I have a '74 L-82 with a complete 2.5" exhaust system - including the exhaust manifold. Would I notice a big performance difference with headers? Long or short? My current sound is fine. Thanks!

 

Yes

Here are the ones I went with. 100% happy: Alhough, to be fair, I also edited the location of my catalytic converter.

Doug's Headers

 

Pure performance probably increase but how much??…seems fitment and ancillary issues another issue.
it would be fantastic to dyno before and after a stock engine!
go fund me? Im in to see differences if stock exhaust not plugged or mufflers rusted.

 

depends
if you already have a good hp then probably no.
if you want/need every little bit then yes.

 

The stock exhaust manifolds are 2 inch. So if you have upgraded to 2 1/2 inch manifolds and took the time to port match them to your heads. Then you already have a upgrade over stock.
If you went from a completely stock exhaust to headers with a 2 1/2 inch system and free flowing mufflers. Yes you would see a huge increase.
From where you are now however,
Low end and mid range power would be very close. Only up in higher RPM's are you likely to really feel a difference.
And then there are the draw backs with headers. Under hood heat, fitmit issues, spark plug wire re-routing, etc, etc.
I run ceramic coated 2 1/2 inch manifolds that have been port matched. I run stock plug wires in the stock location and have no trouble with burnt plug wires. I run my stock ign. shielding. Bolts never come loose. My air-con compressor mounts just fine. My power steering hoses don't get fried by the heat.
And, on the street, my car makes very good power and torque.
Just my 2 cents.

 

Good quality long tube headers worth about 10% increase, give or take. Shortys not worth much over stock.
stay with a smaller primary tube diameter for good bottom end, midrange increase.

 

Define performance, we talking MPH or less seconds between stop lights?

 

With the L-82 I think you might see a bigger increase in performance with long tube headers vs an L-48. you have a cam that has more overlap and is going to like easier breathing exhaust. And it will like the scavenging effect long tube headers offer. You also have a cam that likes higher RPM where free flowing exhaust can really shine. If it were mine I'd do it. I'd also be sure to get them ceramic coated.

I have side pipe headers ceramic coated. No issues with burning anything, plug wires stock routing and A/C stock installation. Primary size...eh I'd probably get 1 3/4".

 

Well, in terms of buying h.p. With long equal length tube headers it will buy you more h.p. for you dollars than anything else. If you are looking at the shortys I would save my money over factory 2 1/2” rams horn exhaust manifolds. As others have mentioned port matching to your heads will pick you up some power. Both the 2 1/2” rams horn and the BB stock Corvette exhaust manifolds are pretty good and you paint them with high heat paint, bolt them on and you are done. You don’t have to worry about rusting out, leaks, and re-routing wires. Paint does not last long on headers so you will want to go to the expense of ceramic coating to keep them looking nice.

 

If you do go with a header, in a relatively stock engine, yeah I'd use the 1 5/8" headers. If you have gone with major engine upgrades, go as big as you can find. 2 1/2" mandrel bent all the way back, but absolutely put in either an H pipe or X pipe. Your ears will appreciate that. I have a fairly well built SB (434 cu in) and just installed an H pipe into my 3" SS exhaust. Im using 1 7/8" headers. Believe me, the exhaust note changed considerably. Its quieter, I can hear my stereo. The wifey says the house no longer rattles when I start it. Power is still
unbelievable. I just did this over the last 3 days so no dyno runs yet. But it was a very positive upgrade. I've said it again and again. Be careful what you build.

 

You will notice a bigger increase if after installing headers you retune your carburetor and ignition timing.

 

Headers allow everything else to work. My LS5 turbo 400 was a bit of slug 30 years ago when I got it. Headers and cam did help a bit. But really not worth the effort. The 3.73 gears helped more than anything.

I fought the issue hood of clearance and that was reason to not make my car actually fast. Putting off the L88 hood for as long as possible, but (went long L88 to avoid the wiper door), but finally had to give in. I spun a bearing at 110,000 miles, so the choice was big crate motor or making the little LS5 work…

It wasn’t until, the air gap style performer, 850 Holley, iron head bowl work, MSD and roller conversion do I think the headers started to matter. Years later I had a head gasket issue between cylinders, so yes, out with the small valved iron heads and into Brodix Race Rite aluminum heads, also did big aluminum radiator and electric fan, borgosan steering box. Now I am sure the headers matter. I’d post pictures of the engine, but it looks like every other. There is no spacer under the carb, even with a drop base, there is ZERO hood clearance.

