Aaron R.

I have an IROC 305 5 spd. I understand that these were the H.O. engines. What's the difference with this engine vs the standard 305. I understand it puts out a little more power, but why?

IROCtheThird

iTrader: (15)

I take it you have the L69 H.O. They had a more aggressive cam, 750 q-jet, dual snorkel intake, and I believe they had a better flowing exhaust. Plus 5 the spd and I think they were the only 3rd gens to come through with 3.73's from the factory.

JamesC

iTrader: (5)

The IROC didn't automatically come with the L69 (vin G). Mine was originally an LG4 (vin H).

https://www.thirdgen.org/forums/faq-...5-engines.html

JamesC

Dens71TA

iTrader: (5)

The 8th digit in the VIN would be the letter G to be an L69 5.0L HO car. The L69 had a better camshaft with more duration and lift, flat top pistons for 9.5:1 compression with electronic detonation control, exhaust manifolds with larger outlets, larger diameter exhaust system with higher flow catalytic converter, retuned carburator and computer programing for more ignition advance, electric cooling fan, and 3.73(10-bolt) or 3.70(9-bolt) rear axle ratio.

Some of the L69 improvements were eventually incorporated into the base LG4 5.0L engine and by 1987 it was producing an additional 25HP over it's original 1982 145HP rating.

five7kid

iTrader: (14)

https://www.thirdgen.org/forums/faq-...5-engines.html

https://www.thirdgen.org/1987-chevy-camaro
You'll find no L69 there.

You may have an LB9, with TPI. However, it was not designated "HO".

Aaron R.

Yep, I looked it up again. Guess it is the LG4.

five7kid

iTrader: (14)

Are we talking about the '85?

Aaron R.

yep.

five7kid

iTrader: (14)

Little tidbits like that are nice to know when questions like this are asked.

Joiner

Vin letter H is the L69, which my car has.

Joiner

And I don't believe I have the 3.73 but how could I find out? I only have one wheel peel right now and rear drums. I believe it's a GM 10 bolt.

five7kid

iTrader: (14)

VIN letter H is the LG4, the lo-po version.

The L69 is VIN letter G.

Joiner

I have a 305 with an electronic controlled Q-jet carburetor but I only have one snorkel because it's a firebird, and I'm sure it's Vin is H.

Joiner

Just went outside, Vin H. And I didn't think LG4's came in Trans Ams unless they had the manual, which mine does not.

Joiner

Damn, did some more research and my car has the LG4, how depressing.

Dens71TA

iTrader: (5)

The standard engine in the Trans Am was the LG4 from '82-87. Manual trans was standard with automatic optional.

LG4 is VIN H for all years. L69 is VIN 7 in '83, and VIN G for '84-86. The L69 was only available in the Z28 and Trans Am. No lesser model Camaros or Firebirds.

Trans Am LG4 and L69 used the same single snorkle air cleaner with functional ram air for '83-84. Since the refreshed T/A went to a flat hood in '85 the L69 cars got the same dual snorkel air cleaner that the Z28 L69 cars had from the beginning.

armac

I have a set of HO heads in the garage and the exhaust valve is larger than the intake. That is the main diff between the two engines. They did also come with a more aggressive cam as posted above.

five7kid

iTrader: (14)

I don't know what you're looking at. LG4 and L69 heads were identical in every detail. And, intake valves are always larger than exhaust valves.

DartByU

I'd like to see a picture of those heads, they must be one of a kind and very valuable!!!