1971 skylark gs 350 to 455

Discussion in 'Street/strip 400/430/455' started by motard23, Apr 18, 2012.

  1. motard23

    motard23 Active Member

    Ive got a 1971 buick skylark GS 350 that im considering on making into a stage 2 clone car and I had a couple questions Im not sure if you can help me out on. First off I would want to stay completely buick on this but Im not really feeling the buick 350 thats curently in the car and the urge to just go chevy small block with a turbo 350 sounds really good to my wallet but Im not sold on this either. (1) I know that with most if not all chevys/fords the cross member and front springs need to be replaced when going to a big block(455) and im honestly just not sure with my buick if thats necessary? (2) Im not looking to build a motor for fear of spending 10,000$ and forgetting to install a freeze plug or something stupid, but I have been looking at some pre assembled turn key motors ($10,000) and some others with factory heads close to factory specs for around 3-5,000$ and Im not sure if anyone can recommend a shop that does good work? (3) Once again being new to buicks would I need to replace the transmission by going to a big block?

    Sorry for asking so many questions but any feedback is greatly appreciated! Im loving my buick and really want to do it the right way.
     
  2. flynbuick

    flynbuick Super Moderator Staff Member

    TH400 trans are cheap. They came with 455s. Th 350s are pretty tough but I would go with the TH 400.

    But if you are going to have a stage 2 455 Buick engine built by one of a handful of the Buick specialty shops the cost is way beyond your budget. You would need to be looking for a deal on a used engine. And there are some deals on this Board.
     
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Let me start off by saying that you can do whatever you like with your car. But to be honest, every time I see someone mention putting a SBC into their Buick, I just shake my head. To me, the car is no longer a Buick once you do that. I would rather see you just sell the car as is, to someone who will keep it Buick powered That's just the way I feel, and I'm going to tell you that since you posted on a Buick bulletin board about switching to Chevy power. Buicks cost more to build. When I go to a car cruise, I see Chevy engines all over the place. I'm usually one of a hand full of Buicks there, sometimes the only one. I like that. Anyone can go the Chevy route. That's the easy way, and with no doubt, the cheaper way.

    Now that I got that off my chest. I have a few questions for you. Who said you have to go from SBB 350 to Stage2 Buick 455 all in one fell swoop? Why can't you just find a used BBB 455, transplant it or freshen it up, and then transplant it? You can always up grade it with aluminum heads, and other parts. Look at what Car Craft and Hot Rod magazines did with a junk yard BBB. My point is that you don't have to do this all in one shot. The THM 350 in your car will bolt right up to your 455. If that THM 350 is in good shape, it will be fine as long as you don't bolt a pair of slicks on it, and launch it on a sticky track. Of course a Stage 2 motor, or any modified BBB is going to need a THM 400 if you plan on racing it or even do some spirited driving on the street. There is a good chance that you won't need to change the front springs in your car. The BBB is only 75 lbs heavier than a SBC. Put on an aluminum intake and it gets even lighter. You have lots of options if money is a problem. If you take your time doing this, you can enjoy the better performance, and your wallet need not take the big hit all at once. Less down time for your car too. Good luck.
     
  4. motard23

    motard23 Active Member

    Yeah I understand completely what youre saying and Im not really looking to do a hybrid and want to keep it buick, just thinking of my options.. That was stupid of me to even mention putting a chevy drivetrain in my car on a buick forum.. That being said I do want to keep the car all buick and with it being an actual GS im a little torn between even changing out the factory 350 and making it into a stage car.. When I dropped the tank I actually found the factory spec sheet, so I have my proof its a real gs also.. But im also looking at this as a long term project so not too worried about getting it on the road right away, I would much rather do it right the first time. Or as close to right as I can afford haha..
    Currently the car is being stripped to metal and Im replacing the trunk panels and lower quarters so its going to take a little while anyways..

    Ive found some running 455's with factory carbs, intake, etc on craiglist for relatively cheap (800-2000$) that would work, probably just change out the motor mounts from the sound of it. Thanks for the heads up on the suspension too, I hate suspension work.. Ill check on the forums on here and see if anyone in southern ca is selling any 455's in my $ range.. Once the body work is done im going to be looking to get the motor/trans going. Also sounds like I should keep my eye out for a TH400 transmission since both of you mentioned it.
     
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I feel much better now:grin: You can always drive around with the 350 while you build a killer 455. Then transplant it and keep the numbers matching motor in storage. The 350 transmission will be fine as long as it's in good condition, and you don't ask too much of it.
     
