HomeHome  PortalPortal  CalendarCalendar  GalleryGallery  FAQFAQ  SearchSearch  RegisterRegister  Log in  

Share | 
 

 Not a lot of power... exhaust valve?

Go down 
AuthorMessage
kameron m



Posts : 28
Join date : 2016-08-04
Location : South Bend Indiana

PostSubject: Not a lot of power... exhaust valve?   Sun Aug 21, 2016 4:22 am

So I've noticed that my 87 electra estate doesn't have a lot of "gusto". Empyr (the wagon) starts and idles ok ish, couple misses here and there. MPG so far is acceptible but not great, but the lack of power is painfully apparent.

My mechanic friend thinks it's the valve in the exhaust manifold. (Is there just one of these or are there two?!) I checked it and the vac solenoid was pretty toasted looking. Because yes! Putting a rubber doodad that takes vacuum pressure to move right by the exhaust = good idea.

Nonetheless, is deleting the valve and seeing where I am after that a sensible step to take or are there other things to check first (or should the valve be deletes anyways as well?)

Also if I'm going to stick the valve open, which way do I turn it? I think I turned it the way the vac can would if it pulled to open, which is how I was told it worked but I'm not entirely sure so I'm asking. If thst is so then I'd suspect the valve not being the issue (unless there are two.)

I'm considering ditching the C.C. quadrajet and going for an edlebrock. I'm sure someone out there has an opinion and one that counters it. Is it possible to even do this without ECU throwing a fit?

I don't suspect EGR because check engine idiot light isn't on (but functions) I did see it once the other day for about a minute (gave me a scare) but it went away.

I also think the butterfly valve on the carb is sticking some. Maybe that is a part of the problem too.

Thoughts?
Back to top Go down
paart



Posts : 93
Join date : 2015-10-10

PostSubject: Re: Not a lot of power... exhaust valve?   Sun Aug 21, 2016 4:54 pm

Are you new to the vehicle? Electra Estate wagons with a 307 don't have a lot of "gusto" to start with"! Smile

A simple way to check the valve you mentioned is to apply a good vacuum source to it, and see if it moves. If it doesn't, then the valve is stuck--probably in the closed position. If it moves, then check to see if the line to it is providing "good" vacuum".

The purpose of this valve is to divert exhaust gas through the intake manifold to heat the intake, to improve gas vaporization when the engine is cold. After warm-up it is pulled to the fully open position.

In the climate where I'm located, I've found these to be more trouble then they are worth, and usually remove them. The electronic Rochester carb that's on your car has a sophisticated cold enrichment circuit, in addition to the choke, that provides very good cold start performance, nearly as good as fuel injection. I wouldn't substitute another type of carb for yours, unless it's not repairable.

A way to test for exhaust blockage is with a common vacuum gauge. Hook it to to an intake manifold source, start the engine, and observe the vacuum at idle. It should be close to 20 inches, perhaps more. Anything below 16 inches usually indicates exhaust blockage. I've seen it as low as 10 inches from a blocked catalytic converter.
Back to top Go down
kameron m



Posts : 28
Join date : 2016-08-04
Location : South Bend Indiana

PostSubject: Re: Not a lot of power... exhaust valve?   Sun Aug 21, 2016 11:33 pm

Ok, thanks for the info. I don't suspect my 87 electra to be a racecar, but the preformance is noticeably lacking, especially on the highway, and it seems slightly variable which indicates something is going on. I am new to this car, yes.

I thought that was a different valve. There seem to be two valve things on the exhaust. One which is on the air cleaner which diverts warm air up from around the manifold towards the carb directly, and one which is IN the exhaust stream, or maybe these are both a part of the same system and the one is just to warm up the exhaust manifold faster?

I was not planning on ditching the carb right away, maybe I won't at all. I'll do an ignition service and pull that valve and then see where I am after those things, maybe she'll be running like a dream, or something.

