CUTLASS Long-neglected, my 1979 Cutlass Calais swap plans. Or lack of plans. Or . . what makes sense in 2021?

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Master Mechanic
Thread starter
Jul 17, 2013
Sicklerville, NJ
Well, I definitely want air conditioning. Though, I imagine at some point my existing factory compressor (likely other components, too) will be replaced with . . I guess the Sanden ones are more efficient, and the most common/popular? I haven't done more than a few minutes of researching into this.

Back to the engines... I would like it to be 87-octane friendly, if that doesn't sacrifice too much in terms of power/efficiency/emissions (yeah, I don't necessarily HAVE to worry to much about that, but I'd LIKE to keep things clean and make the most of what fuel I'm burning). Since it's not going to be a daily driver, higher-octane requirements would be fine. That said, while 93 octane is very commonly available in NJ, I guess it's not in some other states, and who knows what'll happen in the future.

Now, 403 vs 455 - Let's see if I have the advantages/disadvantages right:
  • 455
    • Pros
      • Stronger block
      • No cooling problems
      • More torque easily attainable at lower RPMs
    • Cons
      • Possible hood clearance
      • Drop air cleaner may be needed
      • W/Z manifolds available, but still not as good as headers would be
      • If going headers, there are very few options for BBO in G-body
  • 403
    • Pros
      • No fitment issues, and all brackets from 260 fit
      • A little bit lighter
      • Big bore will more easily allow for bigger valves/less shrouding (if needed)
      • Better availability of intakes/a little more intake height clearance
      • Better availability of headers/more options/long tube headers
    • Cons
      • Weaker block (but not an issue for my preferred idle-to 5000-ish max RPM range)
      • Cooling problems?
      • Fewer piston options (I would guess?)

If I'm correct about the greater intake/exhaust options for the SBO, would the better intake-exhaust flow make up for the lesser cubes?

Also, does the lesser strength of the 403 make stroking (mildly) the engine a terrible idea?

At some point I will NOT be scattered all over the place on this! I swear!
Oct 14, 2008
The Olds 455 also tends to run on the warmer side, get a good rad. Your current 455 would run easy on 87. There are brackets to covert the 455 to a serpentine set up using sbc truck brackets. Also available for the 403. There are adapter brackets to convert the R4 junk compressor to a Sanden. Yeah a RPM fits on the SBO but needs a drop base air cleaner. Some have got the SBO G body Hedman headers to fit the 455. A offset ground stock crank only adds 20 ci max to the 403. I would not use the stock 403 crank to stroke, it is pretty weak. Consider the new Edelbrock heads for either, if workable for the budget.
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Apr 25, 2009
455. Build for torque at cruise RPM and don't worry about horsepower.
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Living in the Past
Jul 19, 2009
Permanent Temporary
Go for torque.
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