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Opeler
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1,133 Posts
If your hose is plugged onto the modulator well and the modulator is healthy, as well as, the hose, then the problem is probably not enough vacuum. These trannies are sensitive to poor vacuum. If you use a Combo cam they will upshift and downshift prematurely. Your problem is probably with plugging the hose into your Holley. It should be connected to a manifold port. Go to the auto store and get a T-fitting with a 1/4" barb sticking out of a 1/2" T and splice that into your brake booster line. I have had to do this will all my down draft/side draft/and FI set ups. Make sure to get a metal or brass one, do not buy a plastic one, they break. If you can't find that 1/4"/1/2" combo, then go to a hardware store, like ACE, and mix and match barbed brass plumbing fittings to make what you need.
I’m using a custom cam:

Camshaft:

Intake: Duration: 222 Lift: .455
Exhaust: Duration: 228 Lift: .448
Lobe separation: 112

Here’s the fittings that are on the Sniper...

432328


I’ll attempt a splice in to the brake booster hose if need be. I didn’t notice an issue prior to installing the Sniper and changing the transmission fluid/filter/gasket.
 

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Opel Rallier since 1977
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2,130 Posts
You should be connecting the line from the trannie's vacuum modulator to the 3/16" Manifold vacuum port, and the booster would be to either that or the 3/8" manifold vacuum port. Connecting the vacuum modulator line to the Ported vacuum port on the Sniper will cause all sorts of hard-to-predict shift variations.

Low vacuum in the manifold will cause delayed upshifts, and premature downshifts. Question: If you use light to medium throttle and gradually rev higher than normal, will the tranie finally upshift from 1-2 or 2-3? Your symptom description of "not shifting from 1 to 2 to 3" sounds like delayed upshifts.)

This can be caused by several issues:
  • Your cam is producing low vacuum in the intake manifold (which would be common or a moderate cam like yours)
  • Any intake manifold leak, from the Sniper base, to the manifold gaskets, to the brake booster and/or hose, the vacuum line to the vacuum modulator on the trannie, or a faulty vacuum modulator (This last problem will usually cause a LOT of smoke out of the exhasut!)

Measure your vacuum at idle and let us know what you have. Also. low vacuum can be caused by other vacuum leaks anywhere in the system.

Other possible problems are low trannie fluid or low pump pressures. But let's hear a better symptom description and see what you have for vacuum first.
 

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Registered
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21 Posts
Hi all, this isn’t exactly on-topic but does relate to a couple of the older posts. I removed the auto from my car and I’m planning to store it, at least until perhaps I overcome my hoarding tendencies and perhaps sell it. Anyway, are there specific recommendations on the best way to do this? I’m thinking about building a wooden crate for it along with the shifter etc (sort of a “kit” in case someone wants to convert a manual car to an auto). Do I need to keep the trans flat, or can it stand on its bellhousing? I drained the fluid; should I do anything else? I plan to stick the crate out in my shed.
 

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Detroit,where my home was
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2,925 Posts
..... Do I need to keep the trans flat, or can it stand on its bellhousing?
Keep it flat ATF still will drip out

I drained the fluid; should I do anything else? I plan to stick the crate out in my shed.
If I had to store an auto trans I would top it of with [fresh] ATF oil, so no air could get in the trans
 

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Just Some Dude in Jersey
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14,839 Posts
Eric, if for some reason you removed your modulator, there is an approximately 1" long 1/4" diameter sheet metal tube in the hole. If it fell out or you lost it the tranny will not shift. The diaphragm inside the modulator presses on that tube and actuates the shift function in the tranny.

Manta Rallier appears to be correct: Only the 2 lowest vacuum ports seem appropriate for a tranny vacuum line. The one labeled for vacuum advance to the distributor would probably not apply enough vacuum to make the tranny shift.
 
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