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1 5/8” headers and 500hp?

General engine tech -- Drag Racing to Circle Track

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n2omike
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Re: 1 5/8” headers and 500hp?

Post by n2omike »

travis wrote: Sun Aug 23, 2020 9:32 am Would adding some exhaust duration reduce some of the loss?
Cam design likely plays a significant role. Cams that rely on a lot of overlap would likely suffer more with the small tubes, as there would be more reversion. Opening the exhaust valve sooner by spreading the LSA and advancing the cam to compensate might yield the best results. Adding a little exhaust duration to go along with it probably wouldn't hurt. Someone can correct me if they disagree...
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Re: 1 5/8” headers and 500hp?

Post by dondon »

1972ho wrote: Fri Aug 21, 2020 7:27 pm Some of stock eliminator racer would pay 2500-3000 for that 8 hp header.
I agree with that, but I was assuming it was a street car, no 408 sbf in stock elim that I know of. Love stock eliminator, favorite class
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Re: 1 5/8” headers and 500hp?

Post by digger »

bob460 wrote: Sat Aug 22, 2020 10:02 pm
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?
i can't see 60hp peak improvement (10% gains) in those headers from a bit less length and different style of collector

its a relative thing, maybe if the larger header was a steaming pile then yeah smaller headers would work better but those bigger stepped ones from LM look pretty good to me already

rather than say 1-5/8" can support 80 hp per cylinder that's not practical guidelines just because an engine did. While you can make 640 from a 1-5/8" it takes much more engine than it needs to be and perhaps the pumping losses are much too high that if you went up a size the gains would increase disproportional with more sensible pumping losses or whatever.
i guess you start off with a small size and increase until no more gains and then go back down a size . its a bit like ignition timing you only want as much as you need.
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Re: 1 5/8” headers and 500hp?

Post by gmrocket »

This is in a truck right? :D Refresh my memory
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Re: 1 5/8” headers and 500hp?

Post by travis »

gmrocket wrote: Sun Aug 23, 2020 11:06 pm This is in a truck right? :D Refresh my memory
That is correct. This will be for my ‘87 F150, which feels to be considerably lighter than my ‘83. After building the current 351w for the ‘83, which should fall somewhere in the 350-375hp range, I was kind of disappointed with the final result. The weight just sucks the life out of it. So...more power is needed :D
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Re: 1 5/8” headers and 500hp?

Post by lefty o »

travis wrote: Sun Aug 23, 2020 11:55 pm
gmrocket wrote: Sun Aug 23, 2020 11:06 pm This is in a truck right? :D Refresh my memory
That is correct. This will be for my ‘87 F150, which feels to be considerably lighter than my ‘83. After building the current 351w for the ‘83, which should fall somewhere in the 350-375hp range, I was kind of disappointed with the final result. The weight just sucks the life out of it. So...more power is needed :D
4.88's will fix it. 8)
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Re: 1 5/8” headers and 500hp?

Post by gmrocket »

travis wrote: Sun Aug 23, 2020 11:55 pm
gmrocket wrote: Sun Aug 23, 2020 11:06 pm This is in a truck right? :D Refresh my memory
That is correct. This will be for my ‘87 F150, which feels to be considerably lighter than my ‘83. After building the current 351w for the ‘83, which should fall somewhere in the 350-375hp range, I was kind of disappointed with the final result. The weight just sucks the life out of it. So...more power is needed :D
So a big heavy truck..with a 406 mostly lower rpm like 6k max?

Where will the engine make peak power?
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Re: 1 5/8” headers and 500hp?

Post by travis »

I’m thinking somewhere in the 6000-6200 rpm range for peak, with a fat torque curve. As much as some deeper gears would help, I like the 3.55’s as a compromise gear because it’s nothing here to have to run 80+ mph to keep up with traffic. I use and drive my junk, so it’s always a compromise.

The easy solution would be to simply find a lighter car, but I can’t fit my 14’ aluminum boat in the trunk of a car :lol:

I’m actually on the hunt for a car that I can fit my 6’4” ass into comfortably to stick this 351w in that I built for my ‘83, and then put something milder back in that truck.

I’ve got a lot of ideas...just need the time and money to do them!
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Re: 1 5/8” headers and 500hp?

Post by travis »

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)

Would you happen to have the full power curves?

Playing with EA3.4 tonight, fwiw, it predicted that the combination that I entered (10.5-1, 210cc victor jr heads and intake, and a number of different cams) wouldn’t start having “significant” power loss until over 5500 rpms. For a hot street truck it didn’t look like anything to lose sleep over.
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Re: 1 5/8” headers and 500hp?

