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whtats this?

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Its an exhaust brake! /forums/images/graemlins/smirk.gif /forums/images/graemlins/whistling.gif

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I screwed up one time and installed my exhaust so that the butterfly was stuck shut. Made a good "exhaust brake", I couldn't go over 55mph because the motor would get too hot. Took me a long time to figure that out, and I'm talking about several months and $1000 wasted trying to fix a cooling system that wasn't broke.
 
Its actually called an EFE riser ( early fuel evaporation ) . Needed to bring the truck to temp quickly so the emissions ( namely converter ) can work sooner . I chucked mine , but I live in the desert /forums/images/graemlins/k5.gif /forums/images/graemlins/k5.gif
 
There is a vacuum diaphragm that is supposed to connect to the linkage ball of the EFE valve. The diaphragm has a mounting tab, which attaches to one of the three manifold exhaust pipe studs. Then there is a short piece of vacuum hose that plugs onto the diaphragm, which connects a pre-formed piece of steel line for the vacuum up to the engine. The diaphragm is connected to manifold vacuum (I think). It as been a while since I have had to deal with an EFE valve.
 
[ QUOTE ]
[ QUOTE ]
Its an exhaust brake! /forums/images/graemlins/smirk.gif /forums/images/graemlins/whistling.gif

[/ QUOTE ]

I screwed up one time and installed my exhaust so that the butterfly was stuck shut. Made a good "exhaust brake", I couldn't go over 55mph because the motor would get too hot. Took me a long time to figure that out, and I'm talking about several months and $1000 wasted trying to fix a cooling system that wasn't broke.

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SHITTY /forums/images/graemlins/doah.gif
 
if you put the stock exhaust back on without that it will bust your maniflods when you crank it up and the motor tweaks any. ask me how I know? if your putting it back in take out the flapper and weld up the hole. or put some exhaust sealer in it.

69k5
 
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Just put headers on your engine and forget about that thang.

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thats what I will probably do...
 
I have one of those on my 305--I left it on so the y-pipe would fit right--if I knew which vacuum switch ran it,I'd hook it back up again,because around here in the cold clammy cape cod nights my carb tends to ice up,even if its 50 degrees out,and makes it want to stall at stoplights and run very rich until it fully warms up--I noticed better gas mileage when it worked --but if your putting headers on it,you might as well ditch it though--in cold climates the EFE valve is almost a nesessity,with a stock intake and exhaust at least in my experience with my edelbrock carb--its cold blooded,runs like crap until it gets really warmed up--I blame the aluminum adapter blocking all the heat to the carb. The old Buicks that ran those AFB style carbs had a passage under the carb with exhaust gasses running under it too keep the carb warm enough to work right. Even with the EFE working on my truck I bet the carb is still a bit on the "too cold" side due to that aluminum adapter blocking the heat transfer to the carb.It runs great in the summer--but fall and winter is a bummer. /forums/images/graemlins/frown.gif The EFE heat riser butterfly is vacuum operated--if you have no vacuum to it (dissconnect it)there is a spring in the vacuum canister that should hold the butterfly open if its working properly,so if you want to disable it and use your stock manifolds and y-pipe for the time being you can pull off the vacuum hose and plug it. /forums/images/graemlins/crazy.gif
 
diesel4me, since I live in a cold area, are you suggesting I keep it? Should I not use headers, and just use a y-pipe for single exhaust, then use the EFE valve?
 
In my opinion,the factory setup is the best for ordinary daily street driving.GM spent a lot of time and money to make it all work properly--But all that changes when you start swapping in hotter cams,different intakes,headers,etc. It all depends on what you are going to do with the truck,whether you are going to use it for only wheeling in the warm weather,or as a daily driver in the below zero cold.I can tell you this,I HATE my edelbrock and carter AFB carbs in the cold weather--they suck until its been run for at least 20 minites--while a Q-jet with the stock air cleaner with all the "hot air" hoses and the EFE working is pure bliss--no stalling,loading up,having to "power brake"it at red lights,and best of all--the gas gauge doesnt drop as quickly!.But in the summer months the AFB and edelbrock perform much better,at least it feels like they do to me. Its a matter of personal preference,and what kind of driving and weather conditions that determine what is "best" for you. /forums/images/graemlins/crazy.gif
 
I will probably use the motor for winter driving, or be selling it. I'm not sure. I will keep the EFE valve anyways.

Thanks for the replies!
 
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