Looking for shop to fly cut pistons in-block

[ViperT4]

Hello everyone and thanks in advance for your help. I'm in the middle of my cam/heads build for my 2004 GTO. My new cam is in and my intake valve is hitting the piston. I've called around looking for a shop to cut my pistons while they're in the short block and have had no luck. So far I've called WBD, C&S in Milwaukee and C&M. Does anyone know of a shop that will do this for me and do it well?

[Wagonbacker9]

Do it yourself?

[WickedSix]

this seems like a nightmare for the balance of the engine.... you want to cut valve reliefs without knowing how much material has been removed...and without regard to surface treatment on the pistons.... Two options come to mind

Get a Cam fit for your current valvetrain

or

Pull the motor and get the pistons cut and balanced the right way

[Wagonbacker9]

Rumor has it flycutting is unnecessary as he was going past zero lash.

[Moparjim]

Seems impossible to me to do even remotely correctly while in the block, probably why no reputable machine shop like C&S would do it. For starters the piston isnt fixed securely in the block there is a few thousandths or whatever your piston to wall clearance is for it to float around not to mention the crank rotation allowing it to move up or down in the bore. Second concern would be the chips and or metal dust getting into the assembled shortblock. Other concerns would be weight if material removed, strength of piston afterwards, getting an entire shirt block onto and fixtured into a small milling machine, i dunno you name it i just cannot see it happening with any sort of precision or good outcome...

[JC70SS]

Can I ask what size cam?

[ViperT4]

Thanks for the replies guys. I didn't want to do it myself because A) I didn't want to ruin a cylinder head to do it or purchase the cutting attachment etc. and B) I would fuck it up in a heartbeat and it's too important. This has been done before though so and with proper precaution it can be done without detriment to the engine. I just wanted someone with experience to handle it for me.

As Wagonbacker alluded though I was tightening the rocker bolts about a 1/2 turn past zero lash to make the rocker arm snug when I didn't need to. I do in fact have clearance.

[Moparjim]

No clue on LS engines but on say big block Mopars with adjustable rockers and a hydraulic flat or hydraulic roller camshaft that is exactly what you do - tighten the rockers to zero lash, then another half or even full turn depending on a few factors....

If you were that close I would be worried that at high RPM if your lifters "pump up" or what not that you may indeed have a bad day...

[Wagonbacker9]

I would assume tom got a measurement for PTV clearance... If I recall its .08 exhaust and .13 intake minimum, but its been a while since I was researching that heavily, my relatively short 228/222 .588 cam was well within tolerance even after .028 shaved off the heads.

[ViperT4]

No clue on LS engines but on say big block Mopars with adjustable rockers and a hydraulic flat or hydraulic roller camshaft that is exactly what you do - tighten the rockers to zero lash, then another half or even full turn depending on a few factors....

If you were that close I would be worried that at high RPM if your lifters "pump up" or what not that you may indeed have a bad day...

During final installation with hydraulic rollers that is also the general procedure for LS motors. You are preloading the hydraulic lifters and compressing the bucket whatever your preload is. Measuring for p2v clearance requires a solid lifter, I'm sure you're aware, so anything you tighten past zero lash hangs the valve open before the lifter even gets to a lobe, artificially lessening your clearance. I would think this is also multiplied by the 1.7 rocker ratio.

I was uncertain of the exact condition that is zero lash- I thought everything should be snug, enough so that I couldn't spin the push rod. When I measured at true zero lash I had .105" clearance on my intake.

[Wagonbacker9]

.100 exhaust/.080 intake

I was backwards and off by a bit.

[ViperT4]

I would assume tom got a measurement for PTV clearance... If I recall its .08 exhaust and .13 intake minimum, but its been a while since I was researching that heavily, my relatively short 228/222 .588 cam was well within tolerance even after .028 shaved off the heads.

It's the other way around. Rule of thumb is .080" intake and .100" for exhaust, as the exhaust valve supposedly gets hotter thus expanding more.

Measuring correctly I got .105" for my intake like I mentioned about. My earlier exhaust clearance was .070". I didn't remeasure as I would only gain by stopping at zero lash. Cam for anyone that's curious is 232/236 .600" 113

[JC70SS]

Is this a heads/cam motor? FI? Also stock CI?

[ViperT4]

Is this a heads/cam motor? FI? Also stock CI?

N/A h/c. Just shipped my 243s to Advanced Induction yesterday. Stock 5.7.

[JC70SS]

Just curious why such a big cam? I know it is not HUGE, but a bit big good low/mid range power for a street car.

[ViperT4]

No problem. It is on the big side. The full build will be ported Fast 90/90, ported 243s to Kooks headers. The car is a 6 speed and I've swapped the stock 3.46 rear gears for a 3.91 ratio so will help. I'm shooting for 450+ rwhp and 400+ rwtq. There is a car on the LS1gto board that made 480 with the exact same setup. Ed at FTI designed the cam to have very good mid range power and torque but I also wanted to take full advantage of the new heads and intake so it's a little bigger than my last cam.

I corresponded with Ed personally to help me pick the right cam. He has one of the best reputations on the boards and is know for not overcamming a motor so I trust him entirely. My last cam was a 230/232 .592"/.595" at 111* and it made 350 lb-ft at the wheels and 3,000 rpm. If I remember the calculations correctly this new cam actually has 1* less overlap than that one so I expect it to perform as well if not better on the low end.

That's my plan anyway. See any flaws in my logic?

[Wagonbacker9]

No problem. It is on the big side. The full build will be ported Fast 90/90, ported 243s to Kooks headers. The car is a 6 speed and I've swapped the stock 3.46 rear gears for a 3.91 ratio so will help. I'm shooting for 450+ rwhp and 400+ rwtq. There is a car on the LS1gto board that made 480 with the exact same setup. Ed at FTI designed the cam to have very good mid range power and torque but I also wanted to take full advantage of the new heads and intake so it's a little bigger than my last cam.

I corresponded with Ed personally to help me pick the right cam. He has one of the best reputations on the boards and is know for not overcamming a motor so I trust him entirely. My last cam was a 230/232 .592"/.595" at 111* and it made 350 lb-ft at the wheels and 3,000 rpm. If I remember the calculations correctly this new cam actually has 1* less overlap than that one so I expect it to perform as well if not better on the low end.

That's my plan anyway. See any flaws in my logic?
Yeah, its still NA. LOL

[ViperT4]

Yeah, its still NA. LOL

Lol, and still faster than you Carl.

[Wagonbacker9]

Lol, and still faster than you Carl.

I drive a Tahoe. Aim higher.