TR4/4A Exhaust advice wanted - TR4

Hi all,

I'm trying decide on an exhaust on my TR4, but am having difficulty making choices. I'd really appreciate any suggestions you might have!

This car's engine is moderately tuned. It's intended for street use, but also autocross, maybe eventually some paved rally or vintage racing track time, too. Mostly at a "fun" level, though.

Major engine mods to consider: It has .125 milled head, AE 87mm pistons, oversize gas-flowed valves, 40mm Weber DCOEs, "D" cam and headers with a 2.5" ID outlet. I may replace the headers later, or have this old rusty one ceramic coated. Wrap might be used on a s/s header, but not the mild steel.

So, my challenge is to keep the motor breathing well, but not overly loudly since the car will have to be street legal (an enjoyable). I also want to maintain pretty good torque at lower RPMs.

And, you might as well know, the system I'm replacing was a homemade setup with a Ford muffler of unknown application and 2" ID pipe from front to rear. It really didn't sound too bad, maybe just a little strange. But it was pretty well shot after about 25 years on the car. It also made a nice "thump" over every bump!

I'd prefer a stainless steel system, but would still consider mild steel if it were better suited to the car and/or significantly cheaper. I plan to install a flex-coupling just behind the header to help prevent stress on the system. The car and frame are currently set up for a single exhaust. The header and/or flex coupling will have, or can have, welded bolt-up fittings or whatever.

Car is lowered significantly and sits on 195/60/15 tires. Not a lot of ground clearance, so any system needs to tuck up under pretty well.

Here are the choices I'm finding:

1. Monza performance, mild steel. I've heard good and bad reports on this system. A lot of folks seem to think it's too loud. Others say it tends to rust quickly. It is probably the cheapest at around $200, and easy to find. Uses stock hangers and mounting locations, I believe. I'm not sure the tube ID size is, though.

2. Falcon stainless, with "full flow" muffler(s). About $300. Uses stock hangers and mounting locations. 1-3/4" ID tubes. Some have said these are pretty good, maybe a bit loud. (I know, that's very subjective! Remember the Ford muffler, though!) The tube size seems a little small to me.

3. Bell stainless steel system. Haven't found a source, but have heard it's a good system. Specifications, cost, availability unknown.

4. A custom setup. Either a relatively simple the TR4 single-pipe setup with a single muffler at the rear or a more complex dual tube with a Y-pipe/reducer after a large main pipe passes through the frame, to a pair of smaller mufflers. I do like a dual system, but it seems overkill on a 4-cylinder engine. And there is added expense, plus possible problems routing near TR4 parking brake cables, for example. In either case, a custom system allows for more control over pipe diameters, etc. But, I'm not sure if it will make enough difference to worry about.

5. The most expensive route I'm not really considering. That would be getting one of the kits from the British suppliers such as Revington TR, who offers a 2-1/8" ID stainless "Rally" kit or a 2" ID stainless "Sport" kit. Higher prices, unfavorable exchange rates, shipping time/cost and duties all pretty much rule this option out. Too bad! Seems there is much more to choose from in England, than here in the U.S.!

Am I missing any options? Any suggestions which might be the best way to go here, or sources you can recommend?

TIA!

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It also made a nice "thump" over every bump!

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I've got one of those too. The TR3A has a different clamping/hanger arrangement and never touches anywhere but the TR4 still makes contact at RR tracks & pot holes.

As for systems -- I put a Falcon Stainless on the TR3A 20 years ago, still looks fresh and sounds good.

