Craig B

Here’s the dealio.

1995 Gen V 454 Carb Mag, all stock except Edelbrock Performer intake, Lightning headers.
Before I installed my new cam (Comp Cams XR268 per Dennis Moore's suggestion) we cranked the motor to TDC, two dots on timing gears lined up.
Installed the cam.
Set dist rotor facing #1 after having again made sure TDC via finger in #1 hole.
Ran it through a 20 minute break in.
After break in, had some idling problems, so I started messing with the idle mixture screws before I realized it was a linkage problem (Carter AFB 750).
Took it to the water and it wouldn’t open up, back fired a couple of times and tach was going nutty. An hour later we realized I had the distributor bolt upside down and that was allowing the dist to move. Corrected that, messed with the straight idle screw and started sounding good.
Made one pass, running strong, but forgot the damn GPS in the truck!
Returned to pick up the GPS and after idling out, hear a tapping noise. After scratching heads we smell exhaust and realize we have a manifold exhaust leak.
Torqued down the manifold bolts, let it sit all night and tightened again in the morning. Cranked the motor and problem solved.
Changed out old spark plugs to new merc spec plugs (Champion RV15YC4), had trouble getting the #5 in due to the headers.
Returned to the lake, fired right up and sounded good.
Went to hit it and got a cracking noise coming from the carb, idle is fine, but under load, cracking. The more throttle, the more it cracks.
Limped to a safe spot and verified correct plug on rotor position. Again found TDC and verified rotor facing #1 cylinder. Triple checked correct wire to plug locations. Moved timing forward and back, it doesn’t seem to matter, still spitting/cracking.
Limped back home and said fuggit!

Any thoughts?
This is a cracking/spitting noise coming from the carb under load.

FWK

What is your initial timing?

ragtop409

Rember to get true timming readings on a 1995 TB V distributor you need to ground the purple / white tracer wire that comes off the distrib. plug. Rag's

blue thunder

Did you replace the timing chain and sprocket set with the new cam? If so, did the crank cam have three keyways to chose from depending on desired cam timing?

BT

KH0302

It ran good then puked...I think he jumped timing.

Griff

Sounds like it could have wiped out a cam lobe.

220BR

Hold the phone.

I know this true for SBCs and I believe it is true for all GM V-style engines. When the the dots are aligned at crank at 12:00, cam at 6:00, #6 is at TDC on compression, NOT #1.

#1 is on TDC compression when the dots are at crank 12:00, and cam 12:00. You're 180* off.

red thunder

Not unless he stuck his finger in #6 hole.

220BR

Ah, read too fast. My bad.

dyno

New Cap? A carbon track in the Dist. cap can really piss you off!