TR6 Headers --VS.--Stock header??? tr6

Im thinking about switching back to a late model stock header from the headers I am running now, for less noise and less problems with blowing out gaskets. The late model stock manifold looks like it would flow almost as well especially with an opened up exhaust----any thoughts on this??

Allan,

The difference on a stock engine may not be as noticable as on an engine that has been modified. I'm not sure , but doesn't the later model manifold have different port spacing than early design. The later unit would be a better choice because of the twin pipe outlet.

On the other side of the coin is the question why are you having trouble. I have heard some horror stories about poor fitting headers. I have the MOSS header & they fit perfect & never had a gasket problem. I was overly cautious when installing to make sure the nuts under the manifold were tight & then I retightened them after a day , then after a week. These are prone to loosening & I have seen other TR's with this problem. If these are not seated well & tight, you will create a leak when twisting & turning the rest of the pipes & mufflers on.

The exhaust manifolds didn't change there spacing. Just the intake manifolds. The later, twin down pipe manifolds, would be my stock manifold of choice but then again thats what mine came with. According to Kastner, the stock manifold, especially the twin downpipe, should be more than adequate for street tuned engines. The PI cars used them and they developed pretty respectable bhp as well.

I like the sound of my SS Headers and Falcon Twin Sports exhaust, but if it were very much louder I would go back to the stock exhaust manifold and still use the Falcon system. The Twin Sports system sound very nice with the stock manifold, even on a stock engine.


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Hi Allan,

Mitch has a very good point, why are the headers blowing out the gaskets frequently? That really shouldn't be happening.

In addition to what Mitch wrote, most headers require some fitting work, can't really just be "bolted on". This is often because the tubing warps a little during welding. The "fix" might involve heating and bending the flange a little, or milling it slightly for flatness, or just some work with a file and some fine sandpaper. Sometimes a corner or an edge of the flange interferes with something on the head or block. If the gasket is consistently blowing out in one or two places, those would be the areas to check for fit. This is a good time to check that the ports match well, too. Every installation is a little different.

Also, there are heavy duty gaskets available that are about twice as thick as the stock ones, which might help alot. Check that any gaskets don't intrude upon the port area, either.

Headers are noisier than a cast manifold, but it could also be exhaust leaks you are hearing (small ones initially that are leading eventually to the gasket blowing out).

As Mitch said, headers by themselves will only boost HP a small amount. They are just one of the first steps toward improving performance, and really start to show their worth when the rest of the exhaust system gives a relatively free flow and the engine itself has been improved to take advantage of "better breathing". It sounds as if you already have a freer flowing exhaust system on your car.

Often carbs need rejetting or other adjustment after a header is added. Headers increase the gas flow efficiency through cylinders and head, and carbs will usually need to be tuned accordingly (SUs and ZS compensate for this to some extent, but richer needles might be needed).

There are different types and designs of headers, that give different driving and performance characteristics. Basic rule of thumb is that those headers (sometimes called "Tri-Y") with pairs of primary tubes joined up near the head, and secondaries that merge further down are more flexible for street driving. Headers with long primaries that join farther from the head and nearer the collector will generally give the highest max HP, but that's at very high racing rpms.

I'm not all that familiar with TR6 headers, specifically, but I do seem to recall that all designs worked best when matched up with a single slightly oversize exhaust pipe, rather than the dual pipes found stock on some(all?) TR250-6.

Hope this helps with your decision.

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Hi Alan, the early (before 72) tr6 had single pipe manifold, the later model had a more free-flowing manifold with dual pipes. I have a performance street motor and wonder how much more efficient the headers really are. I have had only an occasional problem with blow out but the main reason I would like to change is for less noise, there are no leaks.

I recently had the Pacesetter headers installed after they were JetHot coated on the inside and outside. There was modifications necessary to the flanges to mate to the intake and the pipes did not fit the stock dual exhaust pipe, which required having a custom shop make a set of mating pipes. However, The rpm's at idle went up nearly 500 rpm and the car has much more power. The stock exhaust now has a nice mellow tone and sounds really good when you push it hard.

Everything I read about headers on the TR6 sya they increase high end HP at the sacrifice of power at the low end. THe loss of power at the low end and the additional heat generated by the headers just ruled them out for me. Then you come along with the good sound! In addition, your comment about added power, albeit measured by the buttometer, is driving me to install one! I am glad you are having good results with the Pacesetter as it seems to be the better value. If I understand your installation is on a '74 TR6 right?

