My valvetrain consists of a GM LS1 HOT cam, Crane hardened 7.400" pushrods, Comp 941 springs with Ti retainers, connecting to Rev stock-size stainless valves in ARE S1 heads.

A mere three blocks from my office, the exhaust valvespring on #1 collapsed. This happened as I was pulling into a restaraunt parking lot on my lunchbreak. Mind you the coolant temps were in the 190-200 degree range, it had two blocks of traffic lights to wait for (Dallas traffic sux), and the spring broke at 1500 RPM in second gear.

I called up Sean at FASTech and had it towed. They tore it down on Tuesday and found the valve collapsed completely; broken in three seperate places along the coil. The piston has a couple nicks in it, but Sean will just smooth it out to prevent a hot spot.

The head went to his machine shop, where they did a valvejob on it yesterday and ordered a replacement valve. The valve came in today, but the head didn't pass the magnaflux. He says there's a crack in the valve seat.

Now I won't have my car back until Tuesday. In the meantime, I'm having Sean throw in a set of 918s, stock retainers, and a TR 224 cam on a 112 LSA. The car put down 391HP/377TQ with the HOT cam, so I'm optimistic about the performance with the "Thunda Wunda." What pisses me off:

-Is my head fux0Red? What sort of "patchwork" is required in machining a new seat? I definitely don't want anything out-of-spec and I plan to keep these heads for the life of the car. The car has only 20K on it right now.

-The downtime is beyond inconvenient. I know Sean is taking care of me, but I haven't had anyone else work on the car; I like to do things myself and I trust everything will be PERFECT when I get it back.

-I'm lucky to be able to work from home this week, but I'll have to go back to the office next week, which may mean I'll have to get a rental. More $$ out-of-pocket for an already expensive repair bill!

-Should I expect this setup to go trouble-free after it's done, and should I take care of anything else while it's down? It already has an ARE oil pump and every bolt on imaginable, aside from major suspension work. I never had any SES lights with the HOT cam, and it put down good numbers with no KR and needed only light (~10%) LTrim enrichment.

 

Oh yea.. and how should I present this to Comp? I want to phone them up and stick them with part of the bill, but the chance that I'll get anything back from them is probably slim to none. Needless to say, I'm very disappointed with the 941.

 

I have doing some research and I have been told that the 941s are not good for our cars. apparently they are brittle and have a rep for breaking.

 

941s are making a hobby out of breaking. We just replaced a set of 941s on a buddy's Formula. A TR224 broke them in no time.

In short, if you're running 941s, I'd swap them out. There have been way too many failures.

 

Imperator
How many miles did you have on the 941's? What was the lisft of the cam? The final question is din't you say the lifter went bad? Could this be the cause of the spring breaking?

 

The 941s had about 2,000 miles on them. The LS1 "HOT" cam features:

Gross Valve Lift: .525/.525
LCA: 109/115
Duration @ .006: 271/280
Duration @ .050: 218/227
LSA: 112

To my knowledge, the lifters are fine. They should be, considering stock valvesprings had been used over the previous 17,000 miles in the short life of the car. The valve spends a lot of time open, but the long lobe ramps and low lift (relatively) should be tame to the valvetrain. I'm just blaming the construction and high spring rate of the 941. It's too harsh to be produced with H-11 tool steel. The 918s should answer all of my problems and put a few extra horses down.

 

I had one bust on me a while back with 18,000 miles on them. That's with the T1 cam and stock heads. I switched to the 918's and no problem so far.

 

Imperator
Forgive me but gota ask... Was the install hight set on the valves when the heads were done? Did you do the valves springs or a shop?
I'm not heading down any road just wondering. I have a set of 941's in my car and I'm about to take it out for the season. At this time changing them is not in the plans.

 

ARE sent the S1 heads with the 941s installed on the Rev valves. They don't use 941s anymore, but their early spec heads used the 941s. To my knowledge, stem height was not set with the springs upon installation. I'm using the same valves with the 918s now.

 

"stem height" that's what I wanted to say. I was told if this is not done the springs can be compressed to much and break. Duno if this is true but sounds right. Think about it... if the valve stim height is to low, then the spring is already compressed a little due to height being to low. There will not be enough distance to compress the spring before breaking.

<small>[ April 19, 2002, 02:40 PM: Message edited by: 2000 Camaro SS ]</small>

 

You are correct. I'm on hold with the machine shop right now. They're specing the head on Monday when the new valve gets in. Apparently the damage isn't as bad as I once thought; the holdup lies in wating for the new valve to be delivered from Rev.

I wanted the machine shop to check the installed height of the valve RIGHT NOW, but he can spec it out just was easily once the machining is complete on Monday. All that's needed is a resurface of the seat and replace the valve guide.

Talking with Comp earlier, both the 941 and the 918 require an installed height of 1.800." This spec should be remain the same if the same valve stem height is used. The 941 spring supports a maximum gross valve lift of .560". The 918 can support over .600," mainly due to the ovate wire design. The 918 gives slightly more seat pressure, but is lighter on open pressure than the 941.

 

Sounds good, glad to hear you will be able to fix things. I took my heads to the best speed shop Iowa City-Cedar Rapids has to offer. When I took them in I made sure they understood that this was IMPERATIVE that they checked the height and they did. Thunder Racing (that's who I got the cam and springs from) said if this is done I should have no problems. Angie has 941's in her car for 2 years with no problems. Hope all works out well for you. By the way when I had my heads done I went with Ferrea valves and had them back cut to help air flow. Think about getting that done while your at it.

<small>[ April 19, 2002, 07:38 PM: Message edited by: 2000 Camaro SS ]</small>