DirtyDaveW

___I'm in the midst of swapping out my ported LT1 castings and installing my Canfields. I dropped off my LT1 heads to the machinist so he could clean them up, check the guides, make sure they're still sealing and replace the valve seals since the heads were off.

___Since the heads were just freshened up in April, 2008, all was good. The thing that perplexed me was that he said a couple of valves tip(at the rocker arms) were, in his words, beat up. He ground them down to dress them up and they look fine now. He wanted to know what rocker arms I'm using. I told him 7/16" 1.6 ratio CC Pro Mags, GM guideplates, custom length Trick flow pushrods(He spec'd the length back in 4/2008).

___To tell the truth, even after adjusting the rockers numerous times in a vain attempt to get the valve clatter noise down, the engine had sounded like it was running 'off' a little at idle. Like one or two cylinders weren't quite pulling their weight. While driving on the street, it ran great and at the strip it ran great (108mph in the 1/8th mile, full street weight, street tires, 3.55 gears, T56, pump gas only).

___Have any idea what the culprit could be here? I didn't get the specific details of what Jim (my machinist) calls 'beat up'. Mushroomed? Metal scoring? I'm going into the garage here in a minute to look at all my rocker tips to see if they exhibit any signs of distress.
Thanks,
Dave

slowride94z

solid rollers, lots of rpm, too much gap, get lash caps

hydraulic rollers, bad lifters?

DirtyDaveW

It's a hydraulic roller(custom Bret Bauer profile cut by CompCams)
The lifters were new CC OEM style Hydraulic lifters(It is interesting to me that you offer that as a suspect).
I'm selling these heads now anyway. Just was curious what could cause this phenomena. I'm going to look at the lifters a bit now.
Thanks for your input.

96capricemgr

massive valve float

cusz28

I wouldn't think valve float could cause that. what he's describing is hard contact between rocker and valve. I'm with slow ride. how was your oil pressure and which cylinders did this?

DirtyDaveW

The oil pressure has been good. 60psi at cruise RPM's and above. As far as which cylinders, I don't even know. I'd just pulled the Ported LT1 castings off without doing a visual inspection on them because they looked so clean at a glance. I just boxed them up and dropped them off to my machinist to get them freshened up, if need be, because I plan on selling them. When I went to pick them up, he told me about the 'beat up' valve tips. He's been out of town since I got them and he was in a rush to leave so I didn't ask him for more details. I *think* he'll be back this Sat so I'll press him for more info and provide that here so we can maybe get a better idea of what he meant. Thanks for your input/questions.

chevz

I had pretty much the same problem. I removed my heads a couple weeks ago and sent them to the machine shop to be reworked and 3 valves had to be replaced because the tips were beat up. My problem was caused from wrong guide plates. I drove the car for 4 years and had numerous problems over that period from broken rocker arms to broke push rods. The last problem I had was the valve tip came thru the rocker arm. That’s when I noticed that the rocker arms were misaligned and even had one cocked sideways that cut half way thru the stud. The valve guides were wore out on the valves that had to be replaced. I don’t know if the wore out VALVE GUIDES had any thing to do with the valve tip being beat up or not. It doesn’t sound like you problem since you are running GM guide plates but I just thought I would throw it out there

DirtyDaveW

Yikes! What guide plates were you running? I'm still going thru the laborious task of getting my Isky adjustables setup perfectly. Very tedious, lol...
What are you running now as far as heads/guideplates/rockers?

chevz

I’m not sure who made the guide plates because there are no markings of any kind on them. They were actually on the car when I bought it. I’m debating on going with the Isky guide plates or the Trick Flow plates. How bad is it to get the Isky’s right? Can you get one right and assemble the rest based off the correct one or is that defeating the purpose? My heads are stock aluminum LT1’s w/ 2.02 intake and stock exhaust valves. The rocker’s I bought are Scorpion 1.7 ratio. I’m in the process of going thru the motor thanks to a piece of the push rod that ended up in the rotating assembly locking the motor up and somehow caused one of my connecting rods to bend while cranking the car. I’m now facing the hard decision of going 360CID or 388CID since I have to replace the rotating assembly anyways.

DirtyDaveW

Here's the Isky's...
Apart

Together

On the heads


It's tedious to get them perfect because you have to mock them up, evaluate the roller tip to stem contact, adjust, make sure they're both (I/E) correct, grind off more if they're not able to get close enough, clean, start over. Once they CAN be placed correctly, take out the loctite, place them correctly, tighten them down without the turn of the stud misaligning them(which it easily does, lol).

___ I do think if you got one setup for Cylinder #1 then repeated that grind on the rest of the Iskys, you would probably get all of them to fit with confidence w/o having to trek to the grinder over and over.

96capricemgr

So you don't think the valves floating causing slack in the valvetrain and the rocker trip crashing back down on the valve could cause the valve tip to get beat up???

How else does metal get mushroomed over???

Seems to me hammering on metal is what does that.

DirtyDaveW

I'll be talking to Jim (my machinist) either today or tomorrow and try to get some specifics on what he saw and his ideas on what he thinks would be the likely cause and put it here. The entire valve train was considered and put in the specification when Bret Bauer designed it. He knew of the boost levels(up to 14psi) , etc so I would hope the spring (Big Block Beehives) would be sufficient to control the valve. He sent me the seats, springs, retainers and locks as well as the cam. I went ahead and put a brand new set of the very same springs, etc on the Canfields. I sure hope it's not valve float but stay tuned in the next racing season. I might find out other wise
THanks for your input guys...

mzgp5x

I had a similar problem on AFR heads with high spring load and .580" lift. The visual result was small metal cracks on the top of the valve ends. I recognized this as a hertzian metal failure caused by point loading of the roller tip on the valve top. The studs were coming loose (or flexing) and some surface failure of the PR plates. This caused the RR_arm to angle over due to the push rod angle (not really square with the lifter bore). Now I loc_tite (red) all the valve components and went with a 7/16 stud. Anything that can move is bad. I reset the valves every year. B.

cusz28

Caprice, this is the real definition of valve float courtesy of about.com, "Definition: A high-rpm engine condition in which the valve lifters lose contact with the cam lobes because the valve springs are not strong enough to overcome the momentum of the various valve train components. The onset of valve float prevents higher-rpm operation. Extended periods of valve float will damage the valve train."
The valve never looses contact with the rocker.
see it for yourself:
http://www.youtube.com/watch?v=_REQ1PUM0rY
the valve tip just wiggles around, no bouncing or slamming of the rocker.

cusz28

Personally, i think bad lifters are the culprit.