Too much Vacuum Advance - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Zeke's Garage** · 11-21-2013, 11:55 AM

If your 307 was like the one I pulled out of my Chevelle wagon, it probably had the nylon teeth coating on the cam gear of the timing set, and they might all now be in your oil pan, causing some crazy timing issues.

Otherwise hook up a vacuum gauge and check for any jumps and variations in the vacuum. The only way the vacuum will drop in the manifold, is if something allows outside air in, like opening the throttle, or a significant leak somewhere. So block off ALL vacuum sources while you're troubleshooting.. power brakes, trans mod valve, vacuum advance on the distributor. If you're still seeing drops and jumps, it's time to check your valve train and verify your static timing.

Good luck with it!

Shawn

airdale94 · 11-21-2013, 08:55 PM

Quote:

Originally Posted by Zeke's Garage

If your 307 was like the one I pulled out of my Chevelle wagon, it probably had the nylon teeth coating on the cam gear of the timing set, and they might all now be in your oil pan, causing some crazy timing issues.

Good luck with it!

Shawn

Good call!

69GMCLonghorn · 11-23-2013, 07:22 PM

Well, my plans of delving into this problem a little further were derailed today. I started driving and suddenly had SMOKE billowing out from under the dash! After a few minutes of being parked, it was OK and I made it home. But nothing screams "GET THE F*** OUT NOW" like a cab full of smoke! Time to start tracing wires and see what was cooking. Whatever it was, it was pretty serious.

11-21-2013, 11:55 AM	#1
Zeke's Garage Senior Member Join Date: Feb 2010 Location: Kennesaw, GA Posts: 288	Re: Too much Vacuum Advance If your 307 was like the one I pulled out of my Chevelle wagon, it probably had the nylon teeth coating on the cam gear of the timing set, and they might all now be in your oil pan, causing some crazy timing issues. Otherwise hook up a vacuum gauge and check for any jumps and variations in the vacuum. The only way the vacuum will drop in the manifold, is if something allows outside air in, like opening the throttle, or a significant leak somewhere. So block off ALL vacuum sources while you're troubleshooting.. power brakes, trans mod valve, vacuum advance on the distributor. If you're still seeing drops and jumps, it's time to check your valve train and verify your static timing. Good luck with it! Shawn __________________ -- '67 Chevy Stepside 250 Inline 6 Megasquirt Fuel Injection T5 5 speed conversion Ferric Oxide impregnation throughout

11-23-2013, 07:22 PM	#3
69GMCLonghorn Registered User Join Date: Dec 2006 Location: Porter Ranch, CA Posts: 978	Re: Too much Vacuum Advance Well, my plans of delving into this problem a little further were derailed today. I started driving and suddenly had SMOKE billowing out from under the dash! After a few minutes of being parked, it was OK and I made it home. But nothing screams "GET THE F*** OUT NOW" like a cab full of smoke! Time to start tracing wires and see what was cooking. Whatever it was, it was pretty serious.



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