Timing my 72

[Jfwh1tt]

Howdy! I'm new to the forums here. I've just been looking and using this for lots of research. I am the proud new owner of 72 LWB fleetside. It will certainly be a project. I looks good now, but there are a lot of hidden things to clean up. It runs OK at idle, but really needs to be fine tuned, which is why I'm here. The truck has a 350, but it is not the original motor, or so I've been told. Correcting the timing would be simple, but the last dude who put the motor in left the timing indicator off the engine. While researching this, I found someone mentioned another method. Have you guys ever heard of this, and is it an acceptable way to set the timing?

"There is a different way to time your engine, and that is with a vacuum gauge. Here is how you do it, find the vacuum port that has vacuum at all times(that is called manifold vacuum) the other is ported vacuum which only has vacuum after you start to open the thottle plates, anyway, put a vacuum gauge on the manifold vacuum and plug the vacuum hose going to the vacuum advance. start the engine and let it idle and ck the vacuum, now turn the distributor either way a very small amount until your vacuum reading changes, if vacuum goes down on the gauge turn distributor other way. Keep turning the distributor until you get max vacuum and adjust the carb idle as you do this to keep rpm around 800-900 max. The goal is to get the highest vacuum reading as possible. If the timing is advance to far vacuum will be low also if retarded to much vacuum will be low. If the engine pings on acceleration after this exercise then retard the timing until it stops. It is little time consuming this way but you will get the maximum timing you can depending on your compression ratio, cam and fuel quality."

Thanks,
John

[GASoline71]

Buy a timing light if you don't have one. The vacuum method will get you close... but not the best way.

Do you have any idea what year engine is in the truck? On later model engines (mid 70's) the water pump was the long style, and the timing tab (pointer) was basically behind the water pump.

So depending on where TDC is on the number on cylinder, will depend on where you need to set your timing tab (pointer). Find TDC for #1 cylinder. If the mark on the balancer is just off to the drivers side, you can buy an aftermarket timing tab, and mount it to the front of the engine with a couple of the timing cover bolts.

Gary

[truckster]

It's backwards from the way I've always done it, and the way most mechanics do it, I believe. You use a timing light to set the timing, and use the vacuum to adjust carburetion.

I'd go to the auto parts store or the wrecking yard and get a timing pointer.

[Jfwh1tt]

Thanks guys. Feel kinda dumb. I was referencing the timing pointer from my father in laws long block ford motor. After checking out some of your pictures on here I found mine. Kinda hidden dead center on the clock just above my balancer. Now that I've found it, what is the stock timing supposed to be set to? I know this is not the stock motor, but I don't know what year truck it's from. Everything on it is stock with the exception of the Holley 80457-3 carb. I've looked around the forums and haven't found much (poor searching skills maybe?) What should the idle be, and where should timing be set at?

Thanks y'all!

[GASoline71]

Try it around 8 degrees BTDC. If it's an auto it should Idle around 700 to 750 in Neutral, and around 500 to 550 with the transmission in Drive with foot on the brake.

Standard transmission can be around 500 to 550 in Neutral.

Gary

[truckster]

I agree, 8 degrees BTDC, but also make sure the vacuum advance is disconnected at the distributor and blocked so there's not a vacuum leak.

[Jfwh1tt]

Sorry, I know it's a noob question, but BTDC - is that before top dead center, or behind?
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[72chevyk10]

btdc is, before top dead center. though id add i usually run my truck at 12*btdc. responds a whole lot better there