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Thread: 455 owner needing help

  1. #1
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    Post 455 owner needing help

    Hi everyone,

    My name is Colin, and I have a 1946 GMC pickup that has a 455 Buick. The motor is I think a 74 or a 75, and had only 80,000 km before I got it. Anyways, I've put 2500km on it now, but I broke a valve spring and am looking for a valve spring and rocker retainer up here in Edmonton, Alberta. I'm having trouble finding parts in Edmonton, and so that led me to this forum to try and find some help.

    My engine has a comp 268H cam, new timing chain and gears, Edelbrock Performer intake, and Demon 650 carb. It ran really well until I broke that spring on #1 cylinder!

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    I am not much help for you up there on the valve spring location, but should be available to be ordered from just about any general parts source. try Rockauto.com

    Also want to say, for you to enjoy your buick 455 power a little more, toss the 650cfm carburetor and get a quadrajet built for the 455. Buicks like air, they are Buicks and not chevy or other brand. The factory placed an 800 cfm carb on that engine, so you are choking it down now, especially with the added cam.
    86 GN, all factory options, engine build in progress
    72 Skylark Convertible, 462, TH 400
    72 GSX Clone 464, TH400, 3:42. 10.71 @126mph best

    We build GM carburetors and specialize in custom built Quadrajets

    www.quadrajetpower.com
    mark@quadrajetpower.com

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    Thanks for the comments. I since found out my heads (and motor) are 1975. I found a guy fairly close to me that has a collection of 455 parts. I should be able to get a set of 1972 heads from him, maybe even a set of *gasp* 1970 heads! He's the only guy that I've been able to find parts from, otherwise I'll be ordering the parts I need from TA or Rockauto. Not that I need more power, but if I need the guide machined on my 1975 heads, I might as well do it to smaller CC heads.

    I must respectfully disagree with your comments on the carb. My 455 is not a race engine, it's a nice mild cruiser engine in a hot rod. I've put 2500 KM's on it now, and it's very happy with the 650 CFM that it's getting. Why do you say the Buick needs more air than anything else? Air flow is air flow, regardless of the engine it's on. 454's came with big carbs too, and they're plenty happy with a 650, I'm curious why you say a Buick won't be? In fact my 455 is very crisp with the 650, throttle response is excellent. The thinking on carbs has changed in the last few years at least in this neck of the woods, especially with smoother air flow in newer carbs, many engines run much better with less CFM than was previously thought to be necessary. I would like to know the thinking behind your comments. I'm not looking for an arguement, just looking to learn something if I can.

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    Ok Colin, you can disagree on cfm if you want.

    first rule I learned when I started working on Buicks was to toss out all my Chevy building knowledge. Buick is a complete different engine design and can't be built like a Chevy. I don't think that's a bad thing myself. But, what works on a Chevy doesn't work on a Buick. Cubic inch isn't just cubic inch. The design of the Buick head is such that the airflow volume is much greater. It needs more air to be efficient. I am not an engineer and cannot give you specifics, but there are many articles that can explain to you. That is why the Buick division had Rochester design and build an 800 cfm quadrajet for all 455 engines from 71 to 76. Not just the race cars. No Chevy quadrajet was this large. Chevy design didn't need the air flow the Buick did. Pontiac ram air 455's got the big carb, and even had other modifications.

    yes, in the older days, I drag raced big block Chevys with a 650 carb. Plenty of fuel for that engine. Not near enough for a big block Buick. In carbs, it is better to be too small, than too large for just cruising. It feels good with smaller carb because you aren't needing more air for mild driving. If, however, you ever want to feel the potential of the big block Buick then give it the air it wants.

    10's of thousands of Buicks can't be wrong. And the group I learned from build and drive the fastest Buicks on the planet.

    so if you want more information, do some research on the head design and air flow characteristics on the Buick. But make sure it is a Buick person you study from.
    86 GN, all factory options, engine build in progress
    72 Skylark Convertible, 462, TH 400
    72 GSX Clone 464, TH400, 3:42. 10.71 @126mph best

    We build GM carburetors and specialize in custom built Quadrajets

    www.quadrajetpower.com
    mark@quadrajetpower.com

  5. #5
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    Quote Originally Posted by carmantx View Post
    Ok Colin, you can disagree on cfm if you want.

