[Colin101234]

So I have a 6th gen ss.
Currently the car is FBO I Haven't started any of the motor mods yet. I have frankenstein heads that are ported but also milled .025 (Their stage 1.5, stock casting w/ new valve seats) on the way aswell as a custom grind cam from cam motion w/ GM caddy racing lifters. Long story short I didn't know they were milled and now I have to figure this out because I'm locked in. I got a thickest cometic gasket to try to make up some of the difference at .060, stock is .052 so in theory its only only like it's milled .017. Question is is my ptv clearance gunna be an issue with a cam=224 in 242 ex, 114.5 lsa +3 (648 in, 639 ex lift) The guy from cam motion says I'll have around .055-.060 in clearance with .100 out clearance he also did state those are most likely hot clearances. He said its the most agg cam he'd go without fly cutting (The whole reason I got a custom cam) I'm just wondering if that's safe given the rule of thumb is .080 and .100 min. The springs are .700 so I'm good there but I just need some opinions. Also is there any other issues I'm going to need to look into with a .017 mill? Ofc I'm gunna have to measure pushrod length but is there anything else? Also anyone know what compression that will put me at on SBE? I really appreciate any advice!

[cmitchell17]

Originally Posted by Colin101234

So I have a 6th gen ss.
Currently the car is FBO I Haven't started any of the motor mods yet. I have frankenstein heads that are ported but also milled .025 (Their stage 1.5, stock casting w/ new valve seats) on the way aswell as a custom grind cam from cam motion w/ GM caddy racing lifters. Long story short I didn't know they were milled and now I have to figure this out because I'm locked in. I got a thickest cometic gasket to try to make up some of the difference at .060, stock is .052 so in theory its only only like it's milled .017. Question is is my ptv clearance gunna be an issue with a cam=224 in 242 ex, 114.5 lsa +3 (648 in, 639 ex lift) The guy from cam motion says I'll have around .055-.060 in clearance with .100 out clearance he also did state those are most likely hot clearances. He said its the most agg cam he'd go without fly cutting (The whole reason I got a custom cam) I'm just wondering if that's safe given the rule of thumb is .080 and .100 min. The springs are .700 so I'm good there but I just need some opinions. Also is there any other issues I'm going to need to look into with a .017 mill? Ofc I'm gunna have to measure pushrod length but is there anything else? Also anyone know what compression that will put me at on SBE? I really appreciate any advice!

I ran a Cam Motion 228/236 - 114 LSA with my milled 0.030 heads with a thinner 0.028 Cometic before I changed out to a BTR 230 cam.

I did notice on one piston there was like a ghost pattern where you could tell and exhaust valve barely made contact, but I'm not sure if this might have because of poor valve control or valve float as it ended up wiping one of the cam lobes on the Cam Motion cam. When I put in the cam motion cam I think I remember having worst case cylinder, at the very edge of the raised embossment in the piston of around 0.060-0.070.

When I put in my new BTR 230 cam I ended up cutting the pistons out I think about 0.100 if I remember right so not much.

I think given that your running a thicker gasket that you know for sure will buy you extra room you should be ok .

[Colin101234]

Yeah after I mocked everything up it checked out good and I measured everything, thanks for the reply!

[cmitchell17]

Originally Posted by Colin101234

Yeah after I mocked everything up it checked out good and I measured everything, thanks for the reply!

If there is any contact it would of course be on the exhaust side, as the exhaust valve is closing and the piston coming up, and I wouldn't think it could cause near the damage if it was on the intake as the piston is coming up and the intake valve going down.

I'm sure you could still bend a valve, but it would probably take a lot of head milling to do it on the exhaust valve, and I would think it could cause not only valve damage, but also piston damage if it was on the intake side.

[Colin101234]

Originally Posted by cmitchell17

I ran a Cam Motion 228/236 - 114 LSA with my milled 0.030 heads with a thinner 0.028 Cometic before I changed out to a BTR 230 cam.

I did notice on one piston there was like a ghost pattern where you could tell and exhaust valve barely made contact, but I'm not sure if this might have because of poor valve control or valve float as it ended up wiping one of the cam lobes on the Cam Motion cam. When I put in the cam motion cam I think I remember having worst case cylinder, at the very edge of the raised embossment in the piston of around 0.060-0.070.

When I put in my new BTR 230 cam I ended up cutting the pistons out I think about 0.100 if I remember right so not much.

I think given that your running a thicker gasket that you know for sure will buy you extra room you should be ok .

You said, "When I put in the cam motion cam I think I remember having worst case cylinder, at the very edge of the raised embossment in the piston of around 0.060-0.070." what did you mean by that? That you had .060-.070 of ptv clearance? That should have been plenty, a lot of people run as low as .040 with the gen v lt1 but that's intake side, did you mean you had .060 ex side? Im confused lol.