I have an ‘84 Firebird w/ the original V6 - The 102HP LC1 engine and 700R4 transmission.

In 1984 there was an optional LL1 ‘HO’ V6 rated at 125HP also available.

If I overhaul my 102HP LC1 engine - what are the differences between it and the 125HP LL1 and can I swap in the LL1 specific components to my LC1?

I think at least the heads may be different: If so, will the FI heads from an ‘85 - ‘89 LB8 2.8L also fit? And work w/ my OE intake/carb/manifolds/EGR etc?

Anything else?

Thanks,

 

Your best bet would be to swap in a 3.4 long block. It has identical heads as the 85-89 2.8. You can bolt all of your external parts to it and off you go with a much better baseline. You may not get the 160hp it was rated at, since that was with fuel injection, but some upgrades will really make a big difference. It will likely be much easier to find than the LL1, unless you have already found one by chance.

 

The HO (LL1) v6 was apparently available in 83 and 84. It's identified in my 84 Owners manual and FSM.

I am guessing the heads may be the only meaningful difference. I'll check my FSM again for any clues. I doubt theres an an easy way to tell them apart.

Can later heads off an LB8 etc. fit an earlier LC1?

Thanks

 

Early 2.8s are ticking time bombs. There's no sense in rebuilding one, regardless what you do to it. Look for a 3.1 or 3.4 to rebuild if you want to stick with the sixer.

 

I thought the camshafts were different as well , 23 ponies on just heads sounds a bit , optimistic considering the engine we're talking about .

100% right on , the early 2.8 has crankshaft weakness problems . To stay with the six , and expect any kinds of zippy acceleration pretty much demands the 3.4 be swapped in .

 

Yeah, I only managed to get 280,000 miles so far out of my early 2.8L - probably won't get another 280k.

 

Interesting. So I could bolt on my carb and mechanical fuel pump and accessories/brackets? Even the exhaust manifolds if I stay with this?

Or for that matter swap the intake/carb for a small 390CFM Holley mentioned earlier?

And cosmetically it would look pretty much identical to the original 2.8L.

Thanks - I'm going to start looking at this option as well!

 

I'd doubt many of the 3.4 blocks will have the provisions for the mechanical fuel pump machined. If you keep the carb, you can just bolt a Purolator, or Mr Gasket, or whatever electric low pressure generic fuel pump the parts stores sell these days, back by the tank. Follow the instructions. If you mount a pump like that in the engine compartment without a pusher back by the tank, the engine will starve when the fuel bowl runs dry, resulting in a nice violent stall.

There's an internal/external balance changeover somewhere around 1987? that made the 2.8 more reliable. Way back my roommate for a time was the local 'Fiero guy'. He must have had a dozen 2.8's piled in one corner of the shop, all with ventilated blocks. His preferred approach was to swap in later 2.8s, 3.1s, 3.4s. I killed an 84 Camaro's 2.8 in one evening of hard beatings, something I'd done thousands of times in my 91 3.1L Firebird. When the Firebird finally went to the junkyard, several years after I sold it, it was because the 700R4 gave out. Hence my suggestion to go with a later engine.

I can't say much about the early 2.8s. I know that different engines in different car lines had different heads, pistons, intakes, cams, even before the aluminum head FWD engines. Couldn't tell you which of those applies to the early HO 2.8. But I know I wouldn't put too much effort into replicating the early HO, since even a HO 2.8 is a LO engine in 2018. I'd expect a person could look in the parts and illustration catalogs and figure out which parts of the engine have different part numbers, but it'd be easier just to follow conventional 60* V6 hop-up wisdom. Step #1 is to increase the displacement.

 

Yeah, sorry forgot about the fuel pump. There is no way to mount the original mechanical one on a 3.4 block. But as Drew said, run an external pump. You will still be way happier with the finished product than dropping a pre-85 2.8 in. You will have a much easier time finding a 3.4 too, there are old 4th gens all over craigslist going for cheap. You can get the engine out of it, maybe even swap out your seats and a few other odds/ends. Then sell the rest of the car, or just scrap it and still get money back