1999FirehawkLS1

iTrader: (21)

Need to know the PTV w a MS4 on a Factory LS1 Bottom end and stock unmilled heads car is a 99 heads have never been off....thx

SS4Luck

iTrader: (10)

umm CLOSE!

definitely something that needs to be double checked or first time you romp it it could be all ******* over


not to mention 99 rod bolts are the weakest of the LS1s i believe

1999FirehawkLS1

iTrader: (21)

I need numbers

02*C5

iTrader: (1)

You mean PVC (Piston to Valve Clearance) right if so it should be no less than .080 with any cam regardless of the chambers size of the heads or milling to the deck anything less and you do not fly cut your asking for trouble.

Jason 98 TA

iTrader: (4)

Not near as close as a lot of competitors camshafts out there! Typically I see right at .070" intake & just a little bit more on the exhaust.

I know a lot of shops sell there huge camshafts at well under .050" on this site. While I've run .040" in testing a few times on the dyno, it's getting pretty close at that point.

DarkJuggalo

iTrader: (6)

.040 thats insanely close LOL. you must have money you just want to throw in the air. next time just gimme a call, you can send me the parts instead of trying to break them

1999FirehawkLS1

iTrader: (21)

Now thats more like it....well i switching to a set of 243s milling them .020 or .030 and shinking the vavles instead of flycuting and was trying to fig out how much to sink the vavles and what shorter push rods too get from my 7.040s

ssfast99

iTrader: (3)

LOL I love this site specifically for this reason. Here is some advise no one gave you. Run a good valve spring and have fun with your new big cam. And my 99 rod bolts love over 600rwhp and torque at 7000rpms

ssfast99

iTrader: (3)

I have never fly cut any t-rex or MS3 or MS4 cammed cars and guess what? They all run strong and hard LOL. And remember to calculate ur head gasket thickness when you do your math for the new set up OP.

PREDATOR-Z

Sure, but what were your clearance margins? I tell you what they were; its called clueless.
I do not understand logic around this way of thinking. No degreing, not PTVC check, no geometry check, no preload check, all in all perfect installation, right?

I have a hard time believing .070 PTVC on MS4. I would have to see that one to believe it, but then again, I never measured one myself.

Some conflicting info from 2007

https://ls1tech.com/forums/8283962-post14.html

* We see average .060 PTV on MS4*

Bottom line, do not take any internet feedback as gospel. ALWAYS check your safety margins YOURSELF. Not 2 motors are alike and any cam spinning 6800>7000 needs to be verified, because with valvetrain fluctuation, especialy with harsh lobes like LSK, a .070 clearance can end up .030 in reality (things stretch and lifters do not always follow cam lobe profile at those rpms ).
The same goes for any other big cam FYI.

ssfast99

iTrader: (3)

nah on cams that big we do degree them but what i was getting at was it will be fine if you do it correctly. but i will be the first to admit my knowledge falls short to people like predator-z and others on here who know a lot more than me. sorry if i came across rude because it was not intended. what i was trying to say was that you do not have to, every time, flycut the pistons with the bigger cams. just do your math first.

01ssreda4

iTrader: (96)

Gotta agree with pred here, You know like measure twice, and cut once. that kinda thing