The Stovebolt Site Forums The Shop Area Engine Shop Rebuilding a 1958 261...need advice..

Hello everyone

Usually do more reading than posting but I have a few questions some of you might be able to help.

Engine is now sitting in machine shop...to be bored out .030...crank at .010 and .010

On balancing.... if I get the crank shaft balanced and I have access to a very precise lab scale in grams.... can I do the inside components myself by grinding down to the lowest weight value.... I will be getting new pistons and would weight these seperate and grind the inside down to the lowest value. Then weight in the rings, bearings, rods, bolts, etc. as six seperate assembly and grind down the rods to the lower value.... Question... on the rods I have seen a weight value for the lower end and for the small end.... does it imply that I would need a special fixture that allows one end to be mounted and free to pivot with the other end resting on the scale...???

Can I get by just doing a full six set weight in and grind just the rod/pistons to even out the weight???...I would focus on the pistons and the rod's small end of the components since they would have the most impact when spinning...

I do not intend to race the engine or run above 4000rpm......

They will balance the flywheel seperate included in resurfacing price.

The damper front pulley is obviously old... need I worry..... I heard they can be rebuilt but not sure where I can get this done in Canada... how do you tell if it is necessary????

I have solid lifters which need to be resurfaced...is this typical... a new stock cam will be installed..???

Since the engine will be installed in a very tight semi COE cab I intend to instal a Pertronix or similar system to keep maintenance to a minimum.....with Platinum plugs.... BUT... I have heard/read some bad expereinces with the Pertronix system ..... any suggestions of make/model... I will run standard 12v system and would like to hide the electronic inside the original distributor if at all possible....???

I would like to shave the heads for more compression... I will be using 235 with drilled steam holes.... but there is very little room to shave..... is it more feasible to shave the deck height by .040 and have the pistons shaved for .020 deck clearance... or am I just wasting money......machine shop will grind deck to at least make the surface perfectly flat and the head to match.

You should know the engine will replace an original 216... and be installed in a 1940 C15a Chev CMP..(Canadian Military Pattern) 4 X 4 right hand drive, 15cwt (3/4 ton) truck..rear axles ration 6.39...top speed with 216 was 46 MPH...on 900 x 16 NDT tires.

Thanks for all the advice....

Bob Carriere
Hammond, Ontario Canada

At a top RPM of 4,000, you won't need to do a precision balance job. Yes, rods need a special hanger fixture to weigh big and small ends individually, with ball bearings at both ends to allow the scale to respond correctly. I match weights on all the moving parts to 1/10 gram, but we wind the race engines up to over 7,000 RPM routinely. For piston matching, weigh all the components together, piston, wrist pin, rings, etc, and keep the parts together after matching the weight to the lightest assembly. They should be very close from the factory, within a couple of grams of each other. That's sufficient for street use, unless you just want to get the weights exact.

Most machine shops will weight-match parts before doing the spin balance on the crankshaft, unless you're trying to save labor costs by doing some of the work yourself. A crankshaft is balanced by bolting a "bob weight" to each rod journal, using the weight of the pistons, rods, rings, etc, to compute the weight of the "bob". Then the crank is spun, and weight is added or removed at the counterweights to dampen out any vibrations. To do it properly, the parts must be weight-matched first. Good luck!

Edit: If new lifters are available, don't try to resurface the old ones. A new cam needs new lifters to go with it.
Jerry