AP2POINT2

I have a strange problem with my ap2 motor, apparently this is the highest point in which the cylinders reach the top of cylinder walls. It look's like it can still go up another 5/16's of an inch. I tore my engine down to replace the cylinder rings and a new head gasket due to all cylinders being at 185psi and cylinder 4 being at 85psi. I had a valve job done a year ago and my vehicle had loss of power and misfiring. Valve job fixed the misfire, but low end continued to have little to no power. The mechanic said that the block may have ap1 piston and rods because the cylinder did not reach all the way to the top. I confirmed that the rods and pistons are ap2 because they have "PZX" stampings on them. Maybe the crank is AP1? If you can help, please reply.

TonysMI4

Im not sure what you have going on there but will be a good find with all the info for the FI guys. Looks like you lowered the compression with stock parts by mistake I do know that the piston will go above the wall ever so little while at tdc, so you are right ... they are not going up all the way. When you built the motor whats ALL the parts you used? what does the block have stamped on top where the head bolts down by the intake mani? Where are the lines on the crank pulley when the piston is at tdc? Please post pics of ALL the part numbers on the pistons and rods.

AP2POINT2

That's the highest point the cylinder reaches. I'm doing a teardown and rebuilding the engine due to lack of power and engine always had low compression. More or less 165-185 psi however my engine began to misfire and once I checked compression I discovered it was at 85psi. I just thought the cylinder not reaching the top was strange. This is my first time working on internals on an s2000 engine. The pistons and rods say "pzx" I believe that those marks are ap2 marks. Are there any marks on the crank to tell the difference between cranks? I have not yet removed the crankshaft.

chris_barry

Measure the stroke with some verniers before you pull it apart. Using the tail of some digital verniers, Put it at TDC, zero the calipers on one pair of pistons, then extend it down to the other pair.

wadzii

If you somehow do have an ap1 crank in the motor you have probably 7:1 compression if not lower.. your car is probably making 120hp lol.

The piston is supposed to come 1mm out of the hole. measure how far down it is from the top of the deck to the piston. AP2 rods are 3.35mm shorter than ap1 rods, it looks like the piston is down alot more than that.

GrandMasterKhan

are all the pistons coming up to the same point?

AP2POINT2

chris: Yes, I'm going to look into that, thanks!


@wadzii: unfortunately it does sound like my car. It lacks power specially in the low end. I bought the car from an auction and unfortunately I couldn't return it. That's a different story LOL. I don't see why someone will
put an ap1 crank on a stock ap2 motor, unless they were boosting?

@GrandMaster: Yes all cylinders reach that exact point. None go any higher.

OemEF

If you're positive that the pistons are AP2 and that the rods are the correct length, it has to be the crank. There's nothing else that would really cause this much drop in TDC. But I'd do what someone above recommended with measuring the stroke without ripping the block apart. Good Luck with finding out what it is :/

TonysMI4

7:1... yep its time to leave it alone and boost the hell out of it.. 7:1 - 35psi+

JK.. If you have to change the rings and other stuff out anyways , go ahead and pull the pistons and rods and we will go from there.

I bet someone spun a bearing and a shop not knowing what they were doing , replaced it with an AP1 crank. Then when it made no power they just sold it and you bought it. ... That just sucks!

AP2POINT2

@TonysMI14: That's exactly what my friend told me! I'm upset, but at this unfortunate point it's a do-or-die and I must rebuild it. Sell it or simply trade it in for something else. I'm leaning more towards the crank, but as other members suggested, I must measure the stroke. There is something wrong nevertheless. I'll make sure to post more pictures for you guys.

@OEMef: Yes it looks like it must be the crank everything else is stamped "PZX" which are ap2 internals. I have not yet confirmed if the crank is also an ap2, but I think it's from an ap1. Are there any stamps on the crank that I can go based off?