Alan, I can't be of much help to you for your TR4 but I am in the process of replacing my Monza system on my TR6 to Falcon stainless headers and duals. I see where you are planning to use flex connectors, I am assuming right behind the exhaust manifold/header. I, too, am faced with the dilemna of having a rigid exhaust system mounted beneath my car and plan on using flex connectors to take the load off the header/engine. I have spoken to Rich at Exhaust Productions, Inc. in Indiana and he will make up the stainless flex connector of the size I choose. Where do you plan on acquiring your flex connector. EPI will weld the appropriate sized pipe extension on both ends of the stainless flex connector but can only use mild steel. Again, does your source offer any other pipe ends and perhaps an alternative to standard muffler clamps? Would be neat to use bolt-on ends but that is getting a little high tech for my home-installed system I have planned. Behind the connectors my system will have to be a rigid mount because the Falcon system has a large muffler that is impossible to hang with rubber or sliding mounts, just no vertical room. The Falcon system offers a very pleasant rumble compared to the Monza, which is harsh. I have had both and can compare. The reason I am re-placing the Falcon system is because of the addition of the headers. (I had them on before and literally "pulled them off" over a bump. They are large and hang really low.) The main reason I would not really want standard "U" clamps is they will crimp the pipes and make future disassembly a real headache or even impossible. Sorry for the lengthy response and no real answer to your question, except that I do like the Falcon but they are tough to hang. Will fabricate some kind of custom brackets as they don't hang where they ought to. Monzas do indeed rust out, especially if you don't run them for extended drives every time and just collect moisture inside. Hecho in Mexico and are no better than cheap econ mufflers. Good luck.

Bill

You can find a link to flex connectors here:
https://www.britishcarforum.com/ubbthread...mp;page=0#94824
D

Hi Bill,

I'm afraid I don't have any magical sources of flex connectors. I think all that I've seen are stainless braid connectors with mild steel fittings at either end. There is someone selling them on eBay at reasonable prices. Lot's of other places to get them too. EPI is one manufacturer I found. They sell through JC Whitney, among other places.

If I use my current steel header, I would just get an 2-1/2" diameter by 8" flex and weld 3-bolt plates to the front of it and the back of the header, and a reducer to the rear end of the flex connector. I can weld mild steel myself, but am not set up for stainless right now. The exhaust system I end up with will determine the size and method of connection I'll use at the back of the flex connector.

Another method is to use slip fits throughout the system. Take a look at the exhausts on Revington TR's website (www.revingtontr.com) and you can see some good examples of this method. It's simply good fitting slip joints that attach together with springs. This allows some give in the event something drags, and then pulls itself back together in most instances. Revington also puts a skid plate on the leading edge of the mufflers. Neil's systems are stainless, too. Nice stuff, but my budget doesn't allow me to import an exhaust system! Plus, they are large "fast road" or "rally" oriented systems, anyway, intended for flat out, high rpm driving. These might be too large for my purposes, a slightly smaller diameter might give more low end grunt.

The depth of most mufflers and low ground clearance of my car are reasons I've toyed with the idea of just building my own system. I've found some "turbo" mufflers as small as 3-1/2" thick, which will tuck pretty well up into the frame (maybe with a piece of Dynamat above it to keep the floorboards from toasting).

Fortunately for me, the TR4 system is almost a straight pipe from front to rear. It only needs two minor bends, one of which might be accomodated by the flex connection. If I do build it myself, I'd work with a local shop and have any stainless parts welded up there, or just clamp it as I've done in the past.

You are right. Clamps aren't the best solution. You usually have to destroy one part or the other taking it apart. After that, the remaining part can be straightened with tools designed for the purpose. Most muffler shops have them. They also use them to expand pipe for slip fits, such as would be used in a system like Revington's, or preparing a system to weld together.

I would be curious if anyone can tell us the inside diameter of the stock TR4 exhaust system's pipes and, possibly, the Monza sport system pipes.

I know the Falcon "Sport" system uses 1-3/4".

The Group 44 race cars used 2-1/2" ID pipes, 40 to 44" long, dumping out the side of the car just ahead of the right tire. But, that might upset my neighbors when I pull out of the garage for those early Sunday morning drives!

Cheers!

Hi Geo,

Is your Falcon system the standard or "sport" system?

Thanks!

Alan I have a 4a, so rear suspension is different but exhaust routing through the transmission tunnel is the same; what worked for me should work for you.
Looking at a website for a company named "Performance exhaust and Undercar Inc." I felt that a 2.25 inch system would be about right for a car in similar tune to yours.
I did not feel it worth spending a lot of money for a stainless system because I mostly drive in nice weather and on longer trips, so mild steel should last quite a while.
The first system I built up myself from tubing bought at a local auto parts place and a $30 free-flow muffler. The whole system cost about $60 or $70 and worked well for 4 years until I ran it over a curb on a race track.
I replaced it with a 2.5 inch system with Holley "Predator" muffler,again $30; this system was fabricated by Midas Muffler, and the piping has noticeably greater wall thickness, and proper welded joints. Cost about $150 total.
This system is a bit louder, and the pipe big enough in diameter that it was in the way when I had to change a propshaft u-joint, making the job more difficult.

