Would it hurt? No. Would it help, well there is the possibility.

 

It would depend on the headers. If your only consideration is the primary diameter, you might get no better results. If you went to the trouble to think out the entire exhaust system, you could probably pick up quite a bit.

 

Vince. The X-pipe gives you a lot more torque than the 1.75"s will. The smaller tubes may give you a little more bottom end, but I think it will hurt you on the big end. Remember, your pushing a brick through the air a over 100mph.

 

IMO, the 1 3/4" headers would be a lot better suited for your combo.

 

A 454HO is only rated at 425 hp and 2" primary tubes would be a 2 tube size error at least.

headerdesign.com likes a 1-3/4" x 36" primary tube with a 2.75" x 14" collector.
Pipemax likes a 1-3/4" x 48" primary tube with a 3" x 27" collector.

 

Right now, I'm running 2"x3" Hedman ceramics.

Runs great, just trying to wring every little bit out of it. BUT, these will be costly to replace, not to mention cutting up the exhaust system to make 'em fit.

 

Right now, I'm running 2"x3" Hedman ceramics.

Runs great, just trying to wring every little bit out of it. BUT, these will be costly to replace, not to mention cutting up the exhaust system to make 'em fit.

If you want to part with the Hedmans let me know.

 

I have 2" on my car now, I also believe what your gaining low end you'll give up at the big end with smaller tubes. I might try some smaller tubes to see any difference. You running 2.15 60 foots??? I know your in a 4 speed but seems some tires would help more than headers???

 

Best 60 is 2.0, with drag radials 275/50/15, its just tough w/a stick to 60 good. If I just drop the clutch it will smoke 'em through the whole 60.

I'll get better though...need to try the MT DR's

 

Best 60 is 2.0, with drag radials 275/50/15, its just tough w/a stick to 60 good. If I just drop the clutch it will smoke 'em through the whole 60.

I'll get better though...need to try the MT DR's

Mine really hooks with the Hoosier Quick Times

 

seems to me that if you can't hook now....how you going to hook with more low end torque? If you could hook I'd say do the swap...but....

 

no way is it worth it to swap your headers. if it were a 396/402 you MIGHT gain some usable power, but i seriously doubt that you'll notice much change at all with a 454. collector length and design as well as the exhaust system are far more important than tube diameter. of course that is just my opinion.

 

I think what he has experienced is that in order not to smoke the tires he has to come off so soft that the motor bogs real bad. Any more throttle to control the bog and the tires get smoked.

 

Doesn't bog, the only time I got it to bog or hesitate was w/drag radials and a yellow spring in the secondaries.

But the motor does feel a little soft till about 3000, then it starts to pull hard. I would think that a motor that makes 16" of vacuum would have enormous amounts of low-end. But again, I don't have torque multiplication or gear, so that in itself may be something.

 

Vince

I think I would stay with the 2". More low-end torque will only make your car harder to hook. What rpm does your engine drop to after you shift gears. I would guess you are only seeing 3,000 rpm one time, but are seeing the upper rpm range at the top of each gear. I would stay big for the top end charge.

Rich

 

Problem is rich is that in high gear (4th) you need torque to trap good. I think (my tach is way off) I'm crossing the line around 4600rpm...right where I need some torque!

 

4600 sounds about right with a 4 speed and a 3.31's
I'm 5,000 w/convertor slippage.
In regards to the smaller headers,it can't hurt to try em.
Buy the Summit brand SUM-G9010
they fit like a glove and if they slow the car down,they only cost you $80 or so and you can put your Heddmans back on
IMHO,there is no "top end charge" with n/a motor. (naturally aspirated)
Usually all A bodys that are n/a pick up 22-24 MPH at the stripe over their 1/8 mile MPH

 

I vote 1.75" tubes, what you lose off the line you will NEVER make up down track.

 

Dont really want to butch-up the existing exhaust system.

Will 1.75 hedmans have the same length as the 2 inchers anybody know?

 

Do your current Hedmans have the ball and socket collector? That has to be one of the best inventions yet, no more blown/leaky collector gaskets.

 

Bob, no they don't :angry: ...these must be older cause I think they all have the ball/socket arrangement now.

These are the coated jobs...makes me wish they were the cheapies sometimes.

 

unless you are taking off at an idle i do not see how the 1 3/4" headers will help your track times at all. you will not notice any difference between 2" and 1 3/4" headers on a mild 454 if they have similar collector size and length, especially if you use the same exhaust system. i'm just trying to save you some hassle and some money. now if you just want to experiment and have time and money to blow, then try it and let everyone know the results.

 

The only way I would even consider trying it is I could avoid cutting you my exhaust system, so I'd have to find a Hedman header.

There was a guy here w/a 396 (mild) that gained a second when going from 2" to 1.75". Sounds like an extreme example, but definitely shows that something is going on.

 

Here's a guy running 10.30's with a 454 and 1-3/4" headers. Probably doesn't lose a lot on the top end....

http://chevelles.com/forums/showthread.php?t=121710

 

Actually, he doesnt use the "top end", does he?

Small primary tubes would defintely help the short end of the track. And what you gain on the short end is worth 2X the top end. Now, whether that .5 sec ( my most aggressive guess) .is worth it to you is your call. Header work is always a complete pita. Installing an X crossover would also help the velocity pull through the pipes and lower peak header torque somewhat. But again, your still into the exhaust system. If you do anything, I;d do smaller pipes. For a minimum of "cobbling" and a max of gain, choose the cheap Summit headers and have some scavenging collectors welded on. Coat and install. Will give the exhuast a similar "pull through" characteristic as an X crossover.

Hedman makes a small pri for the 64-67 chassis bbc, so they defintely have one for you as well...

 

I would agree 1 3/4 would be the best for your combo , however another factor should not be ignored and that is collector diameter is yours 3" or 3 1/2 if 3 1/2 then another option, you may want to consider is adding a set of Flowmaster 4 -2-1 collectors for more bottom end torque ..... I had 2 " headers on the old 396 .added the collectors and it made a difference at launch and especially for street driving .........no idea if as much as going down to 1 3/4 but something to consider FWIW

 

We'll, I'm revisting this again b/c my new combo has me losing even more low-end torque, even with 3.90's. With the combo listed in the sig, peak torque probably now occurs at around 4500+ rpms vs. the 3250 rpm with the 454HO. An extra 20* intake duration sure does move the powerband, cause its all midrange/top-end now. I just figured the new combo would make better use of the headers...not!

Current system is 2"x3" hedmans ceramic, 3" Pypes system with X, and 22" Magnaflows. I need to do major work on this exhaust system b/c when I installed the 22" muffs instead of the 18", I had to butch everything up. Now maybe a good time to start completely over, from the header back. B/c new headers would make me have to modify the exhaust anyway.

Thoughts?