427 bbc conversion - Impala Tech
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post #1 of 7 (permalink) Old 03-31-2018, 07:56 PM Thread Starter
 
 
Join Date: Mar 2018
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427 bbc conversion

I just dropped my 427 t400 in today I'm thinking of purchasing hooker 2 1/8" long tube headers. what's everyone's opinion on exhaust,I want to get the most power out of this swap. so anyone use these without having to smash them,or just use shorty. any and all info will be appreciated
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post #2 of 7 (permalink) Old 03-31-2018, 10:56 PM
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You have a 62 which means you have an X-frame. You really need to be careful about what you order as the exhaust system in an X-frame is probably the most difficult thing to make fit right without having it hanging down under the frame. I'm going with a "W" motor so I know what will work and a couple of companies make headers particularly for that application. The next gen BBC only came in 1963 impalas and was called the Mystery Motor. Less than 50 of those motors were built so the aftermarket really didn't develop for them.
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post #3 of 7 (permalink) Old 03-31-2018, 11:22 PM
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Unless you are twisting it regularly on Sunday afternoons above 6,800 RPM you do not need a tube that big with that small of a motor.

I had Hooker 2-1/8th inch primary tube, equal length competition plus headers in my 1968 Camaro RS SS that required cutting holes in the inner fenders to get half the tubes to fit inside while the other two tubes ran outside the frame rail as a bag of snakes with little room requires cutting or dimpling some thing.

On a 427 driven on the street a 1-3/4" to a 1-7/8th inch will suffice. The bigger the primary the more you give up bottom end torque to get better high end horsepower.

Big Dave
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post #4 of 7 (permalink) Old 04-01-2018, 10:44 AM
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Technically I gotta agree with Dave, a 2 1/8" primary tube is too big for what you're aiming to do and it just opens the doorway for fitment issues.

Something more along the lines of 1/ 7/8" would be way more appropriate for a good street 427cid motor. They'll be easier to find too, thus cheaper, and less fitment hassles to boot.
I can't say which headers best fit the 62 though, maybe someone will come along that has done it already.

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post #5 of 7 (permalink) Old 04-01-2018, 03:52 PM
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Can't really remember the Tube Size on my Hooker Headers, but that's was I used on my '62 with a 396. They were the type that ended under the car, not in the wheel well. They were actually 2-piece Headers. One pipe would disconnect and go through the inner fender. With these, I had to have a Custom Made Exhaust. Stock pipes just would not work. These Headers also hung low and I'm glad to be from the old school where we raised our cars up. I would hate to even drive one on a low rider. This was back in the Mid-'70's by the way.
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post #6 of 7 (permalink) Old 04-07-2018, 05:51 PM Thread Starter
 
 
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thanks guys I went with hedman 1 3/4 coated that look and fit perfect. very happy weren't to expensive but still enough. I have another issue the throttle linkage hit the rear if the motor and stays half to full throttle so I assume I'm gonna have to convert to cable. any ideas or part#
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post #7 of 7 (permalink) Old 04-07-2018, 07:04 PM
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Quote:
Originally Posted by russ75 View Post
thanks guys I went with hedman 1 3/4 coated that look and fit perfect. very happy weren't to expensive but still enough. I have another issue the throttle linkage hit the rear if the motor and stays half to full throttle so I assume I'm gonna have to convert to cable. any ideas or part#
Two issues:

Need a cable long enough to obtain full throttle, and the attachment point can not rotate. Most cables you find in a bone yard are for a Rochester QuadraJet. They won't stay in one place on a Holley carb. You have to buy for about $165 a throttle cable braket or make one out of scrap metal.

Billet Holley Bracket to mount cable
https://www.speedwaymotors.com/Holle...AaAlc3EALw_wcB

&00R4 adjustment cable bracket for above
Holley 20-119: Detent Cable Bracket Only Fits Holley 20-112 Billet Cable Bracket | JEGS

They are easy to make but look like you made it out of an old street sign (which is what I usually do).

You need to watch these videos to adjust your kick down if you have an OD or carb with an electric passing gear like a TH400 does.

Holley Throttle, Kickdown, TV Cable Brackets and Levers | JEGS

Get the adjustment wrong on a 700R4 tranny and it won't make it to the street before burning up the transmission.

Big Dave
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