Engine Build #1: Bottom End


Well, i must be an idiot as i have decided to build myself yet another olds engine after i swore the damn things off.  I pretty much have given up on the 455 olds based engines as after about 10,000$ and 6 blocks. i have come to the conclusion the block itself has an achilles heal. the olds V-8 blocks like you see here have the thrust bearing at the center of the block. i theory is that on the 455’s, when that 80lb crankshaft is under major load like going down the track at the drag strip, the crank bends like a fishing rod flexing the block. the center thrust bearing aids in absorbing the thrust from the front 4 cylinders- but the back 4 cylinders have nothing to help it. basically the #4 main flex’s and shits out the main bearings. some engines do it- some don’t all i can say is balancing and camshaft selection are key with 455 longevity. also- buy a girdle for the bottom of the block. Better yet go buy a chevy based Merlin block and forget about it!!

Anyways, when i finally sold my 462 drag engine a few months back, i got this mid 70’s olds engine in on trade. last friday i tore it down and i have to tell ya, it is one of the cleanest Blocks i have ever seen.S3700146 it literally had a stock bore with no piston ring ridge on the cylinders. the Crankshaft was also spotless with normal wear on the all the bearings. so i elected to re-ring it for future use on a street car i have planned to putz around town in. i am using a mid 70’s 350 block, plain jane crankshaft and the original rods and pistons. the identifying mark on olds blocks sits right on the top of the block behind the timing cover. in the picture here to the right above is the serial number you would look for for the good olds 350 blocks. after 1976, the bottom of the block on most all but the diesel engines had large windows in the supporting cast iron of the block for the main journals making for a very weak block to begin with. in my opinion the only block stronger that these 350 olds blocks are the DX designation 350 olds diesel blocks of the early 80’s(which can be converted to gas).

Now to do up an engine right, your block, crank, heads, rods & pistons need to be checked for wear and damage.  things like journal diameter and cylinder bore wear and taper. if you do not have the machinist’s tooling to do it, find a GOOD machine shop(which can be hard to do) . if you are building a high dollar power plant, you should definitely have the block, crank, and heads magna-fluxed for cracks that cannot be seen by the naked eye. pretty much in my book any engine that will see over 350hp/ 5000rpm OR serious amounts of abuse should be checked. things like lifter valley crack can become major deals the more you push an engine to the limit.

 NOW, does this mean you cannot build an engine without a trip to the machine shop- of course not. in my case i started with a great core and have a 500$ budget to get the thing running, and it will not see serious abuse. if the machine shop is out of the question for whatever the reason….usually cost….here’s a list of things not to forget while tearing down, inspecting, and re-assembling you short block :

– i always check all 8 bores with a bore gauge for size and taper due to wear. visually check for pitting and wear to the top of the cylinder. slight ridge-ring is not a definite sign of needing machine work. a ridge reamer can take care of a lot of it. as a personal rule if it is over .010″ of wear you really ought to consider boring it out….however if you are building a loose derby motor, ring seal is not quite as critical so .010″-.015″ is not all bad. in that case the engine i built to run extremely hot and will actually run better as it runs hotter due to the tolerances tightening up. it’s a fine line- too much and you will have piston slap.

-always check the journals on the crankshaft with a micrometer and visibly look for hard wear and damage. you are checking for undersize and taper. if the bearings look bad- chances are the crank is screwed. even if it looks good, if your engine was making noise CHECK IT!  you never know when someone else has been into an engine haf-assed the assy with the wrong size bearings at some point in the past and it bites you in the ass(it happened to me years ago). if your sizes are not to factory spec, look over the crank for any markings on the ends. machine shops usually stamp an undersize on one end of the crank on the counterweight.

-check your pistons and the old rings. look for stuck rings. clean any and all carbon from the ring grooves with a piston ring groove cleaner so your new rings will not jam between the cylinder walls. make sure piston pins are free. check the rods for blue marks….some discoloration of the rods is fairly normal, blue indicates heat damage and it must be replaced.

-if you had spun main bearings or severe bearing damage, the alignment bore of the crankshaft in the block could be compromised and you will need to make a trip to the machine shop, or shit can the block if you have a pile of cores….LOL!

-if you are not replacing the camshaft take a pair of calipers and check EVERY lobe for wear. 90% of the time you will find one that is not up to snuff. always replace the timing chain. always dial in your camshaft. if you do not know how to do this- learn how to. over half of the timing chains on the market are not accurate, and camshafts may or may not be ground retarded in the timing from the get go. you can lose incredible amounts of performance because of this! on some applications it can cost you an engine at start up cause the valves hit the pistons!!

-stick your new piston rings into at least one of your cylinders with a piston to center them and check your piston ring end gap. excessive gap for a derby engine is not hyper critical. you just don’t want it to bind.

-if you are going to run it over 5000 rpm on a regular basis, having your rotating assy balanced is a good idea. if you are changing hard parts like rods & pistons and they are not factory replacement, you should definitely have everything re-balanced. new and oversize pistons are suppose to come from the manufacture already weighted to a factory piston weigh, but the quality control on some of these parts can be a little left to be desired.

-when you are installing engine bearings, do not touch the bearings with your fingers if you can help it. the acid from your fingers can put marks on the bearings. i put a glob of lubri-plate engine assy lube in the middle of the bearing and put it together. S3700149you don’t have to lick the bearings and fondle em like your having sex, you just need to throw some on there so it isn’t dry! i also use two pieces of 3/8″ fuel line with dowel rods stuck inside to not only guide the rod ends onto the crankshaft, but it also holds the bearings into the rod ends so they don’t fall out onto the floors while you are trying to install the pistons into the block leaving both hands free to run the piston ring compressor. always use red loctite on the connecting rod nuts.

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