72 emissions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

franko72 · 01-26-2005, 09:54 PM

My 72 truck doesnt have the evaporative charcoal canister for the fuel sytem.Did they come on the 72 super cheyenne w/402?There isnt any type of emission parts that I can see.I know that everything tanked in 73 .I am trying to replace the fuel lines were the dealer added an extra saddle tank on the passenger side. They installed a lot of rubber tubing hose that is getting old and leaking at some fittings and clamps.I noticed an extra line that was not connected.a diagram would be great if someone could show one for fuel line routing on the 72.the tank does not have a return line.

franko72 · 01-27-2005, 06:41 PM

come on experts, I know someone out there has an answer , fake it if nothing else.

rustyold72 · 01-27-2005, 06:45 PM

Didn't think 72 light trucks had any type of emissions control devices

tom hand · 01-27-2005, 07:31 PM

The smallblocks had the evaporative charcoal canister in 72...so I would think the big blocks had it

COBRO · 01-27-2005, 07:55 PM

I think the smog crap was a hit or miss in 72. My 72 C-20 with the 402 didnt have any other than the PCV valve and the breather in the other valve cover plumbed into the air cleaner. Most dont realise that the PCV valve was the first of the smog equip. Just wondering if the hose you found my be a vent hose for the tanks. HTH::::::COBRO

JimKshortstep4x4 · 01-27-2005, 08:20 PM

The C-10's had the emissions setups but the C-20's and larger did not have them.

Engine size was not a consideration as all of the C-10's had the emissions
setups in 72. I am not sure what year emissions controls other then pcv's were added but I believe it was in 1970.

Jim

71meangreenc10 · 01-27-2005, 10:29 PM

Check the fuel neck and the cab, if there is a metal line that runs up the cab corner on the passenger side into the roof and an over flow tube on the filler neck then the truck came with emissions, also there is a metal line that runs beside the fuel pump line on the frame towards the battery,

Smitty

franko72 · 01-28-2005, 05:15 PM

All I have is the PCV .The line that is loose is a return line that was never used I think.

HOTFUN · 01-28-2005, 05:37 PM

Jim is 100% correct. The emission systems were GVW rated and the 10 series all had them small or big block and the 20 series did not. I have both a 10 and 20 big block and the 10 has both the smog pump and charcoal can. The 20 series does not and you can tell by the non ported exhaust manifolds where the air pump tubes attach on the 10 series. Mark

tom hand · 01-28-2005, 07:01 PM

I believe the air pump was a California thing only in 72...the 49 state 72 trucks had the evaporative charcoal canister,PVC,and the transmission controled spark that only allowed the vaccum advance to work in high gear

avejoe · 01-28-2005, 07:31 PM

OK, so can all of this stuff (fuel vapor lines, cannister, spark control, PCV) be eliminated?

69sixpackbee · 01-28-2005, 07:36 PM

My '72 C-20 402 DOES NOT have anything for emissions with the exception of a vented gas cap and a PCV valve. That's all it ever came with.

Harold Shepard · 01-28-2005, 08:00 PM

The return line is not for gas (liquid) but vapor return. If you have a 10 series 72, you will have at least a vapor canister (charcoal canister) that attaches to the metal line on the frame, EEC,which this line hooks to on the gas tank the transmission spark retard and PCV. If equiped with California emissions package, it will also have the smog pump and AIR lines.

franko72 · 01-29-2005, 11:57 AM

wonder why the C 20 s didnt have the canisters with the vapor return and smog pump?

01-26-2005, 09:54 PM	#1
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	72 emissions My 72 truck doesnt have the evaporative charcoal canister for the fuel sytem.Did they come on the 72 super cheyenne w/402?There isnt any type of emission parts that I can see.I know that everything tanked in 73 .I am trying to replace the fuel lines were the dealer added an extra saddle tank on the passenger side. They installed a lot of rubber tubing hose that is getting old and leaking at some fittings and clamps.I noticed an extra line that was not connected.a diagram would be great if someone could show one for fuel line routing on the 72.the tank does not have a return line. __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

01-27-2005, 06:41 PM	#2
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	come on experts, I know someone out there has an answer , fake it if nothing else. __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

01-27-2005, 06:45 PM	#3
rustyold72 Registered User Join Date: Oct 2003 Location: Ark City KS Posts: 505	Didn't think 72 light trucks had any type of emissions control devices __________________ 71 Chevy C10 "The Rust Bucket" 72 Chevy C10 apart in the garage 02 WS6 T/A Fast Black and bad@$$ 93 Nissan Pathfinder "Emily" Totaled RIP girl 05 Jeep Grand Cherokee-HEMI powered 87 Iroc Z28 305 TPI auto (crying out for an LS1 swap)

01-27-2005, 07:31 PM	#4
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	The smallblocks had the evaporative charcoal canister in 72...so I would think the big blocks had it __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

01-27-2005, 08:20 PM	#6
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	The C-10's had the emissions setups but the C-20's and larger did not have them. Engine size was not a consideration as all of the C-10's had the emissions setups in 72. I am not sure what year emissions controls other then pcv's were added but I believe it was in 1970. Jim Last edited by JimKshortstep4x4; 01-27-2005 at 08:22 PM.

