OK, I've been lurking, researching, and learning. First of all, I'm a Pontiac guy through and through. I had a '68 GTO for 25 years. I traded it back in 2017 with no regrets. I had run my course with that car and had a lot of fun along the way. 1967 was my favorite year for the GTO and all GM cars for that matter. My plan was to get a '67 to retire with, but the way the old car market has gone in the last 5 years, I'm out on that idea. I refuse to pay $50k for an average condition car. The first new car I ever bought was a 1983 Pontiac Grand Prix LJ Brougham. I have loved that body style ever since. With the '67 GTO out of the picture, I've decided to pick up a 1981 to 1987 Grand Prix and do an LS swap. I won't go into details of what I want, but I'll be looking for a while before I get one. I have been researching and putting together a plan and wanted to throw it out there for comments to make sure my logic is right and recommendations on some areas that I haven't settled on yet. I plan to go with an LS3. I will bore it out .010" and use a 4.1" stroke crank. Why, you ask? Nostalgia! If you do the math on that combination, it comes out to 427.8 cubic inches. Most would call that a 427, to me, it's a 428. This wasn't the way I really wanted to get there, I wanted to bore an LS3 .060" (4.125") and use a 4" crank. That is almost exactly what the Pontiac 428 bore and stroke was, 4.12" bore x 4" stroke. But that was the old cast iron block thinking, you can't bore an aluminum block that much. Oh well, the .010" overbore and 4.1" stroke gets me there. I will put old '67 to '69 Grand Prix 428 badges on it. Below is a breakdown on what I plan so far:
LS3, +.010", 4.1" crank
Cam, TBD based on recommendations with my goals in mind.
Heads, stock LS3 heads, upgrade the valve train if my cam choice dictates the need.
Intake/throttle body, Stock LS3, but willing to change if it's necessary to get me to my goals.
Rotating assembly will be forged and balanced.
I will want/need an alternator, P/S pump, and A/C, I read something about an F body pulley for one of them to clear, help? Will a stock serpentine system work? Which one?
4L80e, will I need to upgrade it to handle my goals?
Holley Terminator X Max to control the motor and trans. Is there any reason to go with the Dominator other than "It's better"? Does it have any features that I may want? What are some of the inputs/outputs available that may be nice and I'm not thinking of?
Dakota Digital ECD-200 to keep the stock speedometer with the electronic trans.
12 bolt Posi with disc brakes. If I get it going, I want to make sure it stops...
Gears: TBD based on the combination. I'm thinking 3.55's, but I want it to match the cam choice so it gets me into the right RPM range.
I want a stock looking car. I plan on using Wheel Vintiques Pontiac Rallye II's 17" x 9" with 275-40-17 tires in back and Wheel Vintiques Pontiac Rallye II's 16" x 8" with 225-50-16 tires up front. Will 235 50 16's fit up front without rubbing in turns?
I want a stock appearing, very fast car. A sleeper. I would like it to hit 500 hp. I think this is a very reasonable goal, the LS3 is 430 HP stock. I'm thinking that with the added 52 cubic inches and a mild cam upgrade, I should be there. I'm not trying to squeak out every HP I can, I don't want a lopey cam. I had that in my GTO and loved it. But, at my age, I'm past that.
Thanks in advance!
Thoughts and recommendations?
Also subscribing. Being this is my first G Body swap, I will be watching your thread for tips.
My grandfather left me a 1985 Pontiac Grand Prix with a 3.8l. I was going to sell it but it's actually a really nice car to drive to the store or when I need to drive comfortably somewhere, it's easy to jump in and go. After driving a few months I noticed other people taking notice of the car and giving thumbs up as they would drive by. I have had/have a lot high HP cars ranging from 500-1040hp (Mustangs, Camaros, Firebirds, CTS-V, Twin Turbo C5, C7Z Maggie 2650, C8 Z51, Telsa Plaid etc.) so I'm used to having fast cars on the street, strip, and track. Being that I'm looking to have a nice daily driving G Body with more hp, I started looking into swapping in a V8. I have a newly rebuilt '69 327 w/TH350 in the garage, it would have been a straightforward swap into the Grand Prix, but at the end of day it would still be a SBC that got 10-12 mpg making 285-300hp. My hp goal is between 350-400, while getting over 18 mpg, I looked into buying SBC heads (TFS, AFR), cam, Holley EFI intake to increase the hp to 350-385 and get maybe 15-16 mpg...but it ended up coming out to around $5k for those mods.
I then looked at doing an LS swap specifically LS3 or an LT (I still have the stock LT4 supercharger from by C7Z), but while researching and planning I came across an '04 LS1 (Vette) with 50K miles on it (complete drop out w/harness, ECM, TAC/Pedal) for $3500. Any LS1 past 11/2001 had the newer style (LS6) block and intake. The '04 Vette LS1 is rated at 350/350 hp/tq and is all aluminum, so it weighs (450lbs) which is about the same as the Iron 3.8l motor (500lbs), and it's good for about 22-26 mpg while cruising on the freeway. At 450lbs I can keep the OEM ride (stock suspension) and maybe will just replace the shocks and upgrade the rear brakes.
So far I have picked up the following Holley Swap parts:
Pan, Crossmember, Mounts (motor, frame, and clam shell), OEM tank EFI Fuel Pump (return on pump).
I still need to pick up a 4L60e, LT1 F Body Radiator w/support, and ICT Mini Air Con Pump so I can retain the AC in the car. I contemplated the ICT or Dirty Dingo AC high mount relocation, but my friend owns A&A Corvette and I'm sure will make me a great deal on one his C5 Vette Supercharger Kits should I ever decide to move the HP level up to 500hp. But I'm really trying to not do that with this car, I want it to be a tame, smooth, a nice driving car that can pass easily when needed, work well in the hills, and cruise while getting 22-26 mpg.
I still haven't nailed down which dual exhaust to get to mate up to the OEM Vette LS1 manifolds, I may have to go with the Black Heart headers, but I was hoping to retain all of the stock parts from the LS1 drop out.
I was happy to see your post because I haven't found too many Grand Prix threads.