Help with a vacuum leak (possibly on cold engine)

[SDMAN1981]

Sorry if this sounds confusing, I will try and explain the best I can.

This is a 69 el camino 350 with a Holley 600 carb.

OK the last post I had was using a cigar to check for vacuum leaks, so I did today when the engine was 100% cold. I blew smoke in the intake and some smoke came out on two places; the throttle linkage on the drivers side and the gasket on the passenger side were the gasket sits in between the carb and intake manifold.

Now here comes the weird part… when I start the engine cold it will run a little crappy and on the vacuum gauge the needle jumps between 14 and 13Hg and rise to about 16hg as engine gets hot and engine will start to smooth out, so then I turned off the engine and blew more smoke into intake and got no smoke in those two spots I mentioned before. When the engine was cold I also sprayed some carb cleaner where the smoke was coming from and it dropped RPM too, but when I did it at operating temp there was no RPM droppage at all.

What could it be? It can’t be intake or head gaskets because I just had those replaced not to long ago.

Thanks.

Here are the two pictures where I seen smoke, I also drew an arrow pointing to the POSSIBLE leak spots.

Attachments:

• leak1.jpg
• leak2.jpg

Topic

[Tom]

My guess, it is an aluminum carburetor. As it heats up, it expands, and that seals up the leaks.

For the gasket leak, I would say replace the gasket with a new one, make certain the mating surfaces on the carb and intake are clean, smooth, with no pitting, rust, or corrosion, and make certain to torque the carb down evenly, and properly.

For the throttle blade shaft, I think that a leak there requires having the carb rebuilt. I don’t believe there is any other way to address that leak.

[Bill]

It`s normal to have a small leak at the throttle shafts but the gasket should not leak. Everything expands when heated up so the leaks stop.

I would remove the carburetor and obtain a new gasket. Make sure you tell em what intake manifold is on it if it`s not the original. Holley has more configurations of gaskets than I have pairs of socks.

[SDMAN1981]

I did buy a Holley Renew kit a few months ago so I will use the base gasket out of that.

Also, if the carb is in fact warped how much would a machine shop normally charge to use their Straight Edge on it, I really don’t want to fork out $75 for one.

[Chris cagno]

You defiantly need a new gasket it may have been torqued wrong the leak in the linkage is normal for older carb engines a machine shop would charge $40 max for a resurface

[EricTheCarGuy]

Metal expands as it warms up and the small leaks you mention could seal up when warm. You might be able to adjust your choke to compensate. Perhaps make it a little tighter. As for it being warped, it could be the carburetor, the intake manifold, or too much torque on the fasteners that hold the carburetor down.

[Author]

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