I'm building a '53 Chevy 3100 pickup, aftermarket chassis, LS3 (495hp) crate motor and 5 speed. The stock exhaust manifolds clear the chassis just fine. Its seams common to take off the stock manifolds and install SS tube headers with a larger than stock collector. Other than improving the appearance and gaining a little more HP, are there any other benefits?

 

Headers DO improve the appearance and gain a BUNCH more power, but no reason you can't use manifolds in your swap.
BTW, LS3's are stock with 430HP, so what's in yours to kick it up to 495? Unless it's the Hot Cam version. And on that version, headers would uncork even more power!
The stock outlet is 2.5", but the 3" collector diameter of most headers would be better for power output.

 

They add power, and look good. Most headers aren’t garbage like they used to be 20 years ago when they would start leaking every three days

 

A good set of long tube headers (1 7/8" or 2") would be good for about 30 HP and about 15 TQ to the wheels over stock manifolds if they're emptying into a duel 2 1/2 exhaust.

That's more than "a little more HP".

If you're gonna go with a duel 2" exhaust system.....don't bother.

KW

 

LS3 crate hot cam motor, so 495 HP out of the crate. The stock manifold has a 2 1/8" ID collector. At most 9" tires on the back and maybe 650-750# of weight per wheel, so not much grip to ever use up the available torque. I also want a more stock sounding exhaust note (not loud). Would a smaller diameter exhaust tend to be have a lower sound volume?

 

NO. Use a large enough tube so as not to choke the engine. Why use such a powerful engine if you don't want it to breathe right? There are mufflers that will quiet any engine using a dual 3" exhaust system.

 

OK, speaking of mufflers, I called borla and they recommended their crate muffler, but after hearing the sound clip on their website, it'll be way too loud. Any suggestions for an aftermarket muffler that will give a stock level sound? I plan on using 2.5" pipe and an X pipe.

 

Dynomax Ultra-Flos are about as quiet as they get. Summit Racing has them as part numbers WLK-17258 and WLK-17259.

http://www.dynomax.com/mufflers/ultr...ished-mufflers

The Dynomax VT mufflers are even quieter......and I happen to have two never used. PM me if you're interested.....

https://www.summitracing.com/search/...oview=SKU&ar=1

KW

 

Thanks KW. The only drawback to those is they are 409SS and will rust. I like the sound though. The guy at Dynomax said to use a Walker muffler if i want it even quieter.

 

Given these constraints, I see no reason not to use the stock manifolds. If your crate engine is newer, then the manifolds that are on it are for a 5th gen Camaro. If you want a better look, word is that the LSA (ZL1) Camaros used stainless exhaust manifolds. They are probably cast 409, but will probably look better than the cast iron ones you have now.

Andrew

 

Dynomax and Walker is the same company.......with the Walker brand being a bit less expensive and a bit less 'power oriented'.

It's a certainty that the Walkers will make less power......maybe about 10HP to the wheels less.

Also.....by the time the Dynomax mufflers rust, you'll be ready for new mufflers (or a new truck) anyway.

Jus' sayin'.....

KW

 

Thanks for the input. I'm going to use the stock manifolds as they fit the application and coat them with Cerakote so they don't rust, then use a dynomax or walker muffler with an x pipe.