2002_Z28_Six_Speed

iTrader: (19)

I had a local shop build a 408 with forged pistons. This motor has about 10 hours of run time mostly idling because I was trying to test and tune the motor.

I found a knocking sound and eventually tracked it down to the right side of the motor. One of the rockers had some play. Swapping the rocker and pushrod did not fix the issue. I pulled the heads and guess what. The one lifter I can't get out of the bore maps up to where the noise is coming from.

Then I notice this wear pattern. Pulling the motor is going to set me back at least two months so I would like to get feedback if this is a show shopper. There is a definite wear pattern in the 6 o clock position of each cylinder. The honing pattern has been worn away. It is not detectable with my finger nail.


Can anyone comment on the best far forward? I am losing my mind over this. Is it best to ship this thing to a knowledgeable builder or is there someone near DC that can handle this kind of work? What do you guys think this motor needs to be right?

DietCoke

iTrader: (18)

P/W setup too tight as built. Will probably wear in, might have some slap. See this a lot on big stroke deals that let the piston rock. (4.125 on stock sleeves is the worst). Long as the rings are sealing, run it.

2002_Z28_Six_Speed

iTrader: (19)

Would you suggest pulling the motor then? I might use this vehicle 2000 miles a year. Right now isn't a great time for me to pull the motor. Rather have the ability to move the vehicle if needed.

Lifter still stuck in bore BTW. Really stuck!

DietCoke

iTrader: (18)

No. They all look like that on a stock sleeve.

farmington

iTrader: (14)

Have u pulled the cam out yet? Lobe with bad lifter is probably toast.

2002_Z28_Six_Speed

iTrader: (19)

Cam is trashed. Lifter mushroomed. Roller wheel worn down to shaft with roller elements missing. probably in pan.

Guess I need a rebuilt? Would be a bad idea to throw in new cam and lifter set?

moekluse

iTrader: (2)

it would be a bad idea not to

pdxmotorhead

Hard to believe the lifter bore dosen't have some damage and that's not something I'd try and fix in the car.. Unless it was a get me home situation vs getting a toy running..

with the engine that far apart, id pull it, getting it out is part of a day then find your regional SCCA clubs web page, there is almost always a a forum talking about motor building. Typically there will be a builder or two who sponsors the club. The road race guys take no prisoners with engine builders.. Unfortunately the good builders are likely booked this time of year.. (Beginning of the season.)

Or google around for a sprint engine builder at your nearest dirt track,
Local drag strip web page etc.. All the same deal..

s57_s2k

rings need heat and pressure to prevent glazing, idling for 10 hours not good on a new motor.
What oil do you use ? maybe your engine builder did not put oil on the cylinder walls for initial start up and that is why there is a longitudinal wear on the walls.

KCS

iTrader: (20)

I think the cylinder walls are ok, usually the flash from the camera make them look a lot worse then they really are.

However, the valve train damage is a major point of concern. Not just because the need to replace the parts but because that kind of failure shouldn't happen when the engine has just seen idle.

2002_Z28_Six_Speed

iTrader: (19)

I agree that idling is not great for break in. Unfortunately the tuning on the car doesn't allow me to drive it around in traffic safely. It stalls out too much.

I think I am leaning towards a manufacturing flaw with the lifter or something wrong with the aftermarket cam causing the failure.

spy2520

iTrader: (3)

Yeah I was thinking either the wheel was already binding or maybe the lifter never pumped up and bounced on the cam until something bad happened. Just a guess.