Swapping from v6 to my Big block...

Discussion in 'V-8 Buick Powered Regals' started by My86clone, Oct 9, 2015.

  1. My86clone

    My86clone bbb455

    Is there anywhere on the site where there is information on where to drill a new motor mount holes or what sort of brackets I'm going to need in order to swap from a factory v6 to put by big block in the car? We did this once before at the shop but it was about 5 years ago so I'm just kind of looking for some pointers or maybe if someone has got a video or step by step instructions on the mounting procedure thanks in advance.

    STAGE-2 TORQUE STAGE-2 Buick "482 Stroker" soon!

    How's it going?

    For my Buick 455 Regal projects, I first had a V6 Regal Limited.

    If your Regal has TH200 transmission, you can use that cross-member to bolt up a TH400 transmission. I think I just flipped it over for the TH400 if I remember correctly. You will need to slide the cross-member back a small bit though, and I needed to drill 2 new holes for the driver-side of the Regal's chassis to bolt up the factory "200" cross-member. Dual exhaust channel/slot was cut in the cross-member for the driver side of the dual exhaust at Mieneke. Make sure to use TH400 tranny mount.

    Once my friend and I attached the $100-junkyard TH400 short tail 3-speed to the factory 1974 Buick 455 V8, we lowered the motor/tranny into position ... with the 1974 Buick Electra's chassis and motor mounts still connected, as a few guys told me that it all would fit fine because it's all GM.

    They were wrong, as the 74' Electra's chassis mounts made the 455 sit @-inches too high for the 1985's Regal hood to close. For 2 months, I researched/called this mechanic/that mechanic ... they all said it should have fit. Then, I notice a tiny add in Muscle Car for Poston Enterprises (later named Poston Buick before going out of business).

    Jim Poston at the time read my story for me, "So Chris, you put a Buick 455 V8 in a g-body Regal using factory '74 motor and chassis mounts ... and I bet you couldn't close the hood, right?" He then told me not to worry, as they manufacture a kit for that type motor swap. I bought their chassis & motor mount kit. When Dietrich and I installed those babies, I got the idea to lay 455 and TH400 connected into the Regal's engine bay with the chassis & motor mounts from Poston connected ... "loosely" bolt up the factory TH200 cross-member to the TH400, then connect the Regal's drive shaft to the stock 7-1/4-inch (?) regular 2.56-geared rear and the TH400 3-speed tranny with new universal joints. The TH400 will easily use the stock Regal drive-shaft, just make sure to use a TH400 tranny yoke.

    After he and I got everything straight ... then I SPRAY PAINTED THE Poston CHASSIS MOUNTS WHITE making sure to GET WHITE PAINT ON THE CHASSIS area where the new chassis mounts made contact. Then we removed the engine and tranny from the Regal ... removed the chassis mounts/plates ... re-positioned them in the pattern/painted template area on the Regal's chassis, and drilled new bolt holes in the Regal's chassis. Make sure to use steel piercing drill bits ... I broke 2 regular bits before buying the correct one for the job ... went through the chassis like it was butter.

    There is an "oblong" hole in both sides of the Regal's chassis for the fuel lines ... you will need a "swivel" ratchet to tighten at least 2 of the nuts of the bolts that hold down the chassis pads. That was the only way we got them tightened. Understand that these days, TA Performance has the chassis/motor mount kit for this swap. Their pads may differ ... I think they are identical to the Poston type back in the day. I did not install the kit from TA on my current Regal/455 swap, a shop did.

    With the new chassis mounts installed, re-install the complete drivetrain and bolt it all up securely.

    Within a couple of month, I destroyed the stock (very dirty ... leaking oil) Buick 455 motor (over-revving the motor ... no oil pressure gauge nor tach.

    Scotty G. was in Brooklyn at the time at Pee-Gee Performance. I had spoken to him a lot over the phone prior to getting my motor to him. He couldn't rebuild the motor ... the bare block had 2 busted combustion chambers (6 and 8) and could not be sleeved. Scotty sold me a bare block he had in the shop for $200.