01-27-2005, 07:55 PM	#5
COBRO Active Member Join Date: Jan 2005 Location: RDM,Oregon Posts: 285	I think the smog crap was a hit or miss in 72. My 72 C-20 with the 402 didnt have any other than the PCV valve and the breather in the other valve cover plumbed into the air cleaner. Most dont realise that the PCV valve was the first of the smog equip. Just wondering if the hose you found my be a vent hose for the tanks. HTH::::::COBRO

01-27-2005, 10:29 PM	#7
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,159	Check the fuel neck and the cab, if there is a metal line that runs up the cab corner on the passenger side into the roof and an over flow tube on the filler neck then the truck came with emissions, also there is a metal line that runs beside the fuel pump line on the frame towards the battery, Smitty __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 71 C20 Longhorn/Ole Yellor 69 C30 Former Motor Home, Flat Bed time

01-28-2005, 05:15 PM	#8
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	All I have is the PCV .The line that is loose is a return line that was never used I think. __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

01-28-2005, 05:37 PM	#9
HOTFUN Registered User Join Date: Jan 2001 Location: Lincoln, Nebraska Posts: 2,145	Jim is 100% correct. The emission systems were GVW rated and the 10 series all had them small or big block and the 20 series did not. I have both a 10 and 20 big block and the 10 has both the smog pump and charcoal can. The 20 series does not and you can tell by the non ported exhaust manifolds where the air pump tubes attach on the 10 series. Mark __________________ '66 CST BBW swb fleet 327 fac ac '67 CST 4x4 swb 327 stepside project '72 Cheyenne K20 50k original '72 Cheyenne Super K20 project '73 Sierra swb 4x4 frame off in paint stage '74 Cheyenne Super swb w/16k actual '71 & 72 Cheyenne K10 4x4 swb's '70 426 HEMICUDA conv SHAKER 4 sp Dana 60 '60 Impala conv 327 PG fac ac loaded 3rd owner '72 GMC K2500 4x4 '59 Apache CST BBW fleetside swb 283 '73 ElCamino SS LS1 T56 true SS bucket tach '76 ElCamino SS 52k survivor '87 Grand National 41k True 2nd to last built in 1987. '86 K30 454 SRW fleetside CA since new '88 Trans Am GTA 39k bought new 2018 DEMON plum crazy @ 840HP! "Need for speed"

01-28-2005, 07:01 PM	#10
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	I believe the air pump was a California thing only in 72...the 49 state 72 trucks had the evaporative charcoal canister,PVC,and the transmission controled spark that only allowed the vaccum advance to work in high gear __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

01-28-2005, 07:31 PM	#11
avejoe Custer had a plan too. Join Date: Dec 2003 Location: No. California Posts: 344	OK, so can all of this stuff (fuel vapor lines, cannister, spark control, PCV) be eliminated? __________________ 72 K15 GMC (aka Big White) Performance Rockers, Cab Corners, and Floors Fossil Fuel Glutton Neighborhood Nuisance 98 BMW 540i for Speed (Sold ) 05 Subaru Outback for mileage

01-28-2005, 07:36 PM	#12
69sixpackbee Registered User Join Date: Jan 2001 Location: Sabinal, Texas Posts: 1,706	My '72 C-20 402 DOES NOT have anything for emissions with the exception of a vented gas cap and a PCV valve. That's all it ever came with.

01-28-2005, 08:00 PM	#13
Harold Shepard Registered User Join Date: May 2004 Location: Canton North Carolina Posts: 466	The return line is not for gas (liquid) but vapor return. If you have a 10 series 72, you will have at least a vapor canister (charcoal canister) that attaches to the metal line on the frame, EEC,which this line hooks to on the gas tank the transmission spark retard and PCV. If equiped with California emissions package, it will also have the smog pump and AIR lines.

01-29-2005, 11:57 AM	#14
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	wonder why the C 20 s didnt have the canisters with the vapor return and smog pump? __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust



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