71 exhaust damper - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Musicworks · 03-16-2003, 07:13 PM

How important is this exhaust damper? My spring broke. Any ideas? please help. My first 250 I-6.

JimKshortstep4x4 · 03-16-2003, 08:07 PM

Welcome to the board from West Michigan!

My experience indicates that you don't need them, especially in warmer areas. We don't use the heat risers in our exhaust systems in Michigan, but in real cold areas, they may be of some benefit to help the engine warm up faster. The other question,
you may be faced with is does California expect them to work.

Jim

Musicworks · 03-17-2003, 12:14 AM

Thanks for the input jim. 71 is calif. exempt from smog. Do I weld it open or shut?

Longhorn Man · 03-17-2003, 12:19 AM

Be carefull...they are trying to make your truck get smogged again.
With that said, weld it shut.

JimKshortstep4x4 · 03-17-2003, 08:51 AM

I would set it up, so that it is open all of the time. Otherwise the exhaust will back up.

Jim

Musicworks · 03-17-2003, 10:46 AM

How about half way open? Any ideas where I can find some org. side mirrors?

68speedalert · 03-17-2003, 03:17 PM

coming from a mechanic who used to fight engines with carberators, be ready for some things to happen. If you wire it open you MAY have cold engine hesitations. You also may get carb. icing up in cold, humid weather. There were many cases I fixed bad running cars just be lubricating and losening up the heat riser.

The riser being open will not affect emmissions out the tailpipe.

Either wire it open or replace, don't leave it half way.

Steve

Musicworks · 03-18-2003, 12:32 AM

OK I found a spring to put back on this manifold. When it is on, is the damper to be shut or open?

ZOOMY · 03-18-2003, 01:24 AM

Technically, it's know as a heat riser valve & should be closed when cold and wide open when everything is up to operating temp. When the engine is cold gasoline doesn't vaporize very well, so GM put this valve in there to force exhaust gasses thru openings in the head, thru the bottom channel in the intake manifold, thru the opening in the other head & out that exhaust pipe.......Zoomy

Musicworks · 03-18-2003, 10:25 AM

Thanks, Zoomy. I will get this done today.

03-16-2003, 07:13 PM	#1
Musicworks Registered User Join Date: Mar 2003 Location: fresno,ca Posts: 5	71 exhaust damper How important is this exhaust damper? My spring broke. Any ideas? please help. My first 250 I-6.

03-17-2003, 03:17 PM	#7
68speedalert Semi-Senior Member Join Date: Feb 2003 Location: Washington, MO Posts: 390	coming from a mechanic who used to fight engines with carberators, be ready for some things to happen. If you wire it open you MAY have cold engine hesitations. You also may get carb. icing up in cold, humid weather. There were many cases I fixed bad running cars just be lubricating and losening up the heat riser. The riser being open will not affect emmissions out the tailpipe. Either wire it open or replace, don't leave it half way. Steve __________________ '68 50th Anniversery LWB Custom Fleetside, '77 305 v-8, turbo 350, factory speed alert (still works), '71 drivetrain w/front discs. Some call it ugly yellow, others call it Ochre '83 Jeep CJ-7, <80,000 miles, original owner '04 Chevy Suburban, 4x4, 2500, 6.0 ltr, Predator Diablo programmer '95 GMC K1500 Extended cab

03-18-2003, 01:24 AM	#9
ZOOMY Senior Member Join Date: Feb 2003 Location: WIS Posts: 1,752	riser Technically, it's know as a heat riser valve & should be closed when cold and wide open when everything is up to operating temp. When the engine is cold gasoline doesn't vaporize very well, so GM put this valve in there to force exhaust gasses thru openings in the head, thru the bottom channel in the intake manifold, thru the opening in the other head & out that exhaust pipe.......Zoomy

03-16-2003, 08:07 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Welcome to the board from West Michigan! My experience indicates that you don't need them, especially in warmer areas. We don't use the heat risers in our exhaust systems in Michigan, but in real cold areas, they may be of some benefit to help the engine warm up faster. The other question, you may be faced with is does California expect them to work. Jim

03-17-2003, 12:14 AM	#3
Musicworks Registered User Join Date: Mar 2003 Location: fresno,ca Posts: 5	Thanks for the input jim. 71 is calif. exempt from smog. Do I weld it open or shut?

03-17-2003, 12:19 AM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Be carefull...they are trying to make your truck get smogged again. With that said, weld it shut.

03-17-2003, 08:51 AM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	I would set it up, so that it is open all of the time. Otherwise the exhaust will back up. Jim

03-17-2003, 10:46 AM	#6
Musicworks Registered User Join Date: Mar 2003 Location: fresno,ca Posts: 5	How about half way open? Any ideas where I can find some org. side mirrors?

03-18-2003, 12:32 AM	#8
Musicworks Registered User Join Date: Mar 2003 Location: fresno,ca Posts: 5	OK I found a spring to put back on this manifold. When it is on, is the damper to be shut or open?

03-18-2003, 10:25 AM	#10
Musicworks Registered User Join Date: Mar 2003 Location: fresno,ca Posts: 5	Thanks, Zoomy. I will get this done today.



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