ok, so here is what i have in the build, then I will post what the problem is:

2003 5.3L bored to 5.7L
new Forged ICON pistons
new piston rings
new rod and main bearings
Gen 4 floating pin rods
one 853 and one 241 head (both with 2" intake valves)
58X crank (new grey crank sensor)
LS2 front timing cover (new cam sensor)
Double row timing set with rear trunion bearing
ICT Billet cam retainer plate with new tapered bolts
Melling M295 oil pump
Holley Mid-rise intake manifold
Holley Sniper 4150 shiny version
new starter
BTR 7.400 pushrods
new LS7 lifters
Comp trunion upgraded rockers
Camshaft is SUPPOSED to be the Sloppy Stage 1Year: 2000-2007

Compatible with: Chevy

Engine: LS1

Camshaft Type: Hydraulic Roller

RPM Range: 2000 to 4800

Intake Valve Lift: .575"

Exhaust Valve Lift: .575"

Advertised Intake Duration: 286

Advertised Exhaust Duration: 282

Intake Duration @ .050": 220

Exhaust Duration @ .050": 224

Lobe Separation: 112

Intake Centerline: 108
++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++++++++++++++++++++++++

What I am running into is that it will not start. It usually pops really hard a time or two out of the exhaust.
It acts like it has a hint of compression, then just spins no matter what I do with the throttle.
I don't have a compression tester. I wont be able to get one for a while, or at least til I get one of my other 2 engines sold.

When I tighten up the rockers, it seems to be they are pushing the pushrod down quite a ways before it is actually tight at the center bolt.
I plan to make a plate so i can measure the amount it is pushing down with a micrometer.
I know it is supposed to have a little bit of push because of it being a hydraulic roller, but these look like they are going WAY down!!

 

This is a classic sign of too much lifter preload, or in the area of the LS platform…too long a pushrod. I witnessed this multiple times with SBC engines. If you put too many turns in the Oem rocker adjustment nuts, the intake valves wouldn’t seal, and it would pop out the exhaust (and blow flames out the headers) every time, and not start. I’m confident that in what your describing that you’ve got too long a pushrod in place.

 

That is what I was afraid of.

Bad part is I wasted the money on these pushrods.
Good part is I believe somewhere in my garage I have an adjustable pushrod for 7-8" I can use to determine what I need for a pushrod. I also have a dial micrometer with an adjustable base I can use to HOPEFULLY get an accurate measurement for the rocker arm.

 

Well it’s an easy fix and you can sell the pushrods you have. There are many, many threads here on Tech about finding pushrod length. Enjoy the journey sir.

 

Didn't anyone measure for proper length PRs BEFORE they were purchased?

 

Doesn't sound like it....