Hat's off to Ron and his team at Vengence for putting together a comprehensive test of a few C7 header designs. We where doing our own testing at the same time and finally got a chance to test out ARH's 1.75" LT as well....

ALL tests where done with a stock GM calibration, 195-210 coolant temps and 180-200 degree oil temps. Three pulls where made with each header and the runs shown where the middle of each.



The 1.75" header was quite impressive on this 100 percent stock engine. Will be interesting when Ron tries these on his head/cam build and ours on a supercharged engine. Both the 1.75 and 1.875" made the same power over 4800 rpms so it will be interesting to see.

My quick rip around the business park most certainly felt the increase in the punch zone....

Howard

 

Thanks so much Howard...nice to see the results on stock car.

 

Time to sell my Kook's

 

Are the 1.75" ARH mid-lenght or the same lenght as the 1 7/8"? And if they are mid-lenght do they use the 4 cats?
Thanks

 

Wait, the 1.75" (1-3/4) made that much more power over the 1.875" (1-7/8)? Are you backwards on that?

I thought the 1-3/4" were the shorter mid-lengths. If this is correct, then there are a heck of a lot of factors with modifying these engines that affect power curves and needs!

 

Edit: I hope that didn't come off as rude - I was just surprised by the difference if it wasn't a typo.

 

The interesting topic is here is "who decided when the LS3 came out that it HAD to have a 1.875" primary" It just kind of happened and like cattle we all followed because that's what everyone did...so here we are with a similar engine.

I had told Nicky in our last couple weeks of conversations that I think this engine likes a smaller primary just comparing to how the factory system was working. Obviously the goal was to improve from there. A couple sets we tested really dropped off torque down low but improved on top...big deal if you like dyno sheets but we look at average power across the usable RPM range.

The 1.75" primary proves the engine likes a bit of back pressure which is most likely tied to both the tuning of the intake manifold design and the new designed cylinder head. The ARH "mid lengths" also tipped me off as they filled a decent hole in torque that was created from a set of 1.875" LT we tested.

Hopefully Nick's firing out a set of the smaller primaries to Ron at Vengence as I REALLY want to see what they do on his H/C test mule. You need at least two to make an average so even though I'm confident its a better design lets run it through the "Myth Busters" Program....I would think the bigger primary would benefit the more modified engine but header design is much more then bigger pipes. Sound frequency (reversion) has a much bigger impact. Anyone that has worked on two strokes will understand this as the pipe works off this same theory....

I again want to thank Nick for fabricating a one off set of these literally overnight just so we could see if it worked!!!

HT

 

Interesting stuff Howard, thanks for posting.

I'm not surprised in the least, but American Racing Headers is really showing their knowledge and dedication to their products right now in full force.

ARH FTW.

 

Thanks for your hard work Howard!

I am assuming the 1.75" ARH is their mid-length headers?

How did the AFR look with no tune, safe to drive without fear of running lean/rich?

 

The way it was posted I believe they are both the long tubes systems, just one is 1 3/4" and one is 1 7/8". No mid length headers.

 

It was the full length 1.75" header NOT the 1.75" mid length. The fuel curve was also stock starting at about 13.0 at the hit then trickling to 11.4-11.7 through the curve. STOCK Cal so no magic tricks....

HT

 

I didn't put the mid length 1.75 up as the sheet was getting to clouded. The mids did well to fix that "hole" we have spoken about but hands down the 1.75" header rocks. Just took car for a blast to get gas and it really fries the tires....did a pull this morning with a few calibration tweaks and the torque never drops under 450 ft/lbs from 4000-5000 rpms....you can see how flat it was in that dyno report.

HT

 

Regarding the ARH mids... Do they have 1.75" and 1.875" mids or just 1.875? I assume the 1.75 LTs would require some tuning to keep from throwing a CEL?

 

Now we can see what most of us already knew anyway with the fact that ARH is and has always been the way to go. Definitely interesting that the smaller primaries made more power everywhere. Thanks for the hard work and sharing your results Howard!

 

So is ARH going to make the 1 3/4 LTs............

 

Yes we will be offering the 1-3/4" long tubes. Knowing what we've learned with the help of Howard on this last test, we'd be not to.

To clarify something asked earlier, our Mid Lengths are 1-3/4". We do not make a 1-7/8" Mid Length . Anyone that needs help on their particular C7, please feel free to PM me and we can go into everything in detail. We understand that not everyone has the same mods in mind. We believe we have a system that will produce the desired results regardless of the upgrades you have planned.

Ron and Howard, thank you.

Nick

 

Great info

Was this without Cats? If so, did it throw any codes?

 

Thanks again for taking the time to share real results, ARH FTW!

I had no doubt the 1.75" would make more power down low, as that's what I found on my h/c 346. Though am kinda surprised the 1.875" didn't pull away up top, but can kind of see that since the new LT1 even though it has the same bore, it has a slightly smaller cam and lower flowing heads compared to the LS3 or maybe it's more the VVT...imagine they might do better on a h/c motor pulled to a higher rpm or maybe a 1.75 stepped to 1.875 would be the ticket for best average power.

 

They saw 11.4 - 11.7.........Shouldn't the AFR be 12.5 -12.8 for safety? Oh wait, you had no tune so tuning should be able to fix your lean condition.

 

That "factory" AFR curve doesn't get any safer for a NA motor. That's an AFR we run on boosted engines..

The lower the number the "richer" the AFR.

Howard