Post by digger »

Yeah be good to see the Pmax screen shots and outputs for csa, runner length, exh etc
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Re: 1 5/8” headers and 500hp?

Post by PRH »

This will be for my ‘87 F150
If the vehicle will see a lot of DD type use, I personally wouldn’t be too concerned with the HP number, as much as trying to make the motor very compatible with the vehicle it’s going in and how it will be used.
You can really take some big steps backwards with these types of builds, in terms of driveability and mpg, in the quest for some abstract hp number.

I can’t imagine 1-5/8” headers being a “problem” for a build that’s geared towards that type of application.
Somewhat handy with a die grinder.
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Re: 1 5/8” headers and 500hp?

Post by maxracesoftware »

travis wrote: Mon Aug 24, 2020 4:11 am
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)

Would you happen to have the full power curves?

Playing with EA3.4 tonight, fwiw, it predicted that the combination that I entered (10.5-1, 210cc victor jr heads and intake, and a number of different cams) wouldn’t start having “significant” power loss until over 5500 rpms. For a hot street truck it didn’t look like anything to lose sleep over.
Would you happen to have the full power curves?

hi Travis , all the Dyno TQ and HP Curves + Pics were at this Link in this Thread
viewtopic.php?p=874362#p874362
Playing with EA3.4 tonight
let me know what Engine Analyzer predicts
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Re: 1 5/8” headers and 500hp?

Post by gmrocket »

travis wrote: Mon Aug 24, 2020 2:45 am I’m thinking somewhere in the 6000-6200 rpm range for peak, with a fat torque curve. As much as some deeper gears would help, I like the 3.55’s as a compromise gear because it’s nothing here to have to run 80+ mph to keep up with traffic. I use and drive my junk, so it’s always a compromise.

The easy solution would be to simply find a lighter car, but I can’t fit my 14’ aluminum boat in the trunk of a car :lol:

I’m actually on the hunt for a car that I can fit my 6’4” ass into comfortably to stick this 351w in that I built for my ‘83, and then put something milder back in that truck.

I’ve got a lot of ideas...just need the time and money to do them!
That set up would benefit from 1 5/8 , I would think anything bigger would be down on TQ all the through till 5500 or 6k

Probably a fairly tight converter to with the 3:55?
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Re: 1 5/8” headers and 500hp?

Post by travis »

maxracesoftware wrote: Mon Aug 24, 2020 1:03 pm
travis wrote: Mon Aug 24, 2020 4:11 am
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)

Would you happen to have the full power curves?

Playing with EA3.4 tonight, fwiw, it predicted that the combination that I entered (10.5-1, 210cc victor jr heads and intake, and a number of different cams) wouldn’t start having “significant” power loss until over 5500 rpms. For a hot street truck it didn’t look like anything to lose sleep over.
Would you happen to have the full power curves?

hi Travis , all the Dyno TQ and HP Curves + Pics were at this Link in this Thread
viewtopic.php?p=874362#p874362
Playing with EA3.4 tonight
let me know what Engine Analyzer predicts
I guess I should have read back through this again...

Thanks for the info. EA3.4 predicts very similar trends as your dyno results. So it would seem that a 1 5/8” long tube header wouldn’t be a big deal on a sub-6500 rpm 408” motor...especially if the cam was “right”. Depending on the cam used, it predicted a loss of 12-20 Hp between 5500 and 6500 rpms, comparing open 1 5/8”x30” to 1 3/4”x30”
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Re: 1 5/8” headers and 500hp?

Post by travis »

gmrocket wrote: Mon Aug 24, 2020 1:22 pm
travis wrote: Mon Aug 24, 2020 2:45 am I’m thinking somewhere in the 6000-6200 rpm range for peak, with a fat torque curve. As much as some deeper gears would help, I like the 3.55’s as a compromise gear because it’s nothing here to have to run 80+ mph to keep up with traffic. I use and drive my junk, so it’s always a compromise.

The easy solution would be to simply find a lighter car, but I can’t fit my 14’ aluminum boat in the trunk of a car :lol:

I’m actually on the hunt for a car that I can fit my 6’4” ass into comfortably to stick this 351w in that I built for my ‘83, and then put something milder back in that truck.

I’ve got a lot of ideas...just need the time and money to do them!
That set up would benefit from 1 5/8 , I would think anything bigger would be down on TQ all the through till 5500 or 6k

Probably a fairly tight converter to with the 3:55?
I’m thinking somewhere in the 2500-3000 range. That’s another downside to the weight...it makes a looser converter feel even looser under normal driving. I have a heavy duty Hughes 11” in the ‘83 that is rated at 2500. It took a bit of getting used to but it isn’t bad at all.
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