65MalibuSS

I installed my stock style Lunati timing chain and sprockets today (Summit Racing part number LUN-93094).
When turning the engine over by hand I noticed the chain would go from 0.5" slack to no slack at all.
I realized with the Lunati cam sprocket pushed against the front of the cam with the pin at 3 o'clock, the left side of the sprocket can move up and down at least 0.080" as viewed through the bolt hole at the 9 o'clock position.
My original cam sprocket (with 180,000 miles) when pushed against the front of the cam only has about 0.015" of play.

Which means when the Lunati cam sprocket is installed, it's not perfectly centered on the cam (unless you're real lucky, but once the engine starts it could probably move).

I can't imagine that would be good for the chain or the sprockets, or the cam bearings, or the main bearings!

I think I'm going to send this timing set back and order a new set from GM.
Has anyone installed this Lunati stock style timing set and had any luck with it?

Josh'95Z28conv

Go double roller and call it a day

96capricemgr

Just thinking out loud, but had you considered the possibility the aftermarket had slightly larger bolt holes to allow the necessary slop should someone want to use degree bushing on the pin?

MikeGyver

Is that too loud for the knock sensor? And I don't think a double roller will fit in there..?

65MalibuSS

A few double roller timing chain sets are available and they fit fine.
I don't have knock sensors since I'm converting to a carburetor and installing in a dragster.

I guess it's possible that the holes in the cam sprocket are intentionally oversized but I measured all the holes and diameters today and they are only 0.003" over the stock sprocket holes.

The biggest difference is the overall outer diameter of the gear behind the cam sprocket that drives the water pump drive gear. This is 0.025" smaller in diameter than the stock gear. I don't know if that gear is used to help center the cam sprocket on the cam or not, but if it is, the Lunati sprocket is no good.

I'm going to return the Lunati timing set and get the Cloyes stock type timing set. I read somewhere that the Cloyes set is identical to stock and even says GM with the same part number. And if it isn't the same part number or if it doesn't fit as well as stock, I'll return it and get a stock set from GM.

I'll be sure to post the outcome so other members in the future know which timing set to get.

n2ceptor

You might e-mail Lunati of your findings and see how they reply..... Might be a QC issue or done for a reason??

bw_hunter

I run a cloyes double row timing chain setup and don't have any problem with knock showing up on scans. Gear drives are too noisy for the knock sensor...

They fit under the stock cover with a small amount of clearancing...2 minutes with a dremel tool. The only issue is that you can't use the stock cam driven water pump as there is no provision to drive the idler. That's no problem for me..I've run an electric water pump for years.

If you want a good timing set and retain the water pump drive, consider a GM extreme duty roller chain timing set. They work great....

93camarochrisz28

i had that chain on my car and it did the same thing and work fine for about year before pulling motor out

93camaroLT1

Did you align bore it? I have a seemingly large amount of slack on mine after an align bore.

65MalibuSS

Nope.
But FYI, I think they make timing sets that have oversize chains or sprockets that account for engines that have been aligned bored.

65MalibuSS

Well I received and installed my Cloyes timing set today.
It's definitely not the same as stock.
It's actually quite a bit heavier - 13.5 ounces heavier (more than 3/4 of a pound!).
But it fits perfect, much better than the Lunati - about 0.25" slack in chain no matter what position the sprockets are in when I turn the crank over by hand.
Picture of sprockets attached - Cloyes on left, OEM on right.