Myself, I installed the Falcon stainless steel headers (6-3-2) and had them JetHot coated to boot. As good as the Falcon headers are purported to be, I still had to have them faced to make them perfectly (or almost perfectly) flat against the head. After much research and wasting lots of money on different types of gaskets, I settled on a stock metallic gasket over which I sprayed a copper coating. The thick whitish-colored paper gaskets that are marketed at "header gaskets" are a waste of money as they will burn out in less than a year. Either a header flange fits well or it don't, there really is no long-term short cut to sealing them. I always use new studs when installing as well as new nuts. The use of all-metal locking nuts with their rounded heads made installation of 3 of the nuts doable as the angle of the exiting pipes from the exhaust port is tight, to say the least. Heat within the engine bay, even with the coating, is an issue in traffic. Having no crank fan has exacerbated the problem. Hence, when I approach stop-and-go traffic, I always resort to activating my electric fan in advance of the increasing heat problem. Works for me. The big 16" fan will blow lots of cooler air into the engine bay and reduce radiant heat. The fan comes on automatically if I forget. Never dangerously overheat, even in 98 degree heat. The biggest increase in low end giddyup came when I bought Ab Crevoisserat's (sp?) cool cable linkage for the tri-carbs. Thanks, Ab.

If you are going to invest in headers, really consider stainless. Iron headers work well when coated. The fact that the header never accumulates moisture will negate any problem with rust-out from within. It is just the outside that gets cruddy. Plus, iron will eventually burn out, but that takes a long time. I used to run Hooker Headers on my old rods and never had much problem, but they do look ugly after about a year. I always check the torque on the headers as a safety thing, also part of my Obsessive/Compulsive disorder.

Bill

I like the idea of headers but I always thought they were much better if the tubes were all the same length (tuned headers). Are there any made that way for the TR6.

Pretty much.


Bill

I saw an increase in both low and high end, albeit in my personal opinion, not verified by dyno chart. But I am the driver and know how well it ran before and how it runs after. I also would post a negative issue if I experienced it, so that others would not follow in my same footsteps.

I used a stock gasket from TRF when the work was done and have seen no signs of leakage. I did have all new studs installed in the head and used all new factory spec nuts and washers from TRF as well. I had the retainers powder coated in high temp black to keep rust from forming on the intake or headers, since these parts are cast.

I should mention that when I sent the intake to JetHot for coating, it was only coated on the outside versus both in and out for the headers. But they blasted the inside of the manifold and it looked polished prior to installation.

I'm sure that all of these little things add up to help make it run just a bit better than before.

I did buy the headers directly from JetHot and the price with the coating in and out was the same or cheaper than the headers alone on the open market. That pricing included the freight to RI as well. Very nice people to deal with.

And yes, it is installed on my 74 TR6.

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the main reason I would like to change is for less noise

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Have you considered wrapping them? It's best to do so on stainless steel headers, mild steel will corrode faster underneath header wrap, but it would definitely cut down on noise (and underhood heat).

Someone else mentioned Jet Hot Coating, or ceramic coatings, which would be a better method with mild steel headers, but I don't think would reduce noise as much as wrap. Coated inside and out, headers will perform their best. The smooth, internal coating helps gases move through them faster. Keeping the temps higher inside the header also promotes better gas flow.

Ceramic coating itself is quite a bit more expensive than wrapping. It's probably about an equal cost, comparing wrapping stainless steel headers with ceramic coating less expensive mild steel headers.

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I like the idea of headers but I always thought they were much better if the tubes were all the same length (tuned headers). Are there any made that way for the TR6.

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Hi,

For maximum HP, yes, it's best for all the primaries to be identical in length and relatively long (there is a limit to ideal length, which I'm sure depends upon maximum rpms, compression ratio and some other factors). Diameter of the primary tubing also is important.

However, those large diameter/long primary headers will develop peak HP at very high rpms... Far above the typical redline of most street engines. So, that type header is somewhat of a waste on an engine that's not built to handle and isn't consistently used at those high rpms.

I really don't know if true "tuned" long primary headers are available for TR6, but a set could probably be built pretty easily, if it were practical and I honestly think it's not.

The more common Tri-Y design was used on TR250 with relatively stock engine that was run at Sebring, in '68 or '69, where a more flexible header was the order of the day. 12 hours of endurance was the name of the game, rather than a half hour or hour of very fast laps (and an engine rebuild every few races). I'd recommend a Tri-Y design for any street engine... It might be best for autocross, hillclimb or rally, too.

As mentioned before, I believe either design of header has been shown to work best through a single pipe exhaust system. In the typical rpm range of a street car, I would guess a well designed Tri-Y header fitted to a single pipe system would outperform a long primary header, especially if it were feeding into a dual pipe system. A Tri-Y with a dual pipe would probably be a little less efficient (but that might be improved if some sort of cross-over were built into the system). But, all these are likely better than a stock manifold and stock system.

For max HP on the long primary header, oversize exhaust pipes are also shortened to around 40 inches (usually side exit, which effects ground clearance, too) and fitted with little or no muffler. Again, not very practical for the street!

In addition, seems to me all TR motors are a bit undervalved on the exhaust side. So, if a head rebuild ever becomes part of your plan, you might want to increase intake valve size a little, but mainly try going to the largest possible exhaust valves and then top it all off with a bit of porting on both intake and exhaust. With this additional work you should really see the benefits of a header and freer flowing exhaust system.

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Thanks Alan, again some very good information.

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As mentioned before, I believe either design of header has been shown to work best through a single pipe exhaust system. In the typical rpm range of a street car, I would guess a well designed Tri-Y header fitted to a single pipe system would outperform a long primary header, especially if it were feeding into a dual pipe system.

