Look What I Did!!
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,811
Likes: 2
From: Simpsonville SC
Look What I Did!!
I bent a valve and I then bought some new LS6 heads. So I went ahead and fly-cut the pistons. Just wanted to share my experaince!
It was a little scary at first but very easy!
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It was a little scary at first but very easy!
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Thread Starter
Safety Car
Joined: May 2004
Posts: 4,811
Likes: 2
From: Simpsonville SC
I just vacuumed it out really good right after each cut. It worked better than I thought it would. The guy that help me said thats how he's done all his jobs and never had a problem. Ive been diving around for over 100 miles now and havent had any problems.
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,811
Likes: 2
From: Simpsonville SC
I have the G5X4 and there is some clearance to where if you dont over rev it you'll be fine. Well I over reved it and "kiss the piston". I only cut .040" so that little bit gave me enough clearance so this want happen again. I did a lot of searching and it seems that .040" is enough without damaging the piston.
Tech Contributor
Joined: Jan 2007
Posts: 19,465
Likes: 1,167
From: Dyer, IN
So you removed an amount of aluminum from each piston? Since this was done post assembly, I would surmise your rotating assembly in no longer in balance.
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,811
Likes: 2
From: Simpsonville SC
Oh sorry, misunderstood yea. I used a cut-up ls1 head and they make a tool for fly-cutting the piston. I didnt get a chance to take a pic of the tool. Its pretty much looks like a valve with 4 blades on it. Kinda wild lookin. We attached a cordless drill to it and let it rip. It being aluminum it was very easy to cut. We also used a set of calipers and a depth gauge to make sure we only cut .040" and not more or less.
Tech Contributor
Joined: Jan 2007
Posts: 19,465
Likes: 1,167
From: Dyer, IN
Oh sorry, misunderstood yea. I used a cut-up ls1 head and they make a tool for fly-cutting the piston. I didnt get a chance to take a pic of the tool. Its pretty much looks like a valve with 4 blades on it. Kinda wild lookin. We attached a cordless drill to it and let it rip. It being aluminum it was very easy to cut. We also used a set of calipers and a depth gauge to make sure we only cut .040" and not more or less.
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St. Jude Donor '03
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St. Jude Donor '03
I'm running milled heads and .040" gaskets...I cut .100" deep and ended up with .090" actual p/v clearance.
That means just spinning the motor over by hand, the valves are falling .010" into the pockets I cut. Had I not cut at all, there would have been contact.
If you float a valve, I'm not sure .040" would really make much of a difference. I also wonder how you did so. MY PRC duals are doing fine at 7000 rpm.
That means just spinning the motor over by hand, the valves are falling .010" into the pockets I cut. Had I not cut at all, there would have been contact.
If you float a valve, I'm not sure .040" would really make much of a difference. I also wonder how you did so. MY PRC duals are doing fine at 7000 rpm.
Team Owner
Joined: May 2006
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From: Palmdale, Ca----- 2009 Cyber Gray 4LT A6 F55 452 RWHP 422 RWTQ- RIP 1998 C5 734 RWHP & 585 RWTQ-----
How did you know how much material to take off?
It would seem that if one is more than the others it could be out of balance and lead to some vibration or other serious problems later down the road.
It looks real clean but I hope all is good! and I love the cutawy of the LS Head!
Thanks,Matt
It would seem that if one is more than the others it could be out of balance and lead to some vibration or other serious problems later down the road.
It looks real clean but I hope all is good! and I love the cutawy of the LS Head!
Thanks,Matt
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
The only other thing I would have done is rounded the edges of the eybrow to keep from generating hotspots which could cause ping.
To all those concerned about balance. I did this about a year ago on my motor. I had a small cam but on a 112 and had minimum clearance so I cut .060" on both the intake and exhaust. The weight of that much material is less than .5 gram and didn't put the engine out of balance any I could tell. In fact it seemed to run a little smoother. The fact that the weight removed is reciprocating weight rather than rotational weight also makes it less of a factor.
To all those concerned about balance. I did this about a year ago on my motor. I had a small cam but on a 112 and had minimum clearance so I cut .060" on both the intake and exhaust. The weight of that much material is less than .5 gram and didn't put the engine out of balance any I could tell. In fact it seemed to run a little smoother. The fact that the weight removed is reciprocating weight rather than rotational weight also makes it less of a factor.
Le Mans Master
Joined: Jul 2002
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From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
The weight of that much material is less than .5 gram and didn't put the engine out of balance any I could tell. In fact it seemed to run a little smoother. The fact that the weight removed is reciprocating weight rather than rotational weight also makes it less of a factor.
You would have to remove a lot of material from the reciprocating assembly before you even began to notice it, this little bit of fly cutting is nothing
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,811
Likes: 2
From: Simpsonville SC
I'm running milled heads and .040" gaskets...I cut .100" deep and ended up with .090" actual p/v clearance.
That means just spinning the motor over by hand, the valves are falling .010" into the pockets I cut. Had I not cut at all, there would have been contact.
If you float a valve, I'm not sure .040" would really make much of a difference. I also wonder how you did so. MY PRC duals are doing fine at 7000 rpm.
That means just spinning the motor over by hand, the valves are falling .010" into the pockets I cut. Had I not cut at all, there would have been contact.
If you float a valve, I'm not sure .040" would really make much of a difference. I also wonder how you did so. MY PRC duals are doing fine at 7000 rpm.
Man I hope i cut enough, but if your rev is at 7k, mine is at 6700 I guess I might be ok. We checked clearance and it seemed really good, so I guess I can hope this wont happen again.
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,811
Likes: 2
From: Simpsonville SC
How did you know how much material to take off?
It would seem that if one is more than the others it could be out of balance and lead to some vibration or other serious problems later down the road.
It looks real clean but I hope all is good! and I love the cutawy of the LS Head!
Thanks,Matt
It would seem that if one is more than the others it could be out of balance and lead to some vibration or other serious problems later down the road.
It looks real clean but I hope all is good! and I love the cutawy of the LS Head!
Thanks,Matt
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,811
Likes: 2
From: Simpsonville SC
The only other thing I would have done is rounded the edges of the eybrow to keep from generating hotspots which could cause ping.
To all those concerned about balance. I did this about a year ago on my motor. I had a small cam but on a 112 and had minimum clearance so I cut .060" on both the intake and exhaust. The weight of that much material is less than .5 gram and didn't put the engine out of balance any I could tell. In fact it seemed to run a little smoother. The fact that the weight removed is reciprocating weight rather than rotational weight also makes it less of a factor.
To all those concerned about balance. I did this about a year ago on my motor. I had a small cam but on a 112 and had minimum clearance so I cut .060" on both the intake and exhaust. The weight of that much material is less than .5 gram and didn't put the engine out of balance any I could tell. In fact it seemed to run a little smoother. The fact that the weight removed is reciprocating weight rather than rotational weight also makes it less of a factor.
the 111 lsa will hide that!
