The Stovebolt Site Forums The Shop Area Engine Shop Question about Headers

I'm shopping for a set of headers for my newly rebuilt 283.

I've looked at several types, including some really nice stainless steel ones.

Will there be a significance difference in peformance between those with a 2.25" collector outlet & those with a 3" outlet?

One reason I'm asking is that I'll be putting stacks aft of the cab rather than a standard under chassis dual exhaust. These will likely be 3" - 4" so I'll have to add to the exhaust diameter via an adapter somewhere downstream of the mufflers/resonators.

I don't have a feel for the pros & cons of exhaust bore size beyound the simple issue of back pressure.

Is my first ex-wife right? Does size matter? If so, how much? (I'm not taking the truck to the strip) Is one size significanly better than the other in this application? Will it matter if I go from the 2.25" to 3" (or maybe even 4") downstream for the exhaust stacks?

Also, it's a 58 Apache so I have plenty of room in the engine box for either full length headers or block huggers. Is there any advantage of one over the other?

Please let me know what ya'll think.

THX.

I can help you out. You really only want the big collector size on race motors that rev high and aren't expected to make good torque down low. If you put those 3" collectors on your truck's 283, you will lose torque, and trucks need torque.

I would also like to recommend an X-pipe crossover, because the superior scavenging will pull more torque out of your motor, probably as much as 10 more lb-ft. After that, if you want to open it back up for your stacks, no problem.

Actually, if you can get a Tri-Y header from Doug Thorleys Headers, you'll realize even more torque.
But if not, then a full length 4 into 1 header style is the next best. Shorty headers are better for upper rpm horsepower, but full length headers make better torque.

There's an engineering discussion about "size" on this site.

www.sandersonheaders.com

Bottom line, big is not always best.

LT

Dang! Glad I asked! The Sanderson article was very informative & supported HR Dad's post too. It was 180 degrees from what I thought was the case.

I also learned the hazards of breaking in a newly-rebuilt engine with stainless, chrome, or ceramic headers. That bit of info sure saved me some money & dissappointment! In fact, I just bought a set of $45 throwaway headers from eBay to break in the engine with.

HR Dad - about this x-pipe crossover - what the hey? I don't guess I know what the heck we're talkin about here (not your fault, I'm the one sniffin exhaust fumes). Are you suggesting that I run pipes from the collectors on each side together into a single X-shaped pipe that then splits again downstream to go to the individual stacks?

Thanks for the help. This BBS has made me a whole lot less stoopider than I normally are!

OK, time to stir the pot a little- - - - -
I'm not convinced headers are worth the effort, unless they're a set of tuned-length pipes with exactly the same runner length from each cylinder to the collector. Also, the "tuned" length will only work right at a specific RPM range, so make sure you know where you want the horsepower or torque boost before you have the pipes bent.

My experience with headers, even with round track race engines, is DON'T USE THEM UNLESS YOU'VE GOT TO! A good set of free-flowing stock exhaust manifolds will keep the underhood temperature lower, won't leak and burn up plug wires, and generally will make your life a lot simpler! They also don't have to be re-tightened once a week, and have the gaskets changed semi-annually!
Jerry

No worries, HR Lincoln. Headers aren't for everybody. There is a little more that has to be done for life with headers, but they're not impossible. Some folks don't like to mess with them and that's okay.

However, log-style manifolds do not flow well. They cause reversion and the exhaust gasses have to be forced out by the cylinder. However, some were better than others. Rams horn manifolds weren't as bad as log manifolds, and Mopar always did a pretty good job with some of their manifolds. That's the same thing basically that Sanderson does for their iron headers. Basically, they're just iron manifolds...except that they are molded into a cast iron header. You get the benefits of a header with the benefits of a manifold, so for folks that don't like to mess with headers, Sandersons would be an excellent option.

However, they are not ideal either. And headers do not have to be perfectly tuned length either. It's better if they are, but most of them make compromises.

