Motor Backfires Thru Exhaust When Trying To Start

[Jim Coleman]

The motor has never run before, it came with the car in a crate.

Thanks,

Jim

[Jim Coleman]

Well, I finally got it where it's trying to start again if I turn the distributor to the right. Something is off.
but when I moved the distributor to point at #1, it just fell in place. Thought for sure I had it.

Also, when I checked the spark it looked a little weak to me. The distributor is a brand new GM HEI made by Jegs and
it came with the motor.

I may look in to a hotter coil.
Thanks,

Jim

[patrickt]

Originally Posted by Gaz64

When did the engine run last?

Just prior to the rebuild.

[blykins]

Even if you figure it out, buy another distributor in the near future.

There’s nothing junkier than Procomp. It’s a wonder the rotor even spins on the thing.

If you don’t figure it out, borrow a distributor to try.

[Jim Coleman]

The distributor has a Jegs part number, but I believe in using what you have, so I'll continue using it no matter who made it.

I did notice that after I charged the battery the spark looked hotter.

I was just about ready to pull the water pump, drop the pan and take off the timing cover and check the timing marks --- but thought I'd give it one more shot first at trying to reset the distributor.

What I did was pull the #1 plug and put my finger in the spark plug hole, turned it over until I felt compression -- then turned the motor over until it hit TDC. After that, I got the distributor pointed at #1, and it just fell right in place. Thought for sure I had it,
and it's trying hard to start if the distributor is rotated to the right.

I was hoping someone could tell me the best way to get it to where it will start.
Thanks,

Jim

[Gaz64]

I would verify the distributor can trigger the coil, by spinning the distributor by hand to see what the spark quality is like.

Need the coil lead set up with a 1/2 inch gap to ground, with the ignition on.

Then set the engine at 10-15 BTDC, set the rotor in line with NO.1, noting the reluctor trigger etc.

We are also trying to start an engine that has not run since it was built in the 80s, so some of the valves could be stuck in the guides etc.

Gary

[blykins]

Originally Posted by Jim Coleman

I'm not even sure it's a new ProComp distributor, but I believe in using what you have, so I'll continue using it no matter who made it.

I did notice that after I charged the battery the spark looked hotter.

I was just about ready to pull the water pump, drop the pan and take off the timing cover and check the timing marks --- but thought I'd give it one more shot first at trying to reset the distributor.

What I did was pull the #1 plug and put my finger in the spark plug hole, turned it over until I felt compression -- then turned the motor over until it hit TDC. After that, I got the distributor pointed at #1, and it just fell right in place. Thought for sure I had it,
and it's trying hard to start if the distributor is rotated to the right.

I was hoping someone could tell me the best way to get it to where it will start.
Thanks,

Jim

A Chevy distributor won't generally fall into place like a Ford distributor will. The gears are made differently.

If you follow my instructions from my first post, I will guarantee that it will start. If the distributor doesn't fall into place then you get the rotor pointed in the correct direction, hold down on the distributor, and roll the engine over until the distributor falls down. The distributor gear is made differently plus the oil pump shaft isn't hex, it will only engage in basically two positions, one 180° from the other.

[olddog]

Run a compression check on all cylinders. That's easier than pulling the timing cover.

As someone before me suggested, the valves may be too tight, or a few could be stuck.

If you have good compression, the cam to crank timing is likely close enough to run, and the valves should be loose enough to start.

[Jim Coleman]

Read this online, I think this is where the problem is - I took it apart: When you install a cam or timing chain.. You install it so dot is over dot Cam gear dot at 6:00, crank gear at 12:00 This is NOT the correct placement for ignition timing.. This puts #6 piston at TDC compression stroke. You would need to rotate crank 360*, to get #1 on compression stroke.. Now the crank gear dot will be at 12:00 again, but cam turns at half the speed of crank, so cam gear will be a 12:00 now as well This is where you can set ignition timing now

Is this correct? Excuse my ignorance on this, I just don't know how to do it. Does this mean it turns over twice to get to 360 degrees? Clockwise?

Thanks,

Jim

[Gaz64]

Originally Posted by Jim Coleman

Read this online, I think this is where the problem is - I took it apart: When you install a cam or timing chain.. You install it so dot is over dot Cam gear dot at 6:00, crank gear at 12:00 This is NOT the correct placement for ignition timing.. This puts #6 piston at TDC compression stroke. You would need to rotate crank 360*, to get #1 on compression stroke.. Now the crank gear dot will be at 12:00 again, but cam turns at half the speed of crank, so cam gear will be a 12:00 now as well This is where you can set ignition timing now

Is this correct? Excuse my ignorance on this, I just don't know how to do it. Does this mean it turns over twice to get to 360 degrees? Clockwise?

Thanks,

Jim

4 stroke engine, 720 degrees to complete 4 strokes.
Camshaft turns once 360 degrees, to crankshaft of 720 degrees.

I thought you had this Jim, when you pulled NO.1 spark plug.

Turn the engine BY HAND until you feel compression pressure under your thumb over the spark plug hole, then turn the engine until you are in the 10-30 BTDC range.

