So….more header talk….this had me scratching my head

[MOPARMAGA]

Post number 9 touches on this, we just ex

Yep, I have to agree with post 9.
With the exception of bigger tubes pulling harder on the booster, in your case the headers are optimum to your engines wants. Shape, length, collector all make a big difference

 

[MOPARMAGA]

Ac



Actually, if it goes lean with a header change you can bet the header isn’t functioning correctly.

When you change from one header to another and you have to take jet out (because it’s rich) you know the header is doing it’s job. There is a reason for that and it’s important, not only for header function but any time you do work on the induction or exhaust. Any time you have to take jet away (for the most part) you will make more power and be quicker and faster on the track.

I agree with you 100% especially with post 9 on leads car, I was thinking though about the flying toilet scenario being a little different but I definitely can be wrong. But it seems to me that flying toilet could load up fairly easy and an engine would have to really work to compensate for all that air & fuel being blocked by a low pressure wave in that header up until a point where it's scavenging efficiency is near it's peak.

 

[MOPAROFFICIAL]

We race a number of Small block Mopars.
Even our Superstock 340 Duster was definitely quicker
with 1 3/4 Hooker Headers than any 1 7/8
Header we tried and we tried a lot (The TTI Step 1 5/8 to 1 3/4
is faster yet in our applications particularly with correct stepped collector)
It was one of the First A body Superstock cars in the 9's (Especially
in SSKA @ 3400 lbs).
Of course for the last 30 years we have gone to Proprietary Multiple
Steps headers which a quite a bit faster than any single tube size pipe
header. We guard the specs on these and collectors pretty closely.
If you get to a Division or National Race try to get a peek at the headers
on any cars with similar engine family to yours (If you can without getting attacked).

Agree. Imo a person would be better off with typical 1 5/8 than 1 7/8.
The diff between 1 5/8 & 1 5/8 to 3/4 step tti was imo a 15-20 hp diff on my 410 combo with 'off idle' tq almost staying the same, 3000 ^ midrange to the top increased.

 

[Rat Bastid]

I agree with you 100% especially with post 9 on leads car, I was thinking though about the flying toilet scenario being a little different but I definitely can be wrong. But it seems to me that flying toilet could load up fairly easy and an engine would have to really work to compensate for all that air & fuel being blocked by a low pressure wave in that header up until a point where it's scavenging efficiency is near it's peak.

Yeah, that’s a head scratcher on the toilet. I’m trying to think it through but I’m not getting anywhere.

 

[Sr4440]

There is a big difference between a water brake dyno and an inertia dyno. That’s what I was saying. One measures how fast the engine accelerates and the rate of change, and the other doesn’t.

my bad, I must have missed you were talking about an inertia dyno. I can measure the true HP/TQ at any sweep rate, but the rate of change is controlled by the dyno.

Joe

 

[B3422w5]

Agree. Imo a person would be better off with typical 1 5/8 than 1 7/8.
The diff between 1 5/8 & 1 5/8 to 3/4 step tti was imo a 15-20 hp diff on my 410 combo with 'off idle' tq almost staying the same, 3000 ^ midrange to the top increased.

a person might well be better off in stock/ super stock when using a very small iron head. I am not sold on a big stroker with bigger aftermarket heads that is true. At least the cars I know at the track don’t subscribe to that

 

[Sr4440]

Yeah, that’s a head scratcher on the toilet. I’m trying to think it through but I’m not getting anywhere.

Let me tell you about my MFI big block and one of the header swaps. The engine is a 512 B1 head making 840hp @6800. After reading everything Calvin Elston has written, I decided to build a set. the headers that were on the car were 2.25 with a 28" primary going into a 4" collector. The new headers were 2.125 to 2.25 with a OAL 26" the collector is a merge collector with 3.25 choke.
When I swapped the headers, the engine went dead lean. I had to add 10% more fuel just to get back to the same HP level. The Bsfc with the old header was .995 and with the new is 1.10. The new headers didn't make any more HP or TQ, but did show the exhaust was really working well, ordered a new camshaft with less exhaust duration and made some more tq under the curve, but that's for another time.

Joe

 

[justinp61]

No way in hades I’m installing a 1.625” header on my Indy headed 434” small block!

 

[lead69]

Yeah, that’s a head scratcher on the toilet. I’m trying to think it through but I’m not getting anywhere.

