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Hey guys. I’m hoping you guys could help me out. I also hope I can give you enough information to help you guys make an educated guess. I have a 1995 Chevy K1500 with a 350 5.7. It has 200K+ on the body, but probably not more than 50K on a newer engine. However, I’ve owned this truck since I was 20 (young and stupid), and haven’t always taken care of it like I should, hence the engine change. For the last 8 years the truck has pretty much been parked with occasional driving that resulted from my motivation, at times, to fix the truck.

Situation:
My truck will crank up like a champ. It will idle like a champ. It does have the low toned knock for the first two couple seconds until the oil pressure gets up. However, after I’ve driven it down the road I noticed that when I decelerate at a stop sign or stop light I have a puffing noise coming from my right tail pipe (I have straight pipes). This noise sounds almost like you are relieving air pressure from an air line. I wouldn’t consider it a backfire only because I think of backfiring as a gunshot type noise. I feel like I should have bubbles shooting out from underneath my car. LOL! At this point I have not check-engine-light on, nor do I have any stored codes on the computer.

Maintenance Performed:
Replaced Starter/Battery Cable because old wire melted to exhaust manifold
Changed plugs / wires at least two times
Changed EGR valve
Temp repaired Left exhaust manifold cracks (unknown if Right side is cracked due to shroud)
Changed fuel filter
Oil still shows amber color with no signs of contamination
Changed Distributor Cap/Rotor button
Timing is Good (Checked with a light)
Changed MAP Sensor
Changed Idle Air Control Valve

At this point I’m scratching my head. Hopefully you guys can help me out…

Phil
P.S. Yes, I posted this elsewhere seeking out answers.  

i am taking that this is a TBI motor .. not a vortec..

cracked exhaust manifolds will make strange noises...

leaking exhaust valve seats will also do strange things to the exhaust..

low toned knock... might mean that you need to get serious about swapping on a fresh engine oil pump .. at least pressure washing the drivers side of the under motor..   picking up a oil cooler seal kit... checking the operation of the various valves in the oil cooler adaptor...  making sure you have a quality oil filter.. try an AC oil filter.

this is the felpro oil cooler adaptor gasket set.. ES72671




i would check the amount of Orings with the above kit by looking at the info on the box label...

this is the dorman carded kit that a lot of stores also stock .. and its a buck cheeper..  motormite 82560




look at item 10...



 25014006 VALVE. Engine Oil Cooler. Engine Oil Filter. Transmission.
VALVE,OIL FLTR BYPASS(USE W/OIL COOLER)(W/CAGE, SEAT, SPRING & VALVE)(OPENING PRESSURE 11 PSI NOMINAL)(ACDelco #25014006). Required: 01For: K1,2,3 5.0  

Thanks for the intel! I will definately look into it. Also, I did check the compression on the right bank. The highest readin was 150 PSI, but cylinder 6 read 140, which is still within limits according to the hayens manual. Cylinder 6 and 8 both had a a little oil on the spark plugs too. Not sure if thats a bad thing or not.