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Piston arrow wrong direction? One cylinder is dead.
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Radar
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PostPosted: Wed Oct 06, 2010 8:47 am    Post subject: Piston arrow wrong direction? One cylinder is dead. Reply with quote

All,

Has anyone ever installed a Type 1 piston with the arrow facing the
wrong direction? If so, how did the engine react?
Will that cylinder(s) fire at all?
Does it run....but very roughly?

I have one cylinder that is DOA.
It has compression, spark and fuel but will not light off.
Tried 3 different spark plug wires. I can see the spark at the plug,
but nothing.

New Bosch points, condenser, distributor cap, coil, plugs....nothing.

The piston is the only variable that I can think of and I'm 99.9% sure
that it's right. I'm just out of ideas.

Thanks for any thoughts/suggestions,
Radar
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Dale M.
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PostPosted: Wed Oct 06, 2010 9:42 am    Post subject: Reply with quote

Should not make a lot of difference.... Only reason for arrow it because wrist pin is offset a few thousands to one side to help prevent wrist pin slap... Arrow designates proper orientation ... Should not have any real influence on performance if any.... Just may wear bore and rings out a tad bit sooner and make a little noise...

Have you checked valves, maybe intake valve is stuck, or push rod is bent or rocker arm broken.... If there is fire and fuel, its has to run... you have "missed" something in your diagnosis...

Did you try a "leak down" test?

Dale
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Last edited by Dale M. on Wed Oct 06, 2010 9:47 am; edited 2 times in total
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Sawsalesman
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PostPosted: Wed Oct 06, 2010 9:45 am    Post subject: Reply with quote

What's the compression on that cylinder? Sure your intake manifold boots are good and clamped well. Sure it's not firing on just that cylinder? If the intake manifold boots are in bad shape or not clamped well that side of the motor will have a hard time of firing off. Ask me how I know!!!
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Radar
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PostPosted: Wed Oct 06, 2010 10:28 am    Post subject: Reply with quote

"Have you checked valves, maybe intake valve is stuck, or push rod is bent or rocker arm broken.... If there is fire and fuel, its has to run... you have "missed" something in your diagnosis...Did you try a "leak down" test?"

I yanked the valve cover off and watched the valve action as it went
through the stroke (new heads). Intake and exhaust move as they
should.

I also checked the compression. It is 145 psi. Checked the valve lash
3 times. It's a new engine. I've rebuilt it a number of times over the
years but this is the first time for this.

When I first start it, the header for #4 is ice cold. The others are
hot. It just has me totally baffled. There's fire and fuel and in all
the other cylinders but this one.

I even installed a Pertronix electronic ignition, but it still acts the same.
I went back to Bosch points and condenser as another test. Tried
different spark plugs. It's a simple process. I just don't get what
part of the recipe it's missing. It shares an intake and fuel with #3
and it is running just fine.

Amazing.
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Sawsalesman
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PostPosted: Wed Oct 06, 2010 10:32 am    Post subject: Reply with quote

Did you check the intake manifold boots? Didn't see that in your list. My motor did the exact same thing. In order for the fuel to get to both cylinders on that side the boots must be good clamped correctly or all the fuel will go to one cylinder and not both. This is a dual port motor correct?
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RockCrusher
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PostPosted: Wed Oct 06, 2010 11:04 am    Post subject: Reply with quote

Since the question arose (but is definitely not the issue here)....
The arrow is due to wrist pin offset as stated but the effects are somewhat different than described. The offset INCREASES piston side load and friction on the cylinder wall to reduce piston noise and rocking in the bore. This somewhat increases piston and ring life. They don't do it just on a whim. Aftermarket performance pistons usually have the pin dead center in the piston. The old hot rodders trick in V-8's was to switch the pistons from one side of the motor to the other to change the offset the other way and gained 20-25 hp approximately depending on engine size. Did you ever notice the old small block Chevy's had 2 sets of valve reliefs from the factory and wondered why?

On a motor built to see high mileage I wouldn't do it but have done it all the time on short life grenade motors Very Happy . By that, I mean motors that get torn down frequently for one reason or another like off-road or racing that use stock type pistons. I would say that if you tear down your engine at least every 3 years and mileage in that time is 40k or less you are a good candidate for the extra 5-10 hp available for free by flipping the pistons. Instead of pressing into the cylinder wall the piston will now basically have a lift from the wall that reduces drag in a running motor significantly. The amount may be less or more depending on your exact combination.

