Mostly stock power mods?

Discussion in 'Street/strip 400/430/455' started by Jpf, Sep 18, 2018.

  1. Jpf

    Jpf Member

    Still new to the forum , but have started a frame off on a standard matching numbers 70 GS 455 with turbo 400 and 3.42 posi. Looking forward, I plan to keep it as stock appearing as possible but would like to get at least 400 hp out of the engine. I do plan on doing the oil mods and am looking for advice on more power on a budget. Putting most of the budget in the chassis and paint. Stock manifolds preferred but would consider one of the sniper type FI units if it will allow use of the stock snorkel air cleaner. Not building it to race, just want to give it a little more power. Any advice would be appreciated. This is my first Buick and I've learned they are a little different from the other projects I've done.
    Thanks
    JPF
     
  2. Stevem

    Stevem Well-Known Member

    What budget do you invision having to put into the motor?
    Be conservative on this number so you will not be disappointed!
    The good news is I can't see why a solid and easy 375 hp can not be had even if you drop the compression a tad to live on today's fuel.
    375 HP on the street with a bunch of torque that the 455 makes is a hand full!
     
    Last edited: Sep 19, 2018
  3. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    There is very little power to be had with an EFI swap. It'll soak up lots of $$ as well. Put that money elsewhere. A solid rebuild with a decent converter will be your best seat of the pants improvement.
     
  4. techg8

    techg8 The BS GS

    camshaft, dual exhaust, and have the original Quadrajet and distributor rebuild/performance tuned.
     
  5. matt68gs400

    matt68gs400 Well-Known Member

    5C5A6805-4A7D-496C-ABFD-F07924A4E712.jpeg
    You can get an extra 10-12 HP by modifying your intake manifold
     
  6. matt68gs400

    matt68gs400 Well-Known Member

    I shaved off about 0.2 seconds by putting in a torque converter from Jim Weiss.
     
  7. BuickV8Mike

    BuickV8Mike SD Buick Fan

    Matt, Can you feel the difference?
     
  8. matt68gs400

    matt68gs400 Well-Known Member

    Yes for the torque converter. No for the manifold. Hope to test it at the track in a couple weeks.
     
  9. BuickV8Mike

    BuickV8Mike SD Buick Fan

    How are the ported heads coming?
     
  10. matt68gs400

    matt68gs400 Well-Known Member

    I will say also that stepping up to 2.5” dual exhaust with good flowing mufflers rather than stock dual exhaust with crappy muffflers also helped me shave another 0.2 seconds off my quarter mile.
     
  11. Philip66

    Philip66 Well-Known Member

    Hey JPF,
    I was just wondering if your rear gears or whole rearend had been changed?
    Reason I ask is the standard GS 455 ratio was like 2:92:1
    Could have been a 3:08 but not usually a 3:42. I’m not trying to give you a hard time, because changing to a 3:42 or 3:73 can make a huge difference when going from the original 2:92.
    And I 2nd what Matt said about one of JW’s converters! You can absolutely feel a difference when you mash it, but it feels totally normal when cruising. No mushy feeling when part throttle cruising.

    Post some pics of your car, show us what you’re working with.
    We all love to see pics!

    Welcome aboard and good luck!
     
  12. Jpf

    Jpf Member

    On the EFI, just looking for reliability, not so much performance. I will be replacing the converter so an upgrade will be done. Really hate to lower compression ratio. As near as I can tell by turning the yoke it is about a 3.42? Just shy of 3.5 turns for one on the axles. Compression check gave 151 to 161psi, not sure what it should be. Car seems unmolested and has not been apart before I scattered it. Found it to have the F41 suspension package as well. Already has new 2.5" duels. Will do oil mods while freshening up the motor. Chassis and suspension are first, then drive train. Taking the frame for dipping to eliminate rust next weekend I hope. Hoping to not rebore, but we'll see when I get to the engine. Have noticed they're very proud of Buick parts. Car is very solid after replacing both full quarters. Minor floor rust. Budget can be flexible and can do most work myself. Thanks for the responses. I really don't know anyone who knows these Buick.
    JPF
     
  13. Jpf

    Jpf Member

    Forgot the pics. Built the rotisserie for a couple hundred bucks. Well worth the effort.
     

    Attached Files:

    matt68gs400 likes this.
  14. matt68gs400

    matt68gs400 Well-Known Member

    I have 3.31 gears. It’s a good compromise. Too high and it’s sucks driving on the highway too long.

    If you are rebuilding the motor a cam is a must.

    As for EFI, a rebuilt carburetor from some of the board members will be very reliable. And you will be much money ahead over an EFI.
     
    pbr400 likes this.
  15. matt68gs400

    matt68gs400 Well-Known Member

    For me? Haven’t started. Just got the new manifold on. Thinking head porting this fall or next spring. I’m going low buck and very slowly with kids taking most of my time.
     
    BuickV8Mike likes this.
  16. Jpf

    Jpf Member

    Matt68gs,
    Do you have a close up of the modified intake? I'm pretty good at copying things with a good enough look at it. That's how I built my rotisserie. Don't want to ruin a good intake. Still early for engine up grades, but for future reference. With the 3.31 gears what rpm at say 60 mph? Found an old gas mileage log in the glove box averaging 9.5 mpg. I don't expect it to get better.
     
  17. rkammer

    rkammer Gold Level Contributor

    You don't have to reduce the compression to run pump gas. If you port the heads a little and run the right cam, you can run up to 10.5 to 1 compression with no problem. Total timing should also be held to 35 deg. or less at full advance. The key to running high compression with today's pump gas is to select the cam with enough overlap to keep dynamic compression below about 8.0 to 1 even though static compression calculates to over 10 to 1.

    You should be able to reach your 400 HP goal with the right cam and some head-work on the stock iron heads. You can do it with stock manifolds too. The original '70 Stage 1 was rated at 360 HP with the factory cam but, really had 400+ with just basic tuning.
     
    matt68gs400 likes this.
  18. matt68gs400

    matt68gs400 Well-Known Member

    FFC1CC34-A8B9-484E-8927-2E49A2B22A5B.jpeg 32397225-17FE-4236-A72C-A84CEF3CF1B8.jpeg ACD996EB-83DB-4F38-B13E-EF5EFE7C3B67.jpeg
    The first one is from someone else
     
  19. matt68gs400

    matt68gs400 Well-Known Member

    Don’t grind off the bumps on the bottom.
     
  20. Jpf

    Jpf Member

    Thanks for the pics. Should be no problem to do. What rpm range is this mod targeted for. I tend to be conservative on engine abuse. Try to keep so much metal below 5500 rpm. Would the cam come from T/A Performance?
     

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