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Richard Good showed me some dyno tests comparing different exhaust layouts. The large bore single pipe after the Tri-Y did generate about 8 more horspower. However that horsepower difference did not appear until nearly 5500rpm. Purely a high rpm difference and not an overall increase across the rpm range. So unless you are racing, it really comes down to personal choice and aesthetics.

The idea of crossing over the twin exhaust though has been a mod I've planned on since day one. Though I probably won't do it until I fuel inject the engine. I have planned on putting a single O2 sensor in the crossover for tuning purposes. /ubbthreads/images/graemlins/computer.gif

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Shawn,
I thought of making up a crossover for my dual Falcons and could not, for the life of me, figure a way to make it work.
First, the exhaust ends of the split Falcon header exit in a staggered fashion so that will not work (not that you would want to put the crossover that close to the head). Because the Falcons aim backwards at different angles and run so close together that they almost touch, the head pipes are too close together to weld in a crossover, plus they go onto the header at different angles. I have seen sensors welded into bungs in the collector pipes. I do not see where it is doable.

Bill

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Shawn,
I thought of making up a crossover for my dual Falcons and could not, for the life of me, figure a way to make it work.
First, the exhaust ends of the split Falcon header exit in a staggered fashion so that will not work (not that you would want to put the crossover that close to the head). Because the Falcons aim backwards at different angles and run so close together that they almost touch, the head pipes are too close together to weld in a crossover, plus they go onto the header at different angles. I have seen sensors welded into bungs in the collector pipes. I do not see where it is do able.

Bill

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When I had the custom pieces made to connect the headers to the falcon system I discussed the idea with the exhaust guy. We concluded that it is possible to do it in that area. It will be tight but it's do able. Crossovers close to the collectors are actually pretty common. It really ends up being more of an 'X-Pipe' than a traditional 90 degree crossover. The O2 sensor would go in the middle of the 'X'.


My headers are similar to the Falcon's but are not actually Falcons. They came from a shop in Callifornia that supposedly used to bend up Kastners stuff. The collectors were quite large and then they had seperate reducers to match the TR6 exhaust pipe size. Because of that we were able to angle the reducers where we wanted them to give us the most room for a cross over at a later date. Tight is still the name of the game though.

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Which Tri-Y header??, even the stock late model tr6 manifold is a Tri-Y. If you took this stock manifold and went with a 2 into 1 pipe or two with a cross over, I wonder what the numbers would show compared to a header-up to 5500rpm?

The late (dual downpipe) exhaust manifold is more a 6-1 design. All the exhaust mixes together right before flange so there really isn't that much seperation of the front to rear cylinders need to exhale. The stock manifold also makes a pretty sharp turn that can impede flow where as headers still smooth the flow.

Kastner states in a few of his books that the stock TR6 manifold is good for close to 150hp. The placement of the crossover can effect where in the power curve the increase and decrease of power are. I remember reading a few articles on the subject in some Hot Rod magazines. Those mostly dealt with V8's and will serve well for my TR8 but I'm not exactly sure how they will translate to the I6. Similar to the difference between long and short tube headers.

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Lots of good information has already been given in this thread, but the math behind the facts is interesting.

The pulses of exhaust gas travel at about 300-350 ft. per second as they leave the exhaust port, slowing down (and cooling down) as they travel towards the tailpipe. Of course, there are sound waves as well, which, naturally, travel at the speed of sound.
Exhaust manifolds are designed to use the partial vacuum behind each pulse to provide an extraction effect to help pull the next pulse into the exhaust system, and to do this over a range of engine speeds that will be used in normal driving, say 2000 to 5000 revs.
If the engine is doing 2000rpm and the crank must complete 2 full revolutions for each cylinder to fire,(because it is a 4 stroke) then on a TR6 we will have 6000 exhaust pulses per minute, or 100 per second.
Since we said the exhaust gases are moving at about 300 ft/second, the pulses will be spaced 3 feet apart. BUT, the exhaust manifold or header does not pair cylinders which fire consecutively because the firing order is 1,5,3,6,2,4 and the two sets of primaries join the front 3 and back 3 cylinders. This means that when the primary pipes merge into the secondaries the pulses are 6 feet apart at 2000rpm, or only 2 ft apart at 6000rpm.
So if the length of the primaries is 2ft or less then the scavenging effect will be lost at engine speeds over 6000rpm, not relevant for road cars. Below this speed some extraction effect will be gained. Because the partial vacuum behind the pulse wave decays fairly slowly the extraction effect works quite well over a wide range of engine speeds. This is why, for road cars at least, it is not worthwhile trying to get all the primary pipes exactly the same length.
A header with slightly longer primary pipes should extend the power band, though a camshaft with more lift and duration would benefit more from this.
Finally, having primary pipes of too large a diameter will cause the pulses to slow down too quickly, which will reduce the scavenging effect at low revs; though pipes which are too small will restrict flow at high revs.
The stock manifold seems quite well designed for its intended use, though with a modified engine a header may give some benefit.
Simon.