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

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

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 :thumbs:

Use a large steel ball bearing and a powerful magnet to get the dent out.

:iagree::iagree: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

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

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?

Just curious..are your AFRs straight or angle plug? Pics of the dent and clearances would be nice...

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

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

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!! :thumbs::thumbs::cheers: I did not know that:flag:

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

straight plug-I'll see if I can get a photo

who does this-muffler shop?

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.

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