1 7/8" OR 2" Headers
 

On a 550 HP motor how much will the HP increase with 2" headers ?
ET gain ? Currently using Doug's .
Anybody with experience ?

I used 1 7/8 on my pump gas 468 and made 651hp

Remember a Racer is alway stepping up, so BIGGER is better.



GTO George

We use 2” maddog headers on our 434 that made 705 hp with the heads we bought from you. 😉

Brian

Not a comparison, but my pump gas motor made 820 with 2" and the crap/flat collector design Heddmans.

i had dougs 1 7/8" on my 455 thats dynoed 625. Ran it at the strip and then tried hooker 2" and gained nothing in ET. The dougs fit better and easier to put the header bolts in and tighten. Dont waste your $ and time going to 2" on a 550hp motor.Id be curious if you would loose any power with 1 3/4".

Depends on the rest of the system also. If the mufflers/tail pipes are to restrictive the larger header won't help at all. But I agree with Scott70...1-7/8" are most likely all you need.

It does depend on the exhaust system and also the exhaust port. Going to big slows velocity scavenging out of the port too. Low velocity and a port that flows backward well you can get some reversion.

Some info for thought.

2" headers woke up my old 400 n/a combo over the previous 1 5/8", race use, 575 hp at 7000rpm.

Not surprised, as that size tubes are only good for 350 cid & under motors and from what I have seen the 2 inchers you have are a tad too big for a 400 at that level of power .

Your tossing away some average hp and TQ numbers with those 2 inch tubes!

Are you talking about 2" id, or od,

FWIW I run 126mph with 1 3/4 Hookers.

My RAIV 400 400 hp liked 1 3/4 over 2" with a muffler system(2 chamber 3" Flowmasters. It had reversion issues with 2"
Pretty sure JB Clegg's 455 SD Super Stocker has Doug's 1 7/8s. Lots of Engine Masters and Sprint cars use 1 7/8 and making 600 HP.

That formula posted above was published by David Vizard. As many know much of his work has been centered around Chevy engines, especially the 350cid. Therefore I've often wondered if it might be canted in that direction.

That said I've taken note of it and worked the formula around my Edelbrock heads and with porting the exhaust port ended up towards 250 cfm at the upper lifts. As noted David's formula is based on the INSIDE diameter. I run 2-inch headers (outside diameter) on my 505 that makes peak power at 6000 rpm.
Here is another one below that tends to back that up.

How Header Primary-Tube Diameter Affects Performance ?
Tech article from Hot Rod magazine:

http://www.hotrod.com/articles/heade...s-performance/


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This is right on topic as i have thought about this very thing
d-523 on their websites states 2" ID
i'm thinking about replacing the round port 1 7/8 with the 2"
not sure if i will have an oil filter access issue or z bar issue
but i can say the current headers were a dream to install, so easy
WAY easier then the D's i had at one time

Don 79 TA, my Hooker Super Comp 4202 round port 2" good oil filter access and fairly easy to install. Tight on the bolt behind #5-made a special bent wrench. I think Larry Navarro had a set on one of his round port stick cars so should be OK for fit there also. Never had the Hedman 2" for round port so not sure their fit.

My d port headers I built use the hedman adapter plates, have 1 7/8 primary than stepped to 2" od than 3.5 collectors , I didn't think a full 2 was needed, about 550 hp, now with new heads should pick up another 100 hp and leaving them alone. . Header design especially equal length tubes play a big part

2" od, so probably 1 -7/8" id. I believe I got the dimensions from the old Pipemax program/calculator. I ran 9.61@137mph consistently with that combo at around 2800lbs IIRC.

thanks
i know my friend had issues with headmans back in the day, not sure if they changed/improved
if i go with the larger Dougs headers i am hoping it fits up to the exhaust otherwise not really interested
i know the D header swap to the round port Dougs did connect just fine