PTVC question. Someone please try and explain


May 13, 2010
Russellville, Ar
Ok, I have been doing some research about putting cam's in my car and have read a little about Piston to Valve clearance issues with the 99-04 2v's. Here's my question;

Some people are saying that the biggest cam you can run with out notching the piston's is a .500 lift cam, but then HiTech is saying there are no PTV issues with their cams. But then someone on here says there is only .001 clearance with the HiTech cams, but I have personally saw 2 or 3 people run the CMS stage 2 cams (which are bigger than Hitech's) and not get their piston's notched and have no issues. How is this possible?
  • Sponsors(?)


10 Year Member
Jan 31, 2003
Peak lift isn't usually the problem since peak lift generally occurs with the piston some ways down the bore. A limiting factor to lift is springs and potential interference between the retainer and the seal at maximum lift.

For PTV the issue is how far off the seat the valve is when the piston is at or near TDC. This is where the installation angle, duration and the shape of the lobe matters. My fairly mild Comp 262AH cams have 0.550 lift and I have no PTV issues. However, these are mild cams with not a lot of duration.

I don't think there's one single answer. A vendor can grind his ramps to help alleviate the chances of PTV but if you're going with any sort of "aggressive" cam the onus really is on you to verify for yourself that at your installed angle (degreed straight up, advanced, retarded etc), there's adequate clearance through all four strokes. This generally means using clay on piston crowns, installing the heads with pre-compressed head-gaskets, turning the engine by hand and analyzing the thickness of the thinnest part of the impression. Off the top of my head you'd want something like 0.050" minimum on the intake and 0.090" on the exhaust though I'm sure others will supply different values. Certainly, you want more than 0.001" :)



Sep 25, 2009
Max lift and ramp speed have nothing to do with it with any of the cams for these motors. The intake valve is closest to the piston at 5-10 degrees ATDC and the cam lift is in the 0.1-0.3" range. Only thing that affects PTV is the cam duration and install centerline (how advance or retarded)
Thread starter Similar threads Forum Replies Date
G PTVC question 1994 - 1995 Specific Tech 20
bjl95mustang Is there a way to check ptvc with out push rods. Grady here is your tech. 1994 - 1995 Specific Tech 4
My92cashtrap Engine Roller rocker question Fox 5.0 Mustang Tech 2
derek2079 I has question about my radiator temps 1965 - 1973 Classic Mustangs -General/Talk- 3
gearhead77 LED question 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 6
M New member, question about custom order times The Welcome Wagon 0
General karthief Fuel Purge canister question 1994 - 1995 Specific Tech 11
Red50Fox 88 Mustang GT 5 lug / disc conversion (almost done!) parking brake question 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 5
O Questions - Putting a 93 5.0 in a 66 1965 - 1973 Classic Mustangs -General/Talk- 2
R Paint and Body 1991 mustang ssp questions 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 17
B Engine Questions regarding a 93 Cobra Vacuum Leak/Intake Manifold Fox 5.0 Mustang Tech 6
M Question for you (Mustang) paint experts out there Mustang Sound & Shine All 2
F hello new person here. with a question The Welcome Wagon 4
Gs87GT Fox Questions on stock suspension rebuild. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 5
N Bought a unfinished 5.4 dohc into 97 gt project. I)ve got lots of questions. The Welcome Wagon 2
D 1999 cobra blower questions SVT Tech Forum 0
Mystang66 Holley 4180C question 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 1
91GTstroked Engine 3G alternator ground questions. Fox 5.0 Mustang Tech 12
Red50Fox 8.8 Axle Gear Oil and Modifier Question 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 13
M Trans question SN95 4.6L Mustang Tech 2
S 1985 dashpot and kicker questions Fox 5.0 Mustang Tech 10
C 1995 Mustang GT Megasquirt Timing and ignition settings question Digital Self-tuning Forum 36
Mystang66 1977 302 air cleaner assembly question 1974 - 1978 Mustang II Talk & Tech 10
M Questions about a 3.8 swap 1996 - 2004 SN95 Mustang -General/Talk- 0
6 Question about valve covers 1965 - 1973 Classic Mustangs -General/Talk- 6
4 Question about pertronix ignition 1965 - 1973 Classic Mustangs -General/Talk- 0
A Microsquirt setup and first start questions Digital Self-tuning Forum 9
D Engine MAF question for a 4.6 P1SC Procharger SN95 4.6L Mustang Tech 0
Mu-TangClan Drivetrain Question regarding drive shaft flange Fox 5.0 Mustang Tech 0
4 64.5 Coupe question about C4 cooling lines 1965 - 1973 Classic Mustangs -General/Talk- 1
Mystang66 1977 Mustang II Ghia Sport emissions question 1974 - 1978 Mustang II Talk & Tech 17
S Lithium Battery question 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 5
L 1997 Cobra Tune Question (and some background on the car) SN95 4.6L Mustang Tech 3
D Lowering questions SN95 4.6L Mustang Tech 4
D Easy question :) 1996 - 2004 SN95 Mustang -General/Talk- 2
7991LXnSHO Interior and Upholstery Power lumbar questions Fox 5.0 Mustang Tech 5
H 1972 convertible pre-purchase question 1965 - 1973 Classic Mustangs -General/Talk- 8
Woody3882 Intake manifold heater hose general question 1965 - 1973 Classic Mustangs -General/Talk- 0
5 Rack to steering question Fox 5.0 Mustang Tech 3
E Drivetrain First fox with a couple of questions Fox 5.0 Mustang Tech 8
7991LXnSHO RANT!!! Medina questions 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 27
Justin87 Engine Engine intake and installation questions Fox 5.0 Mustang Tech 2
Willybill32 Fox Body Front Suspension Question 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 11
A Question about MIL eliminator 2005 - 2014 S-197 Mustang -General/Talk- 10
voodoo18 1992 Injector question. Digital Self-tuning Forum 2
8 Headlight Switch Electrical Question Fox 5.0 Mustang Tech 2
A Transmission Replacement Question SN95 V6 Mustang Tech 1
F Engine Lifter Replacement (W/ heads off) questions SN95 4.6L Mustang Tech 1
C SVO Suspension questions 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 24
Xkuzme1 Engine Spout Question. Fox 5.0 Mustang Tech 19
Similar threads