Some questions about the different years

[MuRCieLaGo]

Hi,

I got some questions.

1. At what year was introduced the convertible ZR-1?

2. I saw the engine had a boost in 1993 of like 20hp. Is it internal or external upgrade? I mean, could I buy a 1992 and easily get these mods?

3. What are these exterior restylings it had over the years?

Thank you!

[Z06scentair]

Originally Posted by MuRCieLaGo

Hi,

I got some questions.

[COLOR="SandyBrown"]
1. At what year was introduced the convertible ZR-1?

Never introduced to the public .

2. I saw the engine had a boost in 1993 of like 20hp. Is it internal or external upgrade? I mean, could I buy a 1992 and easily get these mods?

Yes 375 to 405. Lots of motor revisions. Different block 2 bolt later went to four bolt. Injector housings, cam timing....lots of things really. Can you make a 375hp motor make 405hp...Yes.

3. What are these exterior restylings it had over the years?

91 changed the front fascia, and wheels from 90.

No change in 92.

93 changed to a machined faced wheel plus 40th anniversary Ruby Red was an option Z25, HP increased to 405.

94 seats changed as well as dash and console, A mold wheels were standard.

95 last year later cars had dunn heads. Dunn was the replacement supplier for Birmall who went through bankruptcy. Dunn heads flowed better which resulted in a little more power according to testing. Only exterior change was the side panels in front of the door.

Thank you!

See above.

[MuRCieLaGo]

Originally Posted by Z06scentair

See above.

1. Ok, I found a ZR-1 convertible in the local ads, that probably means it is not a real ZR-1...
2. I know I can easily mod the motor to have it make 405hp. As you said, it is a different block so I can't mod a 1992 motor to become a stock 1993 motor with 405 hp... Am I right?
3. What do you mean by a little more power?

Thanks for your patience and your clear answers!

[edram454]

it takes very little to make a 1990 motor make 405 hp. the 1990 picks up more horsepower from plenum and injector housing porting because of the smaller ports from the factory. The 1990 has a two bolt main block. Do you need a 4 bolt?? no. remember.. the record breaking car that averaged over 175mph for 24 hours straight had a two bolt block. If you need more than that then you need a full blown race car. If you retime the cams you can pick up some more plus adding headers and tuning. Dont shy away from the 1990. They run every bit as hard as the later ones.

ed ramos #3028

[phrogs]

well there are a few ZR-1 convertible conversions out there but I doubt its real.

[MuRCieLaGo]

Thanks for your simple answers!

I'll make it even easier:

Which engine is the BEST? 1990-1992 or 1993-1995?

[XfireZ51]

Originally Posted by MuRCieLaGo

Thanks for your simple answers!

I'll make it even easier:

Which engine is the BEST? 1990-1992 or 1993-1995?

Supposedly the last 95 motor because of it being a 405hp WITH DUNN heads.
However, the 90 is lighter than the 95 so IMO, # per HP may be the way to look at it. As has been said, 90-92 motors are very responsive to basic mods to level the playing field.

[cvette98pacecar]

Originally Posted by MuRCieLaGo

Thanks for your simple answers!

I'll make it even easier:

Which engine is the BEST? 1990-1992 or 1993-1995?

90-95 is the best engine. There is no difference in strength from the two bolt to the four bolt block.
I do believe Frank's and Al's 441 are both two bolt blocks.

[Paul Workman]

Agree w/ all said so far.

Here's a link to Marc Haibeck's site.

Mark performs performance upgrades to the LT5. You'll see there that where the 90-92 375 hp motors and the 93-95 motors receive the full treatment, their respective performance is equal.

One thing many don't realize too is the head bolts on the LT5 are MASSIVE, compared to a typical SBC. (edit) And, the main bolts of the two-bolt block are also massive, whereas the the bolts in the 93-95 mains are 4/main, the size of the bolts are smaller.

90-92 block

...and examples exist of 415, 427, and 441 cid displacements with 2-bolt blocks that are straddling 700 hp, NA on pump gas. Try that with a SBC!

Aside from sharing bore center dimensions, there are no interchangeable parts with the SBC, and certainly no comparison either with the LT5's rugged "bullet proof" reliability or output per cubic inch for a street driven motor.

So, I wouldn't give 2 vs. 4 bolt LT5s a second thought, especially if it is to be fully ported anyway. And, offsetting the 30 hp advantage of the 93-95 ZR-1s, is the additional weight.

Performance wise, it is pretty much a toss-up across the years in stock form.

[BigJohn]

Originally Posted by MuRCieLaGo

Thanks for your simple answers!

I'll make it even easier:

Which engine is the BEST? 1990-1992 or 1993-1995?

Mine!!!!