Hello,

I have a 94 AC EXT 580 EFI and I am looking to swap out the top end of the engine. I have not found an exact swap as of yet, but I have found top ends from a 96 ZR 580 EFI (which has triple ports), and also a 2001 Panther 550.

It appears both of these options will bolt on, but my question is how will the EFI system on my sled react? And what if any other changes would need to be made?

Or if anyone has a top half to my sled please feel free to post/pm as well.

Thanks in advance!

So what are you trying to achieve and why are you rebuilding the top end? What happened to the cylinders? HAve you determined that they are to damaged to be serviceable? If the nicasil plating is damaged you can have the cylinders replated. There are two, or three replaters in the site sponsor list at the side of the page>>>. Replated cylinders are as good as new for a fraction of the cost.

Generally speaking the EFI system limits changes you can make, and especially with the old systems of your vintage. The 580 and 550 share the same bottom end, but the smaller bore of the 550 will likely have a different fueling requirement. The triple port cylinders will probably have a slightly different fueling requirement too, however, the EFI fuel map is typically biased to the rich side and it may work just fine. I would try the triple port 580 cylinders before the 550 cylinders if I could not find single port 580 cylinders, or get mine replated.

I have used the triple port cylinders on what was originally a single port engine with no issues, it actually ran really good!

~Fast

94ZR580: Someone actually stole the jugs. I cant believe the nerve of some people. So thats why repair is not an option and it must be replaced. Yeah, I was leaning more towards the 580 if I cant find anything else. Thanks for the input!

Fast440: Glad to hear! I think if I cant find a direct replacement, thats the route Im going to try. Thanks!

Well, that would make it a little more difficult! I won't ask you how someone managed to steal your cylinders.

Check the classified sections of this, and the other web forums for parts and engines. You could probably find a complete engine for a good price easier than a couple of cylinders.