iceracercrx

Well guys after running a B18a turbo motor for two race weekends, I found something that doesn't make sence.

The first weekend running we lost hole #2 piston for no reason found yet.
So out came the spare motor. Well this one is a high mileage crap motor that I pulled. There was enough concern in my mind that it would live so it was time to build a motor. So I next day aired in a ton of parts. JE piston, eagle rods, oem gaskets, arp studs, and other ----. It costed me about 1200 bucks with balancing. No bad because it was over 400 dollars in shipping cost.

Here are all the bull ---- ------- things that I have found with this stock motor, just on hole number 2.
1.bore taper is .010
2 .002 cut on the head cleaned everything but around number 2 which took 5 to clean.
3 Same dip in the block also, but about .004 to clean it.
4. piston was in way worse shape
5. rings were junk
6. compression was also lower in just ------- number 2

So I get the new built motor in the car in just under one week. Blow it up on Sunday, build a motor by wed and dyno by midnight on friday.
We made less horsepower because we turned down the boost a little and took some timming out of it. I also welded in some O2 bungs in each 2 and 4 port was so we could watch A/F during a dyno run. Well it was a little bit lean but not that much at all. So uing crome free we added some fuel to 2. 1.010 and it seamed pretty happy. After about 30 runs on the dyno I did a leak down test on it, about 140 water temp. (1 4%) (2 8%) (3 6%) (4 4%) . Well I got back from running it hard all day (won a race!!!) and leaked it down again. All holes were getting better besides ------- number 2, it got worse.

What in the hell is the problem and what is the fix I think it is a water issue, or intake manifold design issue.

Randy
PS pictures on Monday when I get back to the shop.

DrSeuss

At the risk of sounding fascetious (sp?) are you sure its #2 piston and not number 3 (ie you're using the wrong reference point?).

Its just no.3 piston is the one suffering the most thermal stress in operation (hence EGT probes going into the #3 runner). If you had an EGT probe i'd suggest monitoring the EGT's and depending on the outcome adjusting the individual cylinder trim.

iceracercrx

I guess maybe I have it wrong. The hole that I am having problems with is the 2nd on away from the dampener.

Randy

DrSeuss

to me it sounds more like a problem with your tune then a specific mechanical issue. I have no idea which end the piston number is referenced from. I don't want to suggest anything which could make the situation worse rather then better. Using an EGT probe might at least give you an idea of whether your tune is creating any abnormality.

iceracercrx

All of those findings were on a bone stock motor from a good running stock car. I really think there is a problem and I need to find out why before I can turn up the wick.

Randy