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Series III downgrade to Series II

Rolling Thunder

Rolling Thunder

New member
I've got a 3800 SC III out of a 2004 GP GTP. I'm going to stuff this thing into a 1988 Pontiac Fiero GT. I've decided that for my application, I'd like to downgrade to Series II setup.

I know I need things like the throttle body, ECU, PCM, wiring harness... what else do I need?

btw, I'm also refreshing the engine while it's on the engine stand. I'm doing some preventative maintenance. So, I'm replacing the water pump and pulleys and belts... etc. What else should I replace? I work at an auto parts store and I get about 30% off, so these parts are cheap.
 


I've got a black box... I guess it's the BCM... do I need that?

Say, is the stock timing chain a roller type? Now would be a good time to replace it if need be.
 
i dont see why you would downgrade? do you need to do it because the series III setup wont work in the fiero? just asking...
 


I'm going with a manual... that's hard to program if I remember correctly. I'm also avoiding having to reprogram the ECU every time I change the hp a bit (avoiding limp mode). I also want to avoid the sensor pedal and throttle by wire setup. The Series II just seems like it would be much easier. Also, Fiero guys can bypass Passkey II, but the Series III VATS gives us problems.
 
I've got a black box... I guess it's the BCM... do I need that?

Say, is the stock timing chain a roller type? Now would be a good time to replace it if need be.

The oil pan leaks. Is this just the gasket or is there another seal there?
 
I don't know if you need the BCM or not. If you're going to be changing to Series II hardware I'd imagine you would need a BCM that will work with Series II PCMs. I don't know the details of if the BCM is needed in the motor swaps, though.

I'm pretty sure the stock chain is a roller. If you feel like going in there you could replace the plastic damper.

The oil pan gaskets are common. Pull it down and replace or just put some RTV.
 
I'm guessing that the gasket is a better idea than the rtv since it's heat cycled so extremely.

Is this plastic damper known to fail? Here's a pic I found of one. Is it that thing that rubs against the chain?

DSC00617.jpg
 


Yes, that broken part is the chain.

The reason I mentioned the RTV is that the gaskets will always eventually leak. GM eventually just included a channel for some RTV and said "**** it".
 
It looks like a non-roller chain. Any complaints about that?

Who makes throttle body adapters for Series II throttle bodies to Series III superchargers?

Is there a specific Series II throttle body I want or are they all the same?
 
Rolling Thunder said:
It looks like a non-roller chain. Any complaints about that?
Click to expand...

For stock its fine. Even upgraded springs its fine. As the engine gets really old they can stretch a little. The damper is what really wears out though.

If you replace the damper, replace the chain. They're cheap.

Rolling Thunder said:
Who makes throttle body adapters for Series II throttle bodies to Series III superchargers?
Click to expand...

I know ZZP does.

Rolling Thunder said:
Is there a specific Series II throttle body I want or are they all the same?
Click to expand...

I'd look for a 99-05 L67 TB.
 
Rollmaster Roller Timing Sets: 3800 Performance

The only double roller I've found is $300 (above). That sounds ridiculous compared to the one in the link below (I know it's for the wrong engine). The single roller I saw was $150, which is more than I want to spend since I'm never going to see over 300hp.

CHEVY V6 HP True Roller Timing Chain 196 231 3.8L:eBay Motors (item 220418317645 end time Jun-18-09 20:08:13 PDT)

The 99-05 (non TBW) throttle bodies have the mass air flow sensor already in them, right?

Any other parts I should replace or upgrade? Oil pump pickup... supercharger rebuild... random bolt... certain gasket... starter... A/C compressor...
 


Hey sounds like you'll have a real screamer when you're finished. I am working on a similar project... Dropping a series II S/C into a Fiero Kit donor car. But I'm moving at a Glacial pace right now. I'm also wondering what mods to do before I drop in the Engine???? Any suggestions is greatly appreciated.
 
Nothing on the roller chain?

Are the Series II and Series III identical internally... talking about cam and head specs? I'm asking because that Series II ECU will be programmed for Series II specs. I'll get it tuned anyways, but I'm trying to keep this cheap :)

Should I think about rebuilding the supercharger? I'm not talking machine work. I'm thinking of bearings and stuff. I'm keeping the stock pulley.
 
the series 3 heads have larger valves. Cam is the same. Shouldnt be a problem really. Series 3 has stronger internals. Rebuild the supercharger only if it makes noise, probably around 100k it will need a new coupler and rotor bearings.
 
Should I look at getting another oil pump or pickup? I'm going to pull off the oil pan anyways.

Does anyone make decent headers with the outlet at the stock location? The SLP headers I've seen go straight through the Fiero trunk. The stock headers give enough space to work around the trunk. Mustang headers?

Edit: Does it matter what Series II wiring harness I use? Year matters? SC vs non-SC matters?
 
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