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LT1-LT4 Modifications 1993-97 Gen II Small Block V8

gm847 86 kpa @ idle?

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Old Jun 15, 2010 | 11:14 AM
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Default gm847 86 kpa @ idle?
what kpa is your 847 pulling at idle? mine is only pulling 86, that seems really low,so im thinking i might have a intake lifter adjusted to tight.tps % is 0 at idle. what do you guys think,this cam has to pull more than 86 at idle right?
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Old Jun 15, 2010 | 03:49 PM
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i will have to dig up some datalogs and see where i was at.
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Old Jun 15, 2010 | 04:17 PM
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You should be in the 40-55 kpa range with that cam. You either have a vaccum leak or valve adjustment problem.
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Old Jun 15, 2010 | 04:46 PM
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Originally Posted by Tony Shepherd
You should be in the 40-55 kpa range with that cam. You either have a vaccum leak or valve adjustment problem.
I agree with Tony. My car idles at 53-55 kpa all day.
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Old Jun 15, 2010 | 04:57 PM
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didn't find it but my cc306 motor was around 47-50.
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Old Jun 15, 2010 | 07:34 PM
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ok here is the deal, i just installed the engine, it was stock w/ bolt ons and tuned.ive added the mods in my sig,and just started it up trying to get it to idle.it runs great untill it starts to heat up,then rpm falls off and it starts to run like crap. upon closer inspection w/ the vacuum gauge and a log, it does pull a dead steady 70-75 kpa when its running well, then as it heats up and the rpms drop to below 800,it starts to bounce from 80-90 kpa and run like poo.i adjusted the spark correction vs map vs coolant temp table to not pull timing as the engine heated up.it was pulling timing in the 70-80 kpa and 190* area because the stock engine would be under slight load in those cells.so, all the timing data needed to be adjusted for the higher kpa(lower vacuum) this cam pulls.the stock cam pulls 40ish kpa,so i just moved all the data surounding those cells to the 70 kpa area.damn, i miss my hei,lol.
Last edited by dan catalyst; Jun 15, 2010 at 08:56 PM.
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Old Jun 15, 2010 | 09:03 PM
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one other thing i just noticed, in the main spark table,around 70 kpa the timing is 29*,and around 40 kpa its like 34 ish,so i bet after i add some timing to the cells the car is idleing in now, the vacuum will pick up some more.
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Old Jun 16, 2010 | 12:48 AM
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you need to be looking at the closed tps spark table....
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Old Jun 16, 2010 | 12:52 AM
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^Werd

"Closed TPS Spark Advance vs RPM"

That is where you set idle spark. I would start around 29-30deg and bump it up from there seeing what it likes, not going over about 34.

JMO
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Old Jun 16, 2010 | 01:11 PM
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I think mine was bewteen 55 and 60 kpa when idling.
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Old Jun 16, 2010 | 01:38 PM
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yea 87 is definatly not right i had an old cam similar to the cc306 and it idled at like 55 ish........you've got some sort of vacuum leak it sounds like..........my new motor idles at like 75 and ive got a massive cam that dwarfs the 847.
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Old Jun 16, 2010 | 06:01 PM
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ok,thaks alot guys. ive adjusted the closed tps idle advance.it didnt do much, idles a little better.0-0,400-27 800-28,1200-30 its now pulling 70 kpa, but the idle drops and the engine dies when the water temp rises above 140 ish.what does your guys' spark correction table look like? here is mine.



