might be getting a 79 Firebird froma a freind at work, he has a 455 that isnt int he car, and it was originaly equipped with the Olds 403.

couple of questions

will all the brackets and pulleys be a direct swap?

does anyone have header part numbers? I can find them for the 403, but not the 455.

also, he had a different rear end gear put in, and never corrected the speedo. does anyone know of a place i can get something to correct it with? even the speedo gears would be fine, cant find them anywhere anymore. and where would I be able to find the info on which gears to use for the specific tiresize/gear ratio?

thanks in advance
Troy

 

I think Olds is like Pontiac. No differnt sized blocks and what not. SO I would imagine the mounts and all would be the same

 

the blocks are a little different, i know that. the 455 has 1/4 inch more deck height, which is what make the headers different. and ive been lookin into it, and it seems like the headers are the same for all the A bodies and F bodies (at least for the SBC, BBC, and 403) I dont think they list the 455 in the Firebird because it never came stock. so I belive that headers for a cutlass with 455 will work. can anyone confirm this?

I assume that the brackets and pulleys will work also, but I'd like some confirmation from someone that knows for sure.

I THINK the only difference is the deck height, and obviously, everything that affects, which is why I think the brakets and pulleys will be OK

thanks

 

Man im glad I found this thread!
Olds is my specialty.
403 is a small block,455 is a big block,so the headers are different!
The 455 is 3/4 inch taller and takes a differnt intake.
Also the brackets will work but you will need a longer alt belt.
Use the small block motor mounts so the motor will sit a little lower,I think the big block headers will still work.

 

So just for my own clarification....

Olds is not like Pontiac in which all blocks are the same. No big block or small block?

 

i can easily deal with the belt, and the motor mounts will be the stockers, but my big question is, WHICH big block headers work? is it the same ones that fit a cutlass? the guy I might buy this off of had a 455 in there, but at the time the only headers he could find to fit were hooker super comps, and I dont want to pay 350 bucks just for headers at this point. i want to get it runnign if I do get it. he doesnt remember the application the headers that would fit were made for though.

though I just found out he doesnt have heat, so that kinda let the air out of the tires so to speak. if I cant find all the parts it needs for that I just cant do it...

 

OLds is big block and small block.
260,330,350 and 403 or small blocks.
400,425 and 455 are big blocks and nothing like Pontiacs.
I do beleive the headers that fit like a 76 cutlass with a 455 are the same for a trans am.

 

cool thanks

 

You might want to think about changing the front coils. Because the big block weighs considerably more than the 403 and eventually the coils will break. This happened to me when I swapped a 400 Pontiac in place of the 403 in my old T/A.

 

I did this swap with a friend on his 79 ws6 Just about everything swaped over. We used the headers off the 403, the heads are almost the same. meaning they have the same bolt pattern. There was I believe a little problem withthe fit but I think all we had to do was pull the collectors down a little to clear the floor.

 

1: the ports on a big block are about %30 bigger so small block headers will choke them down.
2:Putting the small block headers on a big block will make the collectors face into the transmission pan for a "not so easy hook up.