Block Hugger Headers vs. Stock Exhaust Manifolds - Impala Tech
Performance Our High Performance Area

 
LinkBack Thread Tools
post #1 of 9 (permalink) Old 07-09-2015, 01:39 AM Thread Starter
Senior Member
 
Join Date: Jul 2011
Location: Washington
Posts: 203
 
Block Hugger Headers vs. Stock Exhaust Manifolds

So recently I was thinking about switching out my stock exhaust manifolds and slipping in some block hugger headers in it's place for an easy installation (hopefully). I'm also going to switch out my stock mufflers and put in glasspacks or glasspack like pipes. I'm aiming for a better exhaust flow and more horsepower in the lower/street RPM range.

I'm just curious, how much of a difference is there in between block hugger headers and exhaust manifolds? They do seem like they're closely related.

I've been browsing Summit and they have a lot of choices for an application like mine with the collector pointed straight down and just bolts into the exhaust pipe. I just need to make sure I get the right measurements.

Edit: I was looking at these normal Hedman Street Headers a long time ago and kept it on my Summit wishlist. But they would require me to go to a mechanic since I don't have a welder to put on a new flange: http://www.summitracing.com/parts/hed-68170

1967 Chevrolet Impala 4 door "post" sedan
327 5.4L V8 - 3-speed TH350

Last edited by Classiccarman; 07-09-2015 at 01:58 AM.
Classiccarman is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old 07-09-2015, 08:22 AM
Senior Member
 
Join Date: Jul 2008
Location: Michigan
Posts: 155
 
I can't say for sure, but generally speaking don't count on any aftermarket part "Just Fitting".
sz0k30 is offline  
post #3 of 9 (permalink) Old 07-09-2015, 08:49 AM
Moderator
 
Join Date: Jan 2006
Posts: 12,376
 
There isn't much if anything to be gained on the street (below 5,100 RPM) by using tubular headers. A member put his new 383 on the dyno and tried both shortly headers and two and a half inch (high performance and Corvette manifolds) Ram's Horn style on his engine and the results are listed below:



As you can see there is not much to be gained (five to seven horsepower), money to be lost and the joys of exhaust leaks abound with tubular headers. Above 5,100 the stock exhaust is done and tubular headers rapidly pull away from the stock exhaust in power. If you have a tach you know where your motor spends it's life while cruising on the street. It is generally below 2,400 RPM. unless you have a fairly steep rear gear ratio.

Big Dave
Big Dave is offline  
 
post #4 of 9 (permalink) Old 07-09-2015, 05:08 PM Thread Starter
Senior Member
 
Join Date: Jul 2011
Location: Washington
Posts: 203
 
@ sz0k30 Yeah that's noted.

@ Dave Hmmm...thanks for that. I was reading articles on this beforehand and there was mixed receptions on header benefits. Some said that shorty headers are for lower rpm's and long headers are for racing and higher rpm's. And some also said that they're a waste of money and should only be used for racing.

I'll keep the manifolds and just switch out the stock mufflers for something else, probably glasspacks.

1967 Chevrolet Impala 4 door "post" sedan
327 5.4L V8 - 3-speed TH350
Classiccarman is offline  
post #5 of 9 (permalink) Old 07-10-2015, 07:48 PM Thread Starter
Senior Member
 
Join Date: Jul 2011
Location: Washington
Posts: 203
 
Although an unrelated question, will a 90 degree exhaust pipe angle affect exhaust flow? I'm trying to figure out how the glasspacks will fit in the set up when the stock muffler inlet and outlets were offset. I actually might have some 90 degree angles already in the set up. I'll have to take a closer look.

1967 Chevrolet Impala 4 door "post" sedan
327 5.4L V8 - 3-speed TH350
Classiccarman is offline  
post #6 of 9 (permalink) Old 07-11-2015, 07:55 AM
Moderator
 
Join Date: Jan 2006
Posts: 12,376
 
In terms of fluid friction, any sharp bend will increase the resistance to laminar flow. It won't stop the fluid from leaving, but it really reduces the flow rate which is part of the poor performance offered by a BBC head compared to a modern computer designed SBC head. The exhaust port on the BBC has to make a one hundred and twenty degree bend to enter the exhaust manifold (which is a log type that doesn't flow for beans).

Two forty five bends separated by a short straight beats one short ninety degree bend in water flow as well as in gas flow. The smoother (larger the radii) the bend the better. Things like a spring flex radiator hose really restrict water flow compared to a smooth formed hose.

Big Dave
Big Dave is offline  
post #7 of 9 (permalink) Old 07-13-2015, 05:17 PM Thread Starter
Senior Member
 
Join Date: Jul 2011
Location: Washington
Posts: 203
 
Well in terms of the mufflers. I'm going to try some angled Cherry Bomb glasspacks. I just need to get the right degree measurements, cut the piping to the right length, and it should fit right into the slot the old stock muffler was in. This way I won't have to worry about extra piping and angles to get everything to fit.

1967 Chevrolet Impala 4 door "post" sedan
327 5.4L V8 - 3-speed TH350
Classiccarman is offline  
post #8 of 9 (permalink) Old 07-18-2015, 12:18 PM Thread Starter
Senior Member
 
Join Date: Jul 2011
Location: Washington
Posts: 203
 
What about the block hugger headers vs the stock manifolds in terms of gas mileage? Or is that similar results to horsepower statistics?

1967 Chevrolet Impala 4 door "post" sedan
327 5.4L V8 - 3-speed TH350
Classiccarman is offline  
post #9 of 9 (permalink) Old 07-18-2015, 12:33 PM
Moderator
 
Join Date: Jan 2006
Posts: 12,376
 
Mileage is not a word associated with a heavy V8 powered American car. These cars were built back when gas prices were running 28¢ to 32¢ a gallon for 104 octane leaded gas.

Driving style and your final gear ratio will affect gas mileage a lot more than your peak horsepower numbers will. Once again back in the day, the Shell answer man confirmed that to obtain the best mileage with a V8 powered lead sled, the best way was to accelerate as fast as you can without slipping the tires to get the car into high gear as soon as possible; then let off the gas and drive as if you had an egg between your foot and the gas pedal (this was back in 1973 during the first gas shortage due to the OPEC oil embargo).

Big Dave
Big Dave is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Impala Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome