Mechanical causes of spark knock.

[blackshoebox]

Assuming tune is on the money, what mechanical stuff in the motor should I be checking? Car is 249 stroker(china stuff), with iron heads, 66cpt turbo. 60lbs injectors, double pumper, 218/212 roller cam, etc...has razors single knozzle methonal kit on it. Car has a 5 disk, precision lock up converter(not to excited about it). Using 6.0 Eric chip, with power logger and wideband. Tune set for 10.8 afr. Kept getting what I thought was false knock, unplugged knock sensor, to only start hearing real knock at the top of the traps. Added more fuel, same results. Only 24 psi, 22 degrees of timing, @ the top of third. I should have no problem with that kinda tune up with race fuel and methonal. Looking for opinions. Think I may have pushed a headgasket as a result from testing, but I'm not terriably worried about that, just wondering what I missing here..

 

[BEATAV8]

valve springs are an item

 

[blackshoebox]

valve springs are an item

Like possible a broken one? Or weak springs causing valve float?

 

[BEATAV8]

Yes weak springs causing valve float or springs just not strong enough for the camshaft profile. KR comes up very frequently at high RPM. You might also actually hear the valve float too. "TINK TINK".... something like that.

 

[Quik Six]

Assuming tune is on the money, what mechanical stuff in the motor should I be checking? Car is 249 stroker(china stuff), with iron heads, 66cpt turbo. 60lbs injectors, double pumper, 218/212 roller cam, etc...has razors single knozzle methonal kit on it. Car has a 5 disk, precision lock up converter(not to excited about it). Using 6.0 Eric chip, with power logger and wideband. Tune set for 10.8 afr. Kept getting what I thought was false knock, unplugged knock sensor, to only start hearing real knock at the top of the traps. Added more fuel, same results. Only 24 psi, 22 degrees of timing, @ the top of third. I should have no problem with that kinda tune up with race fuel and methonal. Looking for opinions. Think I may have pushed a headgasket as a result from testing, but I'm not terriably worried about that, just wondering what I missing here..

Post a PL file here with WB type, tire height, fuel you are running and plug type.

NEVER hurts to have another pair of eyes look at it.

 

[broke]

dirty or cracked pistons

 

[Quik Six]

Long list of possibilities. Eliminate fuel first by trying some 101 or 104. If it goes away, you have your answer. If not, you may have a long hunt. I have the GN1 stroker kit, run a 6265 turbo with 80's, single line alky and TT SD chip and I'm not sure I'm feeding it enough fuel even with DW 300 and BAP. If you figure it out, please post it up here.

Knock Problem Check List
1. Start-up knock? Normal and usually caused by the starter engaging the flex plate. Usually sets off 1-3 lights.
2. Possible bad ECM or ESC module. Test with good working units.
3. Exhaust rattle – check the down pipe, tail pipes, and have engine tie down strap
4. Boost creep especially top of 1st gear on 1-2 shift.
5. Lean air/fuel mixture.
6. To low octane gas – bad pump gas – try some race gas
7. Too much timing in chip for fuel used. Try different chip.
8. Try cooler spark plugs – use only AC Delco (R43-TS or R42-TS)
9. Gap plugs to .035
10. Check torque converter bolts to make sure they are tight
11. Loose harmonic balancer. Make sure torqued to 200 ft/lb Is keyway secure?
12. Check internal engine noises like timing chains (roller), lifters/rockers, etc.
13. Damaged knock sensor
14. Check fuel pump pressure and volume
15. Proper torque on knock sensor – 14 ft/lb
16. Check Alternator voltage: 13.8 - 14.5v
17. Check computer power wire - they can break internally.
18. Troubleshoot the computer connector power wires and ground wires.
19. Swap coil pack, wires, plugs w/known good units.
20. Swap MAF with known good unit.
21. Check battery ground connection @ block (clean/inspect).
22. Check/change battery cables (both).
23. Are there MAF leaks in the inlet tube?
24. Are there vacuum leaks. Use carb cleaner or WD-40 & spray everything. Does the rpm change?
25. Disconnect the main injector harness - inspect, WD-40. Check for moisture in main connector.
26. Disconnect the coil-pack connector - inspect pins & spray w/WD-40.
27. Is the cat still installed? Is it good?
28. Have you performed a leak down check?
29. Do the rockers open/close? Do we have a wiped cam lobe?
30. Is the boost/vacuum steady @ idle?
31. Is the engine over revving? Should be 4,800-5,200 rpm
32. Carbon in cylinders? Clean with GM engine top cleaner
33. Inter-cooler dirty? Clean inside inter-cooler and fins
34. Oil in intake tract?
35. Check for exhaust leaks, cracked header
36. Battery good?
37. EGR valve in working order?
38. Check that no cables, wires, etc are touching the knock sensor
39. Blown head gasket? Compression test. Should be around 150.
40. Injectors flowing/working correctly?
41. Check vacuum line to fuel pressure regulator for cracks

 

[SloGN]

if you disconnected the knock sensor and you heard knock? or you still recorded knock with a scan tool?

if you were getting knock (heard it over the engine reving) you may have too much timing for the given octane too much boost (bad boost gauge?) what type of spark plugs are u using ?

