View Full Version : Question about the 425....

Night Wolf
05-17-04, 03:55 PM
I was wondering just how similar the 425 is to the 500.... are the blocks the same? what would be needed to convert a 425 into a 500? would it be cheaper to just get a 500? also, is the 500 a direct drop in for a 425-powered car?

Another thing, are all the parts from MTS compatible with the 425? and if so are the power increasements more noticble on the 425 or 500, or the same? and finally... what would the biggest benifits be of putting a 500 in over keeping the factory 425 on say... a '79 DeVille?

Angela Desmond
05-17-04, 05:51 PM
They lightened the 425 block by removing metal in, what the engineers said, were safe places to take it from. You'd be better of just getting the 500. I did the 425 because I got it for free, otherwise I'd have gone with the extra cubes myself. My machine shop didn't even want to overbore more that .040 over, evedently the water jackets start getting a bit close to the cylinder walls after that. So with the stock crank that gives me only 433CI. The heads are also a little different in the 425. 96cc before unshrouding the valves. Ports are also a little narrower. The intake is absolutly terrible. A single plane that sits lower than the intake ports. Exaust manifolds are also more restrictive than the 500. The 500 is always going to make more torque. "There's no replacement for displacement"...It depends on what parts we're talking about as far as interchangability...