1985_K5_Silverado
1/2 ton status
Which comp cam grind/part number is it?89Burben said:
CK5
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new cam, backfires thru intake
- Thread starter 89Burben
- Start date
1-ton said:
Really???Mine says 1 full turn.. in 1/4 increments
Adjusting them in 1/4 turn increments is only important if the engine is running while you adjust them. It gives the lifter time to adjust itself between turns so that a valve doesn't meet a piston.RootBreaker said:Really???Mine says 1 full turn.. in 1/4 increments
Cranking down too quickly on an engine with tight clearance can supposedly cause expenive problems.alright well i took it for a test drive. the truck idles fine. The timing is set to zero with the black and brown wire unhooked. I have the harmonic balencer marked every 90 degrees in white (when i was adjusting the valves) and for the etched timing mark, its marked in yellow. When the timing light is on the truck and its idleing, you will see the yellow mark, and then every so often you will see the yellow and a white mark also near the left side of the timing mark if you are facing the front of the truck. i am not sure why this would be doing this unless my 87 octane gas isnt high enough and the knock sensor is retarting the timing...???? On the test run when applying gas the truck backfires through the intake and you cannot accellerate hard at all otherwise it will backfire. i am currently running my stock prom chip. any suggestions?
78Suburban
1/2 ton status
sounds like my motor
Are you test driving with the wire unhooked?
chevyk2500hd
1/2 ton status
You should only have the brown wire disconnected when you are setting the timing. During a test drive it should be plugged back together.
chevyk2500hd said:
Exactly what i was implying....
89Burben said:
Didn't mean to offend
We just had someone a couple weeks ago do that, thats what made me think of it...Throwing any codes by chance?
broke73
1/2 ton status
Are the lifters ticking again? If so you may have to replace the nuts had a problem like this recently and it ended up being the nuts backing off the rocker studs.
Not sure if the computer is retarding the timing. I have an 85 that did that, and I ended up bypassing the computer. But the only thing that computer did was control timing on that truck.
the lifters only tick somtimes, i might have to re-adjust when i rev up the motor one of them starts ticking again........but i think somthing else is wrong to make it backfire out of the intake.
What do you all think about me seeing the other marks on the harmonic balencer?
What do you all think about me seeing the other marks on the harmonic balencer?
1985_K5_Silverado
1/2 ton status
I probably missed this, but did you have your TBI's PCM reprogrammed for that cam, or is the PCM still stock? I only ask because that grind has a 110 deg. LSA and isn't billed as completely "computer compatible" with a stock PCM.89Burben said:
when i did the cam i changed the heads to 67 427 corvett heads, this raised my compression to 9.25:1 so says desktop dyno. anyways my point is if i needed a higher octane fuel could the knock sensor retard the timing enough to make my truck run crappy?
i once had a 350 that acted similar to what u are desribing idlied good and u could actually rev it and no backfire but when driven and put under a load it would backfire though the intake thats why i suggested checking the lobes
i just changed the distributor with one that i had thinking maybe it was the pickup coil. no change.......
the truck runs well and doesnt seem to backfire when its cold and first started. once its warm and running off its own sensors you can slowly rev it up to only about 3000 rpms and it starts breaking up and backfired through the intake.
im starting to think the problem is fuel related. i am going to put in the burnt chip i got from "tbichips" even though it was made for my truck just with and intake and headers....
the truck runs well and doesnt seem to backfire when its cold and first started. once its warm and running off its own sensors you can slowly rev it up to only about 3000 rpms and it starts breaking up and backfired through the intake.
im starting to think the problem is fuel related. i am going to put in the burnt chip i got from "tbichips" even though it was made for my truck just with and intake and headers....
This isn't meant to insult your inteligence...but you are ABSOLUTELY sure that the plug leads are in the correct order?
