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Overhauling the 305 V8 (LG4) from '87

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Old 08-27-2009, 09:39 AM
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Car: Pontiac Firebird ´87
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Overhauling the 305 V8 (LG4) from '87

Hey Guys!

I already wrote in an other thread about my car.. bought it from a guy near me.. he had it in his garage since 1996 and didnt move it for long time.

Car wont start when I bought it > carb. was reeeally dirty, fuel line was completely rusty in the back, and also the gas-tank wich I had to swap cause of the rust in the inside..

now the motor is running again, but sounds not too healthy - I guess also cause of the old oil.


So I want to overhaul the motor, but cant find a good thread about which parts to change... what would you change ?

and is there an onlineshop where I can order all that stuff?
>> I am sitting in Austria (Europe!!) ..
its not that easy for me to get those parts here :\

!! ... !!
Old 08-27-2009, 04:36 PM
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Re: Overhauling the 305 V8 (LG4) from '87

before you rush into an overhaul, let's focus on the rough running. No need for a nuclear missile to kill a mosquito. So, let's start with the basics. Does the check engine light come on when you first start the car, like it should? Does it stay on, like it shouldn't? If so, check the trouble codes. Next, How do the vacuum hoses look? Are they all dried out after just sitting so long? What's the timing set at? How do the plugs, wires, cap and rotor look? What's your fuel pressure? Look at all that, then report back, and we can go from there.
Old 08-28-2009, 01:59 AM
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Re: Overhauling the 305 V8 (LG4) from '87

Sparks are new (changed it last weekend) the old one´s were dirty.. but I guess this is of all the tries to get it run (before we didnt knew that there is no fuel comming throu the fuelline)

Also the oil looks worse, and I´ll change it and clean the oil-catch-thing (dont know the word in english)

some hoses in the front look dried out and porous.. thats why I thought it would be good to change them.. later or sooner I´ll have to do it..

Spark-Wires, plugs and Fuel Pressure is a good idea to check. I´ll check this!

The Errorcodes are empty. I checked this already when I bought the car, and after it run the first time at my place

thanks for your helP
Old 08-28-2009, 03:48 PM
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Re: Overhauling the 305 V8 (LG4) from '87

dirty spark plugs can be cleaned and reinstalled. A wire brush works fine, as does careful sand blasting. Plugs get replaced for being visibly worn away, not for being dirty.
Old 08-29-2009, 01:43 AM
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Re: Overhauling the 305 V8 (LG4) from '87

yes you´re right, but with the car came in its trunk new sparkplugs, air intake filter, fuel filter, oil filter, break-kit (complete for rear)

so I just swapped the old ones.. and its a good idea to change 13 year old sparks against new ones I guess
Old 08-29-2009, 03:32 AM
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Re: Overhauling the 305 V8 (LG4) from '87

Well when i rebuild my engine all i did was replaced the main bearings, cam bearing, piston rings, lifters, and the oil pump but i wasted over $500 for that
Old 08-29-2009, 07:32 AM
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Re: Overhauling the 305 V8 (LG4) from '87

The LG4 should have a quadrajet carburetor, export version may be mechanical with no computer, and no codes to check. Does the carburetor have two (2) electrical connectors attached? One on top with two wires and one towards the front driver's side with three wires?

Either way that carburetor has been sitting for a long time without running. It will likely benefit from a rebuild to clean it out and replace old gaskets and rubber pieces inside. I'd also replace all of your plug wires and vacuum lines.
Old 08-29-2009, 09:38 AM
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Re: Overhauling the 305 V8 (LG4) from '87

Double post
Old 08-29-2009, 02:54 PM
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Re: Overhauling the 305 V8 (LG4) from '87

Originally Posted by JR350tpi
Well when i rebuild my engine all i did was replaced the main bearings, cam bearing, piston rings, lifters, and the oil pump but i wasted over $500 for that
that sounds good to me.. I thought when I change those parts now I wont have any problems for the next 5-10 years (except the normal oil change things..)

900 € I payed for the car, here they sell normaly for about € 3.500++
Good condition with targa for ~ 7000 (from 1985++, older ones even more expensive)... so I guess those 500$ would be a good invest

and do you know a online store somewhere around, where I can get those parts?

Originally Posted by naf
The LG4 should have a quadrajet carburetor, export version may be mechanical with no computer, and no codes to check. Does the carburetor have two (2) electrical connectors attached? One on top with two wires and one towards the front driver's side with three wires?

Either way that carburetor has been sitting for a long time without running. It will likely benefit from a rebuild to clean it out and replace old gaskets and rubber pieces inside. I'd also replace all of your plug wires and vacuum lines.
yes I´ve got the computer controlled quadrajet.. I just cleaned it with .. I dont know the word in english .. its called Bremsenreiniger >> Break Cleaner? I read that it can be done with this very good

I saw those rebuild kits.. maybe I´ll get one of those too.


... I think there are two wires.. but i´m not sure
Old 08-29-2009, 03:38 PM
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Re: Overhauling the 305 V8 (LG4) from '87

I got the parts from summitracing.com they will tell you excatly what you need too
Old 08-29-2009, 03:50 PM
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Re: Overhauling the 305 V8 (LG4) from '87

thanks a lot =)
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