Timing ...help!! 94 k1500, 5.7, $OD, 7427

So, I've got knock counts...alot of them... and I keep getting a handful of cells showing knock retard. I'm starting to think my issue is probably mechanical (bottom end) but I am hoping I'm overlooking something in my tuning. I get the knock retard mostly in the load area (high map / 1600-3600 rpm range). I've continually adjusted the open throttle SA pulling timing out which has only helped a little. I started with a standard vortec timing table and have since slowly pulled timing out. Today, fed up I tried going all the way back to my old swirl port head SA table and the knock retarding was worse or at least more frequent. :mad1: I'm puzzled because I can't even hear the knocking or pings, not even a little..

So, in regards to timing, I have only adjusted the open and closed SA tables.
- Is there another table (or anything in the bin) that I should be looking at?
- I have eliminated the EGR (and changed a few things to shut it off so i won't get a code), is there something i need to change because the EGR is off?
- Is it possible the knock sensor is bad? It is aftermarket.

i know I'm grasping at straws here guys...I really hate the thought of pulling this engine, especially if it is a programing/tuning issue.

As always, I truly appreciate everyone's help & opinions. Here is a list of the changes I've made.
Vortec heads
Roller Cam (GM #14097395)
-Duration 196/206
-Lift .431/.451
-LSA 109
GMPP Intake (GM #12496821)
TBI "Ultimate Mods"
EP377 Fuel Pump (Currently set at 22psi)
Hypertech Power Bowl
Shorty Headers
Upsized Y-pipe (2" to 2-1/4')
Eliminated catalytic convertor
3" Catback
Eliminated EGR

Keep pulling timing down in that area to see if it stops. My dad thinks his roller rocker arms my be to noisey, he is having same issue, vortec v6, 427 ECM. He tried corvette knock sensors but ECM didn't like them.
I am by no means an expert tho!!!

How did you eliminate the egr valve? I ask this because if you just turned off the error code, the PCM is still going to use the egr routine. Make sure you maxed out the Temperature for EGR On scalar. I also maxed out the Minimum Speed for EGR scalar.

Brian

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Originally Posted by BigBanks78

Keep pulling timing down in that area to see if it stops. My dad thinks his roller rocker arms my be to noisey, he is having same issue, vortec v6, 427 ECM. He tried corvette knock sensors but ECM didn't like them.
I am by no means an expert tho!!!

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I had thought about double checking the adjustment on my rockers but Is a knock sensor that sensitive that it will retard the timing because of rocker arms or lifters being a little noisy?

Quote:

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Originally Posted by sturgillbd

How did you eliminate the egr valve? I ask this because if you just turned off the error code, the PCM is still going to use the egr routine. Make sure you maxed out the Temperature for EGR On scalar. I also maxed out the Minimum Speed for EGR scalar.

Brian

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Pretty sure I made those changes to the egr but I will double check my file when I get home.

My dad was reading about a corvette with stock roller rocker arms had to make some knock sensors that were less sensitive so they wouldn't pick up rocker arm noise.

Notsaying thats your problem just that if you pull timing and you still have same knock go over mechanicals!!

i keep having software problems that turn out to be mechanical :-)

Big....It is certainly worth looking into.

Btw, Brian, I double checked and I have already made those changes for eliminating the EGR. I thought I had...I'm sure I read to do it on a thread somewhere in this forum.

Thanks for the suggestions guys.

I would make sure the exhaust isn't rattling or rubbing against the frame etc. I would also make sure I wasn't running lean. If vehicle is in PE mode, you really need a wideband to know what your afr actually is.

I have pretty much the same setup and the only difference with my problem was that I could actually hear
pinging.I turned off "Altitude Spark Bias" and the problem went away. Couldn't hurt to try. I found the answer
In this thread;
http://www.gearhead-efi.com/Fuel-Inj...=altitude+bias

I'm going to have to read that a few times to grasp it all...but i will try that and see what happens. Thanks!

