I'm trying to

 

Are the exterior badges "Z28" or "Irocz"? Because if they're "z28" they're not original.

You haven't told us where you're located, but generally in the US a 90 Iroc is going to have at least the TPI 305 as the base engine.

 

There are not any 1990 Z28's. Z28 production ceased briefly in 1987 and resumed in 1991. There were IROCs available in 88, 89 and 90 however. If it's a 90 and not an IROC, you probably have an RS. Look at your SPID label, if it's original to the car it will tell you what you have.

 

I'm around

 

Technically, all IROC-Z's are Z28s, not all Z28s are Irocs. From 88-90 you couldn't get one without the other. In those years all the exterior badging will say "IROCZ". The dash badge still said Z28, and the SPID still listed the Z28 RPO code. So yes there are 88-90 Z28s, they're just all IROC-Z28s.

As a side effect of the Iroc package being standard on the Z28 in 88, the Iroc package didn't always mean much more than just a cosmetic package. Things like the 15" Z28 wheels, and the TBI 305 could be had in an Iroc.

So... If your interest is in resale value, you don't want a TBI anything anyway. Even if it's an IrocZ, with the TBI engine it'd be the base version, pretty much a Z in name only. Generally a good rule of thumb for the thirdgen enthusiast is to stick with 305 TPI/5spd and 350 TPI cars. When you step down to the 305 auto, performance generally takes a huge hit. Another step down to TBI, and performance is in the toilet.

 

Starting in 1990 the IROC's all got TPI power, either the LB9 305 or L98 350.

Check the RPO codes and the VIN # to be sure. Then check the stamp on the block and heads. If it's got LO3 it is the TBI motor an should be an RS.

 

Ok,I'll do that.That's what I figured with the "iroc" issue .I talked to the guy again and asked him if it was a true "z28" ,he swears it is..I'm thinking he bought it thinking it was and now is trying to pass on.I've never seen a 90 z28 without it being a "iroc" and having that badge on the dash.Dma,I was all excited too,thought I finally found me a ls swap candidate ..

 

In 1985 when the IROC came out it was an option package on the Z28 - RPO code B4Z. It was like that from 1985-1987.

In 1988 when they dropped the Z28 and just had the IROC as the high performance model all IROC's got the RPO code Z28. The B4Z RPO code was dropped. That was the case from 1988-1990. So if it's a legit IROC from 1990 it should have RPO code Z28 in addition to a TPI motor.

 

Idk about the code because

 

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