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Engine Specific Info and Questions => IDI Engine => Topic started by: Patrick on December 13, 2009, 01:11:06 pm

Title: Compression limits? AAZ
Post by: Patrick on December 13, 2009, 01:11:06 pm
Got an AAZ out of a '93 Golf sitting on the floor, going to put it into a cherry gas '92 jetta. Plans include a T3, 2.5" straightpipe, 16V clutch, boost and pyro gauges, and all the fuel and boost it will handle.

 
Engine has about 420,000 kms as far as I can tell. Car would start and run okay when I pulled it out this summer.  Just did a compression test, ranges from about 385 pounds to about 410 across  4 holes.
Will this thing start when it's 25c below??  Or do I bite the bullet and pull the whole thing apart now?
Title: Re: Compression limits? AAZ
Post by: vanbcguy on December 14, 2009, 08:33:41 am
Compression sounds pretty good...

If it were me though, and I was planning on putting any kind of mileage on the beast, I'd probably do the rings/bearings before dropping it in the car.  Otherwise I'd be constantly kicking my own butt going "why didn't I just DO that before I put the engine in?"
Title: Re: Compression limits? AAZ
Post by: Patrick on December 14, 2009, 07:32:30 pm
Last one I checked (which I'm driving) went about 480 lbs. I'm leaning towards agreeing with you.......   And my wife is telling me why do half a job? do it right the first time. I just dread the thought of having to bore it and buy pistons. Don't think they're cheap.
   
Title: Re: Compression limits? AAZ
Post by: vanbcguy on December 15, 2009, 10:34:38 am
If your compression is that good currently then you probably don't need to bore or replace pistons...
Title: Re: Compression limits? AAZ
Post by: carrizog60 on December 15, 2009, 12:20:22 pm
lucky...
mine did 22bar(319)24,28 and 30...
on cold starts usually i have to auxiliate with a spare batery...
soon going to pull the engine apart,do you think i would need to bore and buy pistons?
only has 225.000km(but run on low oil for a time with the other owner,due to a bad reanding of oil level..)
Title: Re: Compression limits? AAZ
Post by: Patrick on December 16, 2009, 03:21:37 am
I once pulled apart a 1.6, best reading was 275 lbs. Engine had over 500,000 km, with poor maintenance. would have needed to be bored and have oversize pistons, bad wear in the cylinders.
Title: Re: Compression limits? AAZ
Post by: cyrus #1 on December 16, 2009, 11:06:34 am
soon going to pull the engine apart,do you think i would need to bore and buy pistons? only has 225.000km(but run on low oil for a time with the other owner,due to a bad reanding of oil level..)

I think you would.  I'm rebuilding a 1.6 that had about 200,000km on it with unknown maintenance.  I had to bore .5mm over to get rid of the ridge at the top of the cylinder.  If yours has been run low on oil it could have quite a bit of scuffing on the cylinder walls and especially the piston skirts.

That being said, you won't know for sure until you pull it out and inspect.