Go Back   Corvette Forum > C3 Corvettes, 1968 - 1982 > C3 Tech/Performance
Sign in using an external account
Register Forgot Password?
Register Search Today's Posts Mark Forums Read FAQ Vendor Directory
Search
C3 Tech/Performance
V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette Sponsored by
VBP

Welcome to Corvetteforum.com!
Welcome to Corvetteforum.com.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join Corvetteforum.com today!


Corvette Store
 
 
C7 Parts & Accessories
C6 Parts & Accessories
C5 Parts & Accessories
C4 Parts & Accessories
C3 Parts & Accessories
C2 Parts & Accessories
C1 Parts & Accessories
Wheels & Tires
Sponsored Ads
 
 
Vendor Directory
  
Reply
 
 
 
 
Thread Tools Search this Thread
Old 08-18-2014, 04:04 AM   #1
brian76
CF Senior Member
 
brian76's Avatar
 
Member Since: May 2006
Location: Columbus Ohio
Default 1 5/8" versus 1 3/4" headers

I have a set of 1 3/4" inch Hooker Competition Jet Hot coated headers on my vette. One of the primary tubes has a dent in it about the size of a quarter, and is about 1/4" deep. I noticed that when I ran it at 3000rpm for awhile, that the tube would turn red while the others didn't. I figured it was probably restriction because of the dent. Anyway, I was looking around for another set of Hookers would cost about $750 with the same size primaries. Hooker makes another set that the only difference is that the primaries are 1 5/8", and costs over $ 300 less. My question, is there really any difference in performance for a street car between the two? There' a difference of 1/8" between them. If I can't notice a difference when I drive it why spend alot more? My motor is a 383 with 9.7 comp., RPM airgap intake, AFR 195 street heads, 750 Holley annular booster carb, and a Comp Cams solid cam .530 lift and 236/242 at .050 with 1.6 1 rockers. I heard that the smaller primaries will make more torque down low but top end may suffer. Help me out here-thanks
brian76 is offline   Reply With Quote
Old 08-18-2014, 07:10 AM   #2
Lt1er
CF Senior Member
 
Lt1er's Avatar
 
Member Since: Dec 1999
Location: Reno nevada
Default

A small dent is only a small impedance to flow. So I have know idea why it appears to run hotter than other cylinders. For a header to glow without a motor load is usually caused by excessively rich A/F ratio causing fuel burning going out the pipes.

With no load my pipes never glow.

You can't use smaller primary dia. Your AFR heads have big diameter exhaust ports. So adjust your primary jets, adjustment screws, and or drill your primary throttle blades to get the proper a/f ratio
Lt1er is offline   Reply With Quote
Old 08-18-2014, 01:45 PM   #3
MotorHead
CF Senior Member
 
MotorHead's Avatar
 
Member Since: Apr 2000
Location: Never argue with Morons. If you do, you'll lower yourself to their standards, and they'll win, based on experience !!!
Default

Figure out why it is glowing first, I have had much bigger dents in headers and the pipe doesn't glow, no need to spend money on new headers only to find out the same un-dented pipe glows red. It is either a lean condition in that particular cylinder or un-burnt gas loading up in the pipe, take them off and check the gasket to see if there it any sign there first
MotorHead is offline   Reply With Quote
Old 08-18-2014, 03:48 PM   #4
MIKE80
CF Senior Member
 
MIKE80's Avatar
 
Member Since: May 2005
Location: East Amwell NJ
Default

Use a large steel ball bearing and a powerful magnet to get the dent out.
MIKE80 is offline   Reply With Quote
Old 08-18-2014, 04:06 PM   #5
7t9l82
CF Senior Member
Support Corvetteforum!
 
7t9l82's Avatar
 
Member Since: Oct 2010
Location: melbourne florida
Default

Quote:
Originally Posted by MIKE80 View Post
Use a large steel ball bearing and a powerful magnet to get the dent out.
or just force the ball past it.or have a body shop weld a couple pins for a dent puller on it.but that would screw up your jet hot
7t9l82 is offline   Reply With Quote
Old 08-18-2014, 06:18 PM   #6
427Hotrod
CF Senior Member
 
427Hotrod's Avatar
 
Member Since: Jan 2000
Location: Houston, Tx
Default

Generally a "good" 383 such as yours will like 1-3/4" headers. If you never rev it much you'd probably not notice much in normal driving if you could get them to seal to the heads.

As mentioned I'd fix the dent and then figure out why it's turning red. Something is going on with it that needs fixed.

JIM
427Hotrod is offline   Reply With Quote
Old 08-18-2014, 06:39 PM   #7
brian76
CF Senior Member
 
brian76's Avatar
 
Member Since: May 2006
Location: Columbus Ohio
Default

Quote:
Originally Posted by MIKE80 View Post
Use a large steel ball bearing and a powerful magnet to get the dent out.
I have never heard of that! Where can I get a magnet that powerful? Dent is right in the bend. Car does run extremely rich-burns my eyes in the garage with the door open obviously. On regular Holleys, the normal amount of turns out on the metering blocks are 1 1/2 and go from there. On annular carbs, it's a whole new ball game. I called sean murphy induction who installed them, he told me to just turn them out a 1/2 turn. I did this and car still runs rich. Any ideas?
brian76 is offline   Reply With Quote
Old 08-18-2014, 08:14 PM   #8
DucatiDon
CF Senior Member
 
DucatiDon's Avatar
 
Member Since: Oct 2011
Location: Sacramento California
Default

Just curious..are your AFRs straight or angle plug? Pics of the dent and clearances would be nice...
DucatiDon is offline   Reply With Quote
Old 08-18-2014, 08:33 PM   #9
427Hotrod
CF Senior Member
 
427Hotrod's Avatar
 
Member Since: Jan 2000
Location: Houston, Tx
Default

Install larger idle air bleeds to lean it out some. How much vacuum does it have?

