tech180

So I am rebuilding this 5.3 and have a set of engine tech flat top pistons I wanted to run.
Will the the valves be ok with the cam I am running? Block is at the machine shop getting .50mm bore/20 over bore. Should put me just over 10:1 cr I am thinking?

CAM SPECS

COMP Cams#249-54-455-11
LS1 Camshaft
Hyd. Roller
1300-6500rpm
Adv. Dur. 265 Int./273 Exh.
Valve Lift .604 Int./.610 Exh.
Lobe Angle 112 deg.

96capricemgr

iTrader: (1)

Peak lift and piston TDC occur nowhere near the same time, duration is more important and most folks would rather see .050" duration not advertised.

tech180

Thanks for the reply! So I should be ok with the duration on this cam?

KCS

iTrader: (20)

You should be fine. That's an itty bitty camshaft. It would be a good idea to check once it's in though.

svede1212

iTrader: (3)

Check the PTV and degree your cam

Aston Tibs

iTrader: (3)

I am running the cam one step up from this and had to retard the cam 4 degrees to get acceptable intake PTV clearance. It really is worth degreeing to make sure.

tech180

damn, well, I guess I need to start researching the correct ways to check the clearance.

tech180

would you guys recommend me going with a thicker head gasket to play it safe? If so, how thick? thanks for the help as I need it, this is my first LS based motor build, so I am learning.

96capricemgr

iTrader: (1)

You are quoting duration in advertised numbers and now want to consider screwing up quench and compression for PTV clearance. That much lift on that short a duration is going to be likely hard on springs.

I would settle down, do more research, don't trust catalog companies or Comp for advise which is I would guess how you chose that cam.

SSEUL8R

That's an awful lot of lift for that small of duration. I hope you back that cam up with a good valvetrain.

Darth_V8r

iTrader: (4)

I recommend talking with kip at cam motion. Plus you get a cam dr report with the cam so you know what you got. He will get you a cam that will make plenty of power and easier on the valve train.

Also, keep in mind duration, not lift, causes PTV issues. By the time you get to 600, the piston is halfway down the bore.

Pharcyde50

iTrader: (11)

Always check, its cheap insurance

Darth_V8r

iTrader: (4)

yeah. I'm not saying don't check, just that lift isn't what causes problems. It's duration and proper timing that are critical