Full length HEADERS for BB- 1 7/8" or 2"?
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
Likes: 0
From: Phoenix Arizona
Full length HEADERS for BB- 1 7/8" or 2"?
I am looking to buy a set of full length headers- probably Hedman coated through Jet Hot for my 454.
I am scrapping the side exhaust and Sanderson block huggers and installing some Magnaflow mufflers from Corvette Central. The side exhaust, with the 12" glasspacks welded in are way too restrictive and loud for that matter.
So, should I go with the 1 7/8" primaries or the 2"????
See my motor buildup in my signature....
Thanks!
I am scrapping the side exhaust and Sanderson block huggers and installing some Magnaflow mufflers from Corvette Central. The side exhaust, with the 12" glasspacks welded in are way too restrictive and loud for that matter.
So, should I go with the 1 7/8" primaries or the 2"????
See my motor buildup in my signature....
Thanks!
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Your signature doesn't say if you are using round port or rectangle port heads. If the car is pretty radical with rectangle ports and beercan-sized valves, Hooker makes a 2 1/8 primary. That's what I'm using on mine.
Dep
Dep
Le Mans Master
Joined: Oct 2000
Posts: 6,563
Likes: 2
Hi Bob! Long time, no hear!
I'm no expert, but either one is probably OK. The only place that it makes any difference is in the upper rpm ranges, as far as I know.
There was a recent article in one of the publications- maybe Chevy Hi Perf? (can't remember which one- old age is setting in, I guess) about back pressure, exhaust gas scavenging, etc. The gist of it was that some people are using too big an exhaust, and are actually losing h.p.
Try asking the guys over in the 'Engine Mods' section, too. There's some big gear heads over there-
P.S.
I dunno about the 454, but Chevy recommends a 3" system throughout for the 502.
I'm no expert, but either one is probably OK. The only place that it makes any difference is in the upper rpm ranges, as far as I know.
There was a recent article in one of the publications- maybe Chevy Hi Perf? (can't remember which one- old age is setting in, I guess) about back pressure, exhaust gas scavenging, etc. The gist of it was that some people are using too big an exhaust, and are actually losing h.p.
Try asking the guys over in the 'Engine Mods' section, too. There's some big gear heads over there-
P.S.
I dunno about the 454, but Chevy recommends a 3" system throughout for the 502.
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
Likes: 0
From: Phoenix Arizona
DJ Dep,
I am running stock oval port heads- 049 heads from '73. They had a mild porting job on them with 2.19/1.88 valves.
MassVette,
It has been a while!!! I was in Mass last month for a wedding. I now wished I remembered to contact you ahead of time so I could have stopped by!! NEXT time for sure. I am leaning towards the 1 7/8" tubes at this point. Anything will be a big improvement over the current exhaust!!!
Thanks.
Bob
I am running stock oval port heads- 049 heads from '73. They had a mild porting job on them with 2.19/1.88 valves.
MassVette,
It has been a while!!! I was in Mass last month for a wedding. I now wished I remembered to contact you ahead of time so I could have stopped by!! NEXT time for sure. I am leaning towards the 1 7/8" tubes at this point. Anything will be a big improvement over the current exhaust!!!
Thanks.
Bob
Drifting
Joined: Jul 2003
Posts: 1,253
Likes: 1
From: East China MI
Before you trash the side pipes, you might want to check this out: http://www.spiralturbobaffles.com/
They are the best!
If you still want to go with full exhaust, 2-1/8" is where I would start. BBs don't need low end torque, they have plenty. They need to breathe.
They are the best!
If you still want to go with full exhaust, 2-1/8" is where I would start. BBs don't need low end torque, they have plenty. They need to breathe.
Race Director
Joined: Dec 1999
Posts: 11,096
Likes: 990
From: Sierra Foothills CA
Bob,
With your bigblock there's no reason not to go w/ the 2" primaries. You'll have plenty of torque and better mid-high RPM power. I've been running the Hedman 2" headers for years on my 439 & trust me, there is no downside.
