Inliners International Forums General Discussion Engines New Engine Question

Well, my friend Bill had a change in plans with his new stepside and sold it without the engine and through a series of other complications I won't bore you with, he ended up with a 250 sitting at his mechanics shop freshly, and completely rebuilt. He had no use for it and didn't know what to do, and I did him a favor as well as couldn't pass it up I bought it for the price of him having it rebuilt. It came with all the stuff one the outside of the engine, milled intake/exhaust, new carb, distributor, etc so it is a complete unit, waiting for my next project to come along.

I have a question though, the 250 engine came out of a 69 Chevy Truck, but the mechanic was thinking the head came off of a late model 292 because the head has AIR tubes (that are capped), and the spark plug holes are deeper than a 250. Is this true that a 292 has deeper spark plug holes and takes a longer spark plug?

Also, what is the differences in the heads valve-wise, are the valves a different size? Any other caveats to the different heads? Gonna run the casting #'s tonight...

Thanks

the holes just go down to combustion chamber, but there are at least a couple of different kinds of plugs and they won't interchange. i think the problem you are talking about is the threads are same but outside will be too big to fit in the recessed seat where the plug seats and not allow plug to thread in. i think when this happened i went to part store and they looked and found right size, i had to regap for hei. i have changed and swapped several of these heads 250's and 292's and haven't had any problems with interchangability. i think the small 194's had a smaller combustion chamber but all rest are same i'm told. i have a bunch of heads and can get you plug #'s if you want. good luck sounds like you got a good deal. hr

The heads Ran two different Plugs The Peanut 5/8 plug(short reach) and the is a 13/16 (long reach)
depending on the Yr you could have either one.
The 5/8 plug had the seat built into it. The 13/16 had a compression ring on them.

The reverse of what the mechanic told you about the head is true. Depending on the year and the state smog laws, most 3/4 and up trucks were exempt from smog equip (AIR). Most 250's came out of 1/2s and cars. 292's were usually 3/4 and up.

The AIR ports were in fact from passenger cars with emmission control equipment. The head itself is really no different from an earlier non smog head except for the different thread on the spark plugs as has been mentioned. Running the AIR head with the ports plugged works fine except for the cluttered look the plugs present.