 

[Quik Six]

Long list of possibilities. Eliminate fuel first by trying some 101 or 104. If it goes away, you have your answer. If not, you may have a long hunt. I have the GN1 stroker kit, run a 6265 turbo with 80's, single line alky and TT SD chip and I'm not sure I'm feeding it enough fuel even with DW 300 and BAP. If you figure it out, please post it up here.

Knock Problem Check List
1. Start-up knock? Normal and usually caused by the starter engaging the flex plate. Usually sets off 1-3 lights.
2. Possible bad ECM or ESC module. Test with good working units.
3. Exhaust rattle – check the down pipe, tail pipes, and have engine tie down strap
4. Boost creep especially top of 1st gear on 1-2 shift.
5. Lean air/fuel mixture.
6. To low octane gas – bad pump gas – try some race gas
7. Too much timing in chip for fuel used. Try different chip.
8. Try cooler spark plugs – use only AC Delco (R43-TS or R42-TS)
9. Gap plugs to .035
10. Check torque converter bolts to make sure they are tight
11. Loose harmonic balancer. Make sure torqued to 200 ft/lb Is keyway secure?
12. Check internal engine noises like timing chains (roller), lifters/rockers, etc.
13. Damaged knock sensor
14. Check fuel pump pressure and volume
15. Proper torque on knock sensor – 14 ft/lb
16. Check Alternator voltage: 13.8 - 14.5v
17. Check computer power wire - they can break internally.
18. Troubleshoot the computer connector power wires and ground wires.
19. Swap coil pack, wires, plugs w/known good units.
20. Swap MAF with known good unit.
21. Check battery ground connection @ block (clean/inspect).
22. Check/change battery cables (both).
23. Are there MAF leaks in the inlet tube?
24. Are there vacuum leaks. Use carb cleaner or WD-40 & spray everything. Does the rpm change?
25. Disconnect the main injector harness - inspect, WD-40. Check for moisture in main connector.
26. Disconnect the coil-pack connector - inspect pins & spray w/WD-40.
27. Is the cat still installed? Is it good?
28. Have you performed a leak down check?
29. Do the rockers open/close? Do we have a wiped cam lobe?
30. Is the boost/vacuum steady @ idle?
31. Is the engine over revving? Should be 4,800-5,200 rpm
32. Carbon in cylinders? Clean with GM engine top cleaner
33. Inter-cooler dirty? Clean inside inter-cooler and fins
34. Oil in intake tract?
35. Check for exhaust leaks, cracked header
36. Battery good?
37. EGR valve in working order?
38. Check that no cables, wires, etc are touching the knock sensor
39. Blown head gasket? Compression test. Should be around 150.
40. Injectors flowing/working correctly?
41. Check vacuum line to fuel pressure regulator for cracks

Thanks. Wish I could take credit for it but somebody with a whole lot more turbo Buick knowledge than me did this. I used to have a file with this in it but couldn't locate it but did a search on this board and found it.

Do have one to add which is really an extension of #41. Check the "O-ring" on your FP regulator if you've taken it off and re-installed it. Mine was gouged and the pressure was inconsistent. I found it when I installed the new FPR.

 

[GNRick]

Bad spark plug wire(s)?

 

[Mr.Spool]

what is the fuel pressure at wot?alky pump pressure at wot?regardless of what you think should be safe if the motor wants more fuel or alky or a richer afr you should listen.fyi 10.8 afr in my car wouldn't cut it and at 20psi my car goes 10's,you may be moving more air than you think.

 

[blackshoebox]

Gotta get the logs off my other computer I used for the car and I will post them up. It is plausiable the car just needed more fuel. I am almost certain I heard the "tink, tink" , which could have been the valves floating. Going to pull the plugs and see if they tell me anything. I have heard from some friends the widebands can be notoriously undependable too.

 

[blackshoebox]

what is the fuel pressure at wot?alky pump pressure at wot?regardless of what you think should be safe if the motor wants more fuel or alky or a richer afr you should listen.fyi 10.8 afr in my car wouldn't cut it and at 20psi my car goes 10's,you may be moving more air than you think.

Fuel pressure was around 70psi or so.

 

[bison]

How about turning the boost down and see if
the detonation stops? Id pull the engine to check the bottom end. Verify timing.

 

[blackshoebox]

How about turning the boost down and see if
the detonation stops? Id pull the engine to check the bottom end. Verify timing.

I think I am going to pull the motor and see whats going on. Hindsight is 20/20, I wish I tried turning the boost down to see what happened. The car did push some coolant out of the overflow, so Im not to inclined to try that now..

 

[bison]

I think I am going to pull the motor and see whats going on. Hindsight is 20/20, I wish I tried turning the boost down to see what happened. The car did push some coolant out of the overflow, so Im not to inclined to try that now..

Id pull the engine and go through everything. Check the rods for twist. You will see heavy metal transfer between the caps and the block.

 

[blackshoebox]

Id pull the engine and go through everything. Check the rods for twist. You will see heavy metal transfer between the caps and the block.

I hope it is not that bad! I was already cautioned it will probably need a set of bearings. It does have 4 steel caps, no girdle though. Forged rotating assembly though. I post results and data once we see what happened.

 

[blackshoebox]

Update...pulled plugs, they all looked ok, besides number 6 which was covered in oil. Thinking it hurt a piston or ring. It had a small amount of oil in the coolant resevior, no coolant in the oil..