I just finished reassembling my motor after having the heads off for a porting job. Whenever I try to start it either it just turns over, or if I adjust my timing **** (MSD timing adjuster) one way or the other I get smoke out the carb and engine run on. Does this mean my timing is just WAY off or do I possibly have the distributor off one gear too far?

When I stabbed the distributor in, I had the motor turned to TDC on piston one. I backed the motor up until it was at 12 deg. before TDC on the timing tab (initial timing). I then stabbed and restabbed the distributor until I had the rotor pointing at my number one spark plug location on the distributor cap. I figured this way I could just start it right up when I got it all reassembled.

Is there a way to tell if my timing is too advanced or too retarded? Does the smoke out of the carb indicate things one way or another? Any recommendations?

Thanks

 

It sounds like the way you put your distributor in should get you pretty close. One thing though is when the piston was at TDC was it on compression or overlap? The piston comes to TDC twice for every time it fires. If you weren't thinking about that or checking, your distributor could be off 180 degrees.

Just a thought.

Dan

 

I pulled the passenger side valve cover and used the finger in the spark plug hole trick while watching the rockers to find top dead center for #4 (kept turning the motor over slowly by hand until no more air came out of the hole). I then pulled the distributor cap and the rotor was just barely past the #4 wire. This all looked correct to me so I put it all back together. I then tried to start it again but no luck - only smoke out the carb.

This lead to me to double check the ignition devices. With the MSD 6AL, you can short the leads of the magnetic pickup wire and it should spark from the coil wire if the ignition is in the on position. I tried this and got no spark. However, when I turned off the ignition, I would get a huge spark w/ a squelch noise.

When I had the top end apart, I relocated the MSD 6AL control box to inside the cabin and also installed the MSD adjustable retard module. From visual inspection, all the wire connections are routed properly and I'm confident all my solder joints are solid. I didn't have time tonight to bypass the retard module but I'll try that tomorrow. Besides that, any other ideas?

I'm curious as to why the motor would backfire through the carb in this condition. I wonder if ignition is sparking but at some random timing. It doesn't seem to make much sense.

Thanks for any ideas.

 

You didn't say, but I am assuming you have timed it after dropping the dist. in? Also, when static timing an engine you should not rotate the engine backwards. If the timing chain has any slack (and almost all do if they have any miles at all) it will be induced in the timing. You should note TDC and then rotate the engine forward stopping @12 degrees BTDC. Then install the dist. Being one tooth off only affects the final correct timing position. This is assuming you have enough clearance to adjust the dist. to achieve the correct timing. :smash:

 

You didn't mention what type of distributor you have, but I assume it is not the original HEI system. If it isn't, did you run a wire from the starter relay to the coil? The original HEI system did not require this wire, but when you replace the OEM distributor with some aftermarket items, you need to make sure the new stuff gets a full 12 volts, while cranking. Without the wire, the motor can start most of the time, but when hard starting, like it is now, you will not get a solid 12 volts to the coil, while cranking. Then, when you start to release the ignition switch from the cranking position, you will get a 12 volt surge to the ignition system and it will give you the proper energy to cause a spark. This could be what you are experiencing with the large spark you described.

Provided you have proper fuel flow. You really don't need to get the distributor exactly on, as close will allow it to at least start.

Is it too hard to find the compression stroke on the #1 cylinder? You would be sure you are in the ballpark with the timing, if you use the #1 cylinder. Also, recheck your wires. I have crossed them before and did not realize it.

I run a MSD magnetic trigger distributor, with a 6AL and timing advance/retard module. Although you feel the system is wired right, you are not able to confirm it works properly, as you did not run it prior to the work, I would also recommend taking it out of the system. Also, you might check your wire grounds from the 6AL to the motor or chassis, if you haven't already. You didn't do any welding on the car, while the MSD was still connected, did you?

Just some things to check.

 

Thanks for the ideas. I'm waiting for it to stop raining here so I can start working on the vette again. My garage is too full of junk for the car to fit into. :(

 

Well, I identified the advance/retard module as the culprit keeping it from sparking properly and bypassed it. The motor sounds like it wants to start now but it started raining before I could finishing adjusting the distributor back and forth.

Also, I was trying to get an idea of where the timing was so I hooked up a timing light. However, I got no light at all. I tested the light on my other vehicle and it worked fine. Is there some problem w/ timing lights and MSD ignitions? I have an MSD 6AL and MSD Blaster coil if it makes a difference.

Thanks

 

Good deal on your troubleshooting. I have the same setup and have no problem with my light. I connect the power for my light directly to the alternator terminal and ground on the alternator bracket.

 

After eliminating the MSD adjustible retard module (seems to be defective), I finally got it started. It was sort of a strange ordeal. With the timing where I thought it should be it backfired some and didn't start. Then I retarded it a good bit and it sounded like it wanted to start but wouldn't. I retarded it some more and got it to fire up a little but it wouldn't keep running. I slowly had to advance the timing all the way back to where I had it in the first place step by step and then it worked fine. Strange but worked.

Thanks for all the input!