'81 Exhaust - Hooker Headers

[Tom Bryant]

I checked the application on those mid length headers and they say they won't fit a standard trans. They probably interfere with the clutch cross shaft. You would probably need a long tube since they drop down low before turning rearward. 81's have straight plugs and standard port shape, port spacing and bolt spacing so, unless the header application specifically states that a header is for angle plugs, D ports, the late heads with wider port/bolt spacing or something else odd they would bolt to your engine.

If you find a header on Summit or elsewhere that you like just click on the application tab in the description and it will tell you if it will fit a 4 speed and also any thing special you may need to do with alternator brackets ect.

Tom

 

[SVO]

@ Dirtypants -

If you want to go with a cast iron exhaust manifold, you can use any of the factory Corvette ramhorn manifolds. Dorman makes both the 2" low performance manifold and the 2-1/2" hi-performance manifold. If you go with the 2" manifold, for exhaust pipes, you have a choice of using '70-'74 L48 pipe which will be 2" out to the rear of the car OR you could go with '70-'74 LT-1/L82 pipes which will be 2" where they bolt up to the manifolds but go to 2-1/2" out to the rear of the car. If you go with the 2-1/2" hi-po manifold, then you would need the '63-'65 2-1/2" head pipes, and match them to '70-'74 LT-1/L82 back pipes. Mufflers can be whatever you wish to use. One other change to make is to use the '70-'74 exhaust support ("batwing") that mounts under the transmission. Currently, you should have 1/2 of a "batwing" mounted under the transmission mount to support your single exhaust pipe. Right hand manifold will need a heat riser spacer that matches the exhaust manifold outlet size.

This was a popular swap for '75-'82 Corvettes back in the day to retrofit a dual exhaust system. People who had the late model L82 engine found that the stock L82 mufflers in the dual system gave them the turbo muffler sound.

The thing to remember is the frame under your '81 is the same basic frame dating back to 1963, and the under car exhaust system didn't change that much between 1963 and 1974. When Chevrolet went to the catalytic exhaust system in 1975, things didn't change enough under the car to prevent retofitting a earlier dual exhaust system.

 

[Tom Bryant]

I didn't mention it but I used some '81 manifolds on my '69 C/10 stepside. I removed the smog tubes, heat shields and cleaned up the rough welds before coating them. When I had them to the welding shop to close up the smog tube holes I also had a few cracks welded up where the 4 pipes join together. Just because they are cracked doesn't mean they are junk.

Tom

 

[bskdz]

I have an '81, just finishing up with a HT 383 engine swap. I have about 40 miles on the new engine. I installed Hooker Headers 2456HKR, bought then painted black, thinking that I will need to ding them to make them fit. Turns out each side took about 5 minutes to install! I could not believe how easy they went in. Front end was on jack stands, and installed from underneath the car. Due to tightness of the header tubes, I switched to allen bolts and custom bent an allen wrench to get at all the bolts tightened up. I then got the headers ceramic coated in a local shop. The coating keeps the heat inside the headers and is a must. The car feels different, very crisp throttle response, using EZ Fast EFI throttle body fuel injection. During the break in procedure, accelerating to 55 MPH and keeping it under 4500 rpm, the tires chip during the 1 -2 shift. Auto trans was rebuilt with a shift kit. Next step is for new exhaust and mufflers, deciding on what mufflers, I want quiet mufflers with cutouts. The only thing about the headers, is that on the passenger side, they get to close to about 1/2 inch to a steering component, I had wrapped the steering component with reflective tape. Really please with the engine swap.

 

[dirtypants]