I cannot say for certain if there was any difference in performance, I thought the smaller system might have given a touch more power at moderate revs but too close to be sure. Hope my experiments help you make a choice!
Simon.

"I would be curious if anyone can tell us the inside diameter of the stock TR4 exhaust system's pipes"

Looks like 1 3/4

"Is your Falcon system the standard or "sport" system?"

I suppose standard -- not sure if the sport version was offerred in 1982.

Hi Simon, I'm looking at that site (https://www.performanceexhaust.com) and am more seriously considering building my own system. I guess it's my own uncertainty about what size pipes to use, etc. that's been holding me back. At the same time, the selection of systems in the U.S. is pretty slim.

I find it interesting that the website you mentioned suggests a 2" minimum I.D. pipe size, and up to 2-1/4" or 2-1/2" for tuned TR4-size engines, depending upon the approx. amount of HP produced. Meanwhile, it looks as if pretty much *all* systems offered for TRs in the U.S. use 1-3/4" pipes.

Geo, thanks for the info on your Falcon system. Stainless is definitely the way to go for longevity! I think the only difference with their "sport" system is that it's supplied with a "free flow" muffler. Otherwise, I suspect it's identical to yours.

[ QUOTE ]
...the website you mentioned suggests a 2" minimum I.D. pipe size, and up to 2-1/4" or 2-1/2" for tuned TR4-size engines, depending upon the approx. amount of HP produced. Meanwhile, it looks as if pretty much *all* systems offered for TRs in the U.S. use 1-3/4" pipes...

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Would seem to me that those big diameter pipes would be a really snug fit where the pipe passes thru the cruciform.

I've never measured it but as I recall the 1.75 pipe had less than a quarter inch clearance above & below and needed that to avoid contact during driving.

I can only tell you what I have on my 4A chassis since I'm in the assembly stage at this point. I purchased a mild steel TriumphTune split header from Moss - think it's the TT1100 model. It came with a SS slip on collector that joins the dual outlets into a single pipe and also came with a SS connector pipe for the exhaust system. The connector it came with is Falcon brand which I thought was kinda funny. I sent off the mild steel header to JetHot for ceramic coating and since it was new they guarantee rust out forever (as long as I own it) so I figures that I didn't need to pay extra for SS. I then purchased the Falcon SS dual system bits from TRF with two rear mufflers, complete with hangers and hardware but I opted out of buying the front muffler and will use the connector that came with the header instead. Everything seems to fit up well but it is loosely hung right now. Pipes are pretty small but should open up well at WOT. My engine is similar to your mods but head is only .033 shaved, ported and chambers swept, intakes unshrouded per Kas.
Peter

Yeah, the 2" ID pipe I used before did "clunk" inside the frame over any significant bump. I measured the hole through the frame and a 2-1/4" pipe would be a pretty tight fit. I can't imagine how anyone gets anything larger through there without enlarging the opening, which would weaken the structure, I'd think.

In fact, a 2-1/4" pipe might eliminate the "clunk", being such a tight fit! That close fit probably makes a flex coupling between the header and the front pipe all the more important, to keep all the forward joints from cracking over time with engine torque movement or any frame flex.

I'm not too worried about frame flex in my car, it's had quite a bit of frame modifications done: gussets added at the corners of the cruciform, fully boxed-in cruciform rails, extra tubing welded inside the body outriggers, and a few other things. It will also have a roll cage adding rigidity after the body is installed. Without those changes, or on another model with a less rigid frame, I'd be more concerned.

Alan, my figures were for outside diameter not i.d., and it did fit, though as I mentioned it is tight. My reason for going to the larger system was to try for more high rpm power, but I don't think it worked.
For a modified engine I would try fot 2.25 inches if you can.
Since the body is of my car right now I am interested in your frame upgrades, I was planning just to strengthen the diff. mounts. Could you send a couple of pic?
Thanks! Simon.

