1966-67 HCS %^&#*! wont start when hot

[robert campbell]

Dave,
By the way 10 pounds of vacuum at idle is not good. We need to address that. Call me. Inches of vacuum are not affected that much at altitude. A car the has 16 to 18 inches of vacuum at sea level should have around the same at 5,000 feet.

Main jetting is affected greatly by altitude. As you have less oxygen, you need to lean down the main jets to compensate.

Rob

 

[franklinair]

10" MAP is not good. 15" minimum.
Vacuum leak? How smooth is the idle? Lope?
My fresh rebuild had low vacuum. Found a vacuum leak with the carb spacer gasket.

Neil

 

[p51]

Shot in the dark(?): Low vacuum + overheating... could it be an exhaust restriction?

"Engine Overheating Causes

*Excessive exhaust backpressure -- A clogged catalytic converter will restrict the flow of exhaust and cause heat to back up in the engine. Other causes include a crushed exhaust pipe or a collapsed double wall pipe. Check intake vacuum at idle. If intake vacuum reads low and continues to drop, inspect the exhaust system."

http://www.aa1car.com/library/overheat.htm

 

[66hcs-conv]

Shot in the dark(?): Low vacuum + overheating... could it be an exhaust restriction?


*Excessive exhaust backpressure -- A clogged catalytic converter will restrict the flow of exhaust and cause heat to back up in the engine. Other causes include a crushed exhaust pipe or a collapsed double wall pipe. Check intake vacuum at idle. If intake vacuum reads low and continues to drop, inspect the exhaust system."



Well, I don't have a catalytic converter on the '66, but I will sure check out the exhaust. Shoot, I've been sucking on the vacuum advance unit, I might as well be blow'in on the exhaust!

Thanks, Dave

 

[Mosesatm]

Dave,
Do you have an adjustable timing light?

 

[66hcs-conv]

Dave,
Do you have an adjustable timing light?

I do not.

What do those do? I am way out of date/touch.

dave

 

[Mosesatm]

It has a few advantages over a stationary light.

If you have a balancer that has faint markings all you do with the adjustable timing light is mark TDC then turn the knob on the light to whatever advance you want. If you want to set your timing at 6 degrees TDC will point at the pointer when the light is set at 6 degrees. No more trying to figure out exactly where 6 degrees is, and 12 degrees, etc.

It also lets you easily figure out your maximum advance. For example, if you want your timing to go from 12 degrees to 36 degrees just adjust the light at 12 degrees, set your initial timing, reinstall the vacuum hose, then adjust the light to 36 degrees, rev the engine, and watch your TDC mark move towards the pointer. If it goes past the pointer you're running more than 36 degrees advance. If it doesn't get to the pointer you're running less than 36 degrees. In either situation just turn the knob on the light until the marks line up, then look at the light setting to see the max advance.

Another use is getting a handle on how quickly your advance kicks in. If you place a tach on the fender you can set the advance on the light to whatever you want, rev the engine, and when the timing marks line up take a look at the tach. For example, if the engine doesn't hit 20 degrees until 3000 rpm your advance isn't kicking in fast enough, or you have a leak.

I'm sure there are other ways to play with it but a better mechanic will need to chime in on those.

 

[66hcs-conv]

Thanks Arlie, I appreciate the information