I've been searching for the last hour trying to find the specific difference between the 1982 and 1983 Crossfire / LU5 engines. The 1982 LU5 engine was rated at 165 HP with 8.6:1 compression and the 1983 version is listed as 175 HP and 9.5:1 compression.

So -- what were the differences? Were the heads, cam or pistons different in from '82 to '83 to get the higher compression and slightly higher hp number?

 

actually,'82 LU5 also had 9.5 C/R-i have heard '83s had a better catalytic
(better flowing)than '82. '83 crossfire manifolds have little crossover ports
in the manifold that '82 manifolds lack.'83s also have a different ESC
module and different ECM(more compact but about equal performing.
I have ran both '82 and '83 style ECMs in mine and no difference in running
or performance was noticed.

 

The 10HP difference between the '82 and '83 LU5 engines is nothing more than a slight retune of the PROM to match the '83 Ford Mustang's new 5.0 HO engine 175HP rating.

The basic long block between '82 and '83 engines is the same. 416 heads, flat top pistons yielding 9.5:1 compression, and the L83 Corvette camshaft.

Besides the way the air injection tube attaches to the catalytic converter versus '82 and '83 both years are otherwise the same as is the rest of the exhaust. The '82 LG4 engine used a lesser flowing pellet type catalytic converter but that doesn't apply to LU5 cars.

 

The manifold may be different too, early without the balance holes, later with

 

think 82 had o2 sensor in Y-pipe and 83 had it in the exhaust manifold. But could be wrong and I generally am.

 

Now that's what I'm talking about! Thanks for this info.

It's strange to me that GM could actually get 10 more HP out the CFI set up through nothing more than PROM tuning given the limited processing power of the ECU back then.

 

Pretty sure my old '84 L69 had the O2 sensor in the Y-pipe, but that was a long time ago. My '82 has it in the Y-pipe.

 

My '83's O2 is in the manifold.

 

Manufacture's engine tuning during the smog era of the the 1970's and early 80's was extremely conservative. It doesn't take much to get 10 more HP than a little change of the distributor advance and fuel curves when V8 engines are putting out only around 160HP.

BTW, the L69 engine had the O2 sensor in the manifold. The '82 LU5 is the only V8 3rd-gen I know of that had the O2 sensor in the Y-pipe. At idle it will sometimes cool off enough to set the computer into open-loop mode which is probably why they went back to the exhaust manifold in '83.