I may have another issue though. Looking at my spark advance in my latest data log in Tuner Pro and I have 13 cells where the timing shows at over (I kid you not) 23000 degrees!! This has got to be a glitch but I'm not sure what's going on...maybe a bad ECM or distributor perhaps. I noticed this in one or two cells in past logs but didn't think much of it....but now in 13 cells, I have a growing problem! See attached, I copied the "running maximum" spreadsheet. Anyone seen this before?

So I looked at my spark advance table from my last datalog run and compared it to my timing table in my bin and it is approx. 10° off. Thinking "how could I have missed this before" I played back some older datalogs and my timing was right where it should have been. Long story short, I found that when I had unchecked or un-set backpressure EGR about a week or so back is when the timing table in my datalogs lost the 10°. I'm not exactly sure how they are tied together but the parameter comments on Altitude Spark Bias say "used with back pressure EGR". Maybe doing both (un set backpressure EGR and correcting spark bias) will eliminate my knock count issue. I'll try it this week along with a few other suggestions.

Also, if anyone is interested, in the cells where my timing says 23039°...I think this is where the timing is supposed to be a negative. Again, not exactly sure why it shows +23000...I'll need to figure this out next.

Thanks again for the help guys.

Quote:

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Originally Posted by dispoejoe95

So I looked at my spark advance table from my last datalog run and compared it to my timing table in my bin and it is approx. 10° off. Thinking "how could I have missed this before" I played back some older datalogs and my timing was right where it should have been. Long story short, I found that when I had unchecked or un-set backpressure EGR about a week or so back is when the timing table in my datalogs lost the 10°. I'm not exactly sure how they are tied together but the parameter comments on Altitude Spark Bias say "used with back pressure EGR". Maybe doing both (un set backpressure EGR and correcting spark bias) will eliminate my knock count issue. I'll try it this week along with a few other suggestions.

Also, if anyone is interested, in the cells where my timing says 23039°...I think this is where the timing is supposed to be a negative. Again, not exactly sure why it shows +23000...I'll need to figure this out next.

Thanks again for the help guys.

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Really not sure why you would ever have negative timing with Vortec heads. The minimum value in my timing table is 12-16° on everythimg Vortec I have messed with. Anything under 10° is just not enough timing in my opinion.

Fast...the negative values were from my timing losing 10 degrees because of the Altitude Spark Bias. I don't have the table available to me right now but I would swear that the standard vortec table has some negative values in the extreme low rpm high map cells. Anyhow...could I ask you to post one of your slightly less aggressive vortec timing tables so i could compare it to mine?

Quote:

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Originally Posted by Fast355

Really not sure why you would ever have negative timing with Vortec heads. The minimum value in my timing table is 12-16° on everythimg Vortec I have messed with. Anything under 10° is just not enough timing in my opinion.

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I considered what you said so I found a timing table posted in a thread that was a little more aggressive than a stock vortec table, but my results are still the same...knock counts and some retarding. I didn't think adding timing was going to help me at this point, not until until I figure out my problem but figured you never know. I'll say this, my truck did seem to like the extra timing on a hole shot!

Thanks to the guys who have responded....I've tried or checked just about everything suggested in one form or another but no luck. I'm running out of ideas, I may just pull the engine out and go through it but before I do, I wanted opinions on a couple of other possibilities.

Thousands of guys have eliminated EGRs but has anyone every had a knock count (detonation) issue and eliminated it by putting the EGR back on the engine? They say EGR reduces the temp in the combustion chamber. Maybe that's my issue?
Also, I'm running a 195° thermostat, should I run a 180° with the EGR eliminated?

Last, I'm wondering if i should replace my distributor. It is the original with this truck and has almost 150K on it. I've read an old worn distributor can cause some timing issues. How much play is too much that it might start affecting timing?

Any thoughts? Thanks.