Tech Question - Engine Swap

Q-Mike,

I am refurbishing a 1979 Firebird and removing the 403 engine. I am installing a Pontiac 455 with a/c and auto tranny. Estimated horsepower: 450. I will be replacing the coil springs and need advice on the additional weight requiring a stronger spring.

If this isn’t enough information, just send me an email. This is a common firebird engine exchange, you most likely have a current stock number. - RJ

A - RJ,

While this is a very common exchange, one must be aware of what engine is being used.

Buick, Olds and Pontiac all offered 455 engines and all three had different weights

Buick's weighed 600 Lbs., Olds 620 and Pontiac's 640 Lbs.

The 403 used in 1979 was an Olds engine which weighs 560 Lbs.

So the source of the replacement engine will have a bearing on the springs used.

If the replacement engine were a Pontiac engine then our part numbers for the springs without AC is MC6450 and the P/N with AC is MC1214.

Mike