Yeah I missed the flying toilet part, but you should know, you ran one

 

[MOPAROFFICIAL]

a person might well be better off in stock/ super stock when using a very small iron head. I am not sold on a big stroker with bigger aftermarket heads that is true. At least the cars I know at the track don’t subscribe to that

Combo matters. Small port heads on stockers. Yes.

 

[MOPAROFFICIAL]

Quite common for people to take one-liners out of context and make crowd stirring statements with exclamation marks at the end around here..lol

 

[Rat Bastid]

my bad, I must have missed you were talking about an inertia dyno. I can measure the true HP/TQ at any sweep rate, but the rate of change is controlled by the dyno.

Joe

That’s what I was trying to say lol. You just said it better!

 

[Rat Bastid]

Let me tell you about my MFI big block and one of the header swaps. The engine is a 512 B1 head making 840hp @6800. After reading everything Calvin Elston has written, I decided to build a set. the headers that were on the car were 2.25 with a 28" primary going into a 4" collector. The new headers were 2.125 to 2.25 with a OAL 26" the collector is a merge collector with 3.25 choke.
When I swapped the headers, the engine went dead lean. I had to add 10% more fuel just to get back to the same HP level. The Bsfc with the old header was .995 and with the new is 1.10. The new headers didn't make any more HP or TQ, but did show the exhaust was really working well, ordered a new camshaft with less exhaust duration and made some more tq under the curve, but that's for another time.

Joe

That makes sense. Which is what Calvin always says. When the header works you need to rethink everything else.

Do you mind sharing the cam specs?? If not, I understand.

 

[Rat Bastid]

Yeah I missed the flying toilet part, but you should know, you ran one

Yeah. With any MFI constant flow system there are always puddles of fuel on the back of the valve when it opens. Way more than a carb’d deal.

So maybe the header was was tugging so much harder on the port it was pulling more raw fuel out the pipes. Without knowing if the A/F ratio changed or what it’s hard to say.

As sr440 said above, a good header will change cam timing requirements. His was a great example of that.

 

[Rat Bastid]

The guy you are quoting clearly has never heard of intake reversion. As you make the exhaust more efficient, the intake reversion gets reduced/eliminated. When that happens, the incoming air does not go "backwards" through the booster because of reversion, you will now have a leaner mixture. You can "see" this happening on an engine dyno, the lbs of fuel use goes down, A/F trends leaner and the volumetric efficiency goes up.

As far as the HP "changing" with the rate of acceleration changing on a dyno pull, well it doesn't, only what is measured changes. There is a way to get actuate numbers. I wrote on this same subject on my website, if you want to read it go to http://www.cen-texenginedyno.com/ and read "Joe's BS" at the bottom of the page.

Joe

I forgot I read your link several months ago. That’s worth reading.

 

[Sr4440]

That makes sense. Which is what Calvin always says. When the header works you need to rethink everything else.

Do you mind sharing the cam specs?? If not, I understand.

Sure, it was a 282in and 290ex @ .050 with around .800 lift with 1.7 rockers. Changed to a 282in 284ex @.050 with the same lift. Picked up 25lb ft of TQ under the curve and 2 additional HP. LOL. The tq curve flatten out, makes a nice bracket engine. The BSFC number dropped to 1.02, so I think it needed even less exhaust duration, but i don't have the stones to order a cam with less exhaust duration than intake. I know Calvin said that's not uncommon, i just can't do it. FYI, I am limiting the power/rpm of the engine because it's a stock B block.

Joe

 

[Rat Bastid]

Sure, it was a 282in and 290ex @ .050 with around .800 lift with 1.7 rockers. Changed to a 282in 284ex @.050 with the same lift. Picked up 25lb ft of TQ under the curve and 2 additional HP. LOL. The tq curve flatten out, makes a nice bracket engine. The BSFC number dropped to 1.02, so I think it needed even less exhaust duration, but i don't have the stones to order a cam with less exhaust duration than intake. I know Calvin said that's not uncommon, i just can't do it. FYI, I am limiting the power/rpm of the engine because it's a stock B block.

Joe

That’s awesome Joe. Thanks for posting your numbers.

 

[Hysteric]

Whenever you change headers you ultimately change what's left over in the chamber after a combustion event. It has nothing to do with making the carb richer or leaner as the AFR the carb delivers doesn't change but everything to do with how much residual is left in the chamber to affect the incoming charge and therefore how well the burn proceeds.

