Howdy all,
I've been lurking for a while and learned a ton of useful information from this site, many thanks to everyone who have contributed their experience!
Apologies for the long post, just wanted to include any and all info which may be pertinent as to why oil pressure on a fresh 1965 327 SBC would consistently reach 15-17 psi then drop to 0-2psi. Here's "The rest of the story..."
Recently my son decided he wanted to drive the '64 C20 (with a '65 SBC 327) that I drove in high school, so we pulled it outta the barn after 3 decades for a little father-son project. When it was parked, the 80K 327 would make decent oil pressure with the original canister oil filter mount and an adapter for a spin-on, "decent" being on the right side of the half-hash on the dash gauge, never did put a numbered gauge on it.
The block got a full machine shop refresh including .030 bore. The rebuild kit came with what I would consider good components for a street motor, including Clevite bearings and a stock Melling oil pump. On assembly, the bearings plastigauge'd between .0020 and .0025 (one was tight at .0010). The new configuration included new hydraulic flat tappet lifters and roller rockers in new Summit 165 iron heads, a Comp X4 262H cam with 218 intake duration at .050, Edelbrock RPM intake and AVS2 carb, and MSD 8362 SF distributor. We primed the motor with the old dizzy shaft and drill until we got flow at the rockers,...unfortunately, I didn't pay close attention to the pressure gauge, just the flow, I know...major cranio-rectal inversion on my part.
I can find my way around 7.3L and 5.9L diesels but this is my first SBC from the ground up...so here is our problem: the motor fired right up and ran with no lifter noise or other indications of impending doom but the oil pressure would consistently reach 15-17 psi then abruptly drop off to 0-2 psi, this was at or just above idle (800-1000 rpm). We limited these runs to not heat up the block.
Trouble shooting so far included:
1) Verified oil level at just above full on aftermarket dip stick (4.5 qts. dino 10W30 in original oil pan with the pick up tube 1/2 off the bottom).
2) Fresh oil and filter after the first 4 runs, cut open filter for trash - none found.
3) Swapped oil gauges (mechanical) and tubes (used both nylon and metal lines) - no change.
4) Swapped oil filter adapters, to include one which was full flow - no change.
5) Verified the plug in the vertical oil galley, below the oil pressure adapter, was set at 8 3/8 in depth from top of block face.
6) Verified both rocker banks were getting oil and the dipstick oil level was not changing after drain back.
7) Tried both long and short oil filters - no change.
8) Pulled the distributor, gears looked new and the oil pump shaft appeared pristine.
9) Spun the oil pump with a drill cw (again) and found that when the pressure reached 15-17 psi and dropped off, the torsion on the drill would slack noticeably.
From the recent drill spin, it feels like the oil pump relief valve is just letting go at 15-17...on a fresh pump. When we engaged the dizzy shaft and spun the oil pump by hand, we could feel what I would call normal resistance to flow from the pump. We de-burred the pump and verified fit on install so the only thing I can think of is we got a weak relief spring outta the box (the pick up tube was not brazed with the spring in place). Any other trouble shooting suggestions would be greatly appreciated before we pull the pan and oil pump.
Thanks in advance,
I've been lurking for a while and learned a ton of useful information from this site, many thanks to everyone who have contributed their experience!
Apologies for the long post, just wanted to include any and all info which may be pertinent as to why oil pressure on a fresh 1965 327 SBC would consistently reach 15-17 psi then drop to 0-2psi. Here's "The rest of the story..."
Recently my son decided he wanted to drive the '64 C20 (with a '65 SBC 327) that I drove in high school, so we pulled it outta the barn after 3 decades for a little father-son project. When it was parked, the 80K 327 would make decent oil pressure with the original canister oil filter mount and an adapter for a spin-on, "decent" being on the right side of the half-hash on the dash gauge, never did put a numbered gauge on it.
The block got a full machine shop refresh including .030 bore. The rebuild kit came with what I would consider good components for a street motor, including Clevite bearings and a stock Melling oil pump. On assembly, the bearings plastigauge'd between .0020 and .0025 (one was tight at .0010). The new configuration included new hydraulic flat tappet lifters and roller rockers in new Summit 165 iron heads, a Comp X4 262H cam with 218 intake duration at .050, Edelbrock RPM intake and AVS2 carb, and MSD 8362 SF distributor. We primed the motor with the old dizzy shaft and drill until we got flow at the rockers,...unfortunately, I didn't pay close attention to the pressure gauge, just the flow, I know...major cranio-rectal inversion on my part.
I can find my way around 7.3L and 5.9L diesels but this is my first SBC from the ground up...so here is our problem: the motor fired right up and ran with no lifter noise or other indications of impending doom but the oil pressure would consistently reach 15-17 psi then abruptly drop off to 0-2 psi, this was at or just above idle (800-1000 rpm). We limited these runs to not heat up the block.
Trouble shooting so far included:
1) Verified oil level at just above full on aftermarket dip stick (4.5 qts. dino 10W30 in original oil pan with the pick up tube 1/2 off the bottom).
2) Fresh oil and filter after the first 4 runs, cut open filter for trash - none found.
3) Swapped oil gauges (mechanical) and tubes (used both nylon and metal lines) - no change.
4) Swapped oil filter adapters, to include one which was full flow - no change.
5) Verified the plug in the vertical oil galley, below the oil pressure adapter, was set at 8 3/8 in depth from top of block face.
6) Verified both rocker banks were getting oil and the dipstick oil level was not changing after drain back.
7) Tried both long and short oil filters - no change.
8) Pulled the distributor, gears looked new and the oil pump shaft appeared pristine.
9) Spun the oil pump with a drill cw (again) and found that when the pressure reached 15-17 psi and dropped off, the torsion on the drill would slack noticeably.
From the recent drill spin, it feels like the oil pump relief valve is just letting go at 15-17...on a fresh pump. When we engaged the dizzy shaft and spun the oil pump by hand, we could feel what I would call normal resistance to flow from the pump. We de-burred the pump and verified fit on install so the only thing I can think of is we got a weak relief spring outta the box (the pick up tube was not brazed with the spring in place). Any other trouble shooting suggestions would be greatly appreciated before we pull the pan and oil pump.
Thanks in advance,