Update repeat 1996 Chevy Van problem (ping Ian??)

OK I am stumped. This is a 1996 Chevy conversion van with a remanufactured Vortec 5.7 V-8. There is less than 500 miles on it since install. Once it warmes up,
the engine surges (RPMS flux up and down) when in drive. Almost sounds as if it is breathing. Put it in park, and no more surging. Back into drive, and about 30-60 seconds later it surges again. Been over it with the scanner and it tells nothing. No check engine light.
I thought it may be a bad install of the intake manifold gasket (vacuum leak). I changed it again. Still no luck...
I am at wits end with this thing and do not know where else to check.
Here are some thoughts.....wrong engine application? Bad cam lobe? (I did pressurize the oil system) Intake not seating to the heads? Tranny problem??
I dunno, I have reached the end of my expertice on this one.....
Eightupman
UPDATE...check engine light on all the time now. Calling out engine misfire. Vacuum in the engine is about 20 in/Hg. Fluxes (obviously 15-20 in/Hg in Drive)
Found out that I installed the new distributor minus an "O" ring (I used a gasket that came with the crate motor). The odd angle chewed a bit into the dist gear. Have a replacement on the way. Will the missing "O" ring have caused my problem?
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It is very possible. Crank pressure is regulated by PCV and breather lines, and any change in crankcase dynamics could cause a weird surge due to vacuum/pressure leaks slipping past the o-ring. IIRC, there were a handful of posts like this over the past few years where the dizzy o-ring (or lack thereof) was the problem.
Doc
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Yeah...most were probably mine!!
Hope it works I'll fine out when I get the HuneyDoo list done.
Eightupman

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Eightupman wrote:

I'm not sure what you mean by "O-ring seal". I don't recall any of the chevy small blocks using an o-ring to seal the distributor. They all use the same old paper gasket that has been around for years. Unless the surface of the intake manifold is warped badly where the distributor goes in, or there is something wrong with the geared section of the camshaft, I can't see why you should be having issues with the dist gear getting chewed up.
Ian
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Dunno either. All I do know is that it is chewed and there are a couple people saying that an "O" ring at the point where the dist seats in the intake is the problem. I will post if it works.
Eightupman

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