67-72 engines leaded? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

shifty · 03-24-2005, 04:52 PM

Are the stock engines that come with our truck supposed to use leaded gas? Are the parts hard enough on our trucks that it won't matter if unleaded gas is used? Should I get a lead additive for my gas, or does it not matter?

Just curious...

farside847 · 03-24-2005, 05:00 PM

Yep, they were designed for leaded gas. I would suggest using the additive
until the heads are replaced with hardened heads that can use regular gas.

**CPNE** · 03-24-2005, 05:00 PM

Depends on year of engine. I think starting in 71 all engines got hardened valve seats to compensate for lower lead/unleaded gas.

shifty · 03-24-2005, 05:44 PM

Both of my engines are stamped with 1968, so I'm assuming they're both from 1968.

I'll buy some of the additive tonight and fill up this weekend. I don't think the previous owner actually knew the engine was leaded, so it's been driven for 16-18 months on the weekends with unleaded gas. Dunno if this is the case with the new engine. I know the engine I just put in had a lot of work done on the heads. Not sure about the rest - but it was a pro rebuild, so ...

farside847 · 03-24-2005, 05:50 PM

I would guess the heads were replaced with hardened heads if the engine
was professionally rebuilt.

Jeremy_5 · 03-24-2005, 06:34 PM

How expensive is the additive? You might be better off running without the lead additive and then just adding hardened seats when you start getting exessive valve seat recession. Your intakes should be fine so you would only be looking at replacing the exhaust. Buying the additive could add up in no time and when you are talking about installing 8 seats it doesn't cost that much.

67chevemall · 03-24-2005, 06:54 PM

^what he said. Save your $ for later.

JimKshortstep4x4 · 03-24-2005, 08:13 PM

Me too on the above posts.

The engine in your truck will last a long time without the additives unless you drive in such a way as to run the engine at elevated temperatures as in towing. Short trips and occasional driving should not cause the recession as it happens when the seats and valves get hot and the seat welds to the valve breaking it away. If you are going on a long sustained trip, additives might be a good idea.

Jim

3 on the tree · 03-24-2005, 08:41 PM

I have been told by a trained GM mech not to worry about it. Original engines, if the seats have not been re-ground, have enough lead build up on them to protect them.

see ten · 03-24-2005, 09:20 PM

Quote:

Originally Posted by CPNE

Depends on year of engine. I think starting in 71 all engines got hardened valve seats to compensate for lower lead/unleaded gas.

I think you are right. My owners manual for my 72 states "unleaded fuel only".

72k5 · 03-25-2005, 01:59 AM

3 on the tree's tech has it right. You wouldn't need lead in an older motor unless you used it for all out towing or racing or the like - if it had been run for years on leaded gas. As others said, '72 was definitely built to allow unleaded. I don't know exactly what year that started though.

03-24-2005, 04:52 PM	#1
shifty Questionable Join Date: Mar 2005 Location: Atlanta Posts: 13,373	67-72 engines leaded? Are the stock engines that come with our truck supposed to use leaded gas? Are the parts hard enough on our trucks that it won't matter if unleaded gas is used? Should I get a lead additive for my gas, or does it not matter? Just curious... __________________ If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM.

03-24-2005, 05:00 PM	#2
farside847 Registered User Join Date: Feb 2005 Location: Bay Area, California Posts: 995	Yep, they were designed for leaded gas. I would suggest using the additive until the heads are replaced with hardened heads that can use regular gas. __________________ 1971 Chevy C10 Shortbed Stepside, 307v8 3-on-the-tree

03-24-2005, 05:00 PM	#3
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,662	Depends on year of engine. I think starting in 71 all engines got hardened valve seats to compensate for lower lead/unleaded gas. __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all

03-24-2005, 05:44 PM	#4
shifty Questionable Join Date: Mar 2005 Location: Atlanta Posts: 13,373	Both of my engines are stamped with 1968, so I'm assuming they're both from 1968. I'll buy some of the additive tonight and fill up this weekend. I don't think the previous owner actually knew the engine was leaded, so it's been driven for 16-18 months on the weekends with unleaded gas. Dunno if this is the case with the new engine. I know the engine I just put in had a lot of work done on the heads. Not sure about the rest - but it was a pro rebuild, so ... __________________ If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM.

03-24-2005, 05:50 PM	#5
farside847 Registered User Join Date: Feb 2005 Location: Bay Area, California Posts: 995	I would guess the heads were replaced with hardened heads if the engine was professionally rebuilt. __________________ 1971 Chevy C10 Shortbed Stepside, 307v8 3-on-the-tree

03-24-2005, 06:34 PM	#6
Jeremy_5 Truck addict Join Date: Sep 2003 Location: Lincoln, California Posts: 497	How expensive is the additive? You might be better off running without the lead additive and then just adding hardened seats when you start getting exessive valve seat recession. Your intakes should be fine so you would only be looking at replacing the exhaust. Buying the additive could add up in no time and when you are talking about installing 8 seats it doesn't cost that much. __________________ 1956 Chevy Napco 1972 Cheyenne Super 1970 K20

03-24-2005, 06:54 PM	#7
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	^what he said. Save your $ for later. __________________ 1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD

03-24-2005, 08:13 PM	#8
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Me too on the above posts. The engine in your truck will last a long time without the additives unless you drive in such a way as to run the engine at elevated temperatures as in towing. Short trips and occasional driving should not cause the recession as it happens when the seats and valves get hot and the seat welds to the valve breaking it away. If you are going on a long sustained trip, additives might be a good idea. Jim

03-24-2005, 08:41 PM	#9
3 on the tree Registered User Join Date: Oct 2004 Posts: 392	I have been told by a trained GM mech not to worry about it. Original engines, if the seats have not been re-ground, have enough lead build up on them to protect them.

03-25-2005, 01:59 AM	#11
72k5 Registered User Join Date: Oct 2002 Location: Livermore, CA Posts: 566	3 on the tree's tech has it right. You wouldn't need lead in an older motor unless you used it for all out towing or racing or the like - if it had been run for years on leaded gas. As others said, '72 was definitely built to allow unleaded. I don't know exactly what year that started though. __________________ 350 ETec 170 heads, Performer, HEI, Holly TBI, 700r4, 14 bolt rear, F&R lockers, lots of off road improvements.



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