As far as sealing headers, there is a procedure for success with headers. You have to tighten them periodically because the heat cycling will loosen them. After a couple of months, you can either take them out and put thread locker on the bolts and reinsert them, or use a few other types of bolts that are available. One of the most popular uses a metal fitting that holds the bolt in place against the side of the header, and that fitting is held in place with a simple clip. Or ARP sells header bolts that are drilled for safety wire. Before locking them down, you still have to tighten them as they go through their heat cycling for a couple of months. Then you should have no problems.

Bodega, I'll get to your question in my next post.

Bodega, you don't have to have a crossover, just like you don't have to have headers. But they remove a lot of the harshness from the exhaust noise and actually improve exhaust scavenging, because some cylinders are ideally timed in their firing order but they are on opposite banks of the engine. With the crossover, the suction they produce after their pulse helps scavenge the next cylinder better, even if it's in the other bank.

H-type and X-type crossovers are the two types. There are rpm ranges where each one works best. X-crossovers are exactly as you describe, and generally build better low end torque and high end horsepower. However, from about 3500 to 5500 rpm, the H-pipe works better, perhaps because the X-type might tend to "over-scavenge" at certain rpm ranges.

Summit sells an excellent X-pipe really cheap, along with mandrel 45 degree bends to make it all work. Just cut and weld what you need.
I suggested the X-pipe because torque is important in a truck, and because 283's don't have as much low end torque as 350's, for example. So I figured this would be the right choice for a truck. However, if an X-pipe doesn't fit right (like in my Corvette sidepipes), then an H-pipe might work better. It all depends on what's right for you.

For example, I have a street/strip 1968 Firebird with a Hipo 455 bored 0.040" over. I have my stall selected at 3500 rpm, which is right at my torque peak. 455's redline at 5600 rpm, unless you have really expensive connecting rods. So I chose the H-pipe because I need max power between 3500 and 5600 rpm.

On my IROC, I have a mildly souped up 355 Corvette motor. It makes roughly 2.5 times as much power as the original 305 did. But because it's got a torque-building tuned port induction set up on it, I used the X-pipe. Tuned ports are all done by 5000 rpm or so, so 80% of the usable power band is covered by the X-pipe's response characteristics. And it really works. That car accelerates out of the hole like a cannonball. I don't worry about high rpm power because the tuned port isn't made for that. So I maximized torque. And that's the criterion I would use to select that crossover for your truck.

This is wordy, I know. But hopefully informative.

HRD - Jeezus! I'm gonna need a dang degree in cresent wrench engineering before this is all over!

OK, lemme get this straight - I'm dumping the manifolds in favor of headers because the manifolds create too much turbulence & tend to impede performance because this turbulence forces exhaust back into the cylinders. However, I want to add a crossover downstream to increase turbulence to enhance the performance? God, I love this stuff!

I went to Summit & read some of their marketing copy to get a quick feel for what's going on here & will do some additional research but the question that comes immediately to mind is this: is there anything special about the X junction itself or can I manufacture one here? Sounds pretty daunting when Hedman says stuff like their crossovers are "tangentially sequenced." Doh! I think I left my tangental sequencer in my other pants!

I'm not even sure where I can pull off the junction. If I run individual pipes from the headers straight back into the elbow that'll turn up into the stacks, I can have enuff linear room for the mufflers/resonator. I haven't measured it yet but the distance isn't that great. I suppose that I could run the from the collectors to the X & put the resonators immediately downstream of the X junction right into the elbow.

Well, I'm just thinking on paper, here. What I gotta do is pour a glass of JD & go out and crawl around under the old girl for awhile, but at present it's dark & raining so I guess I'll just settle for the glass of JD.

Ya'll sure have given me some stuff to think about! I appreciate it. Keep the info coming. My brain hurts but I'm hoping it's growing pains!

THX.

