Hey everyone, I've got a 6.2/427 in an 07 NB Silverado. Shortblock came from Scoggin Dickey and it's got a ZR1 cam, Chain Tensioner, Port and polish CNC'ed OEM L76 Heads, 7.49 Hardened Pushrods, Patriot 8501's with Matching components, Scat 1.7 Rockers, Standard Valves, etc. etc. Why does it sound like an 04 Duramax? Any suggestions?

Thanks,
-Robbie.

 

I remember a guy who used the wrong bore head gaskets and it sounded like that. The top outside edge of the pistons was hitting the head gaskets.

 

Sound clip!!!!!!

 

rut roe

 

A loose bore & short skirt pistons will do the same thing, called piston slap. Mine sounds like that ,but quietens down some what after the engine heats up, It don't hurt any thing . Mine been like that for over five years.

 

Is it a 6.2 or a 427? A 427 is a 7.0 liter, I think a 6.2 is a 376.

Either way, have you called Scoggin Dickey yet? I haven't dealt with them in a long time, but I know a number of people who have, and have all had positive experiences...maybe they can help you out.

 

6.2 can be stroked to a 427. That's probably what he meant to say

 

Thats if you use a 4.100" crank & 4.070" bore = 427cid.
Im building a 431cid. with the LS3 4.090" bore X 4.100" stroke

 

That was my thoughts too! I'm gonna check the pushrod length here in a little bit. Got some goodies here. I've checked every other thing you can think of though. No dice. Also I will get a Sound Clip here in a bit. It sounds like hammered dog sh**. Lol.

 

I'd verify head gasket part # as well. We had a car with a 4.100 bore 422 come in here with a noise like that and found out another shop had installed stock VR LS1 4.00" bore gasket... MAJOR bearing damage...

Shane

 

The head gasket is a stock LS3 head gasket.

 

Dropping in those 7.220's you sent me here in about 5 minutes John. We'll see if the downsize works. Hope this works.

 

I sure hope. They seem way too short, but if that is what you measured, then that is what we send.

 

Damn... Well thanks John. 7.220's were too short guys, but that is the problem. the standard 7.4 pushrods on a ZR1 cam for this 6.2 are too long. I decided to start it up and let it idle on 4 cylinders and loosen up the rockers on the side that I had the valve cover off of, and the noise almost disappeared. Going to drop 7.300's in tomorrow and hope for the best. Thanks for all of your suggestions and support. I am beginning a new thread on my G8 that I recently started having problems with after a lifter conversion. So if you guys would like to help, I could really use it. Thanks again.

 

Here's the link to the Sound Clip. Enjoy..... (Or not.)

http://www.youtube.com/watch?v=Jj8hOnPRgHA

 

OH WOW that does not sound pleasing to the ears.

 

Have Yells Terra's in it now with properly set valve lash. Noise is pretty much gone once its warm, but when its cold it still sounds like the rods are falling out of it.

 

Stock rockers work great with a trunion upgrade. I have seen rockers cause strange noises on other applications

Tim

 

Does the ZR1 cam have a goofy lobe type, and it rattles because of it? Does it have special lifters or something like that?

 

Wow, that sounds terrible....for a gas motor.

Off topic, but why did you choose a ZR1 cam? Just to say, "I have a ZR1 cam" or for some actual function purpose? Maybe driveability?