I thought it was a carter carb! shows how much I know as of yet.
Back to top Go down
paart



Posts : 93
Join date : 2015-10-10

PostSubject: Re: Not a lot of power... exhaust valve?   Mon Aug 22, 2016 1:47 pm

Carburated GM cars from this era also had a heated air intake system to improve cold weather driveability and emissions during "warm-up". It consists of a flexible tube from a shield over one exhaust manifold, that runs to the bottom of the snorkel on the air cleaner. It has a vacuum diaphragm that's controlled by a thermostat mounted inside the air cleaner body. It only diverts air from the exhaust manifold during cold starts, or very cold conditions, but should be open otherwise.
I removed the fragile flexible tube from my vehicles, for most of the year, only using it during the winter.

The engine compartment of your car has a "rats nest" of vacuum hoses, all of which are subject to deterioration and leaking by this time. I'd look over every inch of it, and replace anything that looks at all questionable. Any vacuum leaks in these lines can cause poor driveability. Particularly, check the larger hose from the PCV valve to the carb or intake manifold (I forget which on the 307).

Also check the "tightness" of the four bolts holding the carb body to the manifold, and the large rubber hose that goes to the brake booster.
Back to top Go down
kameron m



Posts : 28
Join date : 2016-08-04
Location : South Bend Indiana

PostSubject: Re: Not a lot of power... exhaust valve?   Mon Aug 22, 2016 6:23 pm

Ok so, what does the valve IN the exuaust pipe do?
Back to top Go down
paart



Posts : 93
Join date : 2015-10-10

PostSubject: Re: Not a lot of power... exhaust valve?   Mon Aug 22, 2016 10:19 pm

The purpose of this valve is to divert exhaust gas through the intake manifold to heat the intake, to improve gas vaporization when the engine is cold. After warm-up it is pulled to the fully open position.

When it is closed, it forces some of the hot exhaust gas, that would normally flow out through the valve, into a passage in the bottom of the intake manifold. This heats the intake manifold quickly, and shortens the "warm up time" of the engine. An old common term for this is the "heat riser". If the valve is stuck in the closed position, engine performance will be noticeably reduced, particularly at increased throttle or high RPM conditions.
Back to top Go down
kameron m



Posts : 28
Join date : 2016-08-04
Location : South Bend Indiana

PostSubject: Re: Not a lot of power... exhaust valve?   Mon Aug 22, 2016 10:34 pm

AH Ah! Okay! I can see it now. So it does in fact help with cold start performance, but not as much as the other valve, the little one. Given that I don't really intend on driving a 4200 pound RWD car without ABS in snow anytime soon, I think I'm pretty safe to delete that then.
Back to top Go down
phantom 309

avatar

Posts : 5785
Join date : 2008-12-28
Age : 108

PostSubject: Re: Not a lot of power... exhaust valve?   Tue Aug 23, 2016 6:56 pm

kameron m wrote:
Given that I don't really intend on driving a 4200 pound RWD car without ABS in snow anytime soon, I think I'm pretty safe to delete that then.

I couldn't imagine driving WITH gm's archaic abs in the wintertime,..
Back to top Go down
paart



Posts : 93
Join date : 2015-10-10

PostSubject: Re: Not a lot of power... exhaust valve?   Wed Aug 24, 2016 8:54 pm

phantom 309 wrote:
kameron m wrote:
Given that I don't really intend on driving a 4200 pound RWD car without ABS in snow anytime soon, I think I'm pretty safe to delete that then.

I couldn't imagine driving WITH gm's archaic abs in the wintertime,..

Try out Chrysler's mini-van ABS set-up sometime.
Back to top Go down
Sponsored content




PostSubject: Re: Not a lot of power... exhaust valve?   

Back to top Go down
 
Not a lot of power... exhaust valve?
Back to top 
Page 1 of 1
 Similar topics
-
» Nuclear Power and Capitalism
» NHS - The McCanns Abuse of Power
» IN THE LINE OF DUTY
» Scotland Yard takes over the enquiry
» How Much Power do the McCanns Have? - Pat Brown

Permissions in this forum:You cannot reply to topics in this forum
GM Longroof Forum :: Longroof Tech :: Engine-
Jump to: