First 4 banger, a 29 roadster having problems.

[George Miller]

Originally Posted by Tomy Turbos

I'm puzzled by the 'mis-wired' situation as I always thought it was pretty much impossible to do on this motor, provided that these are stock/original wires.

The wires are equal-length and the Cap's internal routing is such that even if it was not indexed to the Dizzy's base, 180 degrees would produce the same results. And yes, even though the Firing Order is 1243, the visual layout is 1234.

He might have been running a B cap. That use spark plug wires like later cars.

[Russ/40]

If it has backfired, the power valve in the carb is most likely blown, which will make it run much too rich.

[Ratatat]

Originally Posted by Tomy Turbos

I'm puzzled by the 'mis-wired' situation as I always thought it was pretty much impossible to do on this motor, provided that these are stock/original wires.

The wires are equal-length and the Cap's internal routing is such that even if it was not indexed to the Dizzy's base, 180 degrees would produce the same results. And yes, even though the Firing Order is 1243, the visual layout is 1234.

It has the later style distributor cap which I guess is the B cap.

[Ratatat]

Originally Posted by Russ/40

If it has backfired, the power valve in the carb is most likely blown, which will make it run much too rich.

Good observation. I never thought of that, but than again I am definitely no mechanic.

[Ratatat]

Originally Posted by Wilbur

Can you post a picture of the car? I was at the race this fall and shot a bunch of video clips . I would be curious to see how bad she smoked during the race . He may have run the crap of it there and then dumped it onto you. The race was cool, but seemed hellish abusive on the old girls. Some of the non-local idiots actually ran their cars along the edge of the salt water, spraying that corrosive nectar all over the car. I wouldn't be anxious to own a car that was in that race... Unless you plan on racing and getting inside the engine on a regular basis. Blue smoke just means that oil is getting into the combustion chamber, simple as that. Either a broken ring or a beat valve guide. Step number one is a compression test. Good luck!

Blue with black hood #58

[Y-Blockhead]

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A compression test is only going to tell you if your compression rings are fubar or not. It will tell you nothing on the condition of the oil rings...

[1955cj5]

Looks like it at 4:37 into the video

https://www.youtube.com/watch?v=8YPL16bxziM

[Tomy Turbos]

Originally Posted by Ratatat

It has the later style distributor cap which I guess is the B cap.

Copy that.

FWIW, I would not do a Compression test as a first step. (More on this point a bit later)

Backfiring has a schedule of probable causes. Despite what you may have been told, first among these is over-advanced Timing. Next is Mixture, and later followed by possible Valve problems. Last on the list is inadequate cooling.

The fact that the car's behavior changed under operation is making my Spidey-Sense tingle toward it being operator error. One has to realize that these motors are 'tuned' in real-time by the driver, which is totally unlike a post '96 or even a post '80 engine. Many of the old cars that come my way get fixed by putting the base adjustments back where they are supposed to be and then training the owner on how to drive it correctly.

It is unfortunate that basic IC Gas Engine tech is no longer taught. These days it's all 'Read the Code; point at the Part and blame it'. (EG: Code P1110 probably means the vacuum hose is bad, NOT the Turbo Bypass Valve).

Sorry if this seems like a rant but it is just far too often that I see this approach taken by a person who doesn't know why the thing worked in the first place, did something, had a buddy do something else and finally brings it to me to figure out what's REALLY going on.

From where I sit, the only way Compression can cause a backfire is because someone altered one of the above as a method to compensate for poor compression, whether real or perceived.

As far as checking compression goes, there is a relatively new device called a 'Leak-Down Tester', which I always use BEFORE checking compression. The leak-down test often makes the compression test unnecessary except as means of verification.

[700rpm]

Originally Posted by Y-Blockhead

A compression test is only going to tell you if your compression rings are fubar or not. It will tell you nothing on the condition of the oil rings...

Fubar! I haven't heard that since I was in the Navy!

[Wilbur]

It seems the backfire has been elevated to something big here. It's not. The blue smoke is. Backfire is a matter of external tuning and mal-adjustment, related to timing and carb adjustment... Unless an intake valve is chipped and allowing the explosion within the cylinder to ignite gas vapors within the intake manifold. Which, by the way, a simple compression test would help to determine. The smoke is where the money usually goes. Just sayin.

[Ratatat]

The backfiring has been eliminated when I put the spark plug wires in the proper order. When I received the car the #4 and #3 spark plug wires were reversed. There is no more back firing.

[Ratatat]

Originally Posted by 1955cj5

Looks like it at 4:37 into the video

https://www.youtube.com/watch?v=8YPL16bxziM

Yes that's the car and from looking at the video it appears there is some smoke off the line but it appears to clear up after about 30 yds.