From another forum...1 3/4 vs 1 7/8

[GeorgeInNePa]

Stock Motor 1 3/4" Vs. 1 7/8 Engine Dyno Results!!

http://www.ls1tech.com/forums/showthread.php?t=981234

snip...Power output was virtually identical untiL 4800 rpm when the 1 7/8" headers began to outpower the smaller 1 3/4" primaries. ...snip

Read.


Discuss.


I may need to give Nick a call...

;)

[GRRRR8]

George, you and I have identical combos except for headers. Before you call Nick lets see what we get at the track and dyno. Your 1 big diff is the Yank, right now. Hopefully I will have intake and T-body soon and then I will retune for it all. Then this winter I will do cam/heads etc

[MANOFSTEEL69]

If you guys remember, Mike said from the start the 1 7/8's were the better bet for those of us that were going beyond just the normal, intake and tune mods. I went with them not only for the cam, but the Maggie that will be installed in the spring.

[GeorgeInNePa]

George, you and I have identical combos except for headers. Before you call Nick lets see what we get at the track and dyno. Your 1 big diff is the Yank, right now. Hopefully I will have intake and T-body soon and then I will retune for it all. Then this winter I will do cam/heads etc

I'm not really worried about it. The difference is small in the grand scheme of things. A good launch with no wheel spin would make up the difference.

[Andy@Livernois]

generally speaking we install the 1 7/8 headers on just about every car we do. There are some exceptions to the rule (like dead stock 97-00 ls1 cars) On the G8 our standard header install will be 1 3/4 due partly to the baby cam that is in these cars. If someone wanted to do 1 7/8 i think its only 30 dollars more and would be recommended if more mods were in its future...

[Andy@Livernois]

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[SS Enforcer]

I really think there is a lot more going on than just header sizes. I run 1 3/4 ID headers on mine and they perform very well indeed and have no intention of changing them for the moment. It's all to easy to say bigger is better when in fact I have seen 1 5/8th interference headers perform better than 1 3/4 4-1's on bolt on ls1's !!! during a header comparo on a engine Dyno.

A guy in Australia said that adding a camshaft appears to overcome some percieved intake and exhaust problems. I have seen cat backs provide huge increases in peak power but they still don't run a number at the track.

Here in Australia the 1 7/8th combined with dual 3" systems are all the rage but mine has 1 3/4 and 2 1/2 inch and makes as much power or more than a lot of the other similar setups. When I bought mine I asked about the bigger system and the exhaust guy and ex racer talked me out of the big pipes saying the system would provide what I wanted and beyond.

Choice of mufflers and x pipes, kiss systems, H pipes , merge pipes, mandrel bends, collectors , stainless or mild steel pipes, high flow metal cats or std, ceramic coated or non coated headers, intake selection, tune yada yada yada . There is too many other variables in play to simply state that one size will be better than the other.

http://www.xforce.com.au/cars/view_car/38
My car has the 2.5 SS catback shown here but different LT Ceramic headers.

My view is put a system that sounds good on your car and if it happens to have Lt's and is free flowing chances are it will perform good as well.

cheers