Very Early Rat
Q I have an engine block with casting number 3855961. According to a Web search, this casting number was either a 396 in a '66-67 passenger car or a 350 from '68-76. Is there a way to tell if the engine is a 396 or a 350? It is just the bare block with no heads or crank to compare. Also, the block is missing the main caps. Will any other set of main caps fit, and will the caps have to be machined in any way to ensure a tight fit? The guy I purchased the block from 18 years ago said it was a virgin block out of a Corvette! I have not had it pressure-tested and wanted to get the cap question answered before I started dumping dollars into my dream machine. Thanks.Frank Flore
A After checking on Mortech.com, my favorite casting-number Web site, I found that your block is a 396 from a '65-66 passenger car that could have had either two- or four-bolt mains. This could have been an original Corvette block if it has four-bolt mains, but if it's a two-bolt, it is probably from a more pedestrian Impala or the like. Yes, you can install other main caps from a donor block. However, you will need to find a set-and a good machine shop to install them. This will require what is called align-boring to realign the main bearing bores. If the block is a four-bolt, it would be worth it; however, if it's a two-bolt, you should look for another block.
A quirk of the early big-blocks was that the oil-lifter galleys were fed oil through a groove in the rear camshaft journal and a grooved rear camshaft bearing; this was only on the '65 and '66 models. Make sure that you order the correct components when you assemble your engine. You will need the grooved cam and bearing. For '67 and later, GM grooved the camshaft-bearing housing in the rear of the block to feed this oil supply.
Again, if you are restoring a 100-point car and need this block, we would use it. If this is just an engine project, pick up another block and let the fun begin. Make sure that you get a '67-and-later block so the interchangeability that the big-blocks are so famous for will be your friend.
Shocking, Isn't It?
Q I have a '73 Chevy 350 in my '71 Chevy Nova, and one of my cylinders is not firing. How would I go about checking which one it is, and what can I do once I find which one it is? Any help is greatly appreciated.Joe Raggio
A Engine misfires can be pesky to find (at best). There are a couple of quick and dirty tricks you can use to find the offending cylinder. First, do you have headers in your Nova? Hope so! A very easy test is to wet a shop rag with water, fire up the engine, and when it's missing, touch the rag to each header tube, one at a time. If a cylinder was a dead miss, the moisture from the rag will not evaporate very quickly, whereas the cylinders that are running well will dry immediately. If you don't have headers, use insulated pliers to disconnect the spark-plug wires from the distributor cap. You will do this one cylinder at a time. Disconnect the plug wire, and if the miss gets worse, reconnect it. If the miss doesn't change, you have found your cylinder.
As for why your engine is missing, it could be a hundred different things! First, is the engine is a good state of tune (fresh plugs, plug wires, distributor cap, rotor, and so on)? If so, go straight to a compression test of the offending cylinder. You should check all the cylinders and record the results. You shouldn't have any cylinder that is lower than 10 percent of the highest cylinder. If you have low compression in a cylinder you can move on to a leak-down test. This is a special tester that regulates compression through a set of gauges that read out in percentage of air leakage. With this air pressure you can pinpoint if the leak is through the intake valve, the exhaust valve, or a blown head gasket.