Header size too big, is that possible?

[NIsaacs]

One of the guys I sled pull with just had a new engine built. The original plan was to build a 496 Chevy with 2.1 hp per cube and turn 8k rpm. They just run it on the dyno and it produced 960 hp, a little short of expectations but still impressive. The builder claimed the headers were too big, that with a smaller set it would produce more power. I don't have any specs on the run, other than the max hp. I can understand header size to be important in a drag car where when you shift and want/need torque to pull you back up to max hp. But for just flat out maximum hp period, will smaller headers really help??

Nick

[machoneman]

Yes they will. See Ed's nice texts on all aspects of header design:

http://www.headersbyed.com/+hcomments.htm

More here:

http://www.sandersonheaders.com/Lets-Get-Technical.html

[NIsaacs]

Bob, thanks for the links, however it appears the headers mentioned are all designed for low/midrange power, street or strip ET based.

I am wondering about max power, max rpm only. For all out max dyno power with a large cubic inch engine at 6000-8000 rpm, it would seem that bigger is better. I am having a hard time wrapping my little brain around the smaller header making more power than the 960 hp that they got.

Nick 

[jayb]

Header tube primary size affects velocity of the exhaust pulse in the tube.  Down in the collector, when the exhaust pulse comes out of one primary pipe it's speed helps draw exhaust from the other primaries.  If the tube is too big, the speed is slow and this effect is minimized.  If the tube is too small, you get a restriction.  Somewhere between "too big" and "too small" is the ideal size for the engine, and I'm sure this is what they are chasing.  What size primary tubes was the engine using?

[NIsaacs]

Thanks Jay, I will have my Brother ask and find out. Maybe the headers were made for a 650 cid or something, Lol. But the super modified pulling trucks run those huge zommies, they are short with no collector, so I am confused........

When you build an EMC engine, are you restricted to a certain size header per class?

Nick

[machoneman]

Thanks Jay, I will have my Brother ask and find out. Maybe the headers were made for a 650 cid or something, Lol. But the super modified pulling trucks run those huge zommies, they are short with no collector, so I am confused........

Are you talking about supercharged super mod trucks? In fact, a supercharged engine, on gasoline and more so alky or nitro, usually runs the biggest exhaust pipes (and no collector) that can be fitted. But these engines with forced induction don't behave like a naturally aspirated gasoline fueled engine. Think Pro Stock: these 500 CID engines could run much bigger primaries and collectors than they do. They don't simply because a properly sized step-header, with some mighty trick collectors, in a Pro car delivers max hp at launch (which is near red line anyway) and all the way through the run.     

[jayb]

When you build an EMC engine, are you restricted to a certain size header per class?

Nick

Nope, there are no tube size requirements in Engine Masters, although there may be some requirement that they fit a certain chassis; not sure about that one.

[Royce]

The only requirement for engine masters headers is that they fit the dyno cart without interference.. If you want to see a wild header check what John Kaase  used on his 2013 winner.  8 primaries on each side

[Barry_R]

EMC headers only need to be "chassis exit" style - nothing upswept or straight out is allowed.
No rules on size or configuration.
There are definitely "better and worse" sizes on headers, but primary pipe diameter changes are modest if they are reasonably close.  In other words you will see an incremental change going form 1.75 to 1.875, but a much larger change going form 1.5 to 2.0...

[NIsaacs]

Bob, the Super Mod trucks are Naturally Aspirated, the Pro Mod's have blowers, at least in the area I pull in, the rules are kind of all over the place in this sport for some reason. They don't seem to want to standardize.

I think both of these trucks are N/A Alcohol burners.

 

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Nick

[NIsaacs]

 Barry, I wondered about that. I went to Hedman Hustler vertical pulling headers to see what was offered and it seems both Ford and Chevy big blocks run 2-1/8" to 2-3/8". The small blocks seem to run 1-3/4 to 2".

Several of us that pull with this guy are watching this build real close. The driver and the builder are excellent engine builders and have drag raced for years. However, the driver has only pulled about 3 years and currently is running a bad little 393 so I know they are good builders and know what they are talking about.....but me being me....I have questions, lol. One of my relatives drove 500 miles so he could watch the new engine on the dyno!

I will find out what size they used so that will help.

Nick

[NIsaacs]

When you build an EMC engine, are you restricted to a certain size header per class?

Nick

Nope, there are no tube size requirements in Engine Masters, although there may be some requirement that they fit a certain chassis; not sure about that one.

So if you were building a pure dyno Queen, looking for the most maximum HP and never mind less than WOT power or torque, would you be more concerned about too small or too large of a header combo? With big cubic inches, 950 hp or so and 7-8k rpm.

Thanks, Nick

[NIsaacs]

The headers are from the owner/driver, vertical @ 2.250" not sure on collector size. They are not satisfied so they are doing what it takes to get the power they were after. They just pulled the heads and shaved them some more, now at 14.9 compression and gained 30 hp. They are talking to the cam grinder now. I don't know the stroke but the bore is 4.6".

Nick

[jayb]

So if you were building a pure dyno Queen, looking for the most maximum HP and never mind less than WOT power or torque, would you be more concerned about too small or too large of a header combo? With big cubic inches, 950 hp or so and 7-8k rpm.

Thanks, Nick

I'm not sure that question is answerable; I'd be concerned either way.  It is a tradeoff.

FYI on my 970 HP SOHC I'm running stepped headers, 2 1/8" to 2 1/4" to 2 3/8", into a merge collector.  Some pretty knowledgeable people have been telling me that the primaries are too big, and also the bend radiuses in the primaries are too small.  So I'm building another set, 2" to 2 1/8" to 2 1/4", with bigger bend radiuses where possible, and will test them on the dyno when the engine is back together, back to back with the original set.  I'm looking forward to that test, should be very interesting...

[fe66comet]

Length also adversely affects power band, the longer the tube the higher the torque but with a loss of HP in the top end.