1-3/4 vs. 1-7/8.

[Infamous]

I was recently told that the larger diameter headers produce the most power at the higher RPMs as opposed to the smaller diameter headers (1-3/4) which produce the most power at lower RPMs. Opinions?

As a side note: I do understand the reason for having a larger diameter header set up for FI, but is that where the benefit ends?

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[LethalPerformance]

On an NA car you're really not going to see a difference in power between the 1-3/4" and 1-7/8" primaries. However in a high HP blown application you'd be better off with the larger primary.

I recommend going with the larger ones regardless.

Jared

 

[bluebeastsrt]

You'll probably make a few more ponies with the 1 7/8ths. And like said above you'll be set up for future mods. Over on Camaro5 they did a dyno test using all American Racing headers on an LS3. Here are the results below between 1 3/4 vs 1 7/8th vs 2 inch primaries. I'll include the link if your interested in checking out the entire thread.

http://www.camaro5.com/forums/showthread.php?t=63640&highlight=header+dyno+test

JANNETTY RACING HEADER TEST RESULTS
First let me say Thanks to Nick American Racing Headers for building us all 3 size headers, cat converters and test pipes, and related hardware.

Just to keep things Fair I Purchased these Headers for the Test.

Our Test Car is none other than, Bigdogs LS3 Camaro used in our CAI test.
This Car is 100% Stock other than the Headers installed for the Testing.

Stock Peak Numbers 373 RWHP 378 RWTQ
Stock Average Numbers I will post tomorow Forgot to print them.

1.75 long tube headers w high flow cats Peak 401.1 HP 403.8 TQ
1.75 long tube headers w high flow cats Average 281.2 HP 363.9 TQ

1.875 long tube headers w high flow cats Peak 406.8 HP 407.5 TQ
1.875 long tube headers w high flow cats Average 283.7 HP 366.6 TQ

2.0 long tube headers w high flow cats Peak 411.7 HP 408.9 TQ
2.0 long tube headers w high flow cats Average 288.1 HP 368.1 TQ

The 1 3/4 Headers did Surprisingly well.
The 1 7/8 Headers IMO are the best all around header.
The 2.0 Headers are neck and neck with the 1 7/8 but Slightly stronger from 5000 to 6300

In an all out racing application they would be worth the extra investment.

So Now it is up to you to choose what best fits your application.

 

[Zemedici]

You'll probably make a few more ponies with the 1 7/8ths. And like said above you'll be set up for future mods.

curious as to why you think this?

1 7/8 is very large for a NA 302, I'd stick with 1 3/4 unless you plan on going FI. Do not fall victim to 'header envy'.

 

[StangMan04]

I always like to plan for the unexpected when possible. Get 1 7/8ths and be prepared in case your plans change.

 

[bluebeastsrt]

curious as to why you think this?

1 7/8 is very large for a NA 302, I'd stick with 1 3/4 unless you plan on going FI. Do not fall victim to 'header envy'.

See dyno results above. It's not about the size of the engine. It's more about how well the engine breathes. And the coyote has one of the best head designs out there. Don't see how you can argue with the results posted.

 

[Zemedici]

you posted results from a LS3, which is a 6.2l. What does that have to do with a 302 (displacement matters in comparison to header size) ??

LS guys run bigger headers, due to bigger displacement, (6.2l, 7.0l etc etc), as they have the displacement to be able to support it. If you could find a similar comparison with a 302, that'd be relevant data.

 

[Infamous]

I always like to plan for the unexpected when possible. Get 1 7/8ths and be prepared in case your plans change.

I agree, I won't be doing FI for the foreseeable future. But it's nice to already have it on there.

 

[bluebeastsrt]

You'll get the same results for the 5.0. The heads on a 5.0 flow better than LS3 heads. Why do you think the LS3 is making 426HP to the 5.0s 435. If bigger is better and that's all that matters how does the smaller engine make more power? Answer Better flowing heads and better Cam and valve design that allows the smaller motor to breathe better. If your moving more air in you'll naturally want to move more exhaust gases out.

 

[LethalPerformance]

I agree, I won't be doing FI for the foreseeable future. But it's nice to already have it on there.

Go with the 1-7/8" primaries and don't look back. You won't regret it nor will you have to purchase another set if you decide to build a 800+rwhp monster down the road. :cheers:

 

[bluebeastsrt]

Go with the 1-7/8" primaries and don't look back. You won't regret it nor will you have to purchase another set if you decide to build a 800+rwhp monster down the road. :cheers:

I totally agree.:cheers:

 

[Zemedici]

You'll get the same results for the 5.0. The heads on a 5.0 flow better than LS3 heads. Why do you think the LS3 is making 426HP to the 5.0s 435. If bigger is better and that's all that matters how does the smaller engine make more power? Answer Better flowing heads and better Cam and valve design that allows the smaller motor to breathe better. If your moving more air in you'll naturally want to move more exhaust gases out.

Although that is true the 302 does not flow NEARLY enough air to warrant a 1 7/8 header, it just doesn't. Save for a FI build, which seems to be where everyone is headed nowadays, in which case it would be beneficial to pick up the bigger set just so you don't have to purchase different ones in the future.

Its nice to be able to discuss tech with someone whos not talking out of their ass, thank you sir :cheers:

 

[Matte Black]

There is more to primary size then just basic 'power' as an all encompassing term. Primary size can affect the characteristics of the power/tq curve and when peak tq is reached. Its better to determine what your goals are (street car vs race car) and then make your selection based on the info. I will say that Displacement does/should play a roll in the equation, despite what has been said above.

Here's some good info based on header design- if you have a moment, give it a read.

http://www.hotrod.com/how-to/engine/header-basics/

 

[Matte Black]

You'll get the same results for the 5.0. The heads on a 5.0 flow better than LS3 heads. Why do you think the LS3 is making 426HP to the 5.0s 435. If bigger is better and that's all that matters how does the smaller engine make more power? Answer Better flowing heads and better Cam and valve design that allows the smaller motor to breathe better. If your moving more air in you'll naturally want to move more exhaust gases out.

I've seen LS3 heads flow 320+ stock and LS7 heads have been known to flow roughly 360cfm where as with a stock Coyote you are lucky to see 300cfm on the intake side.

'Better flowing heads' is just not accurate.

 

[Zemedici]

I've seen LS3 heads flow 320+ stock and LS7 heads have been known to flow roughly 360cfm where as with a stock Coyote you are lucky to see 300cfm on the intake side.

'Better flowing heads' is just not accurate.

This. The 302 heads flow INCREDIBLE (for their displacement), however, comparatively speaking to a 6.2 or a 427, there isn't a replacement for displacement, save RPMS. RPMS will make up the difference. If you look at the powerband of the 302 vs the 6.2, you'll see where they make power, and you'll see the difference between the two.

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