Now the car feels fast, it is criminal that they put those little valved heads on a big block going in a vette, but now the car feels as it should have from the factory. In retrospect, I should have simply yanked the original LS5 and got a 540 stroker, but ai have no room for a giant motor in my condo.

my C8 should be on the way very soon. These are some older pictures, but the car is the same except for Radial T/As now.

 

You should be wondering why you asked...if its for more power consider this about your motor

9:1 compression which is about as low as you can go and get good power...stock HP is 250 horse. Will it be louder, yes. Will you feel it without changing your heads and your cam, no. THere is no way you would feel a 12 horsepower gain in the seat of your pants which is what you could hope for and it would be at the top end. Bigger horsepower cars can see a 5-15% hp gain as per the dyno shows will tell you but again that is the final HP number at peak power which is a function of torque....its the first thing hotrodders do but it is the least you can actually do to gain torque...
That being said it is a start but dont expect much... Now how many miles are on your engine.....if the rings are warn you will need to address that as you are losing compression there but I will talk about that in the end



The most effective way to get seat of the pants power is to change your rear end gear to a minimum of 3.55, 3.70 is good for running around and not horrible on the highway. If you can afford a 5 speed its even better as the first gear is lower so your torque multiplication is higher. Do you want to do burnouts and snap your neck off the line...thats torque....if you want to go really fast above 5000 rpm...thats HP. TQ x RPM= HP.....you need the first to get the second. And the rear end ratio makes up for a weak engine in the beginning and creates power in the end. Most big tractors can pull your house off the foundation with 40 hp because they have a ton of torque but dont RPM over 3000. Alot of guys are happy with what they have because they dont want to go through all that work or think they cant swap a rear end. Its easy after you do the first one as its stuck in there with a bit of rust and age but once it pops free and you lube the sombreros, the next is easy

your motor is an air pump so the more you can suck in and the more you can blow out, the more power you will generate. Your power is at rpm over 5000 so you need to get there as quick as possible. Low rear gears will make your engine spool up faster which is why your head snaps back...Think of the stock parts as restrictors and you need to make everything bigger so you can move more air

What you want to do is buy everything once with your end goal in mind. If you buy shorty headers you will get noise but no power and will have to replace them eventually so get long tubes and the biggest diameter you can afford. I also suggest getting them ceramic coated so they do not rust, and rot out and will keep the heat down which is a plus...Then you wont have to buy them again and again.

Then if you have a stock cast iron intake , look to find an aluminum one that will fit under your hood. the weight reduction from cast manifolds will add up. The Exhaust manifolds are heavy, the intake is heavy, and the heads are heavy.
If you have a good running 750 quadrajet keep it and just put a spacer under it to help with heat issues. What you can fit under the hood isnt going to effect you that much for the horsepower you are probably hoping for. If you want over 400 then you will want a taller intake which means a hood swap.

next to buy and most important is heads....Name brand aluminum heads that are intake port sized at 180- 185 cant be beat for where you are. but they are the same price as the 195 head, you just need to figure out how big you want to go. They are all 65cc combustion chambers so you will increase your compression slightly too which is a plus. You will get all the HP you want for quite a while as you want more and more for some time. I suggest saving up as long as it takes to get AFR CNCed heads. They always make the most power in every head test I have seen....next would be trick flow, then Brodix, then Edlebrock and the chinese brands. Some folks just get them because they are aluminum but they dont flow all that great and the flow numbers is where the power is. You will spend $2000 on the AFR heads and you will get every pennies worth out of them....

Then its onto cams because you are building a good flowing engine now, you want to be able to use all of it. I do head and cam swaps at the same time and if I want more power I can increase the cam size later without much fuss. I would look at. I would start at a cam right around .500 lift as that is considered pretty mellow still and the are pretty good. That with a bigger lift rocker arm will make a good change. stock is 1.5 ratio rockers and 1.6 is actually better. Ford runs 1.6 stock in the old engines. More lift, more flow, more power. You are probably going to replace them any way. You can still use a stamped style as well without sacrifice any noticeable power but I would use the polylock nuts to ensure they stay where you set them.

