I've just spent an hour searching this forum and several people have asked, but no one has answered.

Has anyone retrofitted the serp belt set up from the later models to the earlier models?

I've done this several times on V-8 applications. Example, converted my '85 Chevy truck 305 to serpentine using parts from a '98 Blazer 4.3.

I'm thinking there must be a good reason nobody is doing this with the 2.5. Anyone know what it is?

I could be talking out of my back side but the 87 is non adjustable timing. This is the first year with the serp belt. The block cast is different and perhaps the auto Tensioner bolts dont even exist on the non serp engines. Also all of the mounting brackets for alt and ac are different.

Isn't done because WP and Alt is in 1 belt plain and AC is on 2nd belt plain for a start.
87 crank "pulley" doesn't have timing marks even if they fit on older L4.
Fiero Belt Tensioner if they fit is very hard to get, if found new often cost $300 or more now.

About only upgrade is SI to CS alt and that often needs to have pulley change.

V-belt is fine as is. More so when people learn how to install right.
See my Cave, Serpent Belt as have correct loading for all Fiero manual adjust belts.

87 and later L4 is another engine that have serpent belt.
See my Cave, Duke Quick Ref
You can't use 87 alt on older L4 because case isn't same.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

quote Originally posted by skywurz: I could be talking out of my back side but the 87 is non adjustable timing. This is the first year with the serp belt. The block cast is different and perhaps the auto Tensioner bolts dont even exist on the non serp engines. Also all of the mounting brackets for alt and ac are different.

There it is. The blocks are different part numbers. I bet the holes to mount the brackets are different. Thanks!

87 & up Block (and head) are different w/ or w/o mounting holes for other parts changes because engine has DIS not HEI.

quote Originally posted by theogre: 87 & up Block (and head) are different w/ or w/o mounting holes for other parts changes because engine has DIS not HEI.

And the 87 is an 87 only block as in 88 they moved to the internal in pan oil filter and balance shafts. This was yet another block change because it eliminate the oil filter port on the exterior of the block (also other stuff but that would be the most obvious). So it gets even more muddied because of that. Im not sure of the non Fiero 89 and up blocks.

quote Originally posted by skywurz: And the 87 is an 87 only block as in 88 they moved to the internal in pan oil filter and balance shafts. This was yet another block change because it eliminate the oil filter port on the exterior of the block (also other stuff but that would be the most obvious). So it gets even more muddied because of that. Im not sure of the non Fiero 89 and up blocks.

Even if you assume all are VIN R, later versions had more changes and often won't interchange parts easy or not at all w/ 87 or 88.
91-92 even have Timing Chains and Grind the Cams for that and block takes chain guide/tension parts.
87-88 Could use the later Head but have to use Intake Man for them too.

Plus FWD cars need different belt map and tensioner to have PS.
Some made "adapters"/mod to fit FWD tensioner... While may seem to work, often they over load the belt and belt or parts driven by it dies.

If you have VIN U or others as donors, almost nothing will fit a VIN R of any year.

[This message has been edited by theogre (edited 02-24-2021).]

quote Originally posted by theogre: [QUOTE]Originally posted by skywurz: And the 87 is an 87 only block as in 88 they moved to the internal in pan oil filter and balance shafts. This was yet another block change because it eliminate the oil filter port on the exterior of the block (also other stuff but that would be the most obvious). So it gets even more muddied because of that. Im not sure of the non Fiero 89 and up blocks.

Even if you assume all are VIN R, later versions had more changes and often won't interchange parts easy or not at all w/ 87 or 88.
91-92 even have Timing Chains and Grind the Cams for that and block takes chain guide/tension parts.
87-88 Could use the later Head but have to use Intake Man for them too.

Plus FWD cars need different belt map and tensioner to have PS.
Some made "adapters"/mod to fit FWD tensioner... While may seem to work, often they over load the belt and belt or parts driven by it dies.

If you have VIN U or others as donors, almost nothing will fit a VIN R of any year.

[/QUOTE]

Thanks I did not know they had swapped to chains. I will file that away. I had read that you could swap a 1993 S-10 that was more efficient and had 100hp directly into a 87-88 (for some reason probably the fuel line routing but maybe not it mentions only 87&88 for this swap) but this now seems like it would need a lot more than just the engine EG electrical & ECU. Plus probably have mounting issues with the water pump ALT and AC. Also probably be obvious when it was smog time.