Low budget intake and exhaust mods.

Discussion in 'Street/strip 400/430/455' started by fflintstone, Dec 22, 2012.

  1. fflintstone

    fflintstone former master curmudgeon

    I have been out of Buicks for 19 years and am just getting back in.
    My previous Buick was a 69 skylark GS convertible. It had a NOM 350 in it and a 2:56 rear axle.

    I built a mild 455 for it. I used a factory replacement block, 1971 heads, an 800 CFM Q-jet, a 268 duration comp cam, Rhodes lifters, MT repro headers and an edelbrock performer intake. I was pleased with the power output. I ground down the governor weights on the Trans to raise the shift points on the TH400. The 2.56 rear end was a bummer on the strip but offered 19 mpg in a car with a passing gear that pulled like a freight train. The late 1980’s were fun for me. At the time TA performance was the only game in town, Poston was just starting up. from what I gather now Poston is long gone.

    Fast forward to 2012. I am recently reemployed after being out of work for 3 years. I used to work in automotive engineering doing computer aided design. I work in computer aided design but make 2/3’s of my previous wage. My build budget is nonexistent. I am now an old man and a first time father of a young son. I want to build an engine with him.

    We picked up a 75 LeSabre convertible at a good price. We picked up a 430 motor to build for it. The car will never see a drag strip, and I don’t like buying tires so no holeshots. I do however drive fast and like to pass people. I picked up another comp cams 268 duration cam at a discount. I plan on doing a very restrained port job (blending the valve guide boss), and polish the combustion chamber.

    To my questions, first is exhaust.

    My motor did not come with exhaust manifolds. Headers are expensive, and I am not seeing any deals on used ones, but it seems criminal to PAY for stock manifolds although I am sure I can find some cheep. (rather put money towards headers)
    Are big block manifolds the same? Is there any year that flow better than another? If I look for used headers are there any brands to stay away from? I am a decent welder and can repair just about any damage, but building them from scratch seems like way too much work.

    Next question intake.

    Given my cam choice and the essentially stock heads is there much of a difference between a stock cast iron intake and an edelbrock B4B? (I assume there are no other dual plane manifolds out there). I would prefer imperial data, (IE dyno results) over a bench racing WAG. Is there anything that can be done to a 430 intake to improve it? is port matching really worth the effort? I do have much more time than money but little of each.
  2. stubnosebrock

    stubnosebrock Well-Known Member

    When you say big block manifolds, a 430 is a big block Buick. So manifolds from a 400/430/455 will all bolt on. As far as any flowing better than the other, I have heard somewhere that a 430 with big port heads had better manifolds. This may not be true, so hopefully someone else will chime in. As far as headers, Im not sure what will fit your Lesabre, and my guess is that your choices are limited. A bodies are easier to find used stuff for. As far as intakes, the only dual planes choices you have as a Performer or B4B. From what ive read, the gains wont be much over your stocker. The B4B is probably a better out the box intake. Either one will save you weight though, and thats free horsepower in itself. Keep your eyes open for used manifolds on here, or post up a wanted add. They do pop up.
  3. flynbuick

    flynbuick Guest

    67 exhaust manifolds are the best year for donors. For this year only there was a more free flowing design on the driver's side. After 67 the drivers side went to a more restrictive log design.
  4. doc

    doc Well-Known Member

    you can do my Doc dual plane mod on the intake and then port match the exhaust manifolds and then check the exhaust system that is on the car now.... Buick was bad to reduce the diameter of the pipe coming out of the mufflers... that is very restrictive.... make sure the pipes are the same size or bigger all the way from the exhaust manifolds to the back bumper.... and get rid of any resonators that it may have....
    also get rid of any baffels inthe air cleaner... and,,,,
    recurve the distributer for a better advance.....:Brow::Brow:
  5. pmuller9

    pmuller9 Well-Known Member

    Here is a snippet from a recent post from JW concerning stock exhaust manifolds versus shorties versus full length headers.

