[DragRacerX]

I have a similar ticking sound (although not that loud) in my ZL1. It is most pronounced when I start it up in the morning and the engine s cold. It lessens in volume when the engine has warmed up. I have taken it to my local dealership, but of course it doesn't do it by the time they get to it. My neighbor & I employed one of the $5 Harbor Freight Stethoscopes (pictured in page 1 of this thread) and the noise is the loudest when we touch it to the fuel rail. It is louder the closer you move toward the back of the engine where it starts going down the firewall. Everywhere else it sounds like a well oiled machine. One of the Chevy technicians that I know said he wondered if it was the fuel pump. He said it was a known trouble on the LT4 engines in the Corvette & thought that there might be a possible recall in the works. The local dealership wants me to leave my ZL1 with them overnight. Since it's my every day driver, it's not an attractive option to me - but I might have to bite the bullet & do it if I want it fixed. Currently I have 5,758 miles on my mechanically bone stock ZL1. Your thoughts & comments?

[kwav8r]

Originally Posted by DragRacerX

I have a similar ticking sound (although not that loud) in my ZL1. It is most pronounced when I start it up in the morning and the engine s cold. It lessens in volume when the engine has warmed up. I have taken it to my local dealership, but of course it doesn't do it by the time they get to it. My neighbor & I employed one of the $5 Harbor Freight Stethoscopes (pictured in page 1 of this thread) and the noise is the loudest when we touch it to the fuel rail. It is louder the closer you move toward the back of the engine where it starts going down the firewall. Everywhere else it sounds like a well oiled machine. One of the Chevy technicians that I know said he wondered if it was the fuel pump. He said it was a known trouble on the LT4 engines in the Corvette & thought that there might be a possible recall in the works. The local dealership wants me to leave my ZL1 with them overnight. Since it's my every day driver, it's not an attractive option to me - but I might have to bite the bullet & do it if I want it fixed. Currently I have 5,758 miles on my mechanically bone stock ZL1. Your thoughts & comments?

I'd leave it with them and ask them for a loaner. Sounds like something needs to get diagnosed and fixed. My .02

[UahFastBoi]

Originally Posted by DragRacerX

I have a similar ticking sound (although not that loud) in my ZL1. It is most pronounced when I start it up in the morning and the engine s cold. It lessens in volume when the engine has warmed up. I have taken it to my local dealership, but of course it doesn't do it by the time they get to it. My neighbor & I employed one of the $5 Harbor Freight Stethoscopes (pictured in page 1 of this thread) and the noise is the loudest when we touch it to the fuel rail. It is louder the closer you move toward the back of the engine where it starts going down the firewall. Everywhere else it sounds like a well oiled machine. One of the Chevy technicians that I know said he wondered if it was the fuel pump. He said it was a known trouble on the LT4 engines in the Corvette & thought that there might be a possible recall in the works. The local dealership wants me to leave my ZL1 with them overnight. Since it's my every day driver, it's not an attractive option to me - but I might have to bite the bullet & do it if I want it fixed. Currently I have 5,758 miles on my mechanically bone stock ZL1. Your thoughts & comments?

My car has about a thousand more miles then yours. Also, mine doesn't quiet down as it gets warmer. It's at the shop at the moment. I would love to hear an update on yours when you have one.

[Can'tHave2MuchHP]

Any chance this sound is coming from the supercharger? Previous Eaton blowers had a problem where the isolator would go bad and begin to make a pulsing grind noise/loud tick.

[UahFastBoi]

Bad lifter...... And bent pushrod.

[BMWM.D.]

Originally Posted by UahFastBoi

Bad lifter...... And bent pushrod.

So the lifter collapsed and the pushrod bent? Hopefully the roller portion didn’t fail.

Valve float is the most common cause of bent pushrods from what I’ve seen. Did they bump up the rev limit when they tuned it?

[Can'tHave2MuchHP]

Originally Posted by BMWM.D.

Valve float is the most common cause of bent pushrods from what I’ve seen. Did they bump up the rev limit when they tuned it?

This. And did you free rev it to 6000+?

[1roadking]

That was my guess hearing it. DragracerX, I believe you have a lazy lifter that bleeds down and takes a while to pump up after sitting. It causes too much clearance between the lifter and push rod eventually ruining one or both of them. It’s a common problem on Harleys��

[Jonru]

Originally Posted by UahFastBoi

Bad lifter...... And bent pushrod.

did you get fix under warranty?

[DragRacerX]

Originally Posted by 1roadking

That was my guess hearing it. DragracerX, I believe you have a lazy lifter that bleeds down and takes a while to pump up after sitting. It causes too much clearance between the lifter and push rod eventually ruining one or both of them. It’s a common problem on Harleys��

Finally took it into the dealership while we were having a REAL COLD week. They told me it was the fuel pump, a known "trouble" - nothing they could do - they are hoping for a recall... NEEDLESS to say, I was NOT amused...

[PinHead]

Originally Posted by DragRacerX

Finally took it into the dealership while we were having a REAL COLD week. They told me it was the fuel pump, a known "trouble" - nothing they could do - they are hoping for a recall... NEEDLESS to say, I was NOT amused...

Thanks for the update,

The Mech. Cam-Driven Fuel pump is NOT an optimum design for a High Performance engine. Eliminating the Mech FP is one of many projects on my List.

I'd like to see the GM Engineering Data of parasitic load/drag from the LT4's Mechanical Fuel Pump.

[BMWM.D.]

Originally Posted by Lt1z350

And how are you going to do this and keep the direct injection on it? There is no possible way to drive those injectors at the high pressure needed. Now you could take it all off and go to a port style setup and stand alone computer but why buy the car and hack it all up. If there was some easy way around the mechanical pump they wouldn’t be adding tons of meth or a haltech seconday port system on top of the factory stuff in high hp cars. As of now no one makes a stand alone electric motor to drive a mechanical pump and if they did it would probably weigh a ton and out weigh the loss of the pump on the cam already. It’s a big issue but no one has a way to provide 1600-2000 psi of fuel to the direct injector other then a mechanical pump.

^^^^^ This. All DI engines have a mechanical pump. Some are driven off the timing chain, some off a camshaft — but it is what it is. The benefits of DI outweigh the downsides in my opinion.

[PinHead]

Originally Posted by BMWM.D.

^^^^^ This. All DI engines have a mechanical pump. Some are driven off the timing chain, some off a camshaft — but it is what it is. The benefits of DI outweigh the downsides in my opinion.

Totally understood.

But there are a few other design options that could of eliminated the parasitic drag of the Mech F/P.

Its a matter of economics, (i.e. GM Making more Money vs GM Making More Money ).