I recently picked up another complete 455 out of a ‘74 LeSabre to put in a ‘66 Skylark that I have. The engine was complete but was stuck when I got it. After I got it torn down I discovered it had mis-matched cylinder heads on it. One of them was casting 1241860 with a date code that jived with the car, the other one was casting 1238148 with a ‘71 date on it. Here’s where I’m confused - the 1241860 head, which is a ‘74 head has the stage 1 size valves in it - 2.15/1.72. The other head had the 2.00/1.62’s. Did someone put those big valves in that late head or did they make that casting with two different size valves? Everything I have read says the 1241860 castings have 2.00/1.62 valves in them. Do I have a unicorn on my hands here?
Till the masters chime in, all I can mention is stage 1 and standard heads all have the same casting #'s. They just took the heads as they ran down the assembly line and machined them and fit the larger valves per stage 1 ordered cars.
Been doing a little more digging - it appears that this big valve head I have is in fact a factory-produced piece. I have it disassembled now and the valves that are in it have GM markings on them. The car this engine came out of was special ordered by the original owner and it was also a 2-door car. Not sure if the engine was classified as "Stage 1" or if the big valve heads were just part of some special heavy duty option the car was equipped with. Either way I feel like this head is probably pretty rare. Wish I had the match!
I've seen many big cars with the big valve heads. Not called stage 1, just larger valves. They also called for premium fuel only.
No, it was clear that both heads had been off the engine recently before it was parked in 1994. They were both clean and painted Chevrolet orange lol. The whole deal is somewhat confounding really. The car was a one-owner with a documented 94k original miles on it, yet the engine had no wear and was very clean externally...and both heads had been off. It's like someone put a new shortblock in the car with two bastard heads. At some point the hood got left opened and rain water accumulated on top of the breather and got into the engine through the stud hole. All 8 pistons were stuck, 6 of them so bad that I had to bust them out with a chisel. I did manage to save the block though, it'll clean up.
"Performance Option" was available for the big cars, standard cam, and standard valves instead of the swirl polished stage 1 valves
There was a Stage 1 option in 73 and 74 I believe - found usually in Riv's but my neighbor had a 74 LeSabre Luxus convertible. I believe they had the big valve heads, but no cam upgrade.
Also in 71 and 72. It did have a different cam than the stock 455 cam, slightly more aggressive but milder than the A body Stage 1. The name of the option was “Modified High Performance 455 with dual exhaust”. I have it in my 1972 Centurion. Little different carb tuning and ignition timing too.
What stuff? Big valve heads didn't start until 1970. The 400 cylinder bore was too small for the bigger valves to do any good.
BUT John has a 430 so IF he wanted he could install the larger Stage 1 valves. BUT he has already had the heads done.
This car also had true duals on it. Still had oem type mufflers with all the factory style hangers. It also had a trailer hitch. I figured the old guy ordered this car to pull a heavy trailer with.
No, I only bought the engine and teansmission out of the car. The car was destined for the crusher. 25 years in the South Carolina rain forest ruined it.