Heh heh heh. Actually, the crossovers don't add turbulence. In a way, you can think of them as adding scavenging, or suction, to help pull exhaust gasses out.

But hey, if you can't work it out, then don't worry about it. You're probably only talking 5 or 10 horsepower anyway.

I actually DON'T have a crossover on my Corvette, because like you, my exhaust spreads apart and goes into sidepipes right away. The only way I could manage a crossover is with a long pipe connecting the sidepipes, and then, I doubt if it would do any good, except maybe to help mellow the exhaust note a little.

Think of a crossover like this, the exhaust pulses are like waves of high pressure gas in the exhaust pipe. Following each pulse, or wave, is a null, which is low pressure. The high pressure pulse that comes along next is sucked into the void, helping to scavenge the cylinder that came out of. Pumping out more exhaust gas.

Now what if the ideal "second" pulse was coming from the opposite bank of cylinders. It's timed just right, if only there was a connection between the left and right exhaust pipe. The X-pipe creates a brief merging between the two. The energy of each pulse is a lot stronger going through there than there would be if it was an H-pipe.

Sorry if that's confusing. But basically, you've got it.

HR Lincoln, I thought about your other point you made, that the exhaust has to be tuned for a certain rpm. It's not that peaky, but yes, the headers are tuned to a RANGE of rpms. The shorter headers do better up high, and the longer headers do better at lower rpms. But even with that, there are variables. The pipe size for one. The bigger the pipes, the freer they flow at high rpms, but they also slow down the exhaust, hurting torque. So you can offset longer pipes by increasing size to get back some high rpm performance.

Just when you thought you had it all figured out, along comes the "merge" collector. This works through Bernouli's law. Gas flows faster through a decreased area. This is tuned so that scavenging increases at a certain rpm range, increasing torque. Get that range nailed just right and you boost horsepower too. Too bad they are selling for stupid money, because it's a good idea.

Look...street cars don't need to get into such high tech for their exhaust. They can benefit from headers, but you'll be just fine without a crossover, merge collector, etc. Just get those smaller headers you were looking at, and it'll run fine.

Good luck with your "Exhaust PHD"...there WILL be an exam.

HRD, most of my "header engineering" has been done on roundtrack racers, and a few 4WD pull trucks. One SuperStock Truck Chrysler 440 we ran turned out 714 HP at 6,500 RPM, after all the humidity and barometric pressure conversion factors were calculated. We figured the volume of the cylinder, and made header pipes to acomodate exactly one cylinderful of exhaust gas for the tuned-length pipes. They were 1 3/4" diameter, equal-length, and 8 feet long, going into a 6" collector. We were going for maximum low-end torque, and we got it in spades! The smallblock Chevy engines we run on the 5/8 -mile banked track at Nashville need short equal-length pipes, into 3" collectors, mated to oval-outlet pipes in front of the rear wheels. We usually come off the banking at 3,500 RPM or so, and wind to 7,500 or more by the end of the straightaway. If the rule-writers allow roller cams anytime soon, we will be able to turn some serious RPM, and the header length will probably change, too!

For street use, headers make about as much sense as a screen door in a submarine. They're not worth the hassle for a little "gee-whiz" appearance impression when the hood is opened. How often does a streetdriven vehicle, especially a truck, run in the RPM range where headers are benefecial?
Jerry

Long winded bunch here, I'll have to come back later to read it all. I like these threads!
Thanks Guys!
I put some old stock Rams Horns on my 283 and have read they flow well, then "X" pipe then a pair of 26" Smithys

(my .02)
Buddy

HotRod,
I couldn't agree more. Headers on street vehicles are more show than go, and a lot of people think they sound better than manifolds. Ramhorn manifolds were put on high-output 350s, so no matter what 283 you build, they should be more than adequate. As far as the X-pipe goes, the real benefit is reducing the resonance of the system, because the 180-degree separation of the pressure pulses coming together cancels the noise out(more or less). realistically, as power goes, a couple of horsepower and maybe 5 ft-lbs is more along the lines of what you can expect.

