Plenum rebuild and tune-up done!
#1
03-14-2011 | 10:31 AM
Thread Starter
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Amateur
Joined: Aug 2010
Posts: 41
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From: MO
Plenum rebuild and tune-up done!
Finally got to tear into the truck.
I replaced:
Plenum gasket
plugs (3923's)
wires
dist (brass term)
rotor
coolant temp sens.
O2 sens.
Plenum did have oil in it. I don't think it was a lot of oil, maybe a tablespoon. As far as the new gasket, I don't buy into the wrong material theory. I think its just a combination of too long of bolts and too far bolt spacing for the thickness of the plate. I made spreader bars that went under each bolt, should address both problems.
I also did a compression check while the plugs were out. Most of the cylinders were at 150, but 7 I could only get a bit over 120, and 8 was 135. wet test didn't seem to make a difference on #8, didn't try it on #7. Should I be concerned?
As far as the results, much smoother running, a little more power. Kinda feels like it is probably about as good as it ran new now. Still think I need to get the SCT, when funds come. Below 2k rpm is still turdish.
The trashy exhaust sound is still there, only when cold though! when it warms up it sounds good. Thoughts? I think the cat would probably mask this sound if it were still there. Maybe just poor manifold/y-pipe design.
I replaced:
Plenum gasket
plugs (3923's)
wires
dist (brass term)
rotor
coolant temp sens.
O2 sens.
Plenum did have oil in it. I don't think it was a lot of oil, maybe a tablespoon. As far as the new gasket, I don't buy into the wrong material theory. I think its just a combination of too long of bolts and too far bolt spacing for the thickness of the plate. I made spreader bars that went under each bolt, should address both problems.
I also did a compression check while the plugs were out. Most of the cylinders were at 150, but 7 I could only get a bit over 120, and 8 was 135. wet test didn't seem to make a difference on #8, didn't try it on #7. Should I be concerned?
As far as the results, much smoother running, a little more power. Kinda feels like it is probably about as good as it ran new now. Still think I need to get the SCT, when funds come. Below 2k rpm is still turdish.
The trashy exhaust sound is still there, only when cold though! when it warms up it sounds good. Thoughts? I think the cat would probably mask this sound if it were still there. Maybe just poor manifold/y-pipe design.
#2
03-14-2011 | 12:10 PM
Retired Moderator - RIP
Joined: May 2008
Posts: 18,729
Likes: 17
From: NH
May just be carbon on the valves from the oil as a result of the bad plenum gasket. Run a bunch of Techron + through it(gas tank) and Seafoam it also(intake). Get a PCV from the dealer too.
Worst case would be cracked head(s) from a clogged cat as a result of the blown plenum.
Worst case would be cracked head(s) from a clogged cat as a result of the blown plenum.
Last edited by zman17; 03-14-2011 at 12:13 PM.
#4
03-14-2011 | 12:39 PM
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Amateur
Joined: Aug 2010
Posts: 41
Likes: 0
From: MO
whats the diagnosis method, leakdown test?
I went to bypass the cat a couple weeks ago and it was already hollow! I've only had the truck since August '10 so I have no idea of how long.
#6
03-14-2011 | 12:42 PM
Administrator
Joined: Apr 2010
Posts: 82,820
Likes: 3,435
From: Clayton MI
Leakdown test will probably tell you things you would rather not know... but, it IS the correct way to find where your compression is going.
Heads on these trucks had rather thin decks, so, cracking is a rather common problem. There are aftermarket heads that solve these issues, that can be had for relatively cheap, 270 a pop for stock size valves, or, somewhere in the neighborhood of 4 to 5 hundred for 2.02 intake valves. Either way wouldn't be a bad plan.
Heads on these trucks had rather thin decks, so, cracking is a rather common problem. There are aftermarket heads that solve these issues, that can be had for relatively cheap, 270 a pop for stock size valves, or, somewhere in the neighborhood of 4 to 5 hundred for 2.02 intake valves. Either way wouldn't be a bad plan.