[grnova]

Hi Everyone,

I have a blown 383 and at cruising speeds there is a kind of thumping noise. Kind of sounds like it is coming from the exhaust. Could this be detonation? I am running an 850-900 race demon,power charger 250 blower and an MSD 6BTM. Timing is set at 34 total plugs are NGK v-power R5673-8. Vacuum is at 12 lbs before boost. And lastly the 3" exhaust flow master 40's ends at the rear with turn downs. I am at a loss.

 

[grnova]

Could this be un burned fuel?

 

[jlowery78]

I'm not sure about it being un-burned fuel. My experience with spark knock (detonation) is that it usually occurs under a heavy load. Not that it can't happen just cruising around with very little load on engine. I would check your exhaust very thourghly, see if anything may be contacting it. I have zero experience with forced induction, some one on here will help you get your problem fixed. Good luck.

 

[6NOVA4]

yea thats a good idea check to see if the exhaust is banging the floor boards. another thing would be to retard the timing alittle see if it makes a difference.