Alan, you might want to try the stock system intermediate pipe for your TR4, Moss list if for the TR4A, but there were alot of solid axle 4A's and Moss didn't make a comment to restrict it and the "Y" lines the rear pipes up nice for a good muffler of about 22 inches, OTTO makes a good sound and with two should be quiter. Hope to put this on my TR6 come spring as I have had the pipe for 20 years or so, I could go down and measure it for the stock size. I did, front of the Y 1 and 3/4 inside, 1 7/8 outside, rear two pipes 1 5/8 outside and 1 1/2 inside. Now we all know what the stock size is or was, 1 3/4 inside from the header pipe sounds about right to me. Wayne

Hi Simon,

Thanks for clarifying outside/inside diameter. That does make a difference! 2.25 outside would be between 2 and 2.125 inside. That's reassuring and, yes, I think it would fit in my car too. Bigger pipes are better for high rpm, and I'm trying to maintain the power curve in the mid range.

I can take pics if you want, no problem. First I need to ask, is your car a 4A? Is it IRS? If so, it's quite different from the ladder chassis/solid rear axle on my 4.

We're really talking about a new thread, but here goes anyway!

I highly recommend Roger William's "Improving TRs" books. They are very well illustrated and cover many frame improvments, including a lot more TR4A/IRS detail than I can give you.

I did the following:

1. One thing Williams didn't cover... I boxed in the C-shaped members that make up the front and rear of the central cruciform. This is pretty standard hot rod stuff. Many older cars used C-shaped frames, in part or entirely. On the TR4, the larger, outer rails are fully boxed, only the cruciform pieces were left open or "three-sided". A piece of 16-gauge steel with a 90 degree, 1/4" flange on each side, fitted and welded inside the "C" and welded at either end, really increases the strength of this area.

2. I welded 14 or 16-gauge gussets about 5 or 6" deep at each of the inside corners of the cruciform. The flange on the big, outer rail makes this easy. There are a total of 8 gussets - 4 top and 4 bottom. Some folks actually add large plates of steel that completely enclose the diamond shaped area of the cruciform, sometimes just on the top, sometimes on both top and bottom sides of the frame. This is a bit extreme for most circumstances, but might double as useful protection for passengers, fuel and brake lines in a rally car.

3. Body mounting outrigger tubes are okay as original, if not rusty or damaged. But since I had plans for a roll cage that will bolt to them, I felt they needed to be beefed up by driving a close-fitting, heavy, weldable tube inside. Then I drilled 8 holes or so at various points along the length, to weld the inside tube in place, and welded up the end.

4. The round cross-member to which the leaf springs mount in the rear can be beefed up the same was as #3. Some folks like to add gussets here, too, but I think that's a little bit of overkill. If the very rear tubular cross member is damaged or rusted, repairs can be done using this method.

5. Exclusive to TR4 up to about CT20000, I reinforced the steering rack mounting ears (~1961 frames lacked gussets, ~1962 frames had them right from the factory).

6. Exclusive to my car with an adjustable camber setup, some reinforcing will be done on the shock towers.

Your car should have the later style steering rack mounts, which need to be carefully checked for any cracks (usually at the base, where it attaches to the frame) rewelded if necessary and possibly gusseted as a precaution.

Your car probably has the later style lower/inner front suspension mounts, which *must* be reinforced and have an additional mounting bolt added. This is a critical improvement.



If you are running lever shocks at the rear, there are larger, heavy duty upgrade shocks that call for a larger, heavier mounting brackets. (BTW, I've still got the original Armstongs on my car and they work well. Meanwhile, a set of 25 year old Konis on the front are worn out, although they are rebuildable!)

Even if using the original size lever shocks, some reinforcement of the mounting brackets is recommended if the car is being driven aggressively. I've not changed the original brackets on my car, yet.

Cheers!

Alan

Hi Wayne,

That would be another solution. I'd considered installing a dual muffler system. I really like the way they sound! It's even better on the 6-cylinder cars.

Hey! Some time we should have a contest and see who has the oldest item in their garage "just waiting for the right time" to put it on their car, but still not installed. Bet we all have a few items squirreled away.

Cheers!

Alan

Alan, thanks for the detailed reply.
My car is irs, so as you point out, quite a different chassis. I like the idea of strengthening the x brace or cruciform area.
On my car I have strengthened the front lower suspension mounts as per competition manual; one had torn out giving lots of negative camber on that side.
Simon.