Header selection...?

[S2Jay]

Header selection?

I did find some info on stroker engine builds with some dyno examples, but nothing that addressed torque so much, or header tube size comparisons.

I would much appreciate any input, suggestions or experiences on header selection concerning primary tube size [diameter, not length] for this application. I am not designing or building a new header, only looking at items available on the market now.

The engine is a stroker conversion, 77.62 stroke, iron crank, 83.65 mm bore, 1706 cc total, 10.5 compression, 125E rods & forged CP pistons [to be ordered]. Expecting to use a 6500 max rpm redline.
The issue is that this will be a road car engine, so mid range Torque will be more useful than high rpm hp.
There is a “small tube” [standard size?] 1-3/8” mild steel header, ceramic coated, for $385. I have also been quoted larger tube stainless headers for about $1k usd. These also require the frame bending or notching. I have found no large tube, mild steel headers, and I would be very interested in info about any available, esp in U.S.

Q: Will the small tube header provide mid range rpm tq as good, better or worse than the larger tube versions with a 1700 cc engine, and how significant would the probable restriction of high rpm power be in comparison to the larger tube version?

[StressCraxx]

A challenging question. A custom fabricated header and tuned on the dyno for both optimum primary length, diameter, and collector design would be the ideal with emphasis on the collector. Cost would be north of $3000 plus dyno time.

The entire system needs to be considered. Carb size, chokes/AVs cams, cam timing, porting, compression ratio, are very important. Generally an engine for the road likes a 4 into 2 into 1 system for better mid range torque. I tried a mild steel 4 into 1 by 1-1/2" on my mostly stock sprint cammed engine many years ago. The collector was very short. It had the dreaded weber flat spot below 3000, but once that was cured, ran much better. It really didn't seen to make more power until about 5000 rpm, then really took off.

I sold that header to a vintage racer and put in one of Dave Bean's 4-2-1 header with a very long collector. The difference was immediate. Engine pulled much better from 4000 to 7000 with a very slight loss of peak HP. The first one I had was mild steel. I wore it out because I had it wrapped(causing creep failure of the primaries). I bought the stainless model and had it ceramic coated inside and out. It has lasted almost 20 years now. Both headers fed into the same exhaust pipe and muffler, a 2" diameter Walker "turbo" muffler. From racing Formula Ford, (pretty much a stock Kent with porting and polishing fed by a 2bbl Weber DGV) I have learned that the collector design is more important for torque curve than the primary size and length.

As far as notching the frame, that can be avoided by slotting your motor mount holes that bolt to the chassis and pushing the engine towards the passenger side.

YMMV

[S2Jay]

@StressCraxx Thanks much for posting this! This is great info & experience that adds to the knowledge base.

I will re-evaluate a bit on my concerns & priorities, and certainly check collector configuration & length.
I am likely stuck with some version of an off-the-shelf item from some source, but easier to consider taking an existing unit & lengthening the collector, rather than having to start at zero.
So, in case anyone has a used header they may want to sell, then I could begin with that & add some inches to the collector. I need to build the rest of the exhaust system in any case.

Much as I may like to, designing, building & testing something new is just not practical for me right now. I am really hoping to get this car back on the road while I can still drive, and my “sell-by” date is approaching fast. Plus, any added delay now would likely have me sleeping in the carport, at best.

So, in case anyone has a used header they may want to sell [within U.S. only, I suppose for shipping issues. I am in Southern California], then I could begin with that & add some inches to the collector. I need to build the rest of the exhaust system in any case.

And thanks for the tip about avoiding the Frame Notch. I had wondered about several such possibilities, but not able to evaluate until I have the pieces together. This may have been discussed on the forum, but I have been out of touch for some time.
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[StressCraxx]

I think your best bet in terms of best off the shelf function and reasonable cost is Bean's 4 into 2 into 1 stainless header. It will fit without notching the frame or other grief. Get it coated inside and out for lower underhood temps and avoiding a hot right foot in the footwell. The mild steel models haven't been made since 2000 or so.

Leave an uncoated inch at the muffler end of the collector so you can weld an exhaust pipe to it. I personally know who fabricated them and his work is absolutely first rate. I wish I could bend tube and weld as pretty as he does, but I don't get enough practice.

[Frogelan]

This is a question to which scientific trial and error checking is probably needed, as suggested by the previous post by StressCraxx. Here are my thoughts...

Ceramic coatings are a good idea, whereas insulating tape is probably the wrong route, as it can retain heat that can warp a cylinder head.

I sat down and ran some figures (for a rally/race engine producing 170 bhp)based on a go faster book (Bell) and 4 x 1.5" primaries (38 cm long) and 2 x 2.0" secondaries (38cm long) were the figures that came back. I was not so convinced about the latter. Bell was emphatic that very large primaries do not help torque.

However, as very few exhaust builders would seem to propose this, I opted for the latest TTR system (1.5" primaries / 1.75" secondaries). I have not tested it yet.

My reasons were:
- cost / homologation risk reduction with the FIA
- ease of fit (according to another member of the forum) as the primaries and secondaries are in 2 parts.
- use of mild steel by TTR rather than stainless (ease of welding, sound quality, use of ceramics acting as anti-rust coating etc)
- compatibility with ground clearance and the rest of the system (that I am building)

Bean trade frequently with TTR and have a reputation for also producing good parts although I have not bought any parts from them as I am in France.

I hope this helps.

[MartinH]

