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Dunebubby Sat Jul 12, 2008 8:56 am

I would have put this in the engine section but since it isn't a v dub engine I'm dealing with I thought this might be better.

I have a ministock racecar,(4 cylinder) that I got from a guy who couldn't find the dipstick to save his life so he wasn't able to pass on what had been done to the car.. This guy is about as clueless as they come automotively speaking.I hadn't raced the car,since it's 120 miles to the closest track that runs ministock around here. I had driven it around my property though and the car was set up well,(to go left :twisted: ),and ran really well but did have some blow by,completely wasted timing gears,(26 degrees of play), and very noisy rear end. My dad wanted the weber carb and intake to get another car running and since I hadn't run the car in a couple years and didn't anticipate racing it soon I told him he could pull the carb and intake. After he did I could see that the intake and exhaust runners had been ported ,(no surprise) but I was wondering if any work had been done to the combustion chambers so I pulled the head. Nothing had been done to the combustion chambers but I was pleasantly surprised to see that it already had a "big bore" kit punching it from 2 liters to a 2130. Then I looked more closely and saw that #2 piston is installed backwards. The arrows on the other three pistons face the flywheel,#2 faces away. I will be interested to see if the connecting rod is backwards also. I was going to rering and slap bearings in it but I was wondering what you guys would do about the flipped piston? At this point I wish I had done compression and leakdown tests before pulling the head. I know it had blow by but I wonder if the readings on #2 were far worse than the others.My feeling is it ran "this long" the way it was so Im tempted to put it back together the way it is.I still need to get it out of the car and pull the pan to see about the con. rod. I know since the rings,not the piston,should be whats contacting the cylinder walls i should be able to flip it the right way but.........Opinions? At this point I'm assuming the conning rod is the right way. If it isn't I will flip at least the rod,(unless I get in there and it's been balanced). What would you do? (Besides getting rid of the non-V Dub)?!

Tram Sat Jul 12, 2008 9:56 am

I'd fix it.

coad Sat Jul 12, 2008 9:57 am

I don't think the manufacturer put the arrow there for looks.

You say the guy you bought it from was an idiot, but you're thinking about doing the same thing he did? Come on, you know the answer is to do it right.

Dunebubby Sat Jul 12, 2008 10:00 am

yeah of course I want to do it right. Maybe a better question would be: What effect might it have flipping the piston now that it's been run the way it is?

If anybody has any REAL advise I'm still listening..............

TimGud Sat Jul 12, 2008 10:31 am

Dunebubby wrote:

If anybody has any REAL advise I'm still listening..............

Ok, yes it's ok to leave it just like it is and run it. The engine will last just as long as if it was installed correctly and maybe even last longer.


There's the answer you want to hear, but personally I agree with coad 100%

You know you have to pull it apart and install that piston correctly.

Dunebubby Sat Jul 12, 2008 10:39 am

It's not that I "want" to hear any answer.I'm not looking for the "easy" way out just didn't know the effect of having run it the wrong way then flipping it. It's not like it's hard to flip it. I don't get what you mean about the wrist pin not getting enough lubrication,I don't see why it would matter but I appreciate the input.

It's a Volvo B20 by the way.

Spezialist Sat Jul 12, 2008 11:06 am

Its a fuckin race engine "destined to blow anyway" flip it around and run it. The arrows are for balance.

Russ Wolfe Sat Jul 12, 2008 11:52 am

Most engines other than VW have the arrows pointing towards the FRONT of the engine, not not the flywheel like VW. So maybe this piston is right, and the rest are wrong.
On water cooled VW's the arrows do not point to the flywheel.
Maybe YOU need to do some READING..... and find out how the pistons are supposed to be.

Chad M Sat Jul 12, 2008 12:45 pm

Spezialist wrote: Its a fuckin race engine "destined to blow anyway" flip it around and run it. The arrows are for balance.

I thought the arrows had to do with the piston pin offset?

Dunebubby Sat Jul 12, 2008 1:03 pm

Russ Wolfe wrote: Most engines other than VW have the arrows pointing towards the FRONT of the engine, not not the flywheel like VW. So maybe this piston is right, and the rest are wrong.
On water cooled VW's the arrows do not point to the flywheel.
Maybe YOU need to do some READING..... and find out how the pistons are supposed to be.

