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1 5/8” headers and 500hp?

General engine tech -- Drag Racing to Circle Track

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digger
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Re: 1 5/8” headers and 500hp?

Post by digger »

length of the tube matters to. in addition to bends 20" of 1-5/8" wont hurt as much as 34" of 1-5/8" so a bigger engine with less rpm and longer required length will suffer higher pumping losses
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Re: 1 5/8” headers and 500hp?

Post by gmrocket »

If it’s a good design with sweeping 90’s then it will make that no problem.

Even if it’s a two step with 1.5” first and 1 5/8 ..it will still make 500
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Re: 1 5/8” headers and 500hp?

Post by bob460 »

IMO collector size and type would make a big difference when chasing every last hp & tq. But yes 1 5/8 headers and 500hp is doable.

Hell didn't Uratchko make 1200hp with 1 7/8 headers!!!! :shock:
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Re: 1 5/8” headers and 500hp?

Post by hoffman900 »

bob460 wrote: Fri Aug 21, 2020 11:57 pm IMO collector size and type would make a big difference when chasing every last hp & tq. But yes 1 5/8 headers and 500hp is doable.

Hell didn't Uratchko make 1200hp with 1 7/8 headers!!!! :shock:
Sprint car builders are making 1000bhp with that.

The internet would have you believe you need that to make 500hp. :lol:

I’ve seen 1 3/8” (off the head) support 58hp/cyl (Elston build). That would be worth 450bhp on a V8.
-Bob
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Re: 1 5/8” headers and 500hp?

Post by travis »

My headers are JBA 6617’s with a 2.5” collector. These was a little tough to install but fit beautifully. The only other off the shelf option is a set by Pacesetter with 3” collectors, but the reviews are pretty bad about them not fitting well.

Would a 1 5/8” shorty with a 2.5” collector be a better option at this power level?
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Re: 1 5/8” headers and 500hp?

Post by hoffman900 »

travis wrote: Sat Aug 22, 2020 4:37 am My headers are JBA 6617’s with a 2.5” collector. These was a little tough to install but fit beautifully. The only other off the shelf option is a set by Pacesetter with 3” collectors, but the reviews are pretty bad about them not fitting well.

Would a 1 5/8” shorty with a 2.5” collector be a better option at this power level?
Again, it depends. It depends how bad the JBA is and how good the shorty is.

We’re talking 1 5/8” for 10” supporting 650bhp. This is with a perfect port / primary interface and everything else that is going on.

Would it work for a cheap straight tube header with questionable bend radii and fit? You might be giving some up and a larger diameter primary might show more improvement over that design. I think the other posts where people mentioned dyno results from shelf headers pointed this out. What they don’t realize is they are leaving a lot of power on the table and probably not realizing it.

Over something like Elston builds? Not a chance.

Also, it should be pointed out, that something like Elston builds allows you to do stuff with the engine that you otherwise couldn’t do, thus realizing even more power gains. This is hard for people who don’t have a very good understanding of how the engine really works to realize.

That said, your application is a street pickup truck? Then I wouldn’t worry about it as you’ll be cruising at part throttle 99% of the time.
-Bob
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Re: 1 5/8” headers and 500hp?

Post by 1980RS »

I was reading Holley makes what they call their Racing Street sock headers in a 1 5/8" stainless tube for $239 that's a killer price and I may need to get a set to try out with this 406 of mine.
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Re: 1 5/8” headers and 500hp?

Post by maxracesoftware »

700.0 Peak HP @ 6700 RPM w/2-Step Headers
with 2-Step Headers 2.000 x 10.5 , 2.125 x 20.5 = 31.5 inches, 4.000 x 10.5 Collectors

Lost = 58.0 Peak HP ( 700.0 - 642.0 ) going to 1 5/8ths Headers
642.0 Peak HP @ 6800 RPM w/1 5/8ths Open Headers

Lost = 61.8 Peak HP ( 700.0 - 638.2 ) going to 1 5/8ths Headers + Mufflers
638.2 Peak HP @ 6600 RPM w/1 5/8ths Headers + Mufflers

these 1 5/8ths Headers were very straight tubes for a good distance
before turning down ( must fit custom Street-driven 1934 Willys Coupe )

1 5/8ths Headers killed a bunch of HP on this combo

However , it does prove 1 5/8ths Header can support
at least 80.25 HP per Cylinder
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Re: 1 5/8” headers and 500hp?

Post by 73c34me »

I add this as a “for what it’s worth”. On my 385” 500 ish hp SBC. I inquired on this forum. The headers are hooker comp. for a C3 corvette, so they are full length but kinda short. Big Joe Sherman replied. He said going up to 1-3/4” headers would be a waste of money. He may have referenced his own testing- it was probably 10- 15 years ago. I felt honored he replied to my question.
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Re: 1 5/8” headers and 500hp?

Post by bob460 »

maxracesoftware wrote: Sat Aug 22, 2020 7:19 pm 700.0 Peak HP @ 6700 RPM w/2-Step Headers
with 2-Step Headers 2.000 x 10.5 , 2.125 x 20.5 = 31.5 inches, 4.000 x 10.5 Collectors

Lost = 58.0 Peak HP ( 700.0 - 642.0 ) going to 1 5/8ths Headers
642.0 Peak HP @ 6800 RPM w/1 5/8ths Open Headers

Lost = 61.8 Peak HP ( 700.0 - 638.2 ) going to 1 5/8ths Headers + Mufflers
638.2 Peak HP @ 6600 RPM w/1 5/8ths Headers + Mufflers

these 1 5/8ths Headers were very straight tubes for a good distance
before turning down ( must fit custom Street-driven 1934 Willys Coupe )

1 5/8ths Headers killed a bunch of HP on this combo

However , it does prove 1 5/8ths Header can support
at least 80.25 HP per Cylinder
I wonder how the 1 5/8 headers would have went if they were built by Elston?
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Re: 1 5/8” headers and 500hp?