    Full Post:

  6. stubnosebrock

    stubnosebrock Well-Known Member

    Im pretty sure thats what I remember hearing now that you say that.
  7. fflintstone

    fflintstone former master curmudgeon

    A 2 ” exhaust is a given. As is a recurved factory HEI distributor. I have read some great info here already. My best friend was supposed to pick up a B4B for me from the metro Detroit craigslist for $100. I told him it was a screaming deal, and to go get it but he screwed around and someone else got lucky. If I knew he was going to screw around I would have driven the 3 hours each way to get it.

    I will be installing a large universal open element air cleaner. At some point it will be enclosed and drawing outside air.

  8. doc

    doc Well-Known Member

    check out the doc dual plane mod... some of the guys have done this on qjet manifolds and i hear that they work good.... just like the nailhead manifolds....
  9. fflintstone

    fflintstone former master curmudgeon

    I did look at what you did, and also looked for someone who did it on a later engine. didn't see anyone do a later engine but it makes sence to me. might be a cheap way to go. virtualy every aftermarket DP manifold has the open plenum between the primary and secondary.
  10. doc

    doc Well-Known Member

    When I did the first one,,,,I did not know how much difference it would make... so,, as a experiment, I did the mod, did not change anything else,,,nothing,,,, and put it back together and when I road tested the car I was totally amazed at the difference...seat of the pants difference.... some have reported .2 sec on the strip and a few more than that....and the gas mileage did not change......between the ddp mod and recurving the dist. and opening up the exhaust side and if you put it,,, the cold air intake aircleaner you will pick a lot of cheap power... that will not go away, with time.....
    I already had my tools, but, the ddp mod cost me about $5.....i did it on a nailhead 425 and reused the intake gaskets... you can do that if your carefull....
    BTW,,, I dont reccomend that you block the intake heat risers at all.... the heat is neccessary to vaporize the cat pee gas.....
  11. fflintstone

    fflintstone former master curmudgeon

    Thanks for all the info. This is just me but working in engineering all my life, I tend to be skeptical of stuf like .2 second claims. expecialy with modern throtle body spacers. IMO if a 1" chunk of aluminum made any diferance what so ever, the factory would make the intake track 1" longer.
    On a carburated engine then things are different.
    This is the great thing with al gore inventing the internet, people can exchange what worked for them.
  12. doc

    doc Well-Known Member

    OK,,,, Dont do it then.....
  13. Rob Ross

    Rob Ross Well-Known Member

    Although the LH 67 makes the most hp, it's not worth it unless you alread have one. I did the dyno comparison here, http://www.buickperformanceclub.com/Exhcompare.htm On the same day at the dyno we also did the intake mod where the stock intake looks like an dual plane, I'd have to look up the data but it was worth approximately 12 hp but helped on torque considerably. I've run exhaust manifolds for years and really like them. True headers may make more hp but as I said, I like manifolds. I'm in SE MI and have a set of exhaust manifolds I'll give you if you want. They do have broken bolts at the flange where the exhaust pipe connects but they are yours if you want them.
  14. fflintstone

    fflintstone former master curmudgeon

    No I want to try it, as I said most every aftermarket DP intake is like that. I didnt mean to sound like I dont think it will work, just that seat of the pants is not a good judge, and that on modern fuel injected engines, people like to think they got some value out of a $50 chunk of aluminum that did nothing but lighten there wallet.

    Rob Ross offers up some imperical data to back up the claim.

    ---------- Post added at 06:10 PM ---------- Previous post was at 06:02 PM ----------

    I will take you up on the manifold offer, but I will keep looking for headers too.
    I would love to see the dyno results on the intake mod, particulary torque from say 1,500 to 3,000.
    thanks for the link and I will check it out.
  15. Rob Ross

    Rob Ross Well-Known Member

    See attached. Where it says "open plenum", that's a stock intake made to look like a dual plane.

    Attached Files:

  16. fflintstone

    fflintstone former master curmudgeon

    wow 15+ ftlb of torque from 3,000 to 5,000! sign me up!
  17. Mark Demko

    Mark Demko Well-Known Member

    No need to use Rhodes lifters with a mild cam like the Comp 268. Any pics of the '75 LeSabre convertible? Im partial to 'em, it was my first car.
  18. fflintstone

    fflintstone former master curmudgeon

    unfortunately I have no god pics. I have bad luck with cheap digital cameras, I go thru them like some women go thru pantyhose.

    here is a bad pic.


    the original CL ad


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