Hmmmm, let me see if I could clear up few things. There is a big difference between the 3800 and 3.8 RWD Buick motor, nothing interchanges, a 3800 is a whole new design the bottom end the top end every thing is different. The GNX, GN, T type & Turbo T, they all have the same motor, a 3.8 SFI turbo charged motor. The GNX had some work done to the same heads that are on all the turbo Regals (GNs, & T Types) they are the same casting # 8445. The GNX also had a better turbo (Ceramic) and true dual exhaust, trans had a better shift kit, and IC was modified with extra cores, better traction control in the rear and a better chip. You take a GN or Ttype and dump around $700.00 in it you will have a turbo regal that will blow the doors of a GNX. Regardless a GNX is A GNX, only 547 made and they still range from 35K to 100K in price. Now the 4.1 is not really a turbo motor from the factory even though there were 20 or so 1982 Grand nationals (yes there were Grand Nationals in 1982) out there with turbo chargers, however, they were carbureted (not fuel injected turbo) and most of the 200 or so (I don’t remember the exact numbers) 1982 GNs were normally aspirated. If you are looking to build a Fiero with GN motor set up, that is what I am doing (I restore Turbo Regals as a hobby and sell them). It is not as expensive as it seems. There are more ways to do this than just using a Turbo Regal block. At first I was going to use a 3.8 FWD block out of a 1987 Bonneville, remember this is the last 3.8 FWD block prior to the new design 3800. The 1987 3.8 FWD block has the crank very similar to the GN; they both have the Fillets on the main and the rods on the crank rolled. The rods are exactly the same as a GN. You need to buy forged pistons (8.5 to 1) around $300.00 for TRW or around $500.00 for J&E’s. The 1987 FWD drive 3.8 block with VIN code # 3 also had a roller cam setup (big HP potential) which GN’s didn’t have, you can send it out and get it reground for turbo application. The head on the 3.8FWD motor also have the same heads GM used on the Turbo TA in 1989 because the strut tower clearing issue with the AC. You can get the heads and intake ported with good spring and things. You can buy after market exhaust manifold the make for TTA, some good injectors, turbo bla, bla ,bla. Most of the thing they make for GN’s or turbo TA will work. Say you don’t want use the 3.8FWD heads came with the motor, no problem the top half of a GN motor (heads and intake will bolt right up to the FWD 3.8 motor no problem. Then you need to use the GN exhaust manifolds. It doesn’t matter which exhaust manifold you use you may have to bolt them backwards and modify the cross over pipe (no big deal) The number one reason I chose this method is that; 3.8 FWD block will bolt right up to the Fiero trans and I was also going to beef up the bottom end of the motor by installing steel main caps that they make for the GNs (the middle two.). I initially wanted a manual trans behind it because I was going to built a Diablo but being on this site and the way Fieros looked I started liking them so I decided to build a Fiero that is fast as I can get it to go, this means NO MANUAL trans. You don’t want a manual trans behind a turbo charged motor especially a motor that revs to only 5500 red line.(in 1989 Pontiac tried a T5 behind the GN motor and ran a full second slower than the 200r4 automatic so they stuck with the auto) So I decided to build the 440/460 trans came out of the Bonneville. After talking with my Tranny guy and looking at all the expense, I decided to use a motor that I recently purchased a TTA motor that built to make about 600hp/700lbs trq. What I was told by my trans guy is that to use the trans out of an 83-85 Caddy eldo, Buick Riv or OLDs Tor. I thing it is called the TH325L4 longitudinal setup (the one with the over drive.) which has the basic internals of a 200r4 which is holding up in my Buick at 10.70 (3800+lbs car). If you want to build a 3.8 or 4.1 out a junkyard you can you will be surprised. In 1987, at the end of the RWD 3.8 block era, GM put lots of (109 block or SGI block, these are turbo blocks) in regular cars that had the 3.8 V6 in it, some even had the good crank in it. You need to look for it to make sure all the fillets are rolled (mains and rods). In 1982-1984 I believe that all the 4.1 had the good crank in it so if you get one of those motors you are good to go. I have lots of friends using 4.1 GM production block in their GNs with out any problem. The only few things I have heard about the 4.1 is that the webbing around the intake valley is not as strong and few other differences, no big deal. You can get a custom wire harness built by Caspers electronic for around $500.00. If you use the FWD 3.8 setup, you can use the same harness out of the donor car. I can go on and on. If you need to know more feel free to contact me. Sorry for the long post.
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87SE 2.8 w/5speed(waiting for a 3.8 Buick GN setup trasplant)
85SE 2.5 w/5speed
1987 Buick GN(10.70@124MPH)
1987 Trans Am SBC 355cid Twin Turbo(no track times yet)
1992 GMC Typhoon(13.20@ 99mph)
Other cars; JaguarXJ6 & Mercedes AMG 500SEC