At this point, the distributor rotor needs to face the NO. 1 terminal on the cap.

Gary

[ERA 626]

sounds like you may have a wire crossed, double check the firing order and the installation of the spark plug wires... Then when you get it running right, pull it out and install an FE

[Jim Coleman]

OK, in checking the balancer, I see there are 4 separate lines with numbered marks. I need to know which line to use as there are
four choices. Got a feeling that I was using the wrong one.


5/8

6/1

2/3

7/4

Is Top Dead Center 6/1 ? That seems to center with the keyway.

Thanks,

Jim

[Jim Coleman]

Has anyone seen this on a 350 Chevy balancer ?

I can't find any information on it anywhere.

Thanks,

Jim

[bobcowan]

Aftermarket balancers often have multiple timing marks, because there are a variety of pointers available, both aftermarket and stock.

Remove all of the spark plugs. Put your thumb/finger over the #1 hole, and turn the engine over with a wrench/handle. You'll feel when that cylinder is on the compression stroke. When it stops pushing air, you're at the top of the compression stroke. Then you can look at your timing pointer, and tell which set of marks you're supposed to use.

If you have a hand made or adjustable pointer, you'll have to get fancy with a degree wheel and a piston stop.

[patrickt]

Follow my instructions on this post: How big an issue are slipping balancers?
and it will work every time to find TDC. Just remember to remove your piston stop before you try and start the car.

[Gaz64]

Originally Posted by Jim Coleman

OK, in checking the balancer, I see there are 4 separate lines with numbered marks. I need to know which line to use as there are
four choices. Got a feeling that I was using the wrong one.


5/8

6/1

2/3

7/4

Is Top Dead Center 6/1 ? That seems to center with the keyway.

Thanks,

Jim

A degreed balancer for a small block in firing order, the first lap is 1872, the second lap is 6543, to give 18726543.

1 and 6 are at TDC at the same time, when 1 is at compression TDC, 6 is at valve overlap,(end of exhaust, beginning of intake).
Same for the pairings, 8 and 5, 7 and 4, and 2 and 3.

I hope you are reading all of this Jim, since many boys have attempted to help you here.
I have seen how to find TDC compression a few times in this thread.

Gary

[Jim Coleman]

Here's what patrickt said to do using a piston stop:


1) Put a pointer, any pointer, aimed at an easily reached spot on your dampner.

2) Put a stick in your #1 spark plug hole and using your wrench on the crank bolt, rotate your engine until you are just past TDC (piston is heading back down the hole).

3) Remove your stick and insert your piston stop and screw the little screw part down until it touches the top of your piston and goes no further.

3) Put timing tape on your balancer with the zero degree mark aimed at your make shift pointer.

4) Rotate the engine in the normal direction all the way around until it stops again because of the piston stop. Note the degree that the pointer is aimed at (for instance, 24 degrees). Divide that number by two (12 degrees).

5) Remove your piston stop and rotate the engine a little bit farther to that number (in this example, 12 degrees).

6) You are now at TDC.

I followed this procedure and TDC shows to be within 1/2" of the 5 - 8 marker on the balancer. I hope I did it correctly as I am extremely not knowledgeable on all this stuff.

Thanks for all your help Gary, I know it must be exasperating to you that I'm having trouble grasping this, and it doesn't help that I injured L-3 in my spine and am taking large doses of pain killer...…….

Jim

[patrickt]

Originally Posted by Jim Coleman

Here's what patrickt said to do using a piston stop:


1) Put a pointer, any pointer, aimed at an easily reached spot on your dampner.

2) Put a stick in your #1 spark plug hole and using your wrench on the crank bolt, rotate your engine until you are just past TDC (piston is heading back down the hole).

3) Remove your stick and insert your piston stop and screw the little screw part down until it touches the top of your piston and goes no further.

3) Put timing tape on your balancer with the zero degree mark aimed at your make shift pointer.

4) Rotate the engine in the normal direction all the way around until it stops again because of the piston stop. Note the degree that the pointer is aimed at (for instance, 24 degrees). Divide that number by two (12 degrees).

5) Remove your piston stop and rotate the engine a little bit farther to that number (in this example, 12 degrees).

6) You are now at TDC.

I followed this procedure and TDC shows to be within 1/2" of the 5 - 8 marker on the balancer. I hope I did it correctly as I am extremely not knowledgeable on all this stuff.

Thanks for all your help Gary, I know it must be exasperating to you that I'm having trouble grasping this, and it doesn't help that I injured L-3 in my spine and am taking large doses of pain killer...…….

Jim

OK, now that you've found TDC. How close are you when your rotor is pointing at #1, to, say, 15 to 20 degrees BTDC?

[Jim Coleman]

I haven't gotten to the rotor yet, back is acting up maybe tomorrow.

Thanks,

Jim

[patrickt]

Originally Posted by Jim Coleman

I haven't gotten to the rotor yet, back is acting up maybe tomorrow.

Thanks,

Jim

Alright, take two pills and call Gaz in the morning.