350 timing using vacuum gauge

[bucata206]

I talked with my old mechanic today and he suggested I check the timing using a vacuum pressure gauge (had issues with the timing marker being off and truck dying when i get close.) He said it may be more accurate since the harmonic balancer can slip. Has anyone done their timing this way and would be willing to explain how to do it?

He told me to hook the gauge up to the vacuum line you disconnect from the distributor, but a couple pages I read said to hook it up elsewhere so now I'm confused.

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[74 Shortbed]

Only accurate way is with a light, but first you need to find absolute TDC, easiest way is with a piston stop, you can buy them or like I do make one out of a junk spark plug..
Screw the piston stop into the #1 spark plug hole by hand, and then slowly rotate the crankshaft by hand until the piston come up against the stop. Mark your balancer with a marker, and then slowly rotate the crankshaft by hand in the opposite direction until you come up against the stop again. Mark your balancer again. Measure the distance between the two marks and divide by 2. This is your TDC, now you'll get an accurate reading with the light.

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[bucata206]

I'll probably try this after the vacuum route.

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[custodian]

I have used the vacuum for setting the timing on a carbed 350. The harmonic balancer had slipped off the original mark. Put the vacuum hose on a direct vacuum source to the manifold. I set it at 17hg. After I installed the new balancer, I used a timing light.

 

[Rusty Nail]

Lolwut?
Hook the vacuum gauge to the vacuum port behind the carb, in the intake..
Loosen the hold down and adjust timing until you see the highest number you can get.
Fine tune a SMIDGEN either way blipping the throttle and lock it down.
It's not hard. You're after a big number.

If you ever manage it with a light, it'll be very close to your max vacuum adjustment. If it drives okay, don't worry about it too much. You need might change it ten times before it "feels right".

 

[bucata206]

Perfect thanks guys! Sounds pretty simple!