Post by Fatman »

maxracesoftware wrote: Fri Aug 21, 2020 3:56 pm Danny Durand sold his SBC442cid 815.8 HP @ 8200-8300 RPM to this Guy
to upgrade to 470cid SBC ... which Danny then made 951.5 Peak HP @ 7700 RPM 702.5 TQ @ 6600 RPM

Customer wanted a strong "Pump Gas" Street Engine ...
so that was main reason of "radical detune"
Customer put the SBC442cid into a 1934 Willys Coupe to drive on the Street
Chris actually drove the Willys around the street a few times , sorting it out ,
for his Customer .

all Chris did was put Arias flat-top Pistons , new Cam with less Lift & duration
and went to Chevron 93 prem Pump Gas + reduced 1650CFM Carb to my 0-9375 1050 CFM Carb
175 cranking psi at 188 RPM
38.0 BTDC

went from 815.8 HP @ 8200-8300 RPM to
700.0 PeakHP @ 6700 RPM and 577.9 Peak TQ @ 5200 RPM
with 2-Step Headers 2.000 x 10.5 , 2.125 x 20.5 = 31.5 inches, 4.000 x 10.5 Collectors

then with 1.625 ( 1 5/8ths ) Headers with 4.000 Collector
642.0 HP @ 6800 RPM -to- 641.9 Peak HP @ 7000 RPM and Peak TQ= 578.2 @ 5000 RPM


then add on Mufflers + exhaust system
636.7 Peak HP @ 6900 RPM with 565.0 Peak TQ @ 5000 RPM


so 815.8 - 700.00 = lost 115.8 to Cam, Carb, Compression Ratio, Pump Gas changes
maximum HP lost 815.8 - 636.7 = 179.1 Peak HP :D

Note : i'm very sure this Engine would have made even lesser HP if we would have put a 3.000" or 3.500" Collector
instead of the 4.000" Collector on those 1 5/8ths Headers 8)
Why do you think this would have made less if you used a 3 or 3.5" collector instead of the 4"?
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Re: 1 5/8” headers and 500hp?

Post by maxracesoftware »

Fatman :
Why do you think this would have made less if you used a 3 or 3.5" collector
instead of the 4"?
mainly 3 reasons :
[1]= because it lost so much HP with 1 5/8ths Headers ( Lost= 58.0 HP to 61.8 HP )
... these were pretty nice straight tubes for very long distance
and they killed a bunch of HP ... i'm very sure testing smaller OD Collector designs
would have not beat the 2-Step Headers !!! 60HP lost is a ton to catchup and beat !

[2]= and the much larger 2-Step Headers 2.000 x 10.5 , 2.125 x 20.5 = 31.5 inches
4.000 x 10.5 Collectors made more TQ and HP ... even the lower RPM TQ was better !

[3]= PipeMax v4.50 predicted : ( was good for this Engine Combo )
2.000" OD straight tube Header x 32.000 inches long
3.750" OD Collector x 17.861 long

so it might have been overall a better Combo
with just a straight tube 2.000" Header + 3.750" Collector
possibly could have made best overall TQ and HP Curve
.... remember all the Dyno tests i Post are with a zero WinDyn filter = 0
.... what you see , is what it really made ! ... no smoothing at all !

but all we had at that time was
1 5/8ths w 4.000 collector
-VS-
2-Step Headers 2.000 x 10.5 , 2.125 x 20.5 = 31.5 inches
4.000 x 10.5 Collectors
..... so Collectors were the same OD ... but it sure did not like 1 5/8ths Tubes !
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Re: 1 5/8” headers and 500hp?

Post by Fatman »

maxracesoftware wrote: Sun Aug 23, 2020 2:53 am
Fatman :
Why do you think this would have made less if you used a 3 or 3.5" collector
instead of the 4"?
mainly 3 reasons :
[1]= because it lost so much HP with 1 5/8ths Headers ( Lost= 58.0 HP to 61.8 HP )
... these were pretty nice straight tubes for very long distance
and they killed a bunch of HP ... i'm very sure testing smaller OD Collector designs
would have not beat the 2-Step Headers !!! 60HP lost is a ton to catchup and beat !
Yep. I misinterpreted what you meant. I thought you meant that a smaller collector on the 1 5/8 headers would make less than the 1 5/8 with the 4" collector.
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Re: 1 5/8” headers and 500hp?

Post by hysteric »

PRH wrote: Fri Aug 21, 2020 7:42 pm A couple months ago a friend wanted to dyno one of his motors that he hadn’t previously run.
368”, 450hp with the headers he runs in the car which are 1-3/4 to 1-7/8 step with a 3” collector.
Tried some 1-5/8 x 3” headers on it just to see what would happen(maybe more tq down low, etc)...... they lost everywhere........ the big number being 15hp lower.

On a stroker SBF, in the 500hp range....... I’m pretty sure 1-5/8” headers are going to be down “some amount” compared to some slightly bigger tubes.
But, without testing a particular combo, who knows if that number is 5hp or 25hp?
Did you retune it when you swapped to 1 5/8's?
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Re: 1 5/8” headers and 500hp?

Post by travis »

Would adding some exhaust duration reduce some of the loss?
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