With your bigblock there's no reason not to go w/ the 2" primaries. You'll have plenty of torque and better mid-high RPM power. I've been running the Hedman 2" headers for years on my 439 & trust me, there is no downside.
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Originally Posted by LT1driver
no bigger than 2" I had 2-1/8" and they hit the underside of the floorpans and created tremendous heat. Just a word of advice.
Dep
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Safety Car
Joined: Aug 2001
Posts: 3,892
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From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
You need to post your combo but even with that I am pretty sure the 1 7/8 would be the way to go. 427 Hotrod did some back to back dyno testing with his 540 and even with that radical motor the 2" tubes (over 2 1/8) made more power all the way up to 5500-6000 rpms if I remember correctly.
As far as exhaust goes the lenght of the collectors has a lot more to do with power than the diameter of the tubes.
If you want some really good exhaust tech check out headerdesign.com
As far as exhaust goes the lenght of the collectors has a lot more to do with power than the diameter of the tubes.
If you want some really good exhaust tech check out headerdesign.com
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
Likes: 0
From: Phoenix Arizona
My 454 has the following specs:
1. APPROX- 9.3 or so to ONE compression???
2. Comp Cams- Extreme Energy XE 274 hydraulic:
230/236 degrees of duration at .050", .553"/.555" lift 110 Lobe separation angle.
3. Performer RPM intake manifold
4. Holley 750 vac. secondaries
5. Sanderson Shortie block hugger headers- 1 7/8" primaries, 2.5" collector
6. 2" side exhaust pipes with a 12" glasspack welded in to kill some noise (and horsepower)
7. HEI distributor
8. 049 1973 heads mildly pocket ported 2.19/1.88
1. APPROX- 9.3 or so to ONE compression???
2. Comp Cams- Extreme Energy XE 274 hydraulic:
230/236 degrees of duration at .050", .553"/.555" lift 110 Lobe separation angle.
3. Performer RPM intake manifold
4. Holley 750 vac. secondaries
5. Sanderson Shortie block hugger headers- 1 7/8" primaries, 2.5" collector
6. 2" side exhaust pipes with a 12" glasspack welded in to kill some noise (and horsepower)
7. HEI distributor
8. 049 1973 heads mildly pocket ported 2.19/1.88
Drifting
Joined: Jul 2003
Posts: 1,253
Likes: 1
From: East China MI
I originally said to go with the 2-1/8 but ran the numbers to check.
Primary.....Peak Tq.......Avg Tq.....Peak HP.......Avg HP
1-7/8......445@4000......389......428@5500.. .....316
2............448@4000......390......428@ 5500.......316
2-1/8......448@4000......389......424@5500.. .....315
XX..........497@4500......429......492@5 500.......352
I used 24" primary length for the sake of comparison. The only variance was that my spec sheet for your cam listed the lobe seperation at 106 so I left it there. I ran the numbers using a full 2-1/2" exhaust with good after market mufflers. As you can see, 2" is the strongest but not by much. The 1-7/8, for the sake of fit might be a good choice. I agree that you can find a lot of performance in primary and colector length, which I did not play with.
I put the XX in to show what 3" exhaust would do (with 2" primaries). Well worth it in my opinion, even with the 1-7/8.
The last time I posted, I got corrected on my spelling. This time I was off on the primaries. Once again, I stand corrected!
Primary.....Peak Tq.......Avg Tq.....Peak HP.......Avg HP
1-7/8......445@4000......389......428@5500.. .....316
2............448@4000......390......428@ 5500.......316
2-1/8......448@4000......389......424@5500.. .....315
XX..........497@4500......429......492@5 500.......352
I used 24" primary length for the sake of comparison. The only variance was that my spec sheet for your cam listed the lobe seperation at 106 so I left it there. I ran the numbers using a full 2-1/2" exhaust with good after market mufflers. As you can see, 2" is the strongest but not by much. The 1-7/8, for the sake of fit might be a good choice. I agree that you can find a lot of performance in primary and colector length, which I did not play with.
