6066 (1960-1966) GMC Truck Club
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-   -   351C questions (https://6066gmcclub.com/showthread.php?t=50747)

Palimino November 29th, 2019 08:26 PM
351C questions
 
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 November 30th, 2019 05:51 PM
Re: 351C questions
 
Quote:
Originally Posted by Palimino (Post 71685)
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 December 2nd, 2019 08:14 PM
Re: 351C questions
 
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:signthankspin:

Palimino December 3rd, 2019 03:59 PM
Re: 351C questions
 
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 December 4th, 2019 08:05 AM
Re: 351C questions
 
Quote:
Originally Posted by Palimino (Post 71699)
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 December 6th, 2019 08:20 PM
Re: 351C questions
 
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. :signthankspin:

Palimino December 20th, 2019 06:58 PM
Re: 351C questions
 
1 Attachment(s)
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...Attachment 8144

jagarra December 21st, 2019 04:56 PM
Re: 351C questions
 
1 Attachment(s)
Here are the torque specs from my GMC Maintenance Manual.

Palimino January 3rd, 2020 09:33 PM
Re: 351C questions
 
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 January 4th, 2020 03:04 AM
Re: 351C questions
 
1 Attachment(s)
Quick search on the net produced this


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