LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Striped Intake Manifold Bolt Cause High BLM's?

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Old Apr 13, 2009 | 08:12 PM
  #1  
feenix88's Avatar
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Striped Intake Manifold Bolt Cause High BLM's?

Around the 140+ range? I plan on heli-coiling the threads this weekend. Fuel pressure gauge looked steady (dont have a vac gauge). Or would this condition cause the BLM's to drop? Thanks.
Old Apr 13, 2009 | 08:14 PM
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Nothing to do with split BLM's.

Someone who knows how to tune can resolve it 4 out of 5 times.
Old Apr 13, 2009 | 08:19 PM
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I think I have one striped on each side, one spins and the other at least get a little torque on it. Previous owner destroyed the threads, I ran a tap through it and I guess there was not enough meat left to get 35 ft-lbs. Both sides are in the mid 140's. I thought a vacuum leak internally might be unmetered air and would cause the o2's to sense a lean condition and jack up the BLM's. I am just looking for someone to verify this or correct me.
Old Apr 13, 2009 | 09:27 PM
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Regardless, you need to repair the holes. I would do that and see if anything changes. No sense in conjecturing.
Old Apr 13, 2009 | 11:27 PM
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If the manifold is loose enough to allow air to leak past the gasket, into the intake runners, it would elevate the BLM's. In that case, you might see oil on the plugs, as well if its leaking on the lifter valley side. If you have two stripped head bolts, that is a distinct possibility. If all you have is a leak at the back of the intake, on top of the block, its not going to affect the BLM's. And if I read the post correctly, BLM's are elevated equally on both sides... not a case of "split" BLM's. I'd think it would be a very strange coincidence if you were getting the exact same leakage level on both banks of the enigne.

Fix the stripped bolts, then see what happens. They should have been repaired when the manifold was installed.
Old Apr 15, 2009 | 05:13 PM
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It is not leaking at the front nor the back. There is one stripped hole on each head, the next to last bolt hole on each side. I plan on pulling the manifold this weekend and then getting some new BLM numbers once its reassembled. I don't remember the BLM's being that high before I replaced the gasket this past time. I am seeing 142 left, 149 right at idle in cell 16 currently. Before, I believe it was 122 left, 136 right. While I had it down I also cleaned and re-oiled the K&N, so when its down again this weekend, i will also clean the maf since that would produce the same symptoms. More than likely, its the maf. Although, I barely oiled the filter.
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