All has been well with the S6/Weber 38 conversion until late... Put it in gear(AUTO 904) with brake on and it stumbles and shakes. Tried tuning to a better AFR with Ebrake on and in gear but then in P or N its a high idle. Suggestions? Maybe a vac issue? Thought about adding a vac canister?

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Life is never straight up, always a slant in there somewhere.

Check for vacuum leaks.

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Joshua

Check the valve lash. (If it is a solid lifter engine)
DD

Do you have power brakes? If so, it could be an internally failed vacuum operated brake booster.

I cleaned and re RTV'd the carb to mani... checked exh mani torque... put sealer around the brake booster grommet... if I hold hand over carb hat until it starves to breathe i hear a hiss coming from exhaust manifold to head area but cannot spray start fluid and hold both hands over carb! It is a late 82 hydraulic motor DD. C'mon evolution... work with us slant six owners... we need an extra arm/hand or two for all this recurve, time, give it gas, hold the vac gauge and check valve lash to make it run just right!
I am using an S6 intake from a 79 and checked before installing with straight edge and seemed ok... I did however use a standard parts store FEL-PRO gasket... possible culprit? Vac is steady 20's at idle.

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Life is never straight up, always a slant in there somewhere.

Like I said, this could be an internally failed power brake boost. Try this- disconnect the hose that goes to the brake booster AT THE MANIFOLD. Now cap the fitting on the manifold for the brake booster hose. Start the car and step on the brakes and see if the engine still stumbles.

It does not stumble with BB disconnected...

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Life is never straight up, always a slant in there somewhere.

This would strongly suggest that the vacuum leak is inside the brake booster then. Only fix is to replace the power brake booster.

Thank you, again!

Here is current pic of (almost purrrrfect) engine.
[img][img]http://i1221.photobucket.com/albums/dd462/Strvnbutdrvn/null_zpsb3eab849.jpg[/img][/img]

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Life is never straight up, always a slant in there somewhere.

and FURTHER testing resulted in it does NOT have to be in gear. In park if I pump up brakes it does the same thing. Just never noticed until I shifted to move and hence had brake pressure. I pumped up brakes prior to starting and then started and felt pedal move a bit and thus supposed to confirm working BB.

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Life is never straight up, always a slant in there somewhere.

FOUND IT!!!!!

Brake booster GROMMET is dry rotted and cracked!

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Life is never straight up, always a slant in there somewhere.

Replaced grommet and still having issues... all tests for brake booster show its in good working order. tested with starter fluid for vac leaks around every known vac source with no change in idle. Could this be a torque converter issue? Does the brake system signal lockup or load in trans (904)? Baffled....

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Life is never straight up, always a slant in there somewhere.

The booster can leak and pass the functional test. Cap off the hose and recheck the idle. If it's better then you need a new booster.

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Joshua

Also test the one-way check valve... to be sure it is working.
DD

What kind of a job is it to replace the brake booster on a 1980 truck? I'm wondering if the dash and steering column have to come out. Haven't looked yet, just trying to get some up front info.