    Once the "built" 455 was back in the Regal with just stock exhaust iron manifolds, after a couple of months, I got a 2-1/2-inch dual exhaust system installed. A couple months later, I bought a GM 8.5 posi-rear 10-bolt (from a 1987 Oldsmobile 455/Hurst with 3.73 gears) and tried to swap out the rears. Big problem; the stock Regal's drive-shaft was @ 1-1/2" too LONG.

    My friend Tyrone Taylor, knew of a guy that has parts. I went to the guy, and he told me that a 1970's Camaro with a big-block, and the GM 8.5-inch posi-rear has the exact length of drive-shaft I need for the "GN" rear and TH400 combo. The other option was to have it cut and balanced for $70 at the time. Mike had 4 of the drive-shafts I needed. I paid him $30 for it. It bolted right up with NO issues ... for this, make sure to use a 1987 Buick Grand National universal joint when connecting the GN rear to the drive-shaft. If you use a Regal's stock TH200 drive-shaft with TH400 short-tail transmission, and GM 8.5-inch 10-bolt rear ... IT ALL BOLTS RIGHT UP without having anything done to the drive-shaft.

    I hope this helps you.
  3. usetaboost

    usetaboost Well-Known Member

    Did mine the same way. It was the most time consuming pita of the whole swap. I did things a bit differently though. I left the old trans in place and bolted the engine to it. To me this felt like the way to get it as close as I could to being factory. No question is a stupid question even though some here may say the info is all here. Well guess what, it's not. Check out my thread. I discuss many of these issues. The ecm side of the harness can be cut out, be careful not to cut the hvac harness out though. You'll see it when you pull the fender off. THis is also a good time to do some cleaning in this area and make sure the drain is empty on the hvac box. 75/76 valve covers are supposed to give you a bit more room around the box but to be honest I didn't see any gain. I got a pair for 30 bucks shipped bead blasted and bare so it wasn't a bad move for me. You'll have to use standard bolts for any bolts that go into the motor. The a/c lines will need to be shortened but you can still wrestle the a/c compressor on for now. BTW, if running a/c you will need the LONG water pump! The power steering pump will need to be swapped to v8 lines. I think you might be able to get away with just the v8 pressure side but I'm not for sure. You will need to make your own fuel feed line. I just cut a section out, flared the ends and put a piece of hose on it. No need to modify the hard lines on the rail. All this is assuming you are using v6 accessories.

    Depending on what trans you use will also add to the budget. I plan on using a 200-4r. This required a carb with a tv bracket, a tv/throttle cable bracket (you can use either one off an olds powered G body or buy a nice pretty one aftermarket like I did), and you will need a spacer no matter what you do if you have a kickdown/tv cable. This obviously applies for the th350 also.

    Cooling you can use just about any gm v8 radiator. I got a nice one from a mid 80s caprice from the junkyard. Picked up a set of 2000 intrepid fans so I didn't have to use a mechanical (I like the open room). Doing this will require you to use a higher amp alternator. Luckily they are all over the place. I chose to use the small 105 amp alternator for weight savings. It's a little difficult to tighten the belt but it can be done. Other alternative would be a LT1/GN alternator or you can use one from a late 80s fwd caddy which should be v belt and require no mods except for maybe cutting your existing plug and adding the 4 pin. No big deal.

    As far as front springs go, you can grab some from an s10, use g body v8 or diesel, or fbody springs. MOOG makes replacememnts for all of these and I would buy new since it takes some work to swap these. No sense in putting in used. Go to maliburacing.com for some general spring info. If your upper control arm bushings are bad or any other suspension/steering that is worn now is the time to change it (doing things twice wastes time).

    If you can swing it I would recommend an aluminum intake. Yeah theyre expensive but WOW what a weight difference! The factory 455 throttle bracket works on the edelbrock intake. V6 throttle cable hooks right up.

    Any questions feel free to ask. You will get frustrated during this swap. Don't expect it to be done any time soon. It's not an overnight drop in like a buick 350 would be. As far as exhaust goes, you can get creative until you have money to get it done right. I bought new pypes kit for my turbo buick so I used the old hooker catback on the 455 car. The electra Y pipe is so close to working it's sick. I ended up bolting up the Y pipe, cut off the ball end, used a flex pipe to tie it in with a 2 1/2 to 2 1/4 reducer. Not the prettiest and doesn't seal perfect but at least I can run the car and think for 15 bucks. I'm using a stock configuration for the simplicity of swapping exhaust later if I choose all I gotta do is click and it's done.

