Olds Big Block Swap

[GbodyTech92]

I needed some help on my 81 cutlass build and my 85 cutlass. I wanted to get some opinions on some good heads that I should use on my 403 in my 81 and should I stick with the 383 stroker set up in the 85 or go with a 455 can't really decide any opinions or comments will be appreciated. Also the 85 is a street car project rolling chassis at the moment.

 

[rccktmn2]

That would depend on your personal opinion. The 403 would definately benefit from better heads, most came with smog heads, aluminum is definately worth the extra money as cast iron heads are starting to dwindle in availability and condition. I believe the number 5 heads from the early 70s were the better flowing head with big valves but the right machine shop can modify just about any head to flow however you want with big valves. The 383 vs 455 again is your opinion, mine would be to stick with all olds power. The 383 will take some modifying to get the same torque numbers a 455 will give you, it will take about the same amount of money to build a 383 vs a 455, the only difference is the kind of transmission your going to put in the car, if your car has the BOP trans then the 455 will bolt right up, the 383 won't.

 

[L92 OLDS]

I needed some help on my 81 cutlass build and my 85 cutlass. I wanted to get some opinions on some good heads that I should use on my 403 in my 81 and should I stick with the 383 stroker set up in the 85 or go with a 455 can't really decide any opinions or comments will be appreciated. Also the 85 is a street car project rolling chassis at the moment.

Spend some timg using the search function on this site or at oldspower.com and you will find everything you need. A quick and less expensive way to build a 403 is not with aluminum heads but with an early small chamber iron head. With some minor modifications, you can bolt a small chamber Olds 350 head onto a stock 403 short block and build some decent power. They key is to bump up the CR. And yes, in stock form, #5 heads are supposed to flow better than the others in stock form....check out my U tube link.

The 383 stroker vs 455 big block is an easy question for me. The 383 will build good power but will likely be set up to build power at mid to high revs. The cam profile, stall reuquired, low vacuum, etc. could make the 383 annoying to drive as a street car. You could build a smooth running 455 torque monster that would meet or exceed the 383 performance level and it would be more fun to drive. The 455 also allows you to keep it all Oldsmobile.