lc5 to lg3 parts interchangebility

[turbobonneville]

Hello, new member here. Names Mike and I have a 1987 Bonneville that I need to rebuild the engine in and I saw somewhere (I forget where) that the rwd 86-87 and the fwd 86-87 3.8L where able to interchange some parts...ie. the heads pistons and rods. Is this true? has anybody here had any experience in this matter? Any help is greatly appreciated. I want forged internals and better flowing heads because I want to turbo the car. I am going to have the transmission rebuilt to be able to handle the power. I'm looking for 300-350 hp at the crank.

 

[Turbo6inKY]

The RWD and Series I FWD engines did share a lot of the guts, so rods and pistons will likely work. Some heads will interchange, too (the 1989 TTA used FWD heads).

But it's rare to overhaul a FWD, since the parts and machine work usually cost more than the car is worth. You'll need to tear it down and measure everything to be sure before you start ordering parts, because nobody's really done it.

 

[turbobonneville]

the series one didn't debut till 91 on the park avenue and 92 on Bonneville lesabre and 88's, the "3800" was midyear 88-91. the 86- early 88 fwd aren't a "series" like later 90's and 00's.. but thank you for the advice about measuring, ive seen and helped in engine rebuilds but never done it my self, What exactly should I be measuring?

 

[turbobonneville]

oh and the turbo ta used 3.3 heads because 3.8's wouldn't fit because of the slant of the hood..

 

[Turbo6inKY]

What exactly should I be measuring?

Everything.

If you do embark on this, get the factory service manual for the car the engine came out of, and do a factory spec rebuild. It's your first build, don't make it complicated.

 

[turbobonneville]

I want it factory specs just forged.

 

[turbobonneville]

I have the factory service manual for my 87

 

[Turbo6inKY]

I want it factory specs just forged.

Then you measure the rod length, big and small end diameters, and talk to your machine shop about sourcing a set of forged rods. You'll also need to check and see if the crank will interchange with a popular one (it should).

If it's the same reciprocating assembly as the RWD version of the engine, and you can verify that by measuring the parts, you'll be good to order from the catalog.

 

[mikestertwo]

Is it a "VIN A" or "VIN 3" car? There's a big difference between the two.