    Anything I didn't cover here feel free to ask. I've been working on this swap since may but I'm not exactly rich or full of time so it's been moving slow. I just gather parts when the money allows.
  4. usetaboost

    usetaboost Well-Known Member

    One other thing, there's a good chance you will have to drill new holes in the flexplate for the torque converter. Have fun:Brow:

    STAGE-2 TORQUE STAGE-2 Buick "482 Stroker" soon!

    I am curious as to why new holes might need to be drilled in the flex plate for the torque converter?
  6. usetaboost

    usetaboost Well-Known Member

    455 flex plate only has holes for th400

    STAGE-2 TORQUE STAGE-2 Buick "482 Stroker" soon!

    I know; I thought a TH400 tranny was considered for this project. I guess I miss-read.

  8. usetaboost

    usetaboost Well-Known Member

    I'm doing what everyone says I shouldn't do. 200-4r with only hardened parts, a d5 converter, electric fans, and a 7.5 rear. All things people told me were no good lol!
  9. 69GS400s

    69GS400s ...my own amusement ride!

    depending on how built up the 455 is, I'd say the rear is going to go out long before the tranny will

    STAGE-2 TORQUE STAGE-2 Buick "482 Stroker" soon!

    Hey, Al. How's everything?

    That's exactly what I asked Roberta Vasilow a few years back regarding the stock Regal peg-leg rears.

    She told me that the GM "7-1/4-inch rear" is stronger than people think. I did burnouts on the 455 Scotty G. built for me every-day with the stock "peg-leg" 2.56-rear, and it lasted until I got a 8.5-inch 3.73 posi-rear. That 455 had a 501-lift Lunati cam.

    That was my experience. :TU:
  11. usetaboost

    usetaboost Well-Known Member

    My buddy had a camaro he used to really beat the hell out of. Foot to the floor gear drops, hard burnouts around corners, donuts on the concrete. I figure if he can't break it, it should be decent. The 7.5 has the same weak point as the 8.5. It's like how some stock trans parts will run 9's and others break while running 12s. Luck has got to be somewhere.

    STAGE-2 TORQUE STAGE-2 Buick "482 Stroker" soon!

  13. My86clone

    My86clone bbb455

    You know I done the swap before as I talked about and I don't remember drilling any holes in the flexplate to do a 200 R4 I know that is more expensive to run that transmission but I want to drive my car on the street .I appreciate all the help and advice . One of the deals I'm working on is trying to figure out what brackets I can use to incorporate the air conditioning I found a few pics it looks like you can use the V6 brackets in order to use modern air conditioning with the big block in the G body . From what I'm hearing it looks like I may have to run a Ford 9 inch rear end to hold up to the amount of torque the stage 2 motor will produce because of the typical weak points in a stock G body rear end even a grand national rear end. If you don't mind me asking what kind of rear ends Are you guys running?

    STAGE-2 TORQUE STAGE-2 Buick "482 Stroker" soon!

    1984 Buick T-Type Regal 8.5-inch posi-rear 10-bolt with 3:42s.
  15. usetaboost

    usetaboost Well-Known Member

    I'm gonna keep running 7.5 rears until I don't have any left. Working on number 3 for a stockpile.
  16. stew'86MCSS396

    stew'86MCSS396 Well-Known Member

    Day late, dollar short...

    @OP Did you read the sticky?

    When I did this swap some 25 years ago, seem to remember that this was indeed true for my '72 455 flexplate. However, since I needed the smaller bolt circle for my application, a quick look on my '75 455 had a dual bolt pattern flexplate.
  17. usetaboost

    usetaboost Well-Known Member

    Interesting. I'll have to look up the part sometime.
  18. papa roger

    papa roger Well-Known Member

    I'm running a Ford 9" in my 470 Regal with 3.89 Detroit locker and Strange axles. Handles the 570 HP and 579 Lbs ft torque very good.. So does my 200-4R trans built by Vince Janis. Roger

    On The Eighth Day God Created Buick

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