Your opinions please...

New cam, heads, LS7 lifters, Manton 11/32 push rods. Engine runs well and makes good power. No fluid leaks. New balancer, belts, hoses.

Experiencing a "tick" that is most noticeable under light load at about 1700 rpm on the drivers side. Seems to diminish as motor gets warmer. Can't hear it at idle or at higher rpm (long tubes and Corsa has something to do with this!).

Sounds like a lifter tick but could be a small exhaust leak.

Thoughts that come to mind:
- defective lifter, or something stuck in a lifter,
- rocker bolt has worked loose (they were torqued to 22 ftlb and secured with blue loctite)
- push rod too short (but why just one?) so not enough preload. Pushrods were measured for 0.060" preload.
- exhaust gasket leak one one cylinder. Might explain why it gets better as motor warms up? No obvious evidence of an exhaust leak

Ideas on where to start to resolve this?

Thanks

 

The best way I've found to find an exhaust leak is get a mechanics stethoscope and pull the end of it off (the big plastic piece with metal tip), take a brake line you get at the auto parts store and stick it in the rubber hose (you'll want a metal line on the hot exhaust parts not the rubber hose that's why you use the brake line) then run the tip of the brake line around your exh flanges/mating surfaces. If you come across a leak you'll know, you'll get wind blowing into your ear.

Bend the end of the brake line to be able to get to the under side of the header flanges, but don't bend it too far and fold it over. If you accidentally fold it over cut it with a pipe cutter and try again.

 

Thanks! I will give this technique a try. Was considering the use of a smoke source but your way seems more definitive.

 

I had a similar situation and it ended up being a header gasket leak at the head underneath where it is hard to see. I happened to see some black on the spark plug that is how i found it. Drove me crazy for 2 weeks because it didn't tick all the time and i really thought i had a lifter tick. I found out like an idiot i put the header gasket in upside down.

 

Header gasket can be installed upside down?? Thought as long as the bolt holes line up it is good to go. Can you educate me on this so I too can confirm that I am an idiot

 

The gm gaskets are marked manifold, so that side faces toward the header

 

The ones you can hang on the outside bolts like this too?

 

.060 preload is not enough for LS7 lifters.

 

.060 is fine.

 

I should clarify regarding preload. As with any motor there was some variation in measured required pushrod length to get exactly the same preload across all lifters. After measuring and talking to Manton I ordered 7.360" 11/32 Manton custom length pushrods. In looking back at the actual measurements this generated a minimum preload of 0.0625" (cyl #1 intake) and a maximum preload of 0.0800" (cyl #3 intake). Most are clustered in the 0.07xx range. This measurement was empirically verified when I was torquing the rockers .... was getting 0.75 to 1.0 turns from zero lash to snug (but not torqued), and my understanding is that 1 turn generates 0.078" preload when using 1.7:1 rockers. Achieving 22 ftlbs from snug took another 0.25 to 0.33 turns.

 

it may be fine but it's not ideal. Ideally you want to be in the middle of the lifters plunger travel. most run LS7's up around .080 or even higher.