Feels slow even after rebuild and rough idle

[honkon]

My truck shows 22-24dg timing at idle. 98 5.7 Silverado. Is that normal?

My '98 factory service manual shows timing should be around 21dg at idle at operating temp.
I'm having the same exact issue with my Yukon, and I can't figure it out. It was slow, I rebuilt the engine, its still slow. Slower than your truck I think.
I also have a somewhat rough idle. It's not misfire rough, it just stumbles a little. It should be smoother.
It runs great otherwise, it just doesn't make the power it should.

 

[kennythewelder]

My truck shows 22-24dg timing at idle. 98 5.7 Silverado. Is that normal?

No, should be @ 0 deg. @ about 1000 RPMs. Timing needs to be set for one thing

 

[Supercharged111]

No, should be @ 0 deg. @ idle. Timing needs to be set for one thing

If you monitor your data then yes, 20 or so degrees at idle is normal. When you set it to zero on a TBI, you're setting it locked. After setting, you then unlock and the PCM can regain control of the timing.

 

[kennythewelder]

Also free flowing exhaust will help. Free flowing cats, headers, and free flowing muflers (NOT Flowmasters). A muffler you can see straight through before installed.

 

[kennythewelder]

If you monitor your data then yes, 20 or so degrees at idle is normal. When you set it to zero on a TBI, you're setting it locked. After setting, you then unlock and the PCM can regain control of the timing.

Yea, I corrected my post, thats 0 @ about 1000 RPMs

 

[Supercharged111]

Yea, I corrected my post, thats 0 @ about 1000 RPMs

I just went back, this is a Vortec. You're confusing CMPRET with ignition timing.

 

[kennythewelder]

If you monitor your data then yes, 20 or so degrees at idle is normal. When you set it to zero on a TBI, you're setting it locked. After setting, you then unlock and the PCM can regain control of the timing.

Also this is not a TBI, it a CPI Vortec. This has a total different timing than a TBI. TBIs are OBD I and Vortecs are OBD II

 

[kennythewelder]

I just went back, this is a Vortec. You're confusing CMPRET with ignition timing.

LOL no Im not confused at all. Just made a simple mistake in my first post, that I corrected

 

[honkon]

I dunno what the hell y'all are talking about but it says right here in the 98 service manual that ignition timing on the 5.7l should be around 21dg at idle.

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Link if you want to download the manual. You should. It's very useful.

 

[Supercharged111]

Kenny was talking about the cam crank correlation, AKA CMPRET. The only thing that's set by twisting the distributor which, on a Vortec, has no effect on timing. 21 degrees advance at idle sounds right.