food nd cars

Im thinking about switching my mid tubes out for some LTs, probably pacesetter coated ones. With my current setup I put down 386 rwhp and was wondering how much you guys think i would gain from a set of LTs. I was sticking with the mid tubes due to CA emissions, but recently found some smog "friends". I know that on stock motors ~20 rwhp could be had but being that this is a built 355 maybe I would gain a little more.

VinR1

iTrader: (17)

...depends on which mids you currently have

food nd cars

Pacesetter mids. imo they aren't worth ****

VinR1

iTrader: (17)

In that case, I think it would be safe to say you'd pick up a significant amount of power switching to a longtube header... how much is impossible to guess but you'll certainly notice it

lt1-xjs

I doubt you'll pickup 20 hp for just the header swap, it depends on what you have for the rest of the system. A single 3" catback is a restriction at your power level, especially with a cat or cats.

food nd cars

It's going to be going through a high flow cat and cut out right after the y pipe merges

93z383

iTrader: (-1)

From personal experience with a similar build you could pick up another 20rwhp up top by switching to longtubes with a heavy build like yours. I had mids on my car for the first tuning/dyno session and was at around 400rwhp.. I went to some plain jane pacesetter LT's (which are extremely nice IMO... the ports need to be smoothed out however) and after another round of tuning/dyno I was at 422rwhp.

On a built motor parts like a 58mm throttle body and longtubes ect really shine. Are you guaranteed to get another 20rwhp? No, is it possible? For sure. No offense but mid's are a waste of money unless you pay for some excellent equal lengths. In any scenario longtubes will make usually more power, but it's generally on the top end.

lt1-xjs

You should be running that setup now with the mids, hopefully you have the 3" y.

ahritchie

iTrader: (1)

ZFreie

What I was about to say

slomarao

iTrader: (6)

LT's + TD's may get you 20hp, but LT's alone...nope.

what peak rpm?

SS RRR

iTrader: (2)

Probably not. If you are referring to going from stock exhaust to getting rid of cat, installing longtubes and an off-road y-pipe then the gains are more credited to getting rid of the cat. I was using Edelbrock shorties with stock y-pipe (cats in place) with a LPE top end (heads/cam/intake) and was running 12.5's @ 110mph. I believe it dynoed 350/350. Went to Hooker LT's/ORY and went 12.2's @ 114mph and dynoed 370/350. You will see gains, but if your cat is already gone then the gain will be minimal.

96capricemgr

iTrader: (1)

In my experience swapping from mids or tri-Ys to longtubes did NOT make a big difference. I race my car though not a bench the guys that race benches will tell you it is a huge thing.
bowtienut the guy with the 10.9 second NA stock shortblock Impala had the same experience, again though he races a car not a bench.

"midlengths are junk" is just used as an excuse for why a car isn't performing the way folks expected and it is usually because their expectations were out of line with reality.

If the OP is getting 386rwhp from an emissions passable cam he is doing OK and an emissions cam will not be as sensitive to the catback as a tight LSA high overlap cam would be.

I am not saying don't try anything different, I am saying keep your expectations reasonable, it sucks to see guys expect unreasonable results and get discouraged when they don't pan out.

bowtienut

iTrader: (1)

I went from 1-5/8" Tri-Y's (which I would classify as mid-length) to 1-3/4" LT's, and picked up somewhere between zero and .05 sec ET, and no noticeable mph change. Dyno'd 425 rwhp with the Tri-Y's. Did not dyno the LT's. Both were run with 3" x 18" collectors, no exhaust system.
The 10.98 run was with the Tri-Y's.

96capricemgr

iTrader: (1)

This is the mids I had and the Tri-Ys both Pat and I had, IMO the worst part of either is the ball and socket fitting small enough to fit a stock catback, still though given the actual performance of the cars with these headers I don't think it a big deal.
You will notice the mids are nowhere near equal length.

lt1-xjs

All I'm trying to say is, the gains he'll make will be from the changes made from the collector back not from the longtube. A dual no cat system with an X pipe and free flow mufflers would pick up the 15-20 horsepower he's looking for.

nitrous2fast

iTrader: (2)

The problem with any exhaust manifold/header system is that many dont take the time to calculate what size header they need. OR they dont properly size the header for the torque boost in the area that they need.

For an all out race car yes get a large diameter header at the proper length. That will give a torque boost in the high rpms where the motor will spend the majority of its time. But many people always get the largest size primaries thinking that they will be the best. This is a very common misconception. Even on the same motor a larger primary tube size will yield a higher rpm torque boost than a smaller primary size. The question is where do you want that extra torque boost?? There are a few questions that you should ask yourself before buying a header.

1 what size engine?
2 what rpm range will it be spun to?
3 where are the other components of my build going to give a torque boost?
4 what type of engine? n/a, turbo, positive disp
5 where should i put another torque boost to help my type of racing/driving?

There is more to selecting header size than just picking the one with the largest primaries.

guppymech

iTrader: (7)

The above is true but in reality the header primary sizes and tube lengths for the available headers for our cars are rather limited.

93z383

iTrader: (-1)

There's a big difference with headers on a big body vs an Fbody... the mids they make for the big bodies are a lot better than the f body mids from I've seen.

I'm just talking from personal experience. I had no problems on my 383, it ran like a top with the mids. Maybe it was more from the tune, but I was making much more power up top with the longtubes. My powerband goes up to almost 7k though.

ahritchie

iTrader: (1)

This seems like a pointless exercise since your car already makes more power that LE advertises for a little cam: "LT1 LE2 heads are capable of producing 370-380 RWHP with our small 218/224 custom cam and 410+ RWHP with our 232/240 custom cam."

http://elliottsportworks.com/home/?page_id=53

I would imagine any peak HP gains on the dyno from longtubes would be negated by loss of torque lower in the RPM range as others suggested leaving real world performance nearly identical between the two. But feel free to try it out and prove me wrong! (I have pacesetter mid-tubes too )