New heads and loss of torque / misfire
#1
New heads and loss of torque / misfire (update)
Hi,
I just had my stock heads replaced by Edelbrock aluminium on my 289. I already had aluminium intake, a 600cfm carb and the car was running great.
Now (that's my first impression), it seems to be pulling really hard when I floor it but I feel a loss of torque in normal driving. Plus (and that is the biggest problem), it is misfiring when I accelerate quickly. For example, it does it when I do a fast double clutch, I am sure that it was not the case before. It also does it if I am driving normally and suddenly decide to floor it.
Can the misfire come from the new heads?
Does a change of heads require a complete tuning? Maybe my carb needs to be adjusted now?
I also had my exhaust replaced by a flowmaster 40series, can it affect it?
Thanks very much!
I just had my stock heads replaced by Edelbrock aluminium on my 289. I already had aluminium intake, a 600cfm carb and the car was running great.
Now (that's my first impression), it seems to be pulling really hard when I floor it but I feel a loss of torque in normal driving. Plus (and that is the biggest problem), it is misfiring when I accelerate quickly. For example, it does it when I do a fast double clutch, I am sure that it was not the case before. It also does it if I am driving normally and suddenly decide to floor it.
Can the misfire come from the new heads?
Does a change of heads require a complete tuning? Maybe my carb needs to be adjusted now?
I also had my exhaust replaced by a flowmaster 40series, can it affect it?
Thanks very much!
Last edited by _Remi; 03-18-2009 at 11:19 PM. Reason: Update
#8
I totally agree Star. Head change or cam change necessarily facilitates a tune up. Is is a missfire or a stumble? It sounds like you are having a lean bog off idle or light cruise. This is easy to diagnose with a AFR meter, but without it, you are going to have to narrow it down with trial and error. You may try increasing the pump cam to a more aggressive one or richen the idle and light cruise mixture. If WOT is good, you probably have your jets about right and just need to work on the transition.
#10
Wow, 17* initial? What total timing are you running? Do you have problems starting it with that much timing before TDC? I am running like 10-11* initial and though that was a bunch. Stock is like 6*.
Last edited by urban_cowboy; 03-13-2009 at 10:11 AM.