To All:
Thanks for your inputs. I haven't been able to look at these replies untill this evening. They are very interesting, and it's clear that there is a large pool of knowledge about these engines on this BB!
I have built several engines in the past, but all have been 'modern' V-8's, such as SBC's and BBC's, along with some Chrysler V-8's. This 261 has been a different kettle of fish!, and much more difficult (read expensive!) than I would have believed!
I went out to the garage to try to find the notes I've made while building this engine, so I could share them with you. I could only find some of the preliminary measurements. I will try to look more tomorrow evening for my build notes.
For what it's worth, here are some of what I've found.
The engine is a 1961 261 'Jobmaster' with the full flow oil filter. It was removed from a '61 dumptruck.
After dismanteling (sp?)the engine, I had the block hot shot cleaned, magnafluxed and minimally 'decked' to present a flat and true deck. The main bearing bores were checked, no align boring or honing required! A deck plate was attached, using the stock head bolts, and the block was bored and honed with it in place. The pistons I purchased are from J&E, .080 oversized, forged flat tops, full floating pins, with moly filled, zero gap rings. The rods are N.O.S. GMC's, magnafluxed, polished, shot peened, bushed for floating pins, and all are 7.000 inches in length. Since the pistons are light weight forgings, I felt (feel) comfortable retaining the stock N.O.S. rod bolts.
The bore: 3.830, stroke: 3.937 (stock), Rod length: 7.000 Piston compression height: 1.840. Deck height of block is 10.870, while deck height of pistons are 10.809. This leaves the deck of the pistons at -.061, below the block deck at TDC.
The crank was magnafluxed, ground and indexed. Mains are .010 undersized, while the rod throws are ground .030, leaving the largest radius possible between throws and cheeks(?). Rod and main bearing clearances are right at .0025-.003.
The camshaft is a Howard's F-298 grind, single pattern, with advertised duration of 268 degrees, and overlap of 48 degrees. Duration at .050 (lifter)lift is 231 degrees as measured. The cam is installed "straight up", and the lifters are new mechanical, from Patrick's. The pushrods are N.O.S. of stock length tubulars from Isky Cams.
I checked all of these measurements several times during assembly.
There's one other thing that may be of interest. I purchased four N.O.S. head gaskets from Tom Langdon. One of these was used during the boring and honing operation. At my request, the speedshop placed a lead shot fishing weight between the torque plate and block deck, so he could measure the gasket's compressed thickness. It was (is).053. I then drew the outline of the fire ring on a sheet of 1/4 inch graph paper, and spent some time filing in the squares, four at a time, and counting them. I did each cylinder, and each one three times! I then averaged the results, coming up with 13.8125 square inches. Multiplying by the ,053 thickness gave me 0.7321 cubic inches, or, 11.999 cc's, gasket volume. (12 cc's, for short :))
This post has been longer than I expected, and somewhat off the subject. I hope, however, that some of you may find it interesting. When I finish this engine, I'm going to write the results in an article for the 12 port news, (if anyone cares):)
