Hello ,
I am reletively new to here the last year or so and have done some upgrades and havent tuned much due to other projects .
I have had off and on lean spots just off idle but have been able to adjust timing some and get most of it to go away.
My new problem is above 30% tps i loose spark advance to around 14-16 degrees .The blms are all within 125-135
The truck is
1993 c1500 350 tbi 4l60e
vortec heads
hi rise single plane w adapter
46mm tbi with cop car injectors at 20 psi
cam motion hyd roller 201/211 454 465 lift
short headers 2/5 y pipe no cat with flomaster
new timing set
new ias
new distributor including new cap &rotor
newer o2
new coil
newer tps
The strange thing is with the old original flat tappet cam it had much more oompf but i noticed today above 30% tps sa is dropping to 15 .i have a aggresive timing table as at 0 intial its a pig so much i pulled the timing cover back off to check if it was a tooth off at cam.it wasnt [i didnt have a puller for the gear or i would have advanced the cam 4 degrees ]its straight up
.
The initial sa at the distributor is 12 .i tried to raise and lower the initial to cheat the engine and it still wouldnt leave the timing in above 30% tps.
At light throttle it seems to run ok it just looses all timing when you try to step on it .I know there may be qualifiers that reduce timing but i havent changed anything .
I have tried suggested vortec timing tables from this site and at 20 through 1200 rpm it does the same even with as much as 27 in same ranges .
I tried to search this but have came up empty .Its almost like the timing advance is backwards ?I have uploaded the data log before and if needed i can again but if anyone can help with suggestions id greatly appreciate it .
It feels like if i can get about 35 degrees sa above 30% tps it will run very well .
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