I own an 86 IROC Z w/ an lg4. It is rated at 165 hp. The berlinetta and sc are rated at 155 hp. What is the distinction between the Different motors? I know the lg4 got a horsepower boost in 86 due to increase of compression, and sparkknock sensor, along w/ electric fan in 86. So Why the ten hp difference?

 

its the cam. Go to www.iroc-z.com for more info on the cam changes and how to spot them using the tachometer as a guide.

 

And it's the lack of power drained by the fan. Electric fans don't take horsepower away.

 

Ah, yes. Forgot about that!

 

Except that the 155 horse LG4 had the electric radiator fan as well.

 

I checked IROC-Z.com and I could not find any info on the cam difference between the 155 hp and the 165 hp engines drknow. I have been happy w/ the way it performs though..... I know it isn't what v8's used to be, like my 68 charger r/t w/440 mag, I owned 34 yrs ago,... but I am happy with it's quickness, and reliability. (not to mention the way it sounds.

 

Glad to hear it! I remember seeing it on there somewhere.... I think if you look at the years of car it says something like ..." the cam was changed mid-year and can be indicated by looking at the tach..." Something about the redline being higher on the later cam or something like that... The problem with this is that many of these cars have had their instrument clusters swapped out.

 

My 85 didn't have the electric.

JamesC

 

I doubt there actually is any mechanical difference (cam, exhaust, etc). If there is any difference at all, it will be in the electronic tuning - the 165hp will have a little more aggressive tune, like the L69 did.

I doubt theres any difference though, just GM playing with numbers, knowing no one will notice a 10hp difference.

 

Hey drknow, I found out that in 86 there were no iroc's w/5500 redline. they all came w/ 5000. The cam in the 85's (in the tpi) was better than 86. they reduced it, for what... God only knows. But that (the cam reduction) is why the redline is lower. I still love chevy small blocks though.. Even my 86 lg4. I mean it runs darn good!

 

Maybe one of you might be able to answer an other question I have.... My RPO's list my iroc w/ open differential, but it has posi. I found this out when I was changing the gear oil. I rev just a hair over 2000 rpm at 70. In my 92 RS I have 273's and it revs at just under 2000 at 70 mph. I would like to know what the ratio is. ??

 

[QUOTE=Stevolwevol;4081129I would like to know what the ratio is. ??[/QUOTE]

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

 

I clicked on that techboard sight, and I must have 3.23 gears!!!! It said; 21... hundred rpm at 70 mph.. Thanks JamesC!