Find answers to Frequently Asked Questions for First Generation Firebirds that have been asked and answered on FGF. Special thanks needs to be given to all the FGF members who took the time to respond to other member's questions.
Exhaust
Q: Exhaust Manifolds
The exhaust manifolds on my 1968 Firebird 350 are cracked (both sides). I’ve been having a hard time finding a pair as most yards I’ve called either don’t have them or don’t know whether they have the right ones. One question i have is whether the manifolds from the “400” engine will be the same. Any insight will be very helpfull, summer is here and I desperately want to get on the road.
A: You can get the repro Long Branch Cast Iron Exhaust manifolds for around $325 pr. These are nice copies of the one’s originally used on HO & Ram Air 1st Gen. Firebirds… and cast using Ductile Iron..much better than originals. One other note.. be careful of buying used manifolds…. after 30yrs and countless temperature changes, many are bound to have stress fractures and/or cracks. I’ve had several pairs over the years (various styles) and those that needed repairs were usually much worse than first glance….many times unrepairable. Only the Ram Air & H.O. Exhaust Manifolds are considered difficult to find…all others can be found for around $100 pair. As far as usage…. The Following ‘D’-Port Exhaust manifolds will fit 1969 Firebird V-8’s
pt. # 9779325(RH)...63 T/4, 63-66 T/8-P/8, 1967-1968 F/8-T/8-P/8 (exc HO/RA) pt. # 9777755(LH)...67- 1968 F/8, pt. # 9791607(RH)...67- 1969 F/8 Ram Air, H.O., 1968 P/8 428 H.O. pt. # 9779493(RH)...67- 1969 F/8 Ram Air, H.O., 1968 P/8 428 H.O. pt. # 9779495(LH)...67- 1969 F/8 Ram Air, H.O., 1968 P/8 428 H.O. pt. # 9777641(RH)...67 GTO Ram Air, H.O. pt. # 9777646(LH)...67 GTO Ram Air, H.O. pt. # 490802(RH)....68 GTO Ram Air, H.O. pt. # 478141(LH)....68 GTO Ram Air, H.O. pt. # 9796992(RH)...69 - 72 F/8-T/8-P/8 exc.H.O./RA, 307 pt. # 9796155(LH)...69 F/8 exc H.O./RA pt. # 9797073(RH)...69 F/8-P/8 RAIII, H.O.
*Basically…65-70 Pontiac Manifolds/Headers interchange with 1967, 1968, 1969 Firebird’s.
*The separate flange may vary btwn Full-Size Pontiac’s and Firebird’s.
*Also, the Ram Air, H.O. Manifolds used a special aluminum oil filter adaptor.
A: I have a 1968 350 and I just got exhaust manifolds for it from a junk yard, they were fron a 73 350 pontiac, and fit just fine
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Content last modified: January 16, 2014 at 5:26 pm
Q: Ram Air III Long Branch Manifolds
Instead of dealing with the problems associated with headers (leaks, etc.) and to just be different, I am considering a set of 1969 Ram Air III “long branch” exhaust manifolds for my 455 with ported 6X heads. Has anyone out there taken a grinder to or otherwise modified a set of these? I am plan to open up the inlets to match the head work as closely as possible and I am also considering having them extrude honed. Does anyone know of a good place to get extrude honing done? While we’re at it, does anyone know if there was an exhaust manifold produced that had better flow characteristics than the Ram Air III long branch?
A: I have the the RA III long branch manifolds installed on my car, (1967). Mine are unmodified, so I can’t speak to modifications you mentioned. However, there is one thing about using these manifolds which is rather annoying and you should be made aware of, (if you aren’t already). In order to use these manifolds, you have to use the oil filter mount which angles the oil filter back towards the rear of the car instead of the standard one which points the oil filter directly down towards the ground.
Even with this angled oil filter mount, you still end up have to drop the exhaust pipe to get the filter off! A royal pain in the backside, especially if you install a cross-over tube, because then you have to drop BOTH sides. I’ve met a few guys which get around this problem by installing a remote oil filter mount.
I think you are making a wise decision by going with the long branch manifolds over headers. I have had all three types of exhaust manifolds on my ‘birds, the stock manifolds, headers, and now the long branches, and I definitely ling the long branches the best. The headers were too noisey and added way too much heat under the hood, especially around the starter. (Kept cooking starter solenoids). The long branches perform as well as the headers, are quieter and don’t through out as much heat.
As long as we are on the subject, does anyone know if there exists a “shorter” version of the PF24 oil filter? If so, it could be used to bypass this clearance problem.
