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I think it is mainly for noise reduction though it does provide some small performance gain. That being said I know on the Corvette there an exhaust can be a challenge so it may be not worth all the work and a straight dual exhaust will work just fine. At some point some of the stuff is not worth 5 or 10 horsepower in hassle / fabrication / inconvenienve.
In some cars, it's worth AHELLUVALOT MORE THAN any 5 - 10 HP. In some, it's less than that.
Only way to know for absolutely sure is to put one in and see.
Best place to locate it, is where the exh temp is the highest. An exh system is a resonant tube, therefore has a pattern of high and low pressure regions all along it. Since temp varies directly according to pressure, the pipe will be hottest where the pressure is highest. You can use a stripe of temp-indicating paint to find the hot places. The greater the difference between the hottest and the coolest places along the pipes, the more likely you will benefit from an H-pipe (crossover) or X-pipe. If you find the variation along the pipe to be large, you will probably pick up power from installing one. Put the crossover at the hottest place along the pipes that you can, as close to the motor as you can, given the constraints of the chassis and whatever else.
Maybe. But that's not really the right question. That's what people say that have mismatched combos, cheeeeeped out on something, half-assed something, all say. "Runs fine". They don't want to hear about how much BETTER it could run with some mistake or cheeeeeeep-out cleaned up.
I'd bet it'll run better with one, than without. Just exactly how much is anybody's guess. Looking for excuses up front for LOSING ("it's good enough") isn't the best way to go about WINNING.
Think of it this way: you're spending $xxxx, and getting yyyy results. A crossover (H-pipe especially) is something your local muffler shop can do if you tell em where you want it, in a few minutes, for less than $100. Maybe less than $50 if it's at the same time as putting on this hypothetical dual exhaust. So, if you could spend $xxxx+50, and get yyyy+100, but decide not to, are you making the right decision?
Thank you guys for your help. I'm not building a race car so I don't care about horsepower gains, and price isn't a factor. I am building the exhaust system and there isn't a lot of room under a 62 Vette for a crossover pipe. So if it doesn't make any difference in how the LS engine runs I will leave it out. Thanks. Bob
The Corvette Kid is really the only who can answer the question for this particular 62 Corvette.
Sounds like a very cool car and sweet project. Would love to see a picture.
Having had a 72 C3 in the family for like 40 years, our collected wisdom, earned the hard way is: Do it right & Do it once.
Is the car a keeper? Do what suits you. Pleasing yourself is what matters.
Is the car a flip or short timer? Do the cross over. Lot of folks like myself see it as a half measure and half assed project to not do it. I'd wonder what other corners were cut with the car if it was offered for sale with the LS3 swap and no X pipe. That probably sound harsh but it's honest. No offense intended.
FWIW - My experience is both Small Block Chevy & LS engines sound better with the X pipe. Both my 72 with a Dart 400 & T/A w/416 and the X pipe improved the sound quality.
Last edited by 99 Black Bird T/A; Oct 3, 2021 at 11:13 AM.
Thanks to everyone for your help and suggestions. At 64 years old this will be my last project. It is not a flip but a car I plan on keeping until I get too old to drive. I will go with the crossover. Hope to have the car done by the spring of 2023. Bob
Thanks, I have another question for you guys. I bought a LS3 / 4L65E connect & cruise set up for my Corvette, are these engines really plug & play or should I take it to someone who knows what they are doing and have it tuned. Thanks, Bob
It is plug and play as sent, If you haven't changed cam or intake/throttle body it should be good to go. I helped install a LS/376 525hp kit a few years ago and it fired right up and ran and drove great.
Thanks, The reason I asked is because the last time I did a LS3 crate engine it seemed to have a slight hesitation or stumble below 3000 rpm. I was just wondering if getting it tuned would fix the problem. Thanks, Bob
It's possible the exhaust configuration/ air box and piping to intake or a combination of things could cause an issue. GM can't possibly tune them for every situation, I would install it and see how it runs. Considering the time and money involved in the project a dyno tune isn't all that expensive.
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Do I really need an exhaust cross-over pipe 
