Does anyone know how tight of a fit it is to drop a 455 into a 85 cutlass? It is a really tight squeeze with the 350. Do headers fit with the 455?

 

The 455 is two inches higher at the deck and two inches wider, It should fit. Don't know about the headers someone else will have to chime in on that. You will have to build up the trans or replace with a turbo 400 which will require further mods

 

It will fit. Ill ask my buddy what he did to get it in. Also i know he ran headers so ill get as much info as i can.

 

This is a pretty common swap into the G-body. The valve covers JUST clear the A/C box on the firewall (ironically, they do not clear the heater-only box, from what I've heard). Use the 307 motor and frame mounts - do not buy "455" motor mounts, they will not work with your current frame mounts. Yes, the 307 mounts bolt to the 455.

 

I'm pretty sure you will have to cut a notch in the heater box. Or just wait until the motor cuts it for you.

 

Summit has a set of headers for Olds motors that are "block Huggers"

There is only one set. Painted and polished are the only choices you have. I'd try that.

Probably would have to use a single plane manifold, the dual plane adds another 2 inches

If a 350 fits under the hood with a dual plane, a 455 will fit with a single plane

 

Block huggers are usually more for a street rod type frame. I don't think they will work with a g-body crossmember.

Hooker used to make BBO super comps for G-bodies. You might look in to them.

 

It all depends on the intake. The early Toro dual plan intake has a recessed carb mounting flange to clear the hood on those cars. This is probably your best choice to provide hood clearance. Most aftermarket single plane intakes (Torker, for example) are actually taller than dual plane intakes to allow for straighter runners. The single plane Victor is taller yet.

 

I'm not worried About the hight I have a cowl on my other cutlass that I can take off that is almost 4 inches high. That would give me plenty of room. My main concern is the room on the sides. Do I have to remove the heater box or can it stay in. I am planing on cutting out all the stuff on the fire wall for the AC but would like to have heat still. It can get chilly in the spring and fall here in minnesota and my girlfriend is a freeze baby.

 

I have not personally done this swap, but others who have assure me that the A/C box does clear factory valve covers. If you plan to remove the A/C but retain the heater, you need the aftermarket conversion box. The A/C installation requires holes in the firewall that the factory heater-only box does not cover. The aftermarket box accommodates these. I do not know how well this piece clears a big block.

 

If the 80s Cutlass originally was available with a 307, wouldn't the 350 be a direct bolt in? BTW, good luck with your project.

 

Yup. Also a 403.

 

Oops. I'm used to the "B" body frame. I was going to put those in that car

 

Let's rephrase that. Blockhuggers typically won't work in ANY car with a crossmember under the engine. That pretty much covers any RWD GM car from 1964-up. Blockhugger headers typically route the collector straight down under the center two exhaust ports. In a street rod this is fine. In a newer car it won't work.

More to the point, shorty headers are typically no better than stock manifolds from a flow standpoint. You'll spend a lot of money for no performance gain. If you want headers, get real headers. If not, stick with manifolds.