Its all about energy imputation and where you use it.

 

[Hysteric]

Bruce knew and wrote plenty about reversion so I have to disagree with that. In fact I recall discussions with him about black up the intake and even into the carbs.

I agree that when statements are taken out of their original context, they may in part no longer be true.
When a carb is delivering a flat AFR in the power band, increases or reductions the velocity through the booster still produces the same AFR.
Of course the first part is critical for the rest to follow.

LOL remember this:

"Often variations in WB readout of AFR are not the cause of the carby they are the cause of ignition timing alterations, that increases CO etc and causes richer readings. If the carby is dropping atomization quality when the manifold pressure is high then sometimes that can cause CO to climb and cause AFR errors. Remember the carby does the same thing each time you pull the same amount of air down its throat with the same blade positions and the same jets etc so if you fiddle with the base ignition timing just as a simple test and you see AFR changes then you have more idea of whats going on. So have a go and experiment".

The main cause of ignition variation to AFR readout is the energy level of the arc. Low energy doesnt start the flame kernel hard enough and you get an incorrect pressure at TDC. Its the mass fraction burnt that matters at TDC. If it produces peak pressure at say 12 ATDC then thats fine but thats only the peak, its not the mass fraction measurement. No point looking at peak pressure points if its not the correct mass burnt. The more mass that has tobe burnt while the piston is descending the colder is the temperature and cold produces CO. Its matters not what the available Oxygen level is if its not hot enough you only get CO. A cold burn thats stoich or leaner than stoich will make lots of CO. I see it all the time on hotrods, massive CO with lots of O2 left over and heaps of HC and sooted up plugs and its because there too lean .


All the way back in 2011.........

 

[9secRR]

honestly, from reading your posts, and the tiny difference in ET/ mph, it’s hard to form much of an opinion unless you have a good number of outings under your belt, and the DA was the same.
Didn’t you just say very recently you hadn’t even been out yet this year?

I got around to making a few passes yesterday. I put 4.86 gears back in so this was the only change I did.

1.33 60’
6.16 to the 1/8
109.66 mph to the 1/8
9.75 @ 136 mph

before the big tube header,

1.39 60’
6.29 to the 1/8
107.56 to the 1/8
9.96 @ 134

there is no doubt that the bigger tube header is working. Quicker in all areas. More TQ and more HP

 

[92b]

I got around to making a few passes yesterday. I put 4.86 gears back in so this was the only change I did.

1.33 60’
6.16 to the 1/8
109.66 mph to the 1/8
9.75 @ 136 mph

before the big tube header,

1.39 60’
6.29 to the 1/8
107.56 to the 1/8
9.96 @ 134

there is no doubt that the bigger tube header is working. Quicker in all areas. More TQ and more HP

View attachment 1715966726

Is the pipe length and diameter after the collector the same as with the smaller headers?

 

[9secRR]

Is the pipe length and diameter after the collector the same as with the smaller headers?

old headers were 1-5/8” with 3” collector under chassis.

New headers are 1-3/4” stepped to 1-7/8” with a 2.25” to 3” merge collector and are fender exit. New headers are way shorter the the old ones. I don’t have all the pipes the same length as I made them to fit the car and be able to remove them with engine in car.

 

[rumblefish360]

Cool! Nice picture.

 

[B3422w5]

I got around to making a few passes yesterday. I put 4.86 gears back in so this was the only change I did.

1.33 60’
6.16 to the 1/8
109.66 mph to the 1/8
9.75 @ 136 mph

before the big tube header,

1.39 60’
6.29 to the 1/8
107.56 to the 1/8
9.96 @ 134

there is no doubt that the bigger tube header is working. Quicker in all areas. More TQ and more HP

View attachment 1715966726

I talked to Chris Hardy agains yesterday at the track for a long time.
He told me for my car( heavy, 3350) and primarily 1/8 miłe ar most events, i would be Best served with a 1 3/4 tube.
Lighter car would like a bigger tube better

 

[33IMP]

I used 2" headers on a small block car, cause they were custom for the chassis, and came with the car when I bought it, less engine, trans, and center section. Though supposedly too big, they seemed to work okay. Maybe cause the car was around 2400# with me in it.
It MIGHT have run better, with a smaller header/smaller exhaust system, but I wasn't gonna spend custom header prices to find out.
(The stainless smallblock headers that prompted this thread cost more than I paid for the car).