EDIT: I would add that the mileage limit I imposed is because the increased rocking has a real impact on ring sealing life while cylinder wear life is extended. (just so those who would like to try this are completely informed)

RC
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Last edited by RockCrusher on Wed Oct 06, 2010 11:11 am; edited 2 times in total
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Radar
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PostPosted: Wed Oct 06, 2010 11:06 am    Post subject: Reply with quote

"Did you check the intake manifold boots? Didn't see that in your list."

Check them for.....?
They are clamped on nice and tight.

"My motor did the exact same thing."

Because of intake boots?
Wow!

"This is a dual port motor correct?"

Correct.

I was going to pull the intakes off as my next test anyway.
I was thinking somehow a shop rag or such was in the intake port of the
head or maybe the intake itself. (Even though I didn't do that to any
of the others....but I'm desperate)

But I will certainly look to see if the intake boot is causing a restriction
somehow. Thanks for the suggestion. I never would have guessed
that could happen. I will keep you posted.

I'm goin' in.......
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Radar
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PostPosted: Wed Oct 06, 2010 11:12 am    Post subject: Reply with quote

RC,

Thanks for the piston offset info. Good to hear that is not my problem.
(And I could not imagine how it would have been either) But I was
grasping at the last final straw. I am 99.9% sure I had them in right
any way.

I had the crowns ceramic coated, and the coating obliterated the arrows.
So I mic'ed them to find the offset side and marked them accordingly.
I double-triple-checked them too. So I feel sure the offset is how
VW intended.

My problem might be the intake boot restriction as the other person
mentions since his did the same. I will check that next. I am out
of ideas.

-Radar
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RockCrusher
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PostPosted: Wed Oct 06, 2010 11:29 am    Post subject: Reply with quote

Switching around the jets is a good idea too.....I didn't think of that at the moment, but substitution to see if a problem follows a part is always a good technique as long as it isn't a damaging problem. Since you got those jets from John you can pretty well bet that if they didn't get some crap in them from the carbs that they are pretty accurate. I think John checks his stuff before it goes out (although I'm not certain of that). You have to figure there is a good reason he has such a good reputation here.

I know I talk up John and Jake here a lot and it's because I have a lot of respect for the solid straight forward help and advice they give and the way they run their businesses. I have no financial stake in either business and, in fact have never had any communication with either one other than a simple email to Jake thanking him for his oil research and recommendations.

RC
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Sawsalesman
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PostPosted: Wed Oct 06, 2010 11:32 am    Post subject: Reply with quote

If the intake boots have cracks in them, air can leak into the intake manifold. I know this sounds crazy but I had the same problem. The intake boots were brand new but one of the hose clamps broke and was allowing air to enter the intake at the boots. Try spraying some carb cleaner at the intake boots and see if you hear the motor RPM increase or change at all. If it does, the boots need to be looked at.
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bunkington
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PostPosted: Wed Oct 06, 2010 12:26 pm    Post subject: Reply with quote

What is your carb setup?
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Radar
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PostPosted: Wed Oct 06, 2010 12:41 pm    Post subject: Reply with quote

"What is your carb setup?"

A Holley 2-barrell "Bug Spray".

The carb has been on the car for over 20 years, without a problem.
It's not a new variable. It's a known constant. It's supplying fuel
to the other cylinders properly.

The carb feeds the usual factory VW dual-port intakes via a central
intake "log".
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XxonValdez
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PostPosted: Wed Oct 06, 2010 1:20 pm    Post subject: Reply with quote

You pull the wire off #4 and see if you are getting spark? Might be a bad spark plug wire, try switching the wires (at plug and distributor) between 3 and 4 and see if you get 3 cold and 4 hot?
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Radar
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PostPosted: Wed Oct 06, 2010 1:25 pm    Post subject: Reply with quote

"You pull the wire off #4 and see if you are getting spark? "

Yep, tried that.
Spark jumps to the plug.
Also tried it with the plug connected and grounded to the head.
Nice blue spark that way too.

"Might be a bad spark plug wire, try switching the wires (at plug and distributor) between 3 and 4 and see if you get 3 cold and 4 hot?"

Tried three different plug wires.
One with metal core.
I ohmed them all out and they're all good.

Tried different spark plugs too.
But the plugs are sparking.
So the electrical charge is getting there.
It's just not lighting off for some strange reason.

But the cylinder next door (#3) is doing just fine.
Weird !!!
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donnieslagle
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PostPosted: Wed Oct 06, 2010 7:38 pm    Post subject: Plugs Reply with quote

I burned up 4 sets of plugs when I first built my engine (flooding). The plugs would spark just fine out of the cylinder, but not enough to run. Have you tried switching the plugs with one from one of the other cylinders you know is hot?
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