the allen bolts are a good idea if wrench clearance is too tight. back in the old days we just had the shop put in a Y to an exhaust cut out..totally open..or could have a small free flow resonator muffler on that Y..easy to open or shut off ..can go to back or side..or down..about anywhere..if there is a cat..can be before at bottom of downpipe.
I have found 2 places that make a replacement header to fit the 81..and prob most other vette 350s...McJakes and Stans-Headers in Auburn Wa..Stans seem to be pretty hi quality..made right there not in china..both tho are about $500 and then $250 range more to have ceramic coat. These for a no emission, no smog A.I.R car. and heat shields prob wont fit (maybe in part with some mods<and likely no heat riser.) there are many othee headers that may have to have some mods to fit..esp if std trans car with the clutch cross shaft. Otherwise only thing for an smog, stock car is to find em used..refurbish em..maybe get em ceramic coated. i am changing cuz ones I have a cracked a little..may be able to fix..but if I am gonna do the work of R and R..thinking spend a little more to get quality new headers that will last..and I do already have a true dual flowmaster exhaust pipe/muffler with no cat, so headers will actually do some good. Aftermarket headers in an 81 may do a little better..than stock..but not much..and not much at all if the rest of the exhaust is stock, and...not much if the intake and tune side is not improved. The 81 were choked up by emission standards and fuel mileage of the day..so no wonder some just change the engine..it takes pistons, heads, intake manif, carb, cam, new distrib and timing (36 deg mech all in at 3000 RPM, should end up about 12 deg static) and dumping the computer, plus exhaust to make it come alive. Well I will have it..except pistons and heads...soon.
by the way since we are on an 81 topic..the handling will be much improved with shocks / struts improvements AND...correct alignment which should NOT BE ORIG factory alignment which was way off. Align: Set rear Camber to,.5 deg, each side, then rear toe, 1/8” total (so 1/16 each side : Tighten pivot bolt to 50 ft lb, but do not put cotter pin in yet. (a recheck and possible final adjustment may be made.) Very thin shims are provided.
Front alignment: Do Caster first, right side 3.3. left at 2.9 Front Camber .29 deg neg, same both sides; Last, set Front toe at 1/8” total of both sides, so 1/16” per side. these specs determined from VDP, Speed Direct and Duntov. This is how my car is now set up and handling is night and day better.
Nick

 

[kpic]

I've always used 12 points with headers as a standard 12 point socket will tighten them. Plus it saves carrying a hex bit socket as a regular socket works.
A set of ARP 12 points is $20 +shipping.

 

[dirtypants]

getting at the exhaust manifold bolts YIPES any tricks?????

My 81, 350, man trans

so tried to get wrenches and sockets on to the exhaust manifold bolts..manifold to head, ..YIPEs....when I can even get something on..then no room to turn it...any tricks, tools..I need? BTW there is a post..that a 12 point socket tends to slip on the bolt head more than a 6 will (?)

I am still mentally struggling with what manifolds/headers to use..but thinking some refurbished originals will avoid problems of clearance, a/c compresser attachment etc..but with the work of getting manifolds in and out..would sure like nice quality new headers that will last..and be done with it. Anyone ever use Stans-Headers..tri Y, or McJacks..for 350.?
Nick

 

[dirtypants]

Help who has installed headers in an 81 4spd What fits

My 81, 350, man trans has all the smog removed..no A.I.R., no egr, no computer, no catalytic, no oxy sensor (running Edelbrock carb, intake and cam)..the left ex manifold has a crack..so time to replace em. What will fit? With all the smog stuff gone..will an earlier vette ex manifolds fit (79-80>) ..what "year" of aftermarket will fit..(cuz the 81 manifolds have all the A.I.R. etc that I do not need.) I don't need to spend a ton on race headers..but I do already have true dual exhaust with Flowmaster mufflers..What header (exh manifold) do I shop for..to fit. Are gaskets to head the same as earlier year..say 79-80? Thanks,
Nick

last call..looking for someone who had installed headers on 81 4 spd..that fit..need to fit by steering, fit by the clutch cross shaft..allow space for plugs/boots..(such as it is) etc. Many on the market say ..fit 81..but then you look and they are generic that fit mustang, dodge dart, old pick ups..so who knows really..So what did you buy and bolt right in???

Thanks
Nick

 

[Antz81]

If you don't get an answer but do find something please let me know what they are. I have headers that were installed by a previous owner who failed to consider the plugs. Changing plugs on mine is almost impossible now; for one of them the only way I can do it is with a ring spanner.

 

[dirtypants]

If you don't get an answer but do find something please let me know what they are. I have headers that were installed by a previous owner who failed to consider the plugs. Changing plugs on mine is almost impossible now; for one of them the only way I can do it is with a ring spanner.

From my looking into this so far..for the 81..options are..used original 81 tube manifolds are available now and then on ebay..expect to pay about $180 to $250 for the pair. Heat shields are also avail..$24 to $70. You can decide if you block off the air, emissions etc if you don't need them. Then you are back to stock and can get to plugs..kinda sorta. OR...and I have not yet seen these nor talked to em about exact fitment..McJakes Corvettes , So Calif makes header for the vette, 350, and Stans-Headers in WA. Hi quality, ceramic coated which really helps get heat out of the engine bay..but exactly how they fit I do not know yet..they say they fit..but then the headers fit a lot of others too..so not really custom for the 81 vette. Many others on line say they fit..but they all have multi applications..Patriot, Sanderson seem to look about right, but the issues are..able to get to plugs, clearing steering box (which is close), clearing std trans clutch cross shaft (so pipe has to go down, not swept back), and for me..made so you can get to the manifold bolts with a wrench/socket.
I am leaning to orig stock replacement manifolds unless I hear of a good fit aftermarket header. After all the OE ones are tubes, and do fit, but are prone to cracking..I don't want to R and R them again. I do already have true dual exhaust with Flowmaster mufflers, and no cat..so in my case headers may help exhaust a little. Headers on a stock exhaust won't improve much.
So..again..hey Y'all...anyone with an 81 350, 4 speed tell me what headers you used.
Nick