Russ Your absolutely right.My typo.They ARE all forward and #2 is facing the flywheel. Speaking off "off brand" stuff on vw forums, what's with the japanese seat in your gallery? I can't believe you'd show THAT on a vw site.
:lol:

Spezialist Sat Jul 12, 2008 1:07 pm

Chad M wrote: Spezialist wrote: Its a fuckin race engine "destined to blow anyway" flip it around and run it. The arrows are for balance.

I thought the arrows had to do with the piston pin offset?

Back to balance again

melville Sat Jul 12, 2008 1:46 pm

Dunebubby wrote: They ARE all forward and #2 is facing the flywheel. Speaking off "off brand" stuff on vw forums, what's with the japanese seat in your gallery? I can't believe you'd show THAT on a vw site.
:lol:

Arrows on VW pistons indicate orientation to get the piston pin offset in the right direction. If the arrows on these pistons are for a similar purpose and you are committed to a re-ring, pull them and measure the skirts and see if the 'wrong' one has a messed up skirt. If so, replace the set. Will the block take another overbore?

JSMskater Sun Jul 13, 2008 12:32 am

arrows on pistons are for nubs.

runslikeapenguin Sun Jul 13, 2008 1:22 am

cant you flip all the pistons in a VW engine? ive heard of this for building 5/1600 engines

Mr. Unpopular Sun Jul 13, 2008 4:24 am

The arrow on the piston is to orient them correctly for piston pin location, not balancing (they are round, that is stupid).

Some guys flip the pistons around to change the pin location usually on high RPM or long stroked motors. Either way, this motor isn't consistent. For best results, make them all match, for turning left in the field behind your house, leave it be, you're much more likely to really screw something up by tearing it apart than that backwards piston will do.

Russ Wolfe Sun Jul 13, 2008 7:21 am

runslikeapenguin wrote: cant you flip all the pistons in a VW engine? ive heard of this for building 5/1600 engines

Nope, there is a slight offset to the wrist pin.

Dunebubby Sun Jul 13, 2008 4:38 pm

Florida_Buggy wrote: for turning left in the field behind your house, leave it be, you're much more likely to really screw something up by tearing it apart than that backwards piston will do.

Doubtful.I've built enough B20 engines that I've VERY comfortable going through it,just never had one with a flipped piston. Seems no one else here has either! There was never a question as to how it should have been put together.The question was more about the effect of flipping it the right way after having been run for an undetermined amount of time backwards. I'm flipping it and goin' through it. The race car is going away but the engine is going into a street car.

drscope Mon Jul 14, 2008 5:10 am

You never told us what engine this is.

Some race engine builders will turn the pistons, or sometimes the rods to get the pin offset they want. This works better in some engines and not at all in others.

In this case, you have 1 that is turned different then the others. My guess would be that the rod is also in backwards and this was simply an assembly error.

In any case, the proper way to deal with this is to take it apart and MEASURE everything.

Take careful notice of the cylinder walls and the surface that is there. You do NOT want a smooth surface on the cylinder walls. There has to ba hatch marks in order for the cylinder walls to retain some oil.

Measure the bore and measure the pistons. reassemble accordingly.

As for this being a "balanced" engine. Engines are balanced prior to assembly. The pistons & rods get balanced OFF the crank and then the crank is balanced using bob weights to simulate the piston/rod assembly. So this would not effect the dynamic balance of the engine.

It may effect the running balance as this one cylinder has the rod centers and maybe the pin center in a different place. The result would be that this cylinder "lays" over at a different point then the others.

The bottom line, is that this is just like ANY other engine job. You MUST MEASURE before bolting parts back together.

bugninva Mon Jul 14, 2008 5:57 am

Dunebubby wrote: [ Doubtful.I've built enough B20 engines that I've VERY comfortable going through it,just never had one with a flipped piston. .

i'm with the good doctor here.... you need to measure the cylinder to see if it is out of round due to more sideload with the piston flipped... if you've actually built engines you already have the instruments and the know-how to use them..(and also the knowledge that makes this thread almost silly)... if you've just assembled a few engines, that's a different story...

bill may Tue Jul 22, 2008 9:14 am

Chad M wrote: Spezialist wrote: Its a fuckin race engine "destined to blow anyway" flip it around and run it. The arrows are for balance.

I thought the arrows had to do with the piston pin offset?

there you go.



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