Worst thing would be to cut out that section of tubing and weld in a new piece and have that header recoated. I've actually heated them up and worked a dent out of it and used high heat paint that matched very well to the coating and no one noticed.

JIM
427Hotrod is offline   Reply With Quote
Old 08-18-2014, 09:21 PM   #10
cuisinartvette
CF Senior Member
St. Jude Donor '05
 
Member Since: Oct 2004
Location: Valencia Ca.
Default

x2 on the air bleeds most overlook this

Turning the screws out will make it more rich.

Running super lean can burn your eyes too
cuisinartvette is online now   Reply With Quote
Old 08-18-2014, 09:31 PM   #11
7t2vette
The ORIGINAL and bestest
Toronto Events Coordinator
Support Corvetteforum!
 
7t2vette's Avatar
 
Member Since: Oct 2000
Location: Toronto
Default

Quote:
Originally Posted by brian76 View Post
Car does run extremely rich-burns my eyes in the garage with the door open obviously.
Just an FYI:

An engine running rich emits too much carbon monoxide (CO) but generally doesn't emit much hydrocarbon (HC). Since carbon monoxide is colorless and odorless, it doesn't burn your eyes. The lack of oxygen prevents the CO from becoming CO2, but the hydrocarbon does oxidize.

An engine running too LEAN has a lot of (HC) going out the tailpipe causing your eyes to water and burn.
7t2vette is offline   Reply With Quote
Old 08-18-2014, 10:04 PM   #12
pauldana
CF Senior Member
Support Corvetteforum!
 
pauldana's Avatar
 
Member Since: May 2003
Location: palmdale ca
Default

Quote:
Originally Posted by 7t2vette View Post
Just an FYI:

An engine running rich emits too much carbon monoxide (CO) but generally doesn't emit much hydrocarbon (HC). Since carbon monoxide is colorless and odorless, it doesn't burn your eyes. The lack of oxygen prevents the CO from becoming CO2, but the hydrocarbon does oxidize.

An engine running too LEAN has a lot of (HC) going out the tailpipe causing your eyes to water and burn.

cool information!! I did not know that
pauldana is online now   Reply With Quote
Old 08-18-2014, 11:59 PM   #13
brian76
CF Senior Member
 
brian76's Avatar
 
Member Since: May 2006
Location: Columbus Ohio
Default

Quote:
Originally Posted by cuisinartvette View Post
x2 on the air bleeds most overlook this

Turning the screws out will make it more rich.

Running super lean can burn your eyes too
what do you mean by x2 on the air bleeds? when turn the metering blocks 1 1/2 turns, it will stall before it kicks in
brian76 is offline   Reply With Quote
Old 08-19-2014, 12:02 AM   #14
brian76
CF Senior Member
 
brian76's Avatar
 
Member Since: May 2006
Location: Columbus Ohio
Default

Quote:
Originally Posted by DucatiDon View Post
Just curious..are your AFRs straight or angle plug? Pics of the dent and clearances would be nice...
straight plug-I'll see if I can get a photo
brian76 is offline   Reply With Quote
Old 08-19-2014, 12:03 AM   #15
brian76
CF Senior Member
 
brian76's Avatar
 
Member Since: May 2006
Location: Columbus Ohio
Default

Quote:
Originally Posted by 427Hotrod View Post
Install larger idle air bleeds to lean it out some. How much vacuum does it have?

Worst thing would be to cut out that section of tubing and weld in a new piece and have that header recoated. I've actually heated them up and worked a dent out of it and used high heat paint that matched very well to the coating and no one noticed.

JIM
who does this-muffler shop?
brian76 is offline   Reply With Quote
Old 08-19-2014, 02:18 AM   #16
Lt1er
CF Senior Member
 
Lt1er's Avatar
 
Member Since: Dec 1999
Location: Reno nevada
Default

changing air bleeds is better off left to a quality carb shop with all the equipment. drilling the primary throttle blades induces a leaner condition and will make the idle adjustment screws functional.

Just look it up.
Lt1er is offline   Reply With Quote
Old 08-19-2014, 02:43 AM   #17
427Hotrod
CF Senior Member
 
427Hotrod's Avatar
 
Member Since: Jan 2000
Location: Houston, Tx
Default

Quote:
Originally Posted by brian76 View Post
who does this-muffler shop?
A good one maybe. Another option would be anyone that does circle track racer building in the area. They tear up lots of headers in a season and fix them regularly. You can buy the tubing as prebent mandrel and can cut/fit it in place. Then anyone with a TIG could weld it real pretty.

JIM
427Hotrod is offline   Reply With Quote
Old 08-19-2014, 02:43 AM
 
Go Back   Corvette Forum > C3 Corvettes, 1968 - 1982 > C3 Tech/Performance
Reload this Page 1 5/8" versus 1 3/4" headers
 
 
 
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Help with two exhaust routes GT's 78 C3 Tech/Performance 7 03-05-2014 09:17 AM
Bent A Header Tube brian76 C3 Tech/Performance 2 02-24-2013 03:17 PM
1 3/4" or 1 7/8" primary tube headers on LS3? Turbo6TA C6 Corvette General Discussion 20 02-15-2012 06:29 PM
Stepped headers MotorHead C3 Tech/Performance 17 10-16-2009 04:21 PM
Lingenfelter headers Chief Muktar C4 Tech/Performance 9 06-12-2002 03:27 PM



Thread Tools Search this Thread
Search this Thread:

Click for Advanced Search

Posting Rules
You may not post new threads
You may not 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 Off
Pingbacks are Off
Refbacks are Off

Forum Jump


All times are GMT -4. The time now is 01:02 AM.


Emails & Password Backup