1 5/8 or 1 3/4?
Thread Starter
Safety Car
Joined: Apr 2001
Posts: 4,795
Likes: 1
From: Regina Saskatchewan, Canada.
1 5/8 or 1 3/4?
I'm hung up on what to do about headers. Hedman only makes their factory side mount exhaust headers in 1 5/8. I've been asking around and people say my near 500hp combo should use 1 3/4. I think maybe it was StingrayRacing that has his signature reading ET and mph's with both 1 5/8 and 1 3/4 and I think there was like .1 mph difference. What should I do? With that amount of difference in mph it shows that the bigger headers weren't making any more hp.
Drifting
Joined: Jul 2000
Posts: 1,861
Likes: 1
From: Bremerton WA
St. Jude Donor '09
Re: 1 5/8 or 1 3/4? (Stingy74)
Go with the 1 3/4 header. If the 1 5/8 header is anything like the Accel/LPE set the collector is only like 2.5 inches round. The 1 3/4 should be a 3 inch collector to go with some nice 3 inch piping. You might as well get the right size on the first purchase. If not, you'll buy them later :)
Cory
Cory
Le Mans Master
Joined: Feb 1999
Posts: 6,172
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From: somers, ny
Re: 1 5/8 or 1 3/4? (CHarris85Vette)
I agree with Cory. Different engines will repond differently to various size headers, but based on theory, you should be well into 1 3/4" territory. Plus your combo is going to want to rev pretty high which strengthens the case for the larger headers.
That said however, i've read several articles (Hot Rod, Chevy HP, etc) comparing headers from 1 5/8 to 1 7/8 and the differences on the dyno were pretty small (like less than 10hp) anywhere on the curve and generally the 1 7/8 units seemed the best to me, even on a mild 350. Maybe someone who still has these articles could post the results.
That said however, i've read several articles (Hot Rod, Chevy HP, etc) comparing headers from 1 5/8 to 1 7/8 and the differences on the dyno were pretty small (like less than 10hp) anywhere on the curve and generally the 1 7/8 units seemed the best to me, even on a mild 350. Maybe someone who still has these articles could post the results.
Burning Brakes
Joined: Feb 2001
Posts: 854
Likes: 0
Re: 1 5/8 or 1 3/4? (Stingy74)
Stingy74. Check......www.stahlheaders.com I'm assuming your after sidepipes also!! I believe they are only 3.5" though. I've got Hookers and sides, but next time i will go with Stahl. Like the SMOOTH long pipe look. JCL :cool: :cool: :chevy
Thread Starter
Safety Car
Joined: Apr 2001
Posts: 4,795
Likes: 1
From: Regina Saskatchewan, Canada.
Re: 1 5/8 or 1 3/4? (CHarris85Vette)
Well, i've got El Cheapo 1 5/8 headers allready with 3" collectors and 3" exhaust. My car is as low as you can possibly get a c3 and i'm tired of scraping not only the collectors but also the pipes in the rear around the lower strut rod attachment point. I want the factory style 69 side exhaust and Hedman makes the headers to do it, but only in 1 5/8. Here's a pucture of the 3" exhaust.
Drifting
Joined: Jul 2000
Posts: 1,861
Likes: 1
From: Bremerton WA
St. Jude Donor '09
Re: 1 5/8 or 1 3/4? (Stingy74)
Here's an interesting note that might help someone else make a decision...
In my case, I found that the Hooker 1 3/4 headers (for a C4) actually have better ground clearance than the LPE headers in my car (about an extra 1/2 inch). They also have slightly better spark plug access ( I can use all 90 degree boot wires now and don't swear so much during install of the plugs). What they don't have is great clearance in the chassis. I didn't have to ding any tubes to fit them, but the passenger side header is very close to the frame. If the engine torques over it only has about 1/4 inch to do so before frame contact. I decided to put a torque strap on my driver side just in case.
Cory
In my case, I found that the Hooker 1 3/4 headers (for a C4) actually have better ground clearance than the LPE headers in my car (about an extra 1/2 inch). They also have slightly better spark plug access ( I can use all 90 degree boot wires now and don't swear so much during install of the plugs). What they don't have is great clearance in the chassis. I didn't have to ding any tubes to fit them, but the passenger side header is very close to the frame. If the engine torques over it only has about 1/4 inch to do so before frame contact. I decided to put a torque strap on my driver side just in case.
Cory
Drifting
Joined: Dec 1999
Posts: 1,462
Likes: 1
From: Reno nevada
Re: 1 5/8 or 1 3/4? (Stingy74)
The size of your exhaust port also determines your header needs. Having a smaller head opening than the header primary gives it some anti-reversion properties. I would also make the shift at the 400 hp range to at least 1 3/4.