 

[dirtypants]

updating my own posts on exhaust manifolds for 81: Hooker 2456 fit..a long tube, available in plain-blackpaint, at around $250, as a 2456-1HKR ceramic coat about $450, or 2456-4 ceramic but with a less shiny "titanium look" also $450. Std ports, 3 in collector so order reducer if needed to go to pipe. comes with bolts and gasket, but check out Remfree gaskets. Depending on car year may need alt or A/C bracket which Hooker also has avail, but on 81 seems the existing A/C compressor spacer will work. Of course this for a no emission set up. Heat riser will be eliminated as will O2 sensor. Ceramic coat for any new header is recommended as With ceramic the annoying heat shields won't be needed as ceramic gets more heat out via the exhaust. Install in my 81 4spd will be next week..I will post how it goes. Clutch cross shaft gets removed for install then replaced.
I will soon have two sets of original 81 tubular exhaust manifolds, stock with A.I.R. now on my bench..available, one perfect, one needed small repair.
Nick

 

[toobroketoretire]

And you will get a ZERO performance gain in the process. But they'll look really racy.

 

[dirtypants]

And you will get a ZERO performance gain in the process. But they'll look really racy.

Too Broke: Did I say anything about expecting performance gain?? NO...but since you made your snarky comment, ..these headers are replacing leaky cracked headers..so that is the main reason..gotta pick some kind..might as well be these..yup they will look racy..
and..now..since they are connected to a full flow true dual exhaust with no cat..and since they go on an engine with Edelbrock intake and carb and cam., and improved ignition system, and correct advance distributor, .I WILL GET a performance gain..more air in, needs more air out. I have read your other snarky know it all (but really don't) posts..that you have said you will tell us about later..or go on and on..frankly tired of em...it IS time to retire. Checkered flag, :stirpotrace is over..no victory lap.
Nick

 

[kpic]

dirtypants
As everyone else does, please excuse toobroke who doesn't understand pulse timing, scavenging and a lot more.

High flow metallic cats are the same as no cats. Dyno tests show that; however toobroke doesn't believe in dynos either.

 

[dirtypants]

dirtypants
As everyone else does, please excuse toobroke who doesn't understand pulse timing, scavenging and a lot more.

High flow metallic cats are the same as no cats. Dyno tests show that; however toobroke doesn't believe in dynos either.

agree Kpic..(first name?) as we know the web forums are like going to city park and listening to the "speakers"..interesting entertainment but a hi filter has to be on. I can't wait for Saturday to learn how to do alignment in my kitchen with a piano tuning fork, a yo yo and a water withing wand.

Since my 81 already had most of the removal of all smog and computer done..I am finishing it up, so far so good. The factory 81 tubular exhaust manifolds were pretty good except being prone to cracking, for those still having all the emissions, A.I.R. computer etc the only fix I have seen so far is to repair the orig existing or find original used exh manifolds. If all the emissions etc is off car, then there are plenty of aftermarket replacements.
Nick

 

[dirtypants]

my 81 already had the removal of all smog and computer done..The factory 81 tubular exhaust manifolds were pretty good except being prone to cracking, for those still having all the emissions, A.I.R. computer etc the only fix I have seen so far is to repair the orig existing or find original used exh manifolds. If all the emissions etc are off car, then there are plenty of aftermarket replacements.
Nick[/QUOTE]
So..I just installed the new Hooker headers, long tube ceramic coat Hooker 2456-1 HKR..YIPPEE..nice look and I like em..no issues fitting given that you do have to R & R alternator, clutch linkage, spark plugs. Nice deep sound under throttle, definite seat of the pants feel of power improvement..(yes..TooBroke..the rest of the system is improved..from intake to exhaust..so the headers do make power). See my full post on the install notes in the 81 sub forum..and BTW..I have the take off original 81 tubular manifolds sitting on the garage floor and avail. Pics of installed Hooker, and the take off orig are avail.
Nick

 

[Tom Bryant]

I'm glad that you are happy with the results. Cool sound. Seat of the pants dyno improvement. What more could you ask for.

Tom

 

[Peer81]

I don't remember in which book i read it but ceramic coating is the best solution to vacate heat from the engine back, and some other things i don't remember. Good luck with the headers!

Greetings Peter