So now you have to consider the age of your motor...age and mileage is wear, and if you have upwards of 50,000 miles those old rings are eating into to your bore and its not round and sealing anymore so after you get the headers and want to swap the heads and cam, you may want to look at your bore and consider if it can get buy with a hone and re-ring or should your bore it and get pistons. If you get new pistons its time to address compression. I like 10.5:1 and higher as I burn the high octane stuff to reduce detonation and with the power I want its necessary..you will have to decide what you want. Okay so you pick away at your motor with headers, a possible intake swap and are now looking at the rest of my list...heads are $2000 grand, pistons, rods, bearings and rings are another $2000 and the machine work is goinng to be $2000.....your $6000 into the motor and we havent talked about the cam cost and folks here still fight of flat tappet vs roller. If you dont know the difference then you want roller as you will have to really pay attention to oils for a flat tappet so add another $1500. Engine power is a steep slippery slope now a days and its expensive as we all want power...but there is another way to get there....you just fell into a $7500 dollar hole because you wanted headers


So lets talk crate motors and reasonable HP....lets say 400 to 450 hp range ...been there, done that and its is good. You are not a racer, you are the cool kid that wants to sound cool and chirp tires and go fast in short bursts...that is your number. Blue print actually dynos them before they go out the door
UNDER $7000 says it low profile and is 9:1 like your motor
https://www.summitracing.com/parts/mll-bp38318ctcv

may not fit with our hood without a manifold change and a low profile air cleaner drop base.....
https://www.summitracing.com/parts/mll-bp38315ctc1

heres the long list but some will be too tall and the lowest price is just over $5000 and most wont fit under your hood the way they are
https://www.summitracing.com/search/...=crate%20motor

In the end I would consider what your end goal is and if you are willing to save up or do it one piece at a time, thats what I had to do and still do....took all fall to actually get enough saved to buy the heads I needed and wanted last summer....life just keeps emptying my account.

you can get that 400 horsepower with $2000 dollar heads and a $1500 dollar cam upgrade and wait until you have so much blow by you need new rings. Maybe it will be years before it gets to that point. It may be worth it to do it slowly if that is how you have to play it.

So becareful getting those headers

 

A gear ratio change doesn't add power it mearly gets the car moving a bit quicker.. a transmission does not create torque. It mearly changes torque multiplication..
And yes headers actually build horsepower and torque without building a nuclear powerplant.

 

If you do nothing else to the engine, you will see a small increase in performance going to a long tube header.
A 10% increase is the average for headers so you might find a little seat of the pants gain.
Adding a performance intake and air cleaner with headers will increase that gain because headers alone will only let more exhaust to exit faster, but you also need to allow the engine to pull in more air to make real performance.
The other thing to consider would be a nice camshaft that makes power between 1500 and 5500 rpm.
You don’t need or want a high performance cam for a nice street driven car, but one that makes good bottom end and mid range horsepower.
Exhaust, intake, air cleaner and a nice street cam is really inexpensive and will make the most street able power.
Some people will take it a notch higher and say you’ll need new performance heads to make it all work, but you really don’t.
For what it sounds like you are after, those oem L-82 heads are all you need.

Many here promote swapping rear end gears, which is fine for light to light around town driving.
But, swapping from 3.08 or 3.36 to 3.55 or 3.70 rear end gears without going to an overdrive transmission will increase you rpm’s while driving on the highway and you may find yourself driving at 60 mph in the slow lane to keep the rpm’s down.
There are several good rear end gear calculators on line.
See what your rpm’s will be at say 65-70 mph with a 3.70 rear end gear using the calculator, then decide if you’ll be happy cruising on the freeway at that speed and rpm’s.
For example, my 73 with 3.36 rear end gears and a TH400 transmission with a 1.0 final gear, tach’d 3,000 rpm at 65 mph which drove me nuts on the highway for any length of time.
3.55 or 3.70 rear end gears would have made it even worse.
Just my $.02 worth.

 

Hey thats what I said!!!

the power gained is so small and with folks here that say your drive train eats up 15 to 20% of your horsepower, you would effectively gain nothing at the wheel. Thats why you need torque multiplication to amplify what you have

 

Less seconds between lights -

 

I don't see headers installed on a stock L82 providing anything that would be considered noticeable for less seconds between red lights.

 

Its a slippery slope...If you want more power, its an addicting pursuit. Its hard to say when enough is enough. I was happy with my 12 second motor but the the rollers cam apart and i had to start over....im hoping this big block will last longer

 

Just to give you an idea, here's what headers did for me on a 200 HP net rated car. My 82 L-83 with just a tune to a tune/headers gain me 0.018 average in the 1/4 mile after DA corrected for weather. Note I had 3 PSI of back pressure right behind the reducer. The headers were plumbed into the stock exhaust system. From what I read the back pressure in the collector needs to be reduced to an absolute minimum in order the headers to work properly. I'm planning on a true dual exhaust system soon.
There's also a hot rod magazine article titled "The good wrench quest" part 1. You can Google it. I do take their findings with a grain of salt though.