sheltonoil

Not sure my timing mark is right bc it seemed so far off (maybe 4" above the tdc mark) , but I went ahead and set it at 10 btdc and although it seemed to run smoother after, it still has the same problem which is after it warms up it struggles when re-starting. I've gone through all the Edelbrock procedures to set the idle mixture twice after setting the timing. I wanted to check the timing mark again, and it just so happened that after the last time I started it the engine had stopped with the timing mark precisely at 10 btdc. I took the number one plug out to check where the piston was, and it seemed VERY close to the top. If it was short of tdc, it couldn't have been by more than .5". Could 10 degrees of timing correlate to such a small amount of linear movement?

oldcutlass

I'm assuming its a 350? What type of ignition is on the engine, points, points replacement, HEI? What exactly does struggling to restart hot mean? Does it try and kick back, crank slowly and stop and then start cranking again?

sheltonoil

Yes, I should've been more specific. It's a 350, crane electric ignition. It starts instantly when cold and runs smoothly on fast idle and then on regular idle. Vacuum is hooked up. If you turn it off after driving for about 15 mins and restart it, it struggles for about five seconds, then starts but runs roughly. Note that it doesn't run roughly nor does the hot light come on BEFORE you turn it off.

oldcutlass

This is a common problem with these older cars. Set your timing where its supposed to be. Don't pump the gas when your trying to start it hot, just hold the gas peddle down about 1/4 way and turn the key to start.

MDchanic

Absolutely not.

The linear movement of the piston in the cylinder is a sinusoidal function.



See:

http://www.intmath.com/cg3/curve-sha...ton-applet.php

and

https://en.wikipedia.org/wiki/Piston_motion_equations

- Eric

joe_padavano

The term Eric is looking for is Sine Curve.

olds 307 and 403

Make sure that POS Edelbrock carb is functioning correctly. You also need to find out what timing curve is in your distributor. Is it Crane parts in a factory distributor?

VC455

As Eric said, definitely yes. And if you look at Joe's graph, imagine the vertical part of the graph from -1 to 1 represents the stroke of the piston. Imagine the horizontal part represents degrees of crankshaft movement. You will see at 90° on the horizontal part of the graph that the piston is at the top of the stroke. Now look at 100° (10° away from the top of the stroke), notice there is almost no movement down. If you looked in through the spark plug opening, you would miss such a small movement.

MDchanic

Which is why we are always telling people who need to find TDC to use a dial indicator (difficult to set up) or a spark-plug-hole TDC-checker (easier), because just sticking a screwdriver or a pencil in there and turning it till it's at the "top" is no good.

- Eric

TripDeuces

Since it's hard starting only when hot I'll go to the two main issues with electronics on cars.
1) Is it getting a full 12v at all times like Crane specifies?
2) Are your grounds adequate?

sheltonoil

Awesome info, guys. I'm sure a search will describe the spark plug hole TDC checker, but if I can't find it I'll follow up. Thanks all.

TripDeuces

If you're handy and can weld you can make a simple one with an old spark plug, a nut and threaded rod or simply a non-adjustable one with an old spark plug and a steel rod.

Fun71

No welding necessary. Just remove the ceramic portion of the spark plug, thread the inside of the plug body with a tap, and insert a long bolt. Instant adjustable TDC tool.