Over the winter I got my motor built up to a fully forged 383 to support my p600b. Went to the drag strip and just touched the rev limiter (stock fuel cut off). Ended up blowing a head gasket. So I upgraded to a Mallary Hyfire ignition so this never happens again. Replaced the head gaskets set the comp 850-16 @ ¾ turn past zero lash. Fired up no problem except lost 1 inch of vacuum as before the gasket blowing. Took it out for a spin around the block first time I got on the gas it pulled strong second time it hesitated at 3500 rpm and at 4000 it picked back up. A clattering sound could be heard while it was hesitating and a scan revieled 4000 increse in knock counts between the 3500-4000rpm hesitation. Before the head gasket going I would next to never see knock now if I rev it up lightly off idle out of gear knock can be seen but not heard. Even light acceleration knock counts increase. Tried setting valve lash while engine was running now three rockers will not stop ticking, not as bad as rocker loosened past zero lash. O2 sensors slowed down from coolant in exhaust tried unhooking sensors but still get the same clatter and stumble tune was good BLM’s 124-130. Pulled the intake off again to see if a gasket is out of place but all looks ok. Please give suggestions.

Things I have considered
Bad lifters…how do you test?
Hyfire causing opti to start failing
Intake leak (would explain lost of vacuum)

Kris

 

sounds like it is picking up knock from the three rockers that are ticking. maybe the rockers are bad if you adjusted them and they wont stop ticking.

 

Not sure…no visible damage or unusual wear to the rocker rollers or bearings. They are Comp 1.6 pro mags, pushrods look good too. Don't really understand the stumble and loss of vacuum. Thinking its mechanical but maybe its ignition.

If it was valve train related wouldn't it get worse higher the rpms?

Kris

 

Update:

Still unsure of the lost in vacuum, but I am sure i found the reason for the stumble. A oil soaked opti would be to blame. Pulled it apart and the optical side covered with engine oil. Looks like it came through between the distributor drive shaft and bearing.

The water pump drive seal was installed wrong and was the source of the leak. Lips of the seal facing out of the timing cover not inside toward the motor. Did the slip on the seal to the polished water pump drive coupling trick and drove it on with a socket...worked awsome!

Hope that's the end of my problems should get it back up and running today...like to go drag racing if the weather holds (crossing my fingers).

Kris

 

cool deal. it is nice to see someone be able to figure out the problem wit their car and get it running right. now if I can only get mine to run like it is supposed to

 

that's cool you fixed it 'cause it sound's like my problem my water pump and opti are covered with oil, all this after cam swap.


since you fixed your car did it run better (faster) i'm still trying to see why i'm so slow with the mods i got.

 

It did make a differance noticed 1" lowwer vacuum shortly after the vacuum loss it started to stumble. Got my 1" of vacuum back and no more stumble...just a broken rear now

This is starting to suck.

Kris

 

broken rear , ouch!


so your saying you increased vacum by 1'' (how) , i'm kind of dumb what excatly do you mean by that?


performance wise did it increase?

 

OK say your car idled at 800 rpm and your seen 14" of vacuum and so you started to play with the tuning on PCM. After tuning the car still idles at 800 rpm but not your vacuum is at 15". This means that the car needs less air to do the same amount of work. PCM sees the decrease in the amount of air being used and automatically decreases the amount of fuel used. In closed loop the ratio of air and fuel is 14.7:1. The car is now more efficient and efficiency = power. I my case I think my timing was erratic and caused the motor to become less efficient.

But if the opti’s your problem I am sure other symptoms would show like stumbling, stalling...etc like in my case started to show after 10 min of driving. If your have performance problems after a cam swap its usually the tuning.

Have you scanned the PCM for codes or do you have access to a datalogger?

Kris

 

i have no a way of scaning the car but i'm working on it,


my car is tuned really good by a profesianal.