valves smacked pistons

[opeltwinturbo]

At BG last week I made 1/2 pass. This was the first pass of the year and it was a granny launch and a mild pass. About 1/2 track it sounded like a gravel mixer. With the motor still running (good oil pz) I pulled the car over to the side along the wall and coasted to a stop on the first exit road Car was towed to the pits and we tried to refire it. Zero compression on all cylinders. Pulled the valve covers, all rockers seemed OK. Pulled the rocker shaft and all push rods were straight. Pulled down the headers and saw all exhaust valve guides broken. Pulled the heads and the six pistons had valve circles on the deck. Valves smacked the pistons. Pulled the front cover to check possible keyway broken. All tight. Idler good. Ironically, timing marks were dead on. Pulled the distributor and it sounded like a castinet. The rotor cap had broken all around the perimeter of the counterweights. Gears on distributor looked fine. Rev limiter was set at eight thousand. Since it was a warm up run I did not have the laptop in the car. Shiftnoid set at 7500. I do not think I winged the motor. Valves were at 20 & 22. Any thoughts on this.

Secondly, now that the valves are toast, should I go with titanium or stainless. I have two sets with titanium and one with stainless. Also, your thoughts on this.

Thanks

John

 

[top gun]

I think it's time for you to step up to a 109 block with Champion heads.

 

[S2V6RACER]

Maybe you hit it with a little too much of that Komer NO2 spray?

 

[Big Stu]

Hey john, sorry to hear the bad luck.. I have titanium intake and stainless exhaust valves for my stage 2 aluminum heads and was told by more than a few people that these motors don't like titanium on the exhaust side of things. I think stainless or inconnel is preferred for exhaust valves. My 2 cents....

 

[opeltwinturbo]

Komer NO2 spray?

Ted: You're talking about Bamford, aren't you? About time to start paying closer attention to all of those heavily taped lines near the engine. Hey, tech guy, look at this !!!!!!!!!!!

 

[Big Stu]

What kind of guides do you have? You coming to vegas this year?

 

[750H.P.V6]

John,

Sounds to me like your exhaust guide clearance was too tight. If there isn't adequate clearance the valves will stick in the guides once they get hot and the pistons will wack them. The pushrods will still be straight.

Neal

 

[EightSecV6]

John,
Did you check to see if the cam key twisted or sheard on the nose of the cam? Everything would look as if it were correct except the valvetrain timing would be out. And Neal is 100% correct on the guide clearance. They will also break if they sre left too long into the port, alot of N/A machinists do that on turbo engines.I would look at both exh wheels on the turbos too, surely that material from the guides put a hurtin' on 'em!
I prefer to use titanium int and exh valves, generally speaking, we dont run them long enough to hurt them.

 

[S2V6RACER]

Originally posted by opeltwinturbo
Ted: You're talking about Bamford, aren't you? About time to start paying closer attention to all of those heavily taped lines near the engine. Hey, tech guy, look at this !!!!!!!!!!!

Yes, it is another quality gas offered by Komer Carbonics right here in our fine city of Detroit. I see he has set up a vendor with a Komer CO2 filling station at BG.

 

[opeltwinturbo]

Bill: We were positive we would find pieces laying in the front cover. Everything was tight. Will check the turbos. What is recommended guide length in the port and exhaust guide clearance? Thanks.

John

 

[750H.P.V6]

John,

I can't speak for Bill but I would tell you an exhaust guide clearance of .0025" would be a good starting place. I expect at the H.P. level you're at that might not be enough. It would depend on the exhaust valve material and actual EGT you typically see. As far as the guide is concerned I like to see the tapered end machined off. In essence the guide will be full wall thickness where it protrudes into the exhaust port.

Neal

 

[TurboTR]

My friend's car (BUICKTR here) recently had the exh valves hang up and get bent as described here... Ported irons on it.

TurboTR

 

[turbodave231]

John,

A valve related question, What springs are you using?

I'll be sending you back your convertor soon. It worked great! Please PM me your shipping address.

Dave

 

[opeltwinturbo]

Dave: Use it and have some fun. Bring it back at Salem. By then, you will not want to give it back.

Check out the picture on the attached link:

http://www.bpgforums.com/showthread.php?s=&threadid=1670

This is what caused all the damage.

 

[turbodave231]

Ouch!!!!!

That is ugly. I hope it didn't hurt too many other parts when it decided to part company with the crankshaft.


I'll bring the TC to Salem.

Dave

 

[opeltwinturbo]

Well................The crank has a major divot. It was already at .020/.020. I'll have it welded up and rechromed to get it back to standard. Looks like a nine iron wacked it. The block is cracked but very fixable. Skirts are chipped down low. Little line bore and it will be ready to go. We are freshening up the other motor and hope to have it ready within 10 days. The broken guides put a few dings in the turbo wheels. The center sections are packaged and will be shipped to Precision on Monday. All in all, a lousy day.

John

 

[opeltwinturbo]

Trip to the machine shop. #520 block needs two liners (#2 & #4) and the block can be welded to fix the crack. The crankshaft is off to Crankshaft Specialists for repair and chroming. The turbos are off to Precision. Gasket sets ordered, bearings ordered. Heads will be stripped, valve springs checked, new guides installed. All that for 1/2 pass. Ouch.