00 Rooster

I have searched and not found the info im looking for (read a great article on a fi c6 with both sizes though). I found a set of 1 7/8 headers for a good price. Problem is that these headers will be my first engine mod. I would like to do a cam and heads but that will be at least a year down the road if not more. Should i wait and find a set of 1 3/4 or will these headers work? Id love to hear some opinions or get some links if they exist!
Thanks

johnnytaboo

I had my heart set on 1 7/8" tubes until I was told it was unnecessary. I was also told that I would likely lose some of my low-end torque, and that the gains wouldn't really show until I either upped the displacement, or did a H/C package.

One of my constraints was money though. I went with a set of LG streets and I am plenty happy. I don't believe you will do any harm going with the larger diameter tubing, just know that you aren't going to gain anything by choosing these over the 1 3/4 headers. If the price is right, and the quality is good, I would say go for it. If you go nuts down the road and do heads, cam, blower, ect you will likely reap the benefits.

I also just wanted to get in a comment before someone told you to do another search (if you do, don't forget the check the Z06 section as well, since this question is tossed around there as well)

bumble-z

Go with the 1 3/4". Being that you are stock, you won't need to go to the 1 7/8" untill you go Super charged, etc.

m6 c5

From research I did awhile ago I believe that I found with an otherwise stock engine you will lose a little bit of power with the 1 7/8 over the 1 3/4 because you will not be moving enough air to scavenge properly. I think that you may be able to modify the engine enough to use the 1 7/8 but I would not get the 1 7/8 unless I was going to get a good deal on them. In my fairly uneducated opinion you would be better off with the 1 3/4.

vettenuts

If you are doing heads and cam later, get the 1-7/8. Don't buy twice. Most testing I have seen loses nothing down low.

ZZOOM06

If the 1-7/8 are a good price, go for them,,,,you'll be dollars ahead in the long run!

Jimbo

C5Natie

I have heads and cam with 1 3/4 headers. Makes plenty of power. 1 7/8 is for bigger cubes or a mean FI setup. If you go 1 3/4 headers with a full 3" system then youll be fine.

flynhi

Beware of clearance problems with spark plugs and plug wires.Heat protection sleeves for plug wires are a good idea.

firefighter813x

I'm going 1 7/8 when I do buy them. Kooks or American Racing.

sami85L98

1 7/8 all the way even though you stock, i regret having 1 3/4" buying another set is mucho $$$ and work both.

00 Rooster

thanks for all the replies guys I feel like a bit of a dbag now. this info is great and all of the replies were helpful. turns out there was a bit of a miscommunication between the seller and I though:o the headers he is selling are 1 3/4. nowIi'm kind of upset they aren't the big ones.
rob

vettenuts

What are they?

Gearhead82

I just researched this topic for the last few months. What I came to find out is theoretically, 1 3/4 scavenge better than 1 7/8 on an otherwise stock motor, which creates a better low-range torque and throttle response (part-throttle power).

HOWEVER, all of the dyno's and testing that I've seen show that 1 7/8 lose basically nothing down low and actually show gains in the mid and top range on an otherwise stock motor. If you are planning on only streeting this car, than it doesn't make much difference. But at the track, top end power is a big deal for me since I stay in that RPM range so often.

Here's a great thread that I found. TSP did an engine dyno comparison on 1 3/4 vs 1 7/8. Keep in mind that they used 2 different class of LT headers, so the collector could have something to do with the performance change.

Overall I decided that 1 7/8 were the best choice on my Intake / Exhaust Z06, plus I planned on doing a lot more work later on so I wouldn't need to swap them out.

~Josh

An identical thread like this was posted about 4-5 months ago.

Tony Mamo (AFR heads) said that for even an aggressive H/C 346 you should use 1 3/4.

He posted a bunch of reasons why. I'd search for the thread, but....

LoneStarFRC

1 7/8", or larger, are best for larger displacement engines, i.e. 413, 427, 454, etc.

Go with 1 3/4".

00 Rooster

thanks for the info and links I have to say it again, I searched and I feel bad about the lame post.

the headers are 1 3/4 which is what I intended to purchase. I thought the seller had 1 7/8. after reading more about the bigger primary headers, it seems, there is little downside if I plan to continue to mod. I may have to change my search. thanks for the education, it will be put to good use on my header purchase

00 Rooster

great read, good info and some drama

R6cowboy

1 7/8" headers won't hurt your engine, but you won't benefit with them either on a stock LS1 engine over 1 3/4". And any loss in power won't be noticeable. 1 7/8" headers are pretty much overkill for just a "bolt-on" LS1. IMO, if your motor is making under 600 horsepower, you won't get much benefit using 1 7/8" headers over 1 3/4". Simply because the engine does not move enough air.
And remember its a good idea to re-tune after adding the headers. So if you plan on adding any other engine mods soon, it might be a good idea to be patient and do all mods at once.

firefighter813x

Here is some more good information... talked with Total Engine Airflow and they mentioned this...

The stock 2.00/1.55 valves will benefit from the larger 1.875" primaries more than the 1.75". If you're using aftermarket heads especially with the 2.02/1.57 valves the 1.75" will be sufficient. TSP and other companies have engine dyno data like TEA that show using the 1.875" primary will gain HP up top with minimal to no loss down low. Are you really going to notice a little of torque/hp down low? I say probably not... same as when people claim to "feel" the difference of a ported TB. You don't race primarily in the low RPM's anyway. <--This is JMO.

firefighter813x

Look at it this way too...if you're going for name brand headers like LG, Kooks, American Racing, etc you're paying at LEAST $1100 new for the set with x-pipe. If you change your setup in the future to FI, or a bigger N/A build it would be nice to have the 1.875" header from the start so you don't ever doubt your self.

If you're purchasing OBX, XS Power or used 1.75" headers then just go for it and don't worry about it.