Really? Details on the block? If this compression test comes back shitty I will be extremely interested.

Brain, I don't think it's an exhaust leak because the sound is coming from the tailpipe.

BTW, since I started it this morning, the sound is now noticeable at idle.

 

Can't you post a soundclip?

 

Didn't have time to get one. Got home from work at about 8:30 and had **** to do. I will try to get one tonight.

 

Block is out of a 97. I can't remember how many miles it had, but it was quite a few. It ran fine when I was autocrossing it before I pulled it for the forged block.

 

How old is your exhaust? Did it possibly blow out a baffle in the muffler?

 

Compression is fine across all cylinders - in the 150s.

Exhaust is brand new. No baffles either, it's just a strait-through can.

 

IIRC its new and he had a friend fab it up for him.

I'd be willing to bet its something to do with the exhaust, seeing that you just put it in recently.

 

I feel like it's too rythmatic to be an exhaust issue.

EDIT: Ok, let's brainstorm - what about the exhaust could it be that would cause it to be directly correlated to RPMs and load?

Could there be something wrong with the valvetrain that would cause it to give good compression numbers but open up an exhaust valve... too early? Causing the farty noise.

 

The very first thing I would do is check the entire exhaust from front to back for leaks or areas where it might be touching. I've seen exhausts rattles turn into songs depending on where they were touching. Most of them are also RPM correlated as well.

 

Thanks - I will check that out when I have some free time.

 

Any update on this? Interested to know what you found.

 

I found nothing. The sound is still present, but not any worse. I'm thinking that it always made the noise because the first time I noticed it is the first time I had the top down with it... which is the only time it's noticeable.

I'm thinking it's just the result of a strait pipe exhaust with a resonator.

 

i didnt read any of this, but the fart noise sounds like combustion. i think you have a car.

/comments.