400 exhaust

[75gmc454]

Did the trucks that came equipped with the small block 400 engine have dual exhaust from the factory? I have a 77 GMC that I ordered the invoice for that had a 400 and dual exhaust but there is no mention of dual exhaust on that invoice. The truck did have bucket seats though that I did not know about.

[cory d]

im not sure but looking at the transmission cross member could give you a hint. if only the passenger side of it is raised it came with a single pipe and if both sides are raised its for dual.

[gchemist]

As far as I know, only 3/4 and 1 ton trucks had factory dual exhaust. They had a factory crossmember for duals. Special edition trucks might have them.

[cory d]

i have a friend with a 77 c10 and it has a dual exhaust cross member. the previous owner switched to a single though. im guessing it was stock with duals becasue the exhasut adnd the wheels are the only thing on the truck that werent stock

[allchevy58]

I ordered a brand new 77' K10 Chevy with a 350, it came with single exhaust, two of my friends bought new 78' K10 Chevys with 400 off the lot and they too had single exhaust. The 3/4 and 1 tons might have had duals.

[Dooley]

All of my pickups came with dualls,(either 400 or BB equipped), and my K10 1977 Suburban with ordered 400 sb.

[ray_mcavoy]

Hi 75gmc454,

My dad's 77 GMC K15 (ordered new by my grandfather) has a 400 with factory dual exhaust. Although the pipes themselves have been replaced, the truck still has the factory dual exhaust hangers riveted to the frame. I don't think the dual exhaust option was listed out separately on the SPID or invoice since it was automatically included with the 400 engine.

I recently downloaded some Vehicle Info Kits from the GM Heritage Center Archive at http://www.gmheritagecenter.com/gm-h...tion-kits.html

Page 90 of the 1977 Chevy truck info kit describes the RPO LF4 400 as being optional in K10-30 and G20-30. And in the "Basic Specifications" list it shows: Exhaust -- Dual ... All

allchevy58, regarding your friends 78 K10's having 400's with single exhaust, I believe that was due to the emissions regulations having changed for 78.

[bmchevy1979]

I was under the impression that you could order factory dual exhaust on any model until 79 when they increased the emissions standards

[75gmc454]

Thanks Ray. This truck has the original hangers rivited to the frame also. The pipes are rusted off of it though! I bought the truck for parts, but I hate to part out stuff. It would be a neat project truck for the future.

Those gm order books for the trucks will tell you bmchevy1979 if duals were available for the 79's.

[beamn7]

My grandfather's truck was a 79 GMC Sierra Grande 25 with a 400, 350 trans (believe it or not) and a 203 full time case and it was equipped with single exhaust. He bought the truck brand new off the lot in 79....

[russgt]

76 K5, came with factory dual exhaust, option N10

[Corts60]

My '78 5.7 diesel also came factory with dual exhaust.