  6. motard23

    motard23 Active Member

    Yeah its the original 350 and it runs great, but burns oil like crazy so Im thinking it could use some love. Eventually ill probably drag it a little bit but its mainly going to be for street, so im not looking for too much power just enough to scare the old lady enough to where she wont want to drive it.. haha
     
  7. boolo55

    boolo55 Member

  8. Briz

    Briz Platinum Level Contributor

    Good deals on used 455's are out there. I bought one for 800.00 and swapped it out with the 350 in a lark and its running low 12's. You can do it just take the time to shop around. Only thing you'll really need to change is the motor mounts and a bigger radiator.
     
  9. motard23

    motard23 Active Member

    Damn, thats a smokin' deal with the trans too..
     
  10. motard23

    motard23 Active Member

    Ive been doing some homework and it the only real immediate problem I see with the 455's is the oil pump which everyone seems to say should be replaced with a high output aftermarket pump. are there any other issues that go inherently wrong the buick 455's? Once again Im not looking to drag this car, maybe occasionally but nothing consistant.
     
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"


    Who is everyone? Whoever that is, either you misunderstood, or they don't know anything about Buicks. Everything you need to know is right here on this board. The Buick V8's have the oil pump as an integral part of the timing chain cover. Clearances inside the oil pump are critical to proper oil pressure. I'm sure you know people who are clueless on how to maintain any engine, and think oil changes are optional. Wear from neglect can wear the inside of the pump, and enlarge the clearances. When that happens, you get low oil pressure. You can get replacement oil pump gears, but they are useless if the pump pocket is worn excessively. The only cure is to replace the timing cover. TA Performance makes a reproduction timing cover. It's pricey, but worth it. In years past, when new timing covers were not available, there was a high volume/high pressure oil pump kit available. The gears were bigger, and it solved the problem, but created another. The bigger gears put more back pressure on the front cam bearing, timing chain, and distributor drive. You don't want to go down that road. The fact is that a stock oil pump, in good shape, with the proper clearances, will produce all the oil pressure you need and more.
     
  12. motard23

    motard23 Active Member

    Just browsing various forums online. I do remember reading about some issues with the timing chain covers needing to be replaced but "they" mentioned doing that without specifying that it was due to clearances required to maintin proper clearances for the oil pump to maintain pressure so the reasoning for it was kind of lost. THis is very good info, thank you for being so thorough on your response. Is there anything else to look out for with rebuilt or high milage Buick 455's?
     
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Two big indicators of the health of ANY engine is proper oil pressure and engine vacuum. Anyone that knows anything about Buick engines will always have an oil pressure GAUGE. A healthy Buick engine will have between 10 and 25 psi at idle, and 11-12 psi for every 1000 RPM. At 5000 RPM, it should have 60-65 psi. These pressures are with hot oil after the car has been DRIVEN for at least 20-30 minutes on the highway if possible. If I was buying any engine, I'd look at the oil on the stick, as well as having a peek under the valve cover. If you see sludge, I'd pass regardless of the price. This goes for any make engine, not just Buicks. There are no guaranties when you buy a used engine. It's always reassuring to hear it actually run in the car if possible. Beyond that, just use your common sense, and don't jump too fast.
     
  14. rmstg2

    rmstg2 Gold Level Contributor

    I'll add my 2 cents worth. I would like to add a little concerning sludge in an engine that Larry mentioned. I have bought and sold cars for years and even owned a used car dealership in the past. From experience I can tell you that Buick 455s are about the cleanest running engine out there. If there is any sludge build up
    in a Buick 455 or 350 for that matter it has been grossly neglected. Also while Chevys are cheaper to build you would still have to spend a considerable amount of money on one to get it to perform as well as pre 75 Buick 455
    with just headers. Add a small cam and the Buick starts kicking butt.
    The 350 Turbo as mentioned is tough and will live behind a mild 455. I wouldn't change transmissions until the 350 breaks. You might be amazed.
    Good luck

    Bob H.
     
  15. motard23

    motard23 Active Member

    Most of the engines Ive seen are not in the car so I would more than likely have to rely on a cold pressure test and possibly take a look under the valve cover for any build up.. Other than that hope they arent lying to me.. If the car hits the mid 13's ill be very happy, 12's and Ill be ear to ear smiles! Grew up in a family of ford and GM mechanics so just trying to figure out all the little thigns to keep an eye out for with buicks.. Every make/model has their issues and I hate suprises..
     

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