Cascade Crew

aaron_sK

Before I get to the problem, here's a basic rundown of the stats on my car:

'87 IROC
5.7L TPI
Low-temp thermostat and chip (probably Hypertec)
Custom exhaust with what appear to be gutted cat and muffler
(I have yet to pull it apart, but the muffler has obviously been cut open)
3.73 rear gears

When I first bought the car it had a tap on accelleration. Since it was only coming from the passenger side, I assumed it was just a header hitting or something and I ignored it. However over the past week I've been getting a quick series of three or four pops or snaps when rolling down from around 2200~3K RPM's.

This morning I took it out and did a bit of testing on it. It happens with and without the transmission in gear. It doesn't happen every time, but consistently enough to start bothering me.

I checked the timing and it came back at straight-on TDC. That seems a little bit retarded to me, but I figured that since the Hypertec basically would just advance it at or near WOT, that someone may have retarded the timing at idle to compensate, so I left it alone. Is this worth putting it back to the stock 6* of advance?

I know that there is a small exhaust leak in the Y-pipe after I bottomed out coming up the Pacific Ave. hill. It has occured to me that the snapping noise could just be an exhaust leak, or maybe to much air is getting into the system.

I'm pretty sure it's not a true backfire. It's no where near that loud, and if there is smoke from the exhaust, it's not enough for me to see while driving.

Right now i'm thinking that a leaking gasket between the header and Y, or a leak in the exhaust would explain both the tap on acceleration, and the pop on deaccel. However I wanted to post here to make sure I'm not missing anything here. Sorry for the length of the post.

Dewey316 · Posted: Mon Mar 13, 2006 12:56 pm Post subject:

It sure sounds like a leak to me.

iansane · Posted: Mon Mar 13, 2006 2:23 pm Post subject:

Leaky leaky. Smile

aaron_sK · Posted: Mon Mar 13, 2006 5:13 pm Post subject:

Well, since that exhaust system is going in the trash anyway, it's no big deal. My second question would be, am I f***ing anything up by leaving the timing retarded to TDC 0*? I'm probably going to pull it back to at least stock to see if I can get any more power out of it, but I'm worried about it detonating at WOT with the chip in there.

Dewey316 · Posted: Mon Mar 13, 2006 5:15 pm Post subject:

Was it set at 6* stock? I don't recall how much the hypertech adds to the tune. If you are workied, you might go at 3*-4*.

aaron_sK · Posted: Mon Mar 13, 2006 5:29 pm Post subject:

It's 6* BTDC stock according to the emissions sticker under the hood.