A: I too will be using the LB manifolds and will be using ported 6X heads on a 455 in my 1968 Bird. I enlarged the manifold ports to match the ports on the heads. I had to remove about .060.090 from the top of the openings on each port. The castings I have are reproduction. They look pretty nice and have 2-1/2″ I.D. outlets. I got them from Year One. I didnt get the flanges though. I will need to get those from somewhere. I am going to get the manifolds hi-temp coated too.
I will use the Dr.Gas “X” crossover and mandrel bent tailpipes. All 2-1/2″ system. I will rig up some type of remote filter.
Forget the extrude honing. It is very expensive. I think the price for cast iron manifolds is around $500. It would be wiser to just get some custom made headers and have them coated.
A: I have a 1969 convertible A/C bird with a .030 over 455, 6X heads and LBram air III manifolds. The oil filter issue does not require the remote solution. Point out this concern when getting your exhaust installed, it can easily be worked. I do have to bring the filter down the frame about six inches until the gap between the frame and the exhaust pipe is wide enough but it does not require unbolting the exhaust. Remember these are stock issue manifolds and GM would have never designed them so that it required exhaust unbolting for an oil change. Also, my LB areactually 2.25″ ID and the 2.5″ exhaust slips right over. The onlynegative I’ve seen from these manifolds (if you ignore cost) is that youwill need to install a heat shield for your starter and solenoid. But then GM also chose to use a shield with the stock issue of these cast iron manifolds. Oh and one last thing if anyone can find an exhaust guy that can install a 2.5″ cross over (X or H) with the convertible body pan in place and with more than 3.5″ of ground clearance let us know.
A: I had a crossover installed on my 68. The installer put a bend (about 30 degrees) in the pipe to rout it around the transmission tailshaft. It hangs no futher down than the transmission pan.
A: What about the GM Oil Filter adaptor used w/the Long Branch manifolds ?
A: Soke the header gasket in warn water for about 1/2hr. before installing it will swell up and seal better. Headers are know to warp. This worked on all the headers i have ever ran before.. I put the long branch manifolds on my 1967 not running yet but thay look good. Don’t for get you have to buy the $75 oil filter adapter also..
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Content last modified: January 16, 2014 at 5:27 pm
Q: Replacement Dual Exhaust on 1968 Convertible
I need to replace my exhaust on my 1968 convertible. I would like to replace with duals. Any sugestions on where I can purchase a complete exhaust?
A: I have just installed the Flowmaster 2.5″ dual exhaust kit with crossover available through Summit (probably through other catalogs too) and didn’t have any problems with it (other than forcing me to replace my saggy rear springs which I was going to do any way), however, my car is missing the crossbrace underneath so that obstacle wasn’t there for me.
The 40 series mufflers fit just fine and the kit includes all of the clamps and new mounts which bolt righ up to stock locations. You will, however, have to go to a muffler shop to have them weld up the pipes from the exhaust manifolds to the kit since it comes with the flanges to bolt up to a set of headers. I bought a set of reducers from Pep Boys to temporarily install in there to get me to the muffler shop (they’re cheap enough).
This may actually be a good time to install headers if you ever thought of doing so.
The sound is great and not too loud (for me anyway). I run my Borla exhaust fully open on my 98 TA so I guess I’m used to it 😉
A: I have Flowmasters on my 1968 convert, and it sounds great. Not too loud at idle, but when you get on it, it sounds like all hell breaking loose. Just got all my leaks fixed after a couple of months. New expensive gaskets for the headers, and two copper ones for the collectors. Very happy to have no leaks, but was not easy.
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Content last modified: January 16, 2014 at 5:28 pm
Q: Dual Exhaust on 1967 326
I would like to know if dual exhaust came with the standard 2 barrel 326 convertible, or if this was an option that had to be ordered.
A: Dual Exhaust was Standard on the H.O., 400 and Ram Air Firebird’s in 1967 and was optional on others.
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Content last modified: January 16, 2014 at 5:29 pm
Q: Exhaust Updates
There was a thread a little while ago that referred to a great article about muffler testing. I printed the article, but I can’t recall the website.
I plan to install the headers I bought and need the rest of the exhaust from headers back. Is there place to call to order these parts already pre-bent for a 68? I don’t want to have to take the car in would rather order and then install in the garage. I can get a welder if needed. Anyway if anyone knows a place let me know. I want to go to the duel exhaust from my now single.
Also what do you all think of walker mufflers? I keep hearing flowmasters but was told by a reliable sorce and trusted car buff that walker was much better. Anyone have input?
