum leaks
is fairly easy if you have a tachometer and a propane torch

yeah the way I find vacuum leaks on carb OR MPFI intake manifolds is clean and easy with no mess. get a propane torch,or you can use your oxy-acetylene welding torch if you have one, (DON,T TURN THE OXYGEN tank/or OXYGEN valve, on the torch ON)

http://www.corvette-101.com/vacuum.htm

viewtopic.php?f=50&t=11089

WATCH THE VIDEO, READ THE LINKS
http://www.youtube.com/watch?v=9CPqbaSg ... re=related

viewtopic.php?f=50&t=1877&p=4936#p4936
you might find the next vacuum leak a bit faster with this method, as you can much more precisely direct the combustible gas flow, at any suspect leak location

(DONT LIGHT IT) just SLIGHTLY open the valve so its allowing gas to flow at a low volume,start the engine and let it idle at the lowest speed you can then place the tip of the UNLIT torch at any suspected vacuum leak and listen for the rpms to increase and watch the tachometer, gas flowing into a vacuum leak will increase engine speed.
look for loose or missing vacuum hoses, cracked or broken power brake connections, emissions system hoses that are loose, vacuum connections to the trans or ignition, loose connectors missing or loose bolts cracked hoses missing accessory connections etc.
naturally this only locates leaks to the outside, and its possible for the intake to suck air from the lifter gallery, so that also needs to be checked if everything else seems to be ok.
http://www.centuryperformance.com/tunin ... g-148.html

http://www.secondchancegarage.com/public/186.cfm
read this
viewtopic.php?f=44&t=464

http://www.centuryperformance.com/tunin ... g-148.html

http://garage.grumpysperformance.com/index.php?threads/fuel-pressure-drops.12123/#post-58318

 

[grumpyvette]

74elco for73SS POSTED THIS INFO BELOW ABOUT CONSTRUCTING A CHEAP{ SMOKE GENERATOR

HERES A METHOD I USE TO FIND VACUUM LEAKS

viewtopic.php?f=62&t=882&p=1390&hilit=+vacume#p1390

If anyone is interested in perfecting this, I found a way to create a cheap smoke machine like auto shops use to pump smoke into your intake to find vacuum leaks. Find the smoke, find the vacuum leak.

Instead of paying around $1000, you can build one for around $35 or so.

Begin with this:

http://www.harborfreight.com/cpi/ctaf/d ... mber=65297

Then buy this: AC Delco # 60G Diesel Glow plug. 8.99 at autozone.

Then, get some 3/8 copper tubing from home depot for @ $10:

Drill a 3/8 hole at the bottom of the can and then thread in the glow plug.

Drill out the spray nozzle at the top of the spray can with a 3/8 drill bit. Run a section of copper tube down to the bottom. Once you get it close, bend the copper tube to where the bottom of it is offset to the outer edges of the inside of the can, so that when you later screw the removable cap on it wont ram the copper tube directly into the glow plug.

Remove the cap with copper tube, take a hammer and smash the last 1/4" to 1/2" of the brass tube to make it virtually air tight. Now, take a very small drill bit, like about the thickness of a paper clip wire. Drill one hole just above the crimped end, so that when you blow air into the copper tube it will be bubbling up thru the baby oil.

Get baby oil! unscented is best, or just get straight mineral oil in the laxative section at your grocery store.

Remove the schrader valve from the valve on the side of the top of the aerosol can. Remove the spring and the schrader valve. now reverse it so and screw it in so the pipe is sticking outwards. Its not the same threads but close enough.

Thats pretty much it. I also used some plumbers putty to seal up the copper tube since I didn't get a perfect fit.

Create a heavy gauge power wire and ground wire with alligator clips at the end to hook up to a battery. Wire up the positive and negative, making sure the positive goes at the end of the glow plug, the negative you can put anywhere on the can just strip the paint off if you do that.

Now add mineral oil to some where like 1/2 way up the glow plug tip or even less than that. Definately don't completely submerge the glow tip or it wont glow too well.

Now I found that this glow plug is a self limiting current kind, so it can take a beating and not instantly blow out and kill itself. I find that if i heat the plug for about 10 seconds, then shake the can a little to splash some oil.

So the copper tube is the air input. Blowing just with your mouth produces about the right pressure to create some pretty good smoke.

I bought some 1/4 clear fish tank vinyl tubing, ten feet long from home depot in the plumbing section and a copper end as my smoke output hose. Plug this onto the output (old schrader valve). Power up the plug, and prepare for the can to get hot. That's usually when I let off the power to the plug.

Plug this into a vacuum port on your intake, like the supply hose to the brake booster or the hose to the vacuum advance.

You'll have to block off the carb top. I found a big permatex hand cleaner "bottle" fits perfectly over the top of the carburetor.

Look for the smoke , and you found your leak!

