I have a 86 IROC I purchased from the second owner of 15 years that claimed it was a 305HO. I forgot to take my RPO and other code lists when I went to buy the car so I wasn't able to verify his claim. The car had the dual air inlet breather which I realize could have been a add on. The VIN and ID Plate in the console say it is an H Code engine but I recently pulled the valve covers and found that if has factory roller rockers. I talked to several classic Chevrolet restorers and owners and all said in some cases you can't go by either of those numbers and need to look under my seats to see if the actual build sheet is still there. They claim that when cars were pretty highly optioned or special ordered they have found differences in the printed codes and actual build sheets. What are the actual differences in the 305(G) Code engine and 305(H) Code engine?

 

No such thing as "factory roller rockers"; so whatever you have, it's something else.

You can ALWAYS go by the option codes to determine WHAT CAME IN a car. Any "opinion" to the contrary is in direct violation of reality. Remember, it's mass production; the thing came from a FACTORY where it had production orders, materials requests, bills of materials, and on and on as it went from being coild of sheet metal to becoming a car, and the "codes" are all intertwined with manufacturing the car. They DO NOT LIE, EVER.

Now, that's not to be mistaken for saying, that just because the "codes" say something, that that's what's ACTUALLY there, now; ANYTHING could have been changed ANYWHERE along the line at ANY time since it left the factory, as evidenced by it having aftermarket roller rockers installed on it.

The H engine is the low-perf LG4, the G is the L69. They used the same block and head castings, same size valves, same intake manifolds AFAIK. In the first few years, the LG4 had lower compression, from different pistons; at some point it started getting the better ones. They had different cams, different carbs, and different ECM programming. The LG4 got a clutch fan, single snorkel intake, 2.73, 3.08, or at best 3.23 gears, and the coffee-stirrer exhaust with the restrictive pellet-bed cat. The L69 got an electric fan, the dual snorkel intake (in Camaros ... Firebirds didn't get that), better gears (3.73 or at worst 3.42), and larger exhaust from the heads to the street including the "honeycomb" cat.

If your VIN code is H, then your car came with the low-perf LG4, not the L69 "HO"; no matter what rockers some PO installed on it. Basically you got lied to when you bought the car, unless some PO had also got a L69 from the junkyard (which is BY NO MEANS impossible) and put it in there. The car might, maybe, have the HO motor in it now, but most likely doesn't (lies being cheeeeper than parts), and MOST CERTAINLY didn't come with it.

 

You have obviously never been in an assembly factory. Being a exhaust systems designer and supplier to the Big 3 from the mid 60's thru the 80's I have enough time in these facilities to apply for a pension check from them. I've seen brown cars at the end of the line with one green fender, cars scheduled for a 302 with a 390 engine at the final check point with 302 labeling in the engine compartment. The green fender was changed but the engine wasn't because it was too expensive to change so they left 302 on the window sticker and the dealer sold it as a 302. I've been to major aftermarket exhaust system retail suppliers investigating system fit complaints only too find the family four door didn't have the engine the badging and window sticker said it had. That being said this Camaro has a factory installeds electic fan with proper fuseing, control relays, wiring in the oridiginal wiring harnesses. The exhaust system is the oridiginal larger system with the pellet converter but has had a Flomaster Muffler added. I can assure you I know what a OEM exhaust system looks like and how it should look at this age. The rockers are General Motors with factory type markings not GM Aftermarket type markings. The car has a 3.73 rear end and it and th 5-speed transmition have the correct ID Markings for this car. We have not pulled enough crap off to check the eingine ID marking yet. If it's a carry over engine from 85, the specs I've found so far show the L69 and LB9 engines have the same cam.

 

Just as interesting info. The White Books claims that only 74 L69's were manufactured in 1986, while there were 68,293 LG4's.

JamesC

 

Wow almost makes an '86 with an L69 seem like it should be a collector!

 

Right, that would be quite a car, if it were the case; but that's not an issue here, as the OP clearly stated. He has the "H" VIN code, so it's a base-model LG4 car, no matter all of his fantasy-land protestations to the contrary.

I think we have a typical new guy here who hasn't done his research yet and therefore doesn't know what he's talking about. That's OK, maybe instead of trying to impress everybody about how much he "knows" which just about every word of which is laughable bishop-buffing, once he's had a chance to look around the site a bit and see that every bit of what he "knows" about his car is WRONG, he'll figure it out.

To the OP: I laid out the facts for you. What you choose to do with them is up to you. You can either continue having fantasies, or you can LEARN SOMETHING. I'd suggest starting here https://www.thirdgen.org/faq and here https://www.thirdgen.org/tech-data. Not everything there is 100% accurate; but a great learning experience would be to check out the cam that came in your LG4, under the stamped NON-ROLLER rockers it came with, and compare it to the L69 cam that was introduced in 83.

We're all kind of used to people coming around and humiliating themselves by claiming they have "the one, the only, the rarest of the rare", only to find out that it's really only mass production after all, and theirs is pretty much like everybody else's; or at least, was when it left the factory. And whatever seems to be different about it NOW, happened AFTERWARDS. This instance will be no different. If we even HEAR FROM this guy again, after he finds out what a fool he just made of himself with all that .... stuff .... he posted.

 

Number one at no time did I claim to have a one of car. All I did was post what we saw on the car. Number two the shop where I have the car happens to be the shop of one of the best Camaro collections around and has had several 60's cars sold for more money than you will ever see sold at Barrett Jackson. He also was a supplier to the Big 3 during the 60's thru the 80's and we met and became friends during one of our many trips to assembly factories. He has seen the same type of mistakes I saw at theses facilities and was the one that advised me to buy the car when I called him to tell him and ask about the car when I found it. He also is intriged by what we are finding as we dismantel the car. I'm sure the proceedures are 1000% better today in assembly plants than during the 60's thru the 80's and mistakes like we saw probably don't happen. If you have never been to an assembly plant you don't have any idea of the material handling feat involved in having a certain component arrive at the line to go on a paticular venicle moving down a line that produces at least one car per minute. Stopping to get the correect part if the wrong one is there is not an option. That being said if Third Generation is made up of crap house intelectuals like you I probably won't revisit. Who would of thought posting what you and a Camaro and General Morors expert saw would darw an idiot like you out of the woodwork.

 

Look for a thread in the FAQ forum about the differences between 305's and performance mods.

Most likely your car was modified, but without documentation one way or the other, impossible to say.

The "norm" was no roller rockers in '86.

 

Wow... I am honored.

The more I think about it, the less I think a reply is necessary.

Have a WONDERFUL day!!