N10 vs L36 dual exhaust (1969)

davepl · Poncho Master!

N10 vs L36 dual exhaust (1969)

2qwik2c · Poncho Master!

N40 vs L36 dual exhaust (1969)

davepl · Poncho Master!

Gardner says they can do it in email, but I haven't made the call to sort out the details yet.

My goodness a 335hp 427 stuff through a 1.875" single exhaust would be like a wicked leaf blower! I thought my 350 was bad with that setup!

-- Edited by davepl on Monday 22nd of January 2018 10:59:56 AM

73SC · A Poncho Legend!

davepl wrote:
Gardner says they can do it in email, but I haven't made the call to sort out the details yet.

My goodness a 335hp 427 stuff through a 1.875" single exhaust would be like a wicked leaf blower! I thought my 350 was bad with that setup!

-- Edited by davepl on Monday 22nd of January 2018 10:59:56 AM

Hence the footnote on every GM engine chart from that era that says "with dual exhausts add 15%"

North · Guru

Gross horsepower (used until 1971) measured engine output with no exhaust so the restriction of an exhaust system was not a factor in the rating. In 71 when they started rating engines with the net system GM listed horsepower with and without dual exhaust. Duals typically added 25 horses.

As for the L36 exhaust system it sounds like it was a bit like the 428HO system on fullsize US cars. The regular duals had two mufflers and two resonators with 2" headpipes and 1.75" tailpipes. The HO system had the long branch exhaust manifolds leading to 2 1/4" headpipes and 2" tailpipes, it still had two mufflers and two resonators but the mufflers were freer flowing. Did the L36 have different manifolds than the lesser big blocks?

davepl · Poncho Master!

So far as I can tell all 427s had the same manifolds. In my parts book they show a separate ST (standard trans) manifold for the passenger side, and they ONLY list an AT (auto trans) number for the driver's side. My driver's side has been replaced at some point with a non-smog piece.

My passenger side has the smog ports and is date-code correct within 2 days of the casting of the other parts, but it's the AT part number.

That's something I'd really like to compare notes with DRPONTIAC on, as he has the only other 1969 L36 manual that I know of. Unless someone else does?

seventy2plus2 · Canadian Poncho Superstar!

I'd say your passenger side exhaust manifold should be 3916178. I don't see any reason it'd be different, as the same manifold was used across all body styles except Corvette.

427carl · A Poncho Legend!

My friends original 395-325 66 Hardtop had single exhaust and posi..

The big old hound would almost blow a hole in the ground . Single with resonator

davepl · Poncho Master!

seventy2plus2 wrote:
I'd say your passenger side exhaust manifold should be 3916178. I don't see any reason it'd be different, as the same manifold was used across all body styles except Corvette.

My passenger side exhaust is indeed 3916178, but that's listed as AT in the parts book, not ST. They simply do not list a driver's side in my book at all, maybe that's why mine is missing, it's THAT authentic?

What would you suggest for a driver's side? 3914617? Or 3914613? One replaces the other in later parts books, btw.

-- Edited by davepl on Tuesday 23rd of January 2018 11:31:46 AM

North · Guru

perhaps a manual trans had a heat riser and the automatic didn't or vice versa?