READ THIS
http://www.aa1car.com/library/vacleak.htm

Oh yea, forgot about the air source:

You can regulate an air spray nozzle down to 1 or 2 psi, fit a rubber hose over the end of the copper tube coming out of the top of the spray can, and fit your barbed air nozzle into the rubber hose.

I've read of other people using a cheap 12 volt emergency air compressor like you get for $10 at kmart. cut off the end of the output hose and just attach this setup to your copper hose. these things dont put out much cfm, but you'll have to experiment and may need a air regulator inline anyway.

watch this video

http://www.redlinedetection.com/video page.htm

 

[grumpyvette]

Can't figure this out. I have a carbureated 383 Gen 1 with 14,000 miles, a dual plane air gap manifold and a relatively new HEI distributor. It's a Holley street avenger with vacuum secondaries. No recent changes to the car and two weeks ago it was running great. Last week it started stumbling a bit and now it runs like crap. I'm missing a cylinder and can't figure out why.

I pulled the plugs and they were all nice light to dark tan except for the #8 cylinder which was white. With the engine running I pulled the plug wire; no change in rough idle but I could hear the spark jumping from the wire to the plug. Put it back and pulled other plug wires and the idle immediately degraded like you'd expect.

Did a physical inspection and resistance check on all the wires, everything looks fine and resistance is 125 - 175 ohms.

Pulled the distributor cap and looked inside. Even wear on all the contacts and no visible defects.

Checked for vacuum leaks and re-torqued the intake manifold to specifications. Nothing.

Replaced the #8 plug and drove about 10 miles. No change; pulled the plug and it looked as clean as it came out of the box, like not a single combustion event had occurred.

Pulled the valve cover and the adjustment was fine on the #8 valves and the rockers and push rods looked fine.

Ran a compression check on the #8 cylinder and found 150 psi.

Adjusted the carb floats and adjusted idle mixture; nothing.

Checked the timing, 14 deg; perfect. It's what the car likes with a 234/244 cam.

I'm really stumped. All the signs say that combustion is not occurring in the #8 cylinder. As is always said, it's either fuel or spark.

Any ideas?

Here's what I'm going to do tomorrow but I'm not optimistic:

1. Put a timing light on #8 plug wire and see if it triggers.
2. Pull opposite plug wire, number 5, and see if it smooths out and runs like a V6 indicating that yes, no combustion is happening in #8.
3. Try a new plug wire on #8.
4. Pull the valve cover and watch the valves while turning the engine by hand to confirm the valves are operating correctly.
5. Pull the carb and look for a bad gasket and other sources of vacuum leaks.
6. Pull the manifold; check the gasket and look for leaks.

Brad

SLOW DOWN AND DO SOME TESTING< THINK IT THRU! DON,T RUSH< THINK! TEST!
it sure sounds like a vacuum leak caused by a loose vacume hose or leaking intake gasket

viewtopic.php?f=44&t=882&p=1390&hilit=+propane+torch+leaks#p1390

http://garage.grumpysperformance.com/index.php?threads/vacuum-gauge-help.9453/#post-34623

its very common for the brake booster or the PVC line or connections,you hook to this fitting or the line it self leaking to cause that

 

[Grumpy]

I got asked to find out why one of the local guys could not get his 1986 corvette started after he had a recent cam upgrade,
I rather quickly checked for fuel pressure,
oil pressure trouble codes and spark at the plugs and pulse at the injectors,
but it became very obvious the intake runners were sucking a great deal of air through the areas the intake gaskets failed to properly seal,
once that was rectified the car started up and ran, and after checking the timing and a valve adjustment it ran even better.

you might find the next vacuum leak a bit faster with this method, as you can much more precisely direct the combustible gas flow, at any suspect leak location
(DON'T LIGHT IT) just SLIGHTLY open the valve so its allowing gas to flow at a low volume,start the engine and let it idle at the lowest speed you can then place the tip of the UNLIT torch at any suspected vacuum leak and listen for the rpms to increase and watch the tachometer, gas flowing into a vacuum leak will increase engine speed.
look for loose or missing vacuum hoses, cracked or broken power brake connections, emissions system hoses that are loose, vacuum connections to the trans or ignition, loose connectors missing or loose bolts cracked hoses missing accessory connections etc.
naturally this only locates leaks to the outside, and its possible for the intake to suck air from the lifter gallery, so that also needs to be checked if everything else seems to be ok.

http://garage.grumpysperformance.co...m-with-how-your-c4-corvette-runs-badly.15212/

http://garage.grumpysperformance.co...rger-intake-runners-l98-tpi.13785/#post-70716

http://garage.grumpysperformance.co...-stock-tpi-engine-components.1509/#post-74581

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-66935

http://garage.grumpysperformance.com/index.php?threads/ideal-tpi-build.12203/#post-59272

http://garage.grumpysperformance.com/index.php?threads/can-you-get-there-with-tpi.10494/#post-44299