A: You’re probably refering to the Jim Hand article on exhaust…
Sorry, I had to remove URL AS REQUESTED. gm
Titled “The Strong Silent Type”. Jim did extensive testing of different brands of mufflers, measuring backpressure, sound level, 1/4 mile performance. He also tested the use of different diameter tail pipes, “H” pipes versus “X” pipes, etc. He’s done more testing than most of us could ever afford.
Walker/Dynomax makes complete dual exhaust systems for headers as well as stock manifolds, as well as mufflers. Try calling Jegs or Summit and see if they can come up with a system for your car. So does Flowmaster, which is designed for headers. But Hugo manager to get one of their systems to work with his stock manifolded ragtop. The Walker is more likely to look stock than will the Flowmaster.
And of course, their is Gardner Exhaust Systems (http://www.gardnerexhaust.com/).
They make replicas of factory systems, which I think is offered in both mild and stainless steel. This is probably the way for Erich Wagner to go for that stock look, and still be able to install it himself. Expect to pay well for this product.
See the above link on some very good independent testing of various brands. While each mfgr. claims the best flow/power output, it’s interesting to see real world, on car testing like this.
On top of all this, an important factor is sound. Some folks like their cars loud (Bob raises his hand), others like them quiet. I like the sound of Flowmasters, while I know a few die hards who think that a set of glasspacks are the living end of great sound. Judging from the testing Jim did, if it’s quiet with superior performance that you are looking for, Walker/Dynomax is probably the way to go.
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Content last modified: January 16, 2014 at 5:48 pm
Q: Aftermarket Headers
I will be redoing my exhaust this winter as part of my refurbishment on my 1968, 350 convertible. I presently have headers on the the vehical. I don’t have a clue as to what kind. They are long over due for replacement.
I have read the recent posts concerning aftermarket headers. The consenus seems to be the at most are running Hedman headers but, that they can be a problem installing them and later and with oil filter changes.
For these reasons I am considering going back to the stock exhaust manifolds? I have checked locally and can’t find any.
Questions:
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Are the stock headers hard to find?
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Will only 1967 and 1968 fit?
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What type of performance loss can I expect to see if I go back to the stock exhaust vs. the headers?
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Does the exhaust kit that Summit and Jegs sells fit up fairly well to headers or is it made for stock manifolds and requires modifcation?
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When using the above exhaust kit do the headers and exhaust fit up under the body nicely or do they hang down? The headers & exhasut I presently have constantly drags on drive ways and such. ( One of the reasons it is all beat up.)
I know, always too many questions.
A: I wish I had answers to all your questions. I don’t, but I think I can help with a few of them.
If by “stock headers” you mean the Long Branch manifolds, the originals are pretty hard to find, and pretty expensive. There are aftermarket repros, which are better quality, and can be ordered from Ames, etc or even direct from the mfg, Ram Air Restorations. They run $369 I think, and require the oil filter adapter. They fit 1967, 1968, and 1969 Birds.
If you use these, I don’t think you’ll see ANY difference from headers in your 350.
However, if you go back to factory “log” manifolds, which are much cheaper and easier to find, then you will probably see somewhat of a performance loss, but it’s hard to tell how much. Remember, the 1969 Grand Prix 400 used the same “log” manifolds and was factory rated at 350HP….
I don’t have any experience (yet) with the Flowmaster exhaust sold at Jegs and Summit, but I think that they all say they wont fit in a convertible.
I, myself am researching a good exhaust system for a 350 bird convertible (69) and I’m trying to find one that is 2 1/4 inch, because I want to get respectible performance and may someday upgrade to a mild 400. So far here’s all I’ve found trying to piece it together:
Flowmaster American Thunder Complete exhaust(2 1/2 inch) PN 17139 $321.95 (17129 for 1967-1968 $261.95) – for use with headers. Uses 2 mufflers under the rear floor area. Includes Crossover setup.
Flowmaster Force II (2 1/2 inch) Complete exhaust PN 17104 $314.95 – for use with headers. Uses single Transverse muffler. Includes Crossover setup.
(I think flowmaster says neither of these fits convertibles)
Flowmaster exhaust pipes only (2 1/2 inch) PN 15801 $99.95
Flowmaster 80 series Transverse muffler, 2 ins/2 outs both 2 1/2 inch, PN 42582 $99.95
Dynomax Transverse Muffler #17725, 2 ins/2 outs both 2 1/4 inch, $76.69
Dynomax Super Turbo Mufflers #17731, 2 1/4 in/out, #17733 (2 1/2 inch) $31.99 each.
