Flycutting pistons

[sparks57]

Does anyone know what is involved with flycutting pistons?



Can any machine shop do it?



How much is the average cost?



Do the pistons have to be removed?



Also, here is the real kicker: is it worth the time and the money to flycut the pistons for a more aggressive cam? Or are the gains not directly proportional to the cost?

 

[Forrest Nearing]

is it worth it? well... if the cam requires flycut pistons and you want the cam, then it's worth it.



Forrest

 

[phillips5]

Man you realy got it bad don't you. Why don't you just get an old dodge bighorn. 855 cubic inches. Or maby a KTVA 2300 in it. That is V12 2300 cubic inches. Would that be enough for you. They are 4 valve heads by the way. Those have like 11/16 headbolts take 1 1/16 socket and 300 ft lbs. Is that big enough and tight enough for you. And the Bighorn trucks have all the big stough 44000 lb. drives. 20 speed trans. What more could you want. Just messing with the kid I couldn't resist!

 

[RTillery]

If your cam is going to position the valves close to the pistons, they will have to be removed and flycut. This is a pretty specialized operation and most of your average engine building machine shops are not setup to do it. It requires an adjustable piston fixture, and it would most likely be done in some sort of vertical mill. Most important, by far, is a machinist who is very knowledgeable about the components you are going to use and has some experience working on your type of engine. This is probably going to be a shop that specializes in performance diesel engine rebuilding. Don't know for sure, but the guys at Piers might be able to advise who could do it. Good luck.

 

[Forrest Nearing]

actually, it's a fairly simple operation because the valves are 90* to the piston face... so all you need to do is bring the piston to TDC, use some clay or grease or teflon paste or something, and use the valves to mark the piston so that you can get your stem center locations...



take them to a good performance machine shop that doesn't blink when you tell them you need them flycut, tell them your valve diameter numbers and how deep you want them cut, and you're in business. I think my machinist quoted me $20 a piston or so...



Forrest

 

[Paychk]

Isky cams has a piston notching tool that is used for this purpose and can be used by the average mechanic at home. the cutters range in size from 1 5/8" - 2 3/8" and the pilot shafts come in 3/8, 11/32, & 3/8". They also rent them, info can be found in Isky catalog on page 17.

 

[Forrest Nearing]

heh, I've got a set in the garage that'll clear a 2. 10" intake and 1. 625" exhaust...



with that said, they are decent if you're trying to save some money and your shortblock is in good shape, but on anything later than a 1st gen, the motor would have to be out of the truck...



but, they're a royal pain in the rear... the head has to come off and on for EACH CUT, and while they're great for making existing notches bigger, they take some serious pressure/rpm to cut new notches. I had to notch the pistons in my small block V8 to clear some heads with altered valve centerlines. serious PITA... and that was with an angled valve... I couldn't imagine trying it w/ a 0* valve angle.



since the engine has to be out of the truck anyhow, I'd just take them to a decent shop and have it done on a bridgeport... do it right, and take it as an excuse to refresh the bottom end at the same time...



Forrest

 

[Forrest Nearing]

oh yeah, the reason cutting new notches is such a PITA is that the cutter tends to load up... you CAN cut a notch on one run, but I found myself removing the head to clean the cutter more often than not... that's all well and good when you're lifting a 25lb aluminum head... wouldn't want to mess w/ it w/ a Cummins head!!!!



Forrest

 

[1stgen4evr]

flycutter

As a machinist, I would go with 'out of the engine'. I would also find someone (a shop) where that is their specialiality. (Performance upgrades and the machining that goes with it. ) Just because someone is a machinist, doesn't mean they have the level of experience to do the job you want. Whether it is done with the 'hand job' or in a mill, you want the depth to be exact. Too much depth and you start to loose compression ratio. Uneven depth from cylinder to cylinder will give differential performance between cylinders. You are already at the point with power upgrades where a gnats a$$ will make a difference in result.



If you made a jig to use with the head off where you could see the cutting and lubricate the cut with kerosene, I am sure you could make the cut without clogging. The stop I see in the picture would set the depth of cut the same on a jig. I don't know if the valve guides are precisely the same highth.



Your question seems to be is the flycutting worth while. Or maybe I just read it that way. If you use a cam that lifts the valve higher while the piston is at top dead center, it is an absolute must. I have seen the reliefs in stock diesel pistons so it must be standard operation for some applications. ( I actually assume that CB knows this but include the comment for the larger forum. )



What will the cam do for your application CB. You must be on the top edge now.



1stgen4evr

James

 

[sparks57]

Thanks everyone. I wasn't asking if flycutting it's self was worthwile, but a cam that requires it. IE: will there be much to gain from a cam that does not require flycutting to hardcore cam that does?



Thanks everyone.



And no, this won't be used in my current application... it's for a project I have in the works.