Should I buy this overhauled engine?

September 1, 2016 | By Staff


An ad in a regional publication offers: “1954 Chevy 235 motor. Has had complete overhaul. $2750. In the same publication another ad says: “1954 235-inch 6-cylinder, complete overhaul, bored .030 over, still in crate, $2700.” Because my 1954 Chevy pickup engine is a little tired, this ad called to me. It would be great to have a fresh engine to install along with a future transmission swap. The question is how do I know what the seller is offering? What questions and answers will help me determine whether I want this engine? Should there be more than these questions:

• What work was done?

• When was the work done?

• Who did the work? (Get contact info.)

• Were the block and head good to start with?

• What parts were replaced?

• Does the engine include an oil pan, side cover, manifolds, carburetor, distributor, water pump, etc.?


When I bought a 283 Chevy small block a few years ago I was told it was freshly overhauled and from a reputable shop.

However, I like to wear a belt and suspenders, and didn’t want to install an engine that was less than optimal, so I disassembled the engine and miked it. As it turned out, the bottom end had been done recently and properly, but the heads hadn’t been touched, and one was cracked. There was nothing to be done for the heads because they were the original correct, small-combustionchamber types that if milled any more would bump the compression too high for pump gas.

I bought newer large-combustion chamber heads and had them machined, and did a complete cleanup on the engine…but when we got it in it didn’t run right. The carb vacuum signal was mushy and there was a big flat spot in the mid-range. I couldn’t figure it out until I took the carb to a friend of mine and he told me that it was a 650 cfm Rochester that looked identical to the 450 cfm that the engine needed.

I found the correct carb, rebuilt it, and that solved the problem. The fellow who had the engine before me had fallen for the “more is better” thinking that a lot of guys use when fiddling with engines, and it is patently not true. An engine is designed to use only so much air and fuel, and unless you modify it considerably, it will not benefit from more. I got it all sorted out and the engine is great, but making it right doubled my costs in the process. That was my experience dealing with a rebuilt engine from a reputable shop.

When considering buying any rebuilt engine, I would want to see all of the notes from the machine shop as to what they did and why. For example, one engine you mentioned was bored .30 over. If so, what brand of pistons was installed? Were the connecting rods straightened and balanced? Was the crankshaft turned? Was the block align-bored and were new rod and main bearings installed? Was the cam reground or replaced? If so, was it a stock or a performance grind? Are the lifters new? How about the pushrods? Were the valves reground or replaced? And were the head and deck shaved flat? On long inline engines, this is important.

Finally, can the purveyors put the engine on a hard stand so you can hear it run and then do a compression check when it is warmed up? If not, is the engine at least warranted in writing as to workmanship and parts? I know all of this is somewhat daunting, and a rebuilder might regard your inquiries as a bit disrespectful, but it is not a matter of trust. It is the only way to be sure your new engine is sound before you go to all the trouble of pulling your old engine and installing a new one.