I put the XX in to show what 3" exhaust would do (with 2" primaries). Well worth it in my opinion, even with the 1-7/8.
The last time I posted, I got corrected on my spelling. This time I was off on the primaries. Once again, I stand corrected!
Last edited by jpatrick636; Nov 26, 2004 at 05:04 PM.
Race Director
Joined: Dec 1999
Posts: 11,096
Likes: 990
From: Sierra Foothills CA
jpatrick,
Those numbers make sense, although I'm surprised that the 3" exhaust would make that much difference. Let me re-phrase that- I'm not so much surprised as encouraged. I've been looking at a way to get a 3" mandrel bend system for my Vette & if I could expect that much improvement it would be worth the cost. My combo is similar except a bit more cam/head flow/compression. What program did you use to get your numbers?
Those numbers make sense, although I'm surprised that the 3" exhaust would make that much difference. Let me re-phrase that- I'm not so much surprised as encouraged. I've been looking at a way to get a 3" mandrel bend system for my Vette & if I could expect that much improvement it would be worth the cost. My combo is similar except a bit more cam/head flow/compression. What program did you use to get your numbers?
Drifting
Joined: Jul 2003
Posts: 1,253
Likes: 1
From: East China MI
PERFORMANCE TRENDS Engine Analyzer. It's a good program.
I went to 3" this year and love it.
How do you like the BG? Which one do you have?
I went to 3" this year and love it.
How do you like the BG? Which one do you have?
Last edited by jpatrick636; Nov 27, 2004 at 06:59 PM.
Race Director
Joined: Dec 1999
Posts: 11,096
Likes: 990
From: Sierra Foothills CA
Originally Posted by jpatrick636
PERFORMANCE TRENDS Engine Analyzer. It's a good program.
I went to 3" this year and love it.
How do you like the BG? Which one do you have?
I went to 3" this year and love it.
How do you like the BG? Which one do you have?
I love the BG. Obviously it was built before they became Demon- it was their Stage 3 carb as I recall & is handported. It'll flow up to 1040 cfm if your motor can pull it. I went from a well tuned 780 vacuum secondary carb to the BG & with no other changes I ran a consistent .35 quicker in the 1/4 mile. Throttle response is excellent.
Last edited by Les; Nov 28, 2004 at 03:24 PM.
Race Director
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
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For your 454, the 1 7/8" ones will work fine. If you intend to step up to a more radical set up later on or more cubes, I'd look into the 2" ones.
I tried some back to back testing on a 427 once too with 1 3/4" and 2". Lost a little 60' time at track and made it up in the mid-top end. Overall about a wash at the level it was at (high11's).
For sure look into a 3" system if you are building exhaust. Can't hurt at all. On my last 427 version in the Vette, it worked fine with 2.5" system. Less than .1 and 1 mph difference between capped and uncapped. But with the 540...it is a whole 'nuther game even with 3" pipes. I will eventually build a 3.5" or 4" oval pipe system for mine.
BTW...if you're looking for some 1-7/8" headers..you might check with Nick (Vettemaniac here on the Forum). He is replacing the 1-7/8" ones on his 540 with some 2" ones right now.You might find a deal there!
JIM
I tried some back to back testing on a 427 once too with 1 3/4" and 2". Lost a little 60' time at track and made it up in the mid-top end. Overall about a wash at the level it was at (high11's).
For sure look into a 3" system if you are building exhaust. Can't hurt at all. On my last 427 version in the Vette, it worked fine with 2.5" system. Less than .1 and 1 mph difference between capped and uncapped. But with the 540...it is a whole 'nuther game even with 3" pipes. I will eventually build a 3.5" or 4" oval pipe system for mine.
BTW...if you're looking for some 1-7/8" headers..you might check with Nick (Vettemaniac here on the Forum). He is replacing the 1-7/8" ones on his 540 with some 2" ones right now.You might find a deal there!
JIM