    first rule I learned when I started working on Buicks was to toss out all my Chevy building knowledge. Buick is a complete different engine design and can't be built like a Chevy. I don't think that's a bad thing myself. But, what works on a Chevy doesn't work on a Buick. Cubic inch isn't just cubic inch. The design of the Buick head is such that the airflow volume is much greater. It needs more air to be efficient. I am not an engineer and cannot give you specifics, but there are many articles that can explain to you. That is why the Buick division had Rochester design and build an 800 cfm quadrajet for all 455 engines from 71 to 76. Not just the race cars. No Chevy quadrajet was this large. Chevy design didn't need the air flow the Buick did. Pontiac ram air 455's got the big carb, and even had other modifications.

    yes, in the older days, I drag raced big block Chevys with a 650 carb. Plenty of fuel for that engine. Not near enough for a big block Buick. In carbs, it is better to be too small, than too large for just cruising. It feels good with smaller carb because you aren't needing more air for mild driving. If, however, you ever want to feel the potential of the big block Buick then give it the air it wants.

    10's of thousands of Buicks can't be wrong. And the group I learned from build and drive the fastest Buicks on the planet.

    so if you want more information, do some research on the head design and air flow characteristics on the Buick. But make sure it is a Buick person you study from.
    Well I found a set of rebuilt heads with only 65KM on them. I got a good deal on them, and I'll probably still rework my originals so I have spares. I ended up buying a couple springs from RockAuto, and they should be here today. The heads I bought have new rocker shafts and everything, so it's pretty cool. They're still 75-76 heads, but I don't need much more power for the cruiser that it is. And the torque is already there so it doesn't matter. Set up as it is it will annihilate the tires and move the truck right along.

    The CFM I chose wasn't based on "Chevy Building Knowledge" or just a wild guess. I am an engineer and know about combustion theory. Not that this matters though, since the calculation is simple. Yes, head design varies, but in the end you have a certain combustion volume, air+Fuel in, and exhaust out. If I were revving the engine above 5000 RPM I would probably want a bigger carb. However, all that comes in to it is your engine size, your max rpm, and your volumetric efficiency. This is what makes internal combustion engines so simple. If I were revving at 6000 RPM with 100% volumetric efficiency (not likely), then 800 CFM is perfect. However, since this is a street engine capped at 5000 RPM, 650CFM is more than enough, assuming about 85% volumetric efficiency. You're talking about race engines, so you are right, but for street engines I'll stick to combustion theory and the calculations.

    In the 70's when these engines were built, the thinking was a bigger engine needs a bigger carb, which isn't true. Just because it came with an 800 in 1975 doesn't mean it needs that much carb for street use. Seeing your engines you run, I have no doubt that you need more CFM. For my mild street build though, a bigger carb will not help me. This engine runs amazing on a 650, and it's exactly what it needs.

    Thanks for the help and input. If you have some of those articles you suggest to read please send them along to me.

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    Ok, I guess if you have what you want you don't need any help.

    I personally like the fact that a quadrajet can deliver the cfm the engine desires. It's not all or none, like most others. With the small primaries and design, they were efficient for fuel economy by delivering only what the engine is capable for using.

    Do what you want, I won't tell you any different. I was only trying to share some expertise to someone that asked for help, my bad in this case.
    86 GN, all factory options, engine build in progress
    72 Skylark Convertible, 462, TH 400
    72 GSX Clone 464, TH400, 3:42. 10.71 @126mph best

    We build GM carburetors and specialize in custom built Quadrajets

    www.quadrajetpower.com
    mark@quadrajetpower.com

  7. #7
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    Quote Originally Posted by carmantx View Post
    Ok, I guess if you have what you want you don't need any help.

    I personally like the fact that a quadrajet can deliver the cfm the engine desires. It's not all or none, like most others. With the small primaries and design, they were efficient for fuel economy by delivering only what the engine is capable for using.

    Do what you want, I won't tell you any different. I was only trying to share some expertise to someone that asked for help, my bad in this case.
    I'm fine with you giving help, and I do appreciate it. However, when you haven't asked what I use the truck for, my gearing, tire size, etc., then it's a little off base to assume the carb is way too small. I asked where to find parts, not anything else. I had another reputable Buick shop tell me that they've done dyno tests on a stock stage one with 650, 750, and 850 Holleys and there was no change in power between them. If I was running a high performance engine at the strip then I would be inclined to agree with you. I'm running a nearly stock engine with open-chamber heads in a street truck that rarely sees 3000-3500 RPM. I need the low end power and throttle response that come with the smaller carb.

    Thanks for your help.

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