Deg. C ----------------------------Kpa
kpa>30 -35- 40 - 45 - 50 - 55 - 60 - 65 - 70 - 75 - 80 - 85 - 90 - 95 - 100
-16 5.0 5.0 5.0 6.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0
-4 5.0 5.0 5.0 6.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0
8 4.0 4.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
20 0.0 -7.0 -7.0 -7.0 -7.0 -7.0 -7.0 -2.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0
32 0.0 -7.0 -7.0 -7.0 -7.0 -7.0 -7.0 -2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0
44 0.0 -7.0 -7.0 -7.0 -7.0 -7.0 -7.0 -2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0
56 0.0 -7.0 -7.0 -7.0 -7.0 -7.0 -7.0 -5.0 -3.0 0.0 0.0 0.0 0.0 0.0 0.0
68 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
80 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
92 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
104 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -3.0
116 0.0 0.0 0.0 0.0 -3.0 -3.0 -3.0 -3.0 -3.0 -3.0 -3.0 -3.0 -3.0 -3.0 -6.0
128 0.0 0.0 0.0 0.0 -3.0 -3.0 -6.0 -6.0 -6.0 -6.0 -6.0 -6.0 -6.0 -6.0 -6.0
Last edited by dan catalyst; Jun 16, 2010 at 09:55 PM.
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Old Jun 16, 2010 | 06:03 PM
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here is my main spark table too
----- 25 - 30 - 35 - 40 - 45 - 50 - 55 - 60 - 65 - 70 - 75 - 80 - 85 - 90 - 95 - 100
400 16.0 16.0 27.0 28.0 28.0 26.0 24.0 24.0 27.0 28.0 26.0 24.0 24.0 11.0 9.0 8.0
600 26.0 26.0 29.5 32.0 32.0 31.0 31.0 25.0 27.0 29.0 26.0 26.0 25.0 18.0 9.0 8.0
800 29.0 32.0 34.0 35.0 35.0 34.0 32.0 26.0 28.0 27.0 28.0 28.0 26.0 20.0 13.0 9.0
1000 32.0 38.0 39.0 36.0 34.0 33.0 31.0 29.0 29.0 29.5 32.0 32.0 31.0 27.0 13.0 9.0
1200 34.0 40.0 39.0 38.0 37.0 35.0 34.0 33.0 32.0 34.0 35.0 35.0 34.0 28.0 16.0 12.0
1400 35.0 40.0 41.0 40.0 38.0 36.0 35.0 34.0 35.0 39.0 36.0 34.0 33.0 27.0 18.0 14.0
1600 35.0 38.0 38.0 38.0 37.0 35.0 34.0 32.0 37.0 39.0 38.0 37.0 35.0 30.0 20.0 16.0
1800 35.0 37.0 40.0 40.0 38.0 36.0 35.0 34.0 39.0 41.0 40.0 38.0 36.0 31.0 23.0 19.0
2000 35.0 37.0 40.0 40.0 38.0 37.0 36.0 35.0 40.0 37.0 33.0 30.0 27.0 26.0 23.0 23.0
2200 35.0 37.0 40.0 40.0 39.0 37.0 37.0 36.0 41.0 39.0 36.0 33.0 30.0 30.0 27.0 27.0
2400 35.0 37.0 40.0 40.0 40.0 38.0 37.0 36.0 42.0 39.0 37.0 36.0 34.0 33.0 30.0 30.0
2800 35.0 37.0 40.0 40.0 39.0 38.0 37.0 36.0 41.0 39.0 38.0 37.0 37.0 37.0 34.0 33.0
3200 35.0 37.0 40.0 40.0 39.0 38.0 38.0 37.0 41.0 39.0 38.0 38.0 37.0 37.0 35.0 34.0
3600 35.0 37.0 40.0 41.0 40.0 39.0 38.0 38.0 42.0 40.0 42.0 42.0 41.0 38.0 36.0 36.0
4000 35.0 38.0 40.0 41.0 40.0 39.0 38.0 38.0 42.0 41.0 43.0 43.0 41.0 38.0 36.0 36.0
Last edited by dan catalyst; Jun 16, 2010 at 09:52 PM.
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Old Jun 17, 2010 | 01:06 AM
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could be an o2 problem that would show up when the car hits closed loop. force it into open loop and see if it'll stay running
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Old Jun 17, 2010 | 07:53 AM
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Look at closed loop BLMs, do you have an exhaust leak?
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Old Jun 17, 2010 | 09:00 AM
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Originally Posted by dan catalyst
here is my main spark table too
----- 25 - 30 - 35 - 40 - 45 - 50 - 55 - 60 - 65 - 70 - 75 - 80 - 85 - 90 - 95 - 100
400 16.0 16.0 27.0 28.0 28.0 26.0 24.0 24.0 27.0 28.0 26.0 24.0 24.0 11.0 9.0 8.0
600 26.0 26.0 29.5 32.0 32.0 31.0 31.0 25.0 27.0 29.0 26.0 26.0 25.0 18.0 9.0 8.0
800 29.0 32.0 34.0 35.0 35.0 34.0 32.0 26.0 28.0 27.0 28.0 28.0 26.0 20.0 13.0 9.0
1000 32.0 38.0 39.0 36.0 34.0 33.0 31.0 29.0 29.0 29.5 32.0 32.0 31.0 27.0 13.0 9.0
1200 34.0 40.0 39.0 38.0 37.0 35.0 34.0 33.0 32.0 34.0 35.0 35.0 34.0 28.0 16.0 12.0
1400 35.0 40.0 41.0 40.0 38.0 36.0 35.0 34.0 35.0 39.0 36.0 34.0 33.0 27.0 18.0 14.0
1600 35.0 38.0 38.0 38.0 37.0 35.0 34.0 32.0 37.0 39.0 38.0 37.0 35.0 30.0 20.0 16.0
1800 35.0 37.0 40.0 40.0 38.0 36.0 35.0 34.0 39.0 41.0 40.0 38.0 36.0 31.0 23.0 19.0
2000 35.0 37.0 40.0 40.0 38.0 37.0 36.0 35.0 40.0 37.0 33.0 30.0 27.0 26.0 23.0 23.0
2200 35.0 37.0 40.0 40.0 39.0 37.0 37.0 36.0 41.0 39.0 36.0 33.0 30.0 30.0 27.0 27.0
2400 35.0 37.0 40.0 40.0 40.0 38.0 37.0 36.0 42.0 39.0 37.0 36.0 34.0 33.0 30.0 30.0
2800 35.0 37.0 40.0 40.0 39.0 38.0 37.0 36.0 41.0 39.0 38.0 37.0 37.0 37.0 34.0 33.0
3200 35.0 37.0 40.0 40.0 39.0 38.0 38.0 37.0 41.0 39.0 38.0 38.0 37.0 37.0 35.0 34.0
3600 35.0 37.0 40.0 41.0 40.0 39.0 38.0 38.0 42.0 40.0 42.0 42.0 41.0 38.0 36.0 36.0
4000 35.0 38.0 40.0 41.0 40.0 39.0 38.0 38.0 42.0 41.0 43.0 43.0 41.0 38.0 36.0 36.0
needs a lot of work
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Old Jun 17, 2010 | 09:39 AM
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It's quite odd
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Old Jun 17, 2010 | 12:13 PM
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yeah, these spark tables arnt working out so well when i try to drive the car....lol.ive gone back to the bolt on mail order timing tables.also im keeping the car in open loop for now. im thinking i have a tight valve or valves.im going to do another valve lash and see if my vacuum comes up any. will report back tomorrow.
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