Flowmaster 50 seris Muffler #42451, 2 1/4 in/out, #42551 (2 1/2 inch) $64.95
Flowmaster Balance Tube Kit #15919, 2 1/4 inch, #15920 (2 1/2 inch) $37.99
Prices as of Sept 1999 – Probably Subject to Change
So where does that leave me. Well, I’d like to use the 2 1/4 Super Tubos and 2 1/4 balance kit, but haven’t yet found 2 1/2 (or even 2 inch) tail pipes for use WITHOUT the transverse muffler, nor have I found 2 1/4 inch head pipes for use with stock manifolds.
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Content last modified: January 16, 2014 at 5:50 pm
Q: Long Branch RA III Headers Bolt to 350 Block
Will long branch RA3 headers bolt up to a 350 block? Mess with performance good/bad?
A: Compared to the stock log manifolds, the Longbranch units are a big win. About the only negative would be dealing with the oil filter location, and there are good solutions to that, and of course, the cost. At nearly $400 new, these aren’t exactly cheap compared to headers. Plus I’d prefer a ceramic coating to preserve them and that would add, what $150 – $200 to the overall cost? On the plus side, better flow on any Pontiac V8 over log manifolds, better ground clearance than headers, and also a more reliable seal. Not that you can’t get headers to seal well as long as the flanges are straight and you use high quality gasket (Felpro metal core, or copper seal).
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Content last modified: January 16, 2014 at 5:53 pm
Q: Long Branch Exhaust Manifolds
Were the 400 Ram Air cars only F-Bodies that have ever had the Long Branch Cast Iron header-style Exhaust Manifolds?
A: NOT TRUE…. 400 H.O.s came with the long branch manifolds and oil filter adapter. Definitive word is still not out on the 350 H.O. M/T cars in 1969 receiving these. Anyone got a 1975 NHRA rule book? This would answer it.
A: Oops ! My mistake. What I meant to say was….
Long Branch Exhaust Manifolds only came on the 400 Ram Air & H.O. engines. (not on 350 H.O.).
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Content last modified: January 16, 2014 at 5:56 pm
Q: Manifold Repair 101
I welded it up but the weld makes it not seat properly (I tried to grind it but I went through 2 grinding stones on my drmmel tool and barely made a dent) so it’s leaking pretty bad.
A: You’re a brave soul welding a cast iron manifold while still on the car. Its quite tricky welding cast iron so as not to have it crack again. Ive successfully welded quite a few exhaust manifolds never to have one crack (even 25yrs later) but its a real science. I had an old timer show me(guess Im qualified to be in that category myself now)
First is to drill on the extreme ends of crack to stop it from continuing. next grind a good size V into crack but not all the way thru. Preheat the cast iron in repair area until cherry red with a rosebud tip. Keep the torch moving or youll blow out a hole in the cast iron. while still red then use a high nickel rod and use less heat (amperage) than you normally would(remember youve already got it hot).
After welding is done work very quickly before it cools and peen it with the pointed end of a welder hammer all over the weld. Next place in a bucket of clean dry sand and completely cover with at least 6 inches of sand .Leave there overnight as you want it to cool very slowly. You can preheat in an oven and cool down in an oven gradually bringing down the temp over a 24 hr or longer period as the pros do.But just remember to take it out before the pizza goes in. Now as Tim Allen says I think Ill go break something so I can fix it.
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Content last modified: January 16, 2014 at 5:57 pm
Q: Exhaust Pipe Size on Convertible
What is a good diameter exhaust for a convert WITH crossmember installed. Will have a shop work 400HP out of original 350 later on. Would like 2.5 Alluyminized. Will this help HP allowances, or will I have to get bigger to get that HP?
A: The real problem is getting anything bigger than 2.25″ past the convertible pan brace. Perhaps that’s what you meant rather than the crossmember. The exhaust has to share this tight space with the transmission tailshaft and the driveshaft. Some list members have reported getting 2.5″ to fit, and I’m sure it took some very creative pipe bending to do so. Or maybe ovalizing would be a better term.
400HP out of a 350? Is that flywheel HP, or rear wheel HP? Either is quite a bit to ask of that small displacement. But I’m sure it can be done. But how driveable will it be? 2.5″ probably won’t be too much of a plug for that HP.
It’s pretty important to keep the brace, by the way. Even if you get subframe connectors, the race car chassis builders like to keep the brace if the car isn’t given a tube frame.
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Content last modified: January 16, 2014 at 5:58 pm
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