So my new H/C engine build is at the chassis dyno today. After the 1st pull, there is an audible tapping sound coming from the valve train. Upon closer inspection w/ a scope, the tuner finds the cyl 6 lifter has collapsed. The lifters are a brand new set of the Caddy lifters.

I'm basically wild right now

It's no ones fault, but I can drive 2-1/2 hours to pick up my broken car, then haul it home, and pull the lousy head off to replace a lifter.

My question is... what do I do??? Replace the bum Caddy Lifter w/ another? Put my stockers back in?? Buy a new set of some other Hi-performance origin??

What will give me the best chance of getting this to work??? Its not about money. Hell, if I put a shop rate on my time... the wasted trip to and from the tuner, time to replace the head, and the trip back to the tuner, I'll call $1500. So I don't care if the lifter set costs $100 or $600. I want to know when everything is meticulasly and neatly put back together that it will just work!!

I'm so frustrated right now.

Also, on the 1st and only full dyno pull, the tuner was telling me that it hit 440rwhp at 6000 rpm and then fell sharply (about 40hp) in the next few 100rpms. Everything was set to safe mode, the timing was down around 18 degrees, A/F hadn't been worked out, and the fuel injectors were looking like they may not be up to the task as they were @ 100% duty cycle. All in all was a decent pull w/ plenty of tuning potential left. But, He's very concerned about valve float from much trouble w/ his past experiences on LS engines.
This combo has a Vengence VRX5 Cam (actually producing 601/605 lift238/242 @ .050, 113LS). The rocker is a Comp Pro Magnum 1.75:1. The valve spring is a piece purchased from the folks that did the CNC porting (they did a great job on the heads), Total Engine Airflow. The spring is a "Dual Platnium" Double Spring, Polished w/ Titanium Retainers. I'm told its a 385 Spring Rate, 150lbs @ 1.800" Installed Height and yields 400lbs open.

Does all this sound like the ingredients to promote valve float? Does it sound like the ingredients to promote a collapsed lifter?

Just so there are no misunderstandings... I am not upset w/ my engine builder, my tuner, or the vendors from which I've purchased all the components from. I think they have all done a great job and am not bashing anyone. I'll tell ya, I'm just sick right now (never thought I'd get to use that emoticon) Yes, I'm irrational, and am ready to roll this thing into a river. Maybe the lifter will fix it self overnight.

 

Sorry to hear about all the troubles but you aren't the first to get bit by the Caddy Lifters: Good friend Tom Wong went through days of testing before he ruled out the lifters...A good thread to read through, maybe give you some direction..
http://forums.corvetteforum.com/c6-z...-cam-swap.html

 

Don't use the Caddy lifters. Even if you get some that don't collapse, you are going to end up with low oil pressure. Stick with the stock lifters.

 

Thanks for the input. So, how much cam lobe aggresion and valve spring seat pressure can the stockers withstand? Are the stock lifters capable of handling the same pressures exerted as, say, the Comp Pro Magnum 'R' lifters? I just don't want to go through this again.

 

There is a secondary rev limiter based on acceleration that probably caused your problem at 6000 rpm, see this post on how to fix it in the tune:

http://forums.corvetteforum.com/1559412511-post13.html

 

As far as the stock lifters. I have been running a VRX5 cam with no issues for a year with the stockers. Car made 451/429. Hope you get your issues sorted out!