How to flycut pistons in an LS1 for free! (almost)
You should measure the eyebrow, the outside arc has to be at least .04 inch bigger. When hot everything expends and the piston actualy rocks. If less than that, your valve could catch the edge and bend or worse.
Just make sure.
Also you might want to deburr any sharp edges to avoid hotspots.
Easy way to test is to clay the relief flat and then free fall the valve. Measure the distance between valve contact at clay and edge of flycut.
If you have .04 or bigger you are good. I would repeat that on all pistons.
Just make sure.
Also you might want to deburr any sharp edges to avoid hotspots.
Easy way to test is to clay the relief flat and then free fall the valve. Measure the distance between valve contact at clay and edge of flycut.
If you have .04 or bigger you are good. I would repeat that on all pistons.
I've seen this method done on here before but I was just worried about getting the right radial clearance from the valve which is why I just rented the cutter for my intake side from Lindy for like $60. It would suck to have to rent two of them if you needed to cut exhaust as well since it would be like $120 just to rent something for a day!
In addition to radial clearance the transition of the floor of the cut is important as well. The guy at Lindy explained any sharp 90 degree corners inside the relief can cause an area that will be prone to fracturing the piston. As you can see in this picture I illustrated the floor of the relief has 3 different surfaces. Blue,red,and black. The yellow on both sides are the pistons top surface. If you removed the red surface and had the black and blue surfaces meet down deeper into the cut it would create a 90 degree corner. This is the corner that can create an area prone to cracking.
Thread Starter
Joined: Apr 2006
Posts: 3,924
Likes: 1,160
From: Grand Rapids, Michigan
I don't have my engine anywhere near me, but my valve reliefs are of that shape. The paper curling around the head of the valve actually puts a nice radius at the bottom of the cut. Of course it's not as perfect as if I had used a cutter, but I don't think my pistons are going to fail because of it.
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TECH Senior Member
Joined: Mar 2004
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From: BFE
While JFM-jr comments are totaly true (about 90* cut), the method you are using does make a slanted cut (I've done it the same way a few times, always bigger valves though)
I've never had any issues with piston cracks, lost a ringland on #7 but no cracks (lean nitrous spike)
I've never had any issues with piston cracks, lost a ringland on #7 but no cracks (lean nitrous spike)
Seriously? his balance will be fine, hundreds if not thousands on this board have flycut pistons with no problems whatsoever myself included. Just think about how little the weight is of these shavings/dust. I means we're talking 0.050" of depth right at the edge which tapers back to zero...the balance will be perfectly fine especially since all 8 pistons receive the same cut. Hell you could probably flycut on one piston by itself and never notice an imbalance.
I don't have my engine anywhere near me, but my valve reliefs are of that shape. The paper curling around the head of the valve actually puts a nice radius at the bottom of the cut. Of course it's not as perfect as if I had used a cutter, but I don't think my pistons are going to fail because of it.
Nicely done. Only downside is you need to drop the motor unless you use a high power right angle drill.
I guess it would be worth it drop it to be able to gain the extra clearance.
I guess it would be worth it drop it to be able to gain the extra clearance.
I just used a plain old drill with a right angle attachment. Of course in the vette it was only needed on piston #8 since the motor isn't hidden under the cowl near as bad. The pistons cut really easily with very little pressure using the Lindy tool.
They say that most inventions came as a way of making life easier. I think this is a great example of what can happen when you have knowledge and some tools. Look out for all the people who do this for a living start to talk crap on how bad this idea is. I am sure a few shops are going to see a drop in business in fly cutting.
They say that most inventions came as a way of making life easier. I think this is a great example of what can happen when you have knowledge and some tools. Look out for all the people who do this for a living start to talk crap on how bad this idea is. I am sure a few shops are going to see a drop in business in fly cutting.
This is a GREAT idea and I take nothing from the ingenuity it took to come up with it. Personally I would still purchase the Lindy tool for the 115 bucks. For a single use its pricey tho. Dont forget most aftermarket pistons come flycut. Its just us cheapskates using the stock flatops LOL
Thread Starter
Joined: Apr 2006
Posts: 3,924
Likes: 1,160
From: Grand Rapids, Michigan
If anyone wants one, I found a few 2.08 intake valves laying around that would work great for any valve size up to 2.05. $15 shipped to your door. I only have 3 of these, so if you want one, PM me.
Also, we ended up going back in and smoothing the eyebrows out and laying the edge back slightly so we can be absolutely sure that nothing will catch in case I float the valves. If I never float the valves, I should have nothing to worry about, since I have .055 clearance to start with.
Also, we ended up going back in and smoothing the eyebrows out and laying the edge back slightly so we can be absolutely sure that nothing will catch in case I float the valves. If I never float the valves, I should have nothing to worry about, since I have .055 clearance to start with.
If anyone wants one, I found a few 2.08 intake valves laying around that would work great for any valve size up to 2.05. $15 shipped to your door. I only have 3 of these, so if you want one, PM me.
Also, we ended up going back in and smoothing the eyebrows out and laying the edge back slightly so we can be absolutely sure that nothing will catch in case I float the valves. If I never float the valves, I should have nothing to worry about, since I have .055 clearance to start with.
Also, we ended up going back in and smoothing the eyebrows out and laying the edge back slightly so we can be absolutely sure that nothing will catch in case I float the valves. If I never float the valves, I should have nothing to worry about, since I have .055 clearance to start with.
i have a few if anyone wants one, just pay shipn