How might I know if it works? If indeed that is what it is.
Tere

I don't think it's an exhaust brake (gaso engines don't benefit from them because the throttle plate - when closed - produces the same effect of turning the engine into a compressor).

A possibility is that it's part of the emissions control system.

I agree with Rusty in not much benefit in a gas engine. Whatever it was it has been wired open. But it looks like it was a vacumn activated butterfly valve.

They did sell exhaust brakes for gas engines years ago, but don't know anyone who bought one.

I think you are looking at a vacume controled heat riser control valve. It stays closed when engine is cold forcing hot exaust to flow thru bottom of intake to other exaust pipe to aid in preheating intake faster.vacume line should go to temp sensor then to vacume source. Make sure butterfly is free and vacume diaphram will pull in if you hook it up to direct vaccume.Stuck in the closed position not a good thing. Stuck in open position will only keep intake frome heating up as fast. On older engines this use to have a bimetalic spring that open them up.

quote:

Make sure butterfly is free and vacume diaphram will pull in if you hook it up to direct vaccume.

I guess I'd have to remove it to look at it?! Will removing it to look at it damage anything? I don't want to start something I can't finish. If so & the diaphram is faulty should I put another one on (if I can find) or will it be ok without? Then where would I hook up the vacuum hose?

Other ??'s about fuel pump:

To get the right fuel pump I will need to have one that is compatible with the fuels we have today, it will have to have a return line on it, & what is the gallons per minute I am looking for?

When I remove fuel pump I will remove hoses first, then remove from engine. When I remove the two bolts holding it on will it come out fairly easily? Looks like there is a hook thingy that goes into the block to hold it. Does the hook thingy have any other purpose?

I have marine grade fuel hoses. Is there any down side to running the hose from the fuel pump to the fuel filter in one long run? The marine grade is a little less flexible than the normal fuel hoses. Of course it will be a splice @ fuel filter then a short run to the switching unit.

I would like to do the same from the sw unit to the rear tank. We are going to drop the tank first & have it sent out for cleaning & recoating.

Seems like i should have a short run of hose (3')from tank to fuel filter then a long hose to sw unit.
Right now the filter is up close to the sw unit. Probably doesn't matter to much.

Ok to buy fuel pump & vacuum modulator from NAPA, Advance or Summit or Classic Industries or GM?

Any thing else I should have on hand before I get started?

I will be taking carb out & sending to Oscar Heritz in OHIO, but know that taking it off requires being able to put it back on when the rebuilt one arrives. Any suggestions. My son in law says to use masking tape & # the vacuum hoses etc(like a clock) but there is a lot of other stuff I have to undo.

I'll certainly take a lot of pics for reference too.

quote:

I think you are looking at a vacume controled heat riser control valve.

Doorman,

Thanks for reminding me what that things was called, I was wracking my brain trying to recall. I once bought a 454 Monte Carlo from a guy who said the engine was going south. It would make a loud ticking noise until warmed up, diagnosis; bad rod bearing. Truth, it was the heat riser valve needing lubrication (that one was on a spring that heated up).

Thanks,

Corey

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Truth, it was the heat riser valve needing lubrication (that one was on a spring that heated up).

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How do I lubricate it?

quote:

How do I lubricate it?

Jim,

It looks like someone has wired it open. That would indicate it was hanging up closed, which restricts your exhaust flow. You could try to make it functional again, although yours is a vacuum operated one and therefore more complex. I would leave it be if you have no cold start issues.

Corey

Jim,

Didn't notice wire. I leave it alone, but would trace vacume line back to source and plug just in case the diaphram is leaking. It helps in cold weather, but you're going to get rid of it when you put your new Doug Thorley Headers on any way.

Doorman

quote:

but you're going to get rid of it when you put your new Doug Thorley Headers on any way.

We already have Doug Thorley Headers. I will trace & plug the vacuum hose.

Just ordered a Bosch Fuel pump & a B&M vacuum modulator. Not sending carb in until I test the new fuel pump.

Rear tank is ready to drop, just need my son in law to take a break from triplets to help me lower. There are some brake lines that are attached to a clamp on the rear axle that I will let him undo. I don't want to damage brake lines.

After we were somewhat "repaired" & we were limping home we stopped for fuel. Turned off engine. Filled up fr tank & then tried to start. Nothing! Tried Aux battery, Nothing! Switched back from aux batt & waited 30 sec, it started right up. My son in law said the older Chevys were notorious for this. We have a metal heat shield on our starter & he suggested a thermo blanket. Where might I acquire one of these?
Tere

I "sidewalk superintended" the removal of the fuel pump last night. Just below the fuel pump is what GM calls a "push rod". It is about 1/2" in diameter and about 4" long. It is held is place by a square bolt. This push rod moves the fuel pump rocker arm back and forth. Should we replace the rod along with the fuel pump? It looks to be in good shape.
Jim

Not necessary - the fuel pump follower is softer than the operating rod, and any wear would be on it - but they're both bathed in oil, so wear is very, very rare.

Oscar Heritz has rebuilt the carb and it's on the way back to us. Our plan is to finish up the fuel lines to the mid tank and fire it up to see if our problem is solved. Oscar said he didn't find a lot of junk in the carb but it did have some other problems that might have caused the problem. We'll see. I feel guilty taking up so much room on the "tech forum", what with four different subjects. Really appreciate all the help.
Jim

quote:

Originally posted by Jim and Tere:
I feel guilty taking up so much room on the "tech forum", what with four different subjects.

I wouldn't worry about it.