Confirmed popping through intake, Timing off? |
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Confirmed popping through intake, Timing off? |
corsepervita |
Jun 2 2010, 10:20 PM
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#1
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Member Group: Members Posts: 327 Joined: 18-April 10 From: Redmond, OR Member No.: 11,631 Region Association: Pacific Northwest |
Ok - so I've sealed up all the potential exhaust leaks except the one possible leak coming from the back of my muffler which may be small - unable to tell.
However, I started noticing a popping noise. I recall it a few times when I first started driving the car but it was so small I couldn't really make out what the noise was. The other day after fixing the exhaust I rolled down the windows and listened more carefully. The same odd "poof" noise I heard behind me was audibly from the engine area. I had my wife get in the car while the car was cold and blip the throttle while it was in neutral to see if it would do it again - it did. It was unmistakably some sort of pop from the intake. It's more of a "poof" than a loud "bang" ... I've heard the noise before on my 924 when the exhaust was partially torn apart - but that was a HUGE lack of back pressure. So that kind of (lack of)back pressure wasn't there since the exhaust is complete, no leak at the heads anymore, and as well only a small one up near the muffler - but even then it's tiny. I remember hearing that popping through the intake is either running too rich, timing off (retarded) or a huge exhaust leak. Since the popping on decel seems to happen very frequently - and just as much so (sometimes more) after the exhaust leaks were taken care of, I'm noticing this more as well. Since decel popping would be culprit to a lean condition - and intake popping would be culprit to a rich condition (at least as far as I know, I may be off on that); My assumption would then be my timing is off? (since obviously you can't have both lol) Wanted to bounce this off everyone here in case I'm crazy. Again - new to working on these little air cooled engines. I'm gonna go put it back up on stands tonight and crawl under and check. A family member also suggested I may have valves that are too tight, but I recall Jim saying he already adjusted the valves and they were adjusted to the .006" mark they were supposed to be at. I plan on replacing the pushrod tube seals here soon - he sent me a procedure on how to do it (i also found a wonderful article on the forum about it) so I will end up double checking them anyway. Any ideas? I'm gonna go get a pot of coffee going and go get it up on stands once I have a brew going and get acquainted with the car some more. |
corsepervita |
Jun 3 2010, 02:02 AM
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#2
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Member Group: Members Posts: 327 Joined: 18-April 10 From: Redmond, OR Member No.: 11,631 Region Association: Pacific Northwest |
Ok minor update - Heat exchangers are off and I'm about to dive in and check valve clearances.
On a simple note - the seals I did on the heat exchangers took great on driver's side. Appears the surface area was perfectly flat and I got the seals heated up just right - they took perfect, no leaks on that side what so ever. On passenger side - it would appear I crunched a seal at an angle just a hair. It still took the seal. Looks like I had a tiny pinhole type leak on one seal but it wasn't too bad - I retorqued them not long afterwards - so it is hard to tell if that one got sealed before or after the re-torque. You can tell it wasn't flat though as part of the seal actually had a small dive in it where it sort of edged in a hair. This also explains why it required more torque to seal it... Aside from that - everything else looks great thus far as far as the heat exchanger job I did. I'm about to take the exhaust out from the rear and drop the bumper so I can inspect the muffler. I do see some weird rust and a water-like rundown from the rusted area - so It may be that it has a crack as mentioned earlier in another thread? Won't know till it's out. Ordered new gaskets and seals just to be on the safe side - have my pushrod seals ready to go (in case I do decide to do it all tonight) etc etc. Taking a minor coffee break right now and having a snack though. The pushrod seals are leaking a good bit though so I guess I may as well just do it all and be done with it so I can get back to enjoying it all. |
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