| Re: [GMCnet] losing power [message #220223] |
Wed, 28 August 2013 13:20  |
KB
Messages: 1262
Registered: September 2009
Karma:
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Senior Member |
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thanks guys. (sorry to hijack the thread)
Vac is about 15- at idle, used to be 18+ish on the old engine.
I've checked for vac leaks and can't find any (yes, I remembered
to goop the right rear bolt hole on the TBI gasket :-). I changed the dist
module and cleaned up the contacts and saw no change. I've double-checked
timing at 8 BTDC, but not sure how I'd tell if the timing mark is
wrong. It's the same balancer as was on the old engine and looked ok
(all this stuff was supposedly replaced only 12k miles ago). Intake is stock
in good condition with Dick P's block-off gaskets. No obvious problems
on the fit.
It runs ok with the computer in control, though the idle isn't
as smooth as I'd like. That could be because the fuel and spark tables
haven't been tuned yet. I went back to an earlier tune closer
to what the amazing Randy uses. On the old engine, I'd been backing
off more and more on the spark trying to reduce knock counts.
Turns out the "knocks" were probably the wrist pin or whatever
is ailing piston number 8, which we couldn't hear until it got really bad.
Current theory is the combination of new engine and RV cam is giving
us a lower vac reading. I noticed the IAC step counts were also
significantly higher than before (ie, has to open more to let in air),
which could also be due to the higher friction of a new engine.
So, I'll just check everything carefully, get the new fan clutch
and shroud installed, and we'll try a very gentle short trip to see what
happens. Fingers crossed... we really want to make Coos Bay.
thanks
Karen
1973 23'
1975 26'
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Karen
1975 26'
San Jose, CA
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