Pauly -

I agree about the headers being for show but that's pretty much the long & short of building a 58 long bed. Ya sure don't build it to race against the kids in their rice burners - especially at my age - and I sure as heck hope my days of hauling livestock are long gone!

Anyhow, you mentioned the X pipe system decreasing the resonance. Does it also decrease the volume?

THX.

b_bob
I think it softens the sound (res. & vol.), a nice low muscle rumble with the Smithys.

Buddy

Well the X seems like a good idea, particularly since the stacks'll be comming right up behind the cab.

I like the throaty rumble of an American V-8 but not a gazillion DB of it and especially not when I'm trying to listen to my favorite hits on the radio by Lawrence Welk & that accordian guy of his!

Bodega,
I don't know whether the volume is actually decreased or not, but the noise is a lot less intrusive, since the jaw-rattling reverberations aren't there anymore.

HEY FELLA'S! new guy to the forum. I have a 69 gmc sierra with a 396 in it. The truck, believe it or not, has a smog pump! I was wondering what difference it will make if I pulled all the emmisions mess off the truck? I had a guy tell me that the engine runs better with the pump. I was thinking the opposite. any help would be appreciated. thanks

back again, I ran the numbers on my 69 gmc 396 and was told it was a factory 375 hp motor. It has a factory cast high rise intake, quadra jet carb, cast manifolds. I am going to rebuild the heads{valve guides are weak} but don't know if I should stay stock or have them upgraded while they are out. any info? thanks

repaired the rear shock mounts on the truck today. what a chore, rivets are hell to get out. welded and replaced the mounts using 8 grade bolts. hope to not have to do that again for a while. Found the original protectorplate for the truck inside the manual. The old man that owned this truck was meticulas about records.

I am begining to wonder if I am just talking to myself on this forum! This truck has an Edelbrock INJETO-SYSTEM installed on it. Something to do with injecting water into the carb at 1500 rpms and vacuum at 30psi. Don't know to what effect that has, any info would be appreciated.

im with jerry on the headers i hate them first sign of trouble and there gone replace with stock manifolds and never look back or have to mess with them again

Hi, Kingpin!
Yes, you're getting through! At this point in time, I doubt if emission controls matter one way or the other. Your truck has fallen off the edge of the world, as far as the emission regulators are concerned. Here in Tennessee, cars in the metropolitan areas from the mid-70's on up must maintain an intact emissions system, because there's a federal-mandated emissions test required before license plates can be issued. In rural areas, anything goes. Of course, there's still a federal law that mandates a $5,000.00 fine and 5 years in jail for EVERY vehicle a mechanic modifies! Ya pays yer money, and ya takes yer chances!
Jerry

kingpin -

The polution control regs might be tougher in CO but my guess is you'd be safe yanking the smog pump. Starting in about 65 or so, the Detroit boys started flirting with the polution control add-ons & the engineering wasn't very good yet.

On the question of will it run better without it - absolutely! You'll probably add another few HP or so just by dumping the booger.

Good luck deciding. Remember, it's always better to ask forgiveness than it is permission!

A smog pump makes virtually no difference in horsepower. It's a low-pressure vane-type pump, and the load on the engine isn't noticeable whether it's running or not. Other emission-related things that might make a difference are carburetor jetting, and the centrifugal advance curve in the distributor. Some models also eliminated the vacuum advance, unless the coolant temperature got high, and a thermal/vacuum switch allowed vacuum advance to come in and cool the engine down. I did a lot of emission-related diagnostics during the 60's and 70's, and it was a real challenge to make the engines perform. Most "improvements" people tried by removing emission controls actually made them run worse, and get lousy gas mileage! It was necessary to do internal carburetor modifications, and recurve the advance systems in the distributor to make any noticeable improvements in power or mileage.
Jerry