I need to replace a broken 350 in my Cutlass. I have a line on a 1975 455. I don't really want to tear the whole thing apart right now but would like to get some more power from it. How would a rebuilt set of 'C' heads impact the performance. Any comments or recommendations are welcomed.

Thanks, Mike

 

that's a lot of work to not "tear the whole thing apart"

I'd either run the 455 as is or do a completer tear down.

 

Can you hear the 455 run? If you can, do a compression test and check the oil pressure to get a handle on the shape it is in. The weak link in the mid-year 455 will be the compression ratio. maybe somebody better with this stuff than me can tell you the difference in compression chamber so you get an idea what will happen to the compression ratio. By itself i don't think the C heads will make that much of a difference. If it ups the compression a little and the lower half will stand up to a little more cam and maybe a better intake & carb you could have a good running car.

 

All big block heads have about the same chamber size. And you can have small valve C heads as well.
As mentioned the low comp ratio will have an effect on your build. You can put a small cam in it, a Performer, 700cfm or so carb and good tuning and have a decent running vehicle. Depends on your budget and goals.

 

Unfortunately, it depends. If this is a street driven car, you'll be hard pressed to see the difference, particularly with the stock 1975 cam and timing. If the old heads need a valve job, then ANY replacement head will show an improvement. If the engine is in good running shape, either run it as-is or consider a cam swap.

 

Mike, it is still a 455 regardless of year. I think you will be surprised that a smog motor will still make power.

 

Agree the cost and time of putting C heads on a smog, stock 455 is practically a waste of effort. After hearing and seeing it run-leaks, smoke, sounds, if okay install and drive it.

 

Thanks for the input. The motor is still in the car so I can get a first hand look at how good it is. I certainly would not be against the idea of a better cam. I assume I would need to replace the tappets. I would appreciate any cam recommendations. It's going into a Cutlass with a Turbo 350 with power brakes. I don't know the gear ratio (but will check). It will be only driven and not raced but I would still like to 'light 'em up' every now and then.