Replacing exhaust system on my 72 240z from the manifold to the back

[jalexquijano]

My car Air galley was removed long time ago. All of the ports in the balance tuve were capped. As i mentioned before, before making the swap of the original exhaust i had  no deceleration popping, I lean the mixture to 2 turns clockwise and i am still having deleration popping at the back where the tailpipe is fasten to the turbo muffler. I even took the car back to the shop, and they told me the connections amongst the pipes have no leaks. WHat could be wrong then?

[Mark Maras]

 What color are the plugs at 2 turns?

[siteunseen]

That's normal with a performance exhaust, both my Zs do it and all the motorcycles I've had did it too.  If it bothers you go to neutral, brake pads are cheaper than transmissions anyway.

Someday you should watch and listen to an F1 race, they pop like crazy and usually have flames coming out.  I think it's unburnt fuel/air mixture that causes it.

[grannyknot]

3 hours ago, siteunseen said:

 I think it's unburnt fuel/air mixture that causes it.

 After burners

[jalexquijano]

well i tightened the tailpipe rear and front clamps as there is no gasket in that área. the only 3 gaskets that come with this exhaust system are the manifold to downpipe gasket and the two pipe to pipe 2.5 inches gasket. I even lowered the mixture to 1.5 turns clockwise to lean the mixture and there is still popping at the exhaust. I guess i will need to purchase a set of better quality gaskets:

http://www.ebay.ca/itm/3-Bolt-2-5-Exhaust-Header-Manifold-Collector-Flange-Gasket-Graphite-Aluminum-/112287982661?hash=item1a24e2a445:g:lNgAAOSwB4NWuPPk&vxp=mtr

I really hate that exhaust popping sound at deceleration and mostly because i did not had it with the stock exhaust. Maybe due to the fact that this is a turbo muffler its different. Anyone?

[87mj]

Back in the olden days of around 1979, I had the same popping noise on my '73.  It ended completely after I disconnected the smog pump. I needed a new muffler at the time. More recently, my new-to-me '71 needed a new muffler.  It also popped.  It is not loud but annoying none the less.  The lack of a muffler made it worse.  I  disconnected the smog pump on that one too.  Then it stopped. 

Personally, I suspect they did that when new.  It was not noticeable because of the stock muffler.

[Mark Maras]

 I agree, I've noticed that as the muffler deteriorated over the years the popping would increase. IMO, If one wants a sweet sounding Z, one will have to put up with some popping on deceleration. Personally, I don't mind it as long as it's not excessive.

[jalexquijano]

Mine is not excessive but does bother a Little bit! I re-tuned the carbs yesterday using the GUNSON COLORTUNE and dialed both carbs to 2.75 turns clockwise until i got the blue color. set the idle to 1000 rpm and did the balance. Good response when accelerating. However i tried to lean the mixture to 1.5 turns which gives me a horrible response when accelerating and the deceleration popping was still present. I even retarded the timing to 11 btdc and its the same. So i believe one of the 2.5 inches 3 bolt pipe to pipe gasket or the manifold to downpipe gasket could be leaking. IF not then i will have to live with the decel popping.

[jalexquijano]

Well honestly my mechanic had removed the anti backfire valve, and emmission devices that where fastened to the balance tube. He also removed the air galley. I dont know if the smog pump was removed or not by Previous Owner. I do believe so as the engine block had the blank space to bolt the compressor bracket to fasten the AC Compressor which i installed last year. Anyway, if i dont have the air galley installed any longer and it forms part of the emission system, even if i source a NOS Anti backfire valve, once installed it would not cause any effect to avoid the deceleration popping at the exhaust. Any other way of preventing the deceleration popping at the tailpipe? Buying a NOS Antibackfire valve is not the solution!!!! I did took a picture of the old Steel exhaust system and only stayed with the original downpipe. The rest was dumped.

The last picture shows how my car was when i bought it. I did stored the anti backfire valve but i dont think it is working and the air galley was rotten so i am not putting it back. with the lousy former exhaust i had no deceleration popping so replacing all of the emmission system parts is not a solution.

Edited May 7, 2017 by jalexquijano

[jalexquijano]

On ‎04‎/‎26‎/‎2017 at 3:45 PM, Travel'n Man said:

Odds are you have blown out a section of your gasket. Dave Rebello and I were just discussing this. He recommends a for exhaust red/orange high temp etc in replacement of the gasket. I did ask him about a copper racing gasket and he has not tested them. They are about $50


Sent from my iPhone using Classic Zcar Club mobile

Travel man,

Which Brand shall i buy? Permatex? Ultra copper or which one?

https://www.permatex.com/products/gasketing/ultra-series-gasket-makers/permatex-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker/

Please confirm!

[Travel'n Man]

Dave Rebello is finishing up my 3.0 stroker engine and finally getting it dyno'd this week.  I have elected a copper gasket from Z Car Depot. Do some research on how copper handles heat - I believe it is the best decision for my application......I will install it dry.

 

 

Edited May 8, 2017 by Travel'n Man

[jalexquijano]

Which of these rtv should i buy to seal the unions and manifold to downpipe correctly? I cant seem to find the permatex ultra copper.