351C questions

[Palimino]

Just picked up this engine last week, came out of a '66 5000 chassis, mileage unknown, first compression check was kinda low in the 40-60 lb. range, shot some Mystery oil down the holes and got better numbers, 90-95 (1-3-5-6) and 89-70 ( 2-4), pulled that head and it looks like head gasket could be the problem, not much if any ridge at top of the 3 bores, no gouges/scoring either. Valves look to be 1 7/8" EX and 2 1/8" IN, the manifolds are the "I" beam style. Are these the "small" valve heads I have heard of? Thnx

[Ed Snyder]

Originally Posted by Palimino

Just picked up this engine last week, came out of a '66 5000 chassis, mileage unknown, first compression check was kinda low in the 40-60 lb. range, shot some Mystery oil down the holes and got better numbers, 90-95 (1-3-5-6) and 89-70 ( 2-4), pulled that head and it looks like head gasket could be the problem, not much if any ridge at top of the 3 bores, no gouges/scoring either. Valves look to be 1 7/8" EX and 2 1/8" IN, the manifolds are the "I" beam style. Are these the "small" valve heads I have heard of? Thnx

The 351C is a non-Magnum engine, so -- yes -- it has the "small" valve heads just like the 305s have. The 351E has the Magnum heads. My one ton Suburban has the 351C in it.

[Palimino]

Thanks Ed, just what I thought, now I need to continue with my tear down, inspection of what I have to start ordering needed parts to get this beast running in top shape

[Palimino]

Ed, what is the major difference between the different heads? Would a little clean up with a die grinder/stones, better exhaust system work etc be beneficial? Thnx Joe

[Ed Snyder]

Originally Posted by Palimino

Ed, what is the major difference between the different heads? Would a little clean up with a die grinder/stones, better exhaust system work etc be beneficial? Thnx Joe

The intake and exhaust ports and manifolds are all larger in cross section (by about 30% if memory serves me) in the Magnum engines, compared to the non-Magnum. I'm sure cleaning up any ports or manifolds would help the flow through them.

[Palimino]

Thnx for that info Ed, any idea where I can get torque info for rods and mains? Was gonna do a complete lower end on this engine, but after looking at a main bearing and rod bearing and checking out the cylinder bores, I think I'll stick with having heads done and new gaskets to get it running again, BTW found this engine in Rogue River.

[Palimino]

Well the rebuild has started, heads back from machine shop, cleaned, valves ground, seals replaced, Olson's had a gasket rebuild kit, and now we begin...IMG_20191220_095749.jpg

[jagarra]

Here are the torque specs from my GMC Maintenance Manual.

[Palimino]

OK, bottom end back together, water pump housing on, crankcase vent filter ordered, can't seem to be able to locate head bolt torque pattern, any help would be appreciated, THNX

[Funky61]

Quick search on the net produced this