I have a H/C LS2 with a mild cam (I have to see if I can get the cam specs but I think 228/228 range-forgot lift) and milled heads for a CR bump. I would assume the pistons were only fly-cut just enough to allow p-v clearance for this particular cam, correct? So if I were to go with a different cam, they would need to be fly-cut further based on the new cam specs, right? What if I were to then go back to a smaller cam, would that cause an issue or power loss? Basically I'm asking if fly-cutting has to be a perfect match to your specific cam or is there some room to play without damage and/or power loss?

Thanks

 

well as for how deep they fly-cuting you would have to ask the people that did it. and you don't want to do it too deep. if you go with a smaller cam yes you will loose power. but your best bet would be to talk to the shop.

 

You can only fly cut to a certain depth before it damages the pistons. I would just ask how deep they originally did it and determine if you can even go deeper. The cuts are fairly small so the effect on HP with be minimal if any.

 

It depends on what heads were used in this package.

No one is going to flycut shallow. The LS3 heads with a 234 on a 114LSA cam will fit with a .060" cut.

Lift has minimal effect on a cam fitting because at peak lift the piston is at the bottom of the cylinder. The overlap period from 0-15degrees past TDC is the critical point in the lift and thats when the intake valve is just off the seat.

If you cant get in touch with the person who did the install, you will need to remove a head. Either way, you need to check fitment and no one is going to say what cam fits or not due to liability. Cams like anything else can be ground wrong.

 

Spin..Are you saying that you must fly cut a stock LS3 with a 230-234 on a 115 LSA cam? I just purchased a cam with those specs thinking I would not have to fly cut if I kept the stock heads and stock head gaskets. Was I wrong?

 

I wasn't looking for anyone to give me a specific cam size, it was more of a general question. The heads are stock ported LS2s. When I had inquired to a shop about swapping out to a different cam, I was told that the pistons would need to be flycut again. It made sense until I remembered that we didn't even discuss cam sizing. How would they know it was necessary until we picked a spec range? That got me wondering about flycutting and different cams. (It's the weekend so I can't get in touch with anyone yet)

 

A 230 cam on a 115 LSA is likely to fit with stock heads/gaskets (I assume you have an LS3). The check fit relies on you and not my statement as there are a ton of variables that come into play and no one wants to take a chance on saying it fits. I think a 228XER/114LSA with 2 degrees advance is .090" with LS3 heads. A 230XFI takes some away and the 115LSA gives some back. If you advanced the cam (+2 or +3), that takes some clearance away again. Cams arent exact cuts. If you order a 230XFI it can be anywhere from 229.1 to 230.9 and still be considered a 230 intake lobe by comp cams. LSA also varies a bit. These facts are why cars with fixed engine specs like the ones Lou Gigliotti races in, order several cams to beat the averages and being able to say their 228/236 on a 115 (I dont know that race's allowed specs) can get 10 cams and one can be a 228.8/236.7 on a 114.4 and still be accepted as within specs.

So you are on the line in the .075-.080". Thats likely ok, but dont miss a shift/float a valve. which is good advice for everyone.

Stock LS2's with unmilled heads and stock gaskets fit cams in the 234 on a 112 range. If you mill heads and use thinner gaskets it will require fly-cutting. If there are .040" gaskets used with .030" milling, then a .060" flycut is the minimum. Fly-cutting is more dangerous the deeper you go so I wouldnt take out the max on a H/C swap. If you are going bigger, it would stand to reason you need more depth to a cut.

If you are only getting a cam swap then the labor required for a fly-cut is going to be had because they have to see how deep the existing cuts are. If they dont fly-cut, they still have to open it up and the labor to do so is 95% of the job if they do fly-cut. The actual removal of metal from the pistons is the easiest/minimal amount of a charge for fly-cutting and you dont know if you need it so you have to pay that labor even if you dont need it.

The only way out is to use the same guy for the new job as the old. Its about 4-5 hours to get the heads off so plan on doing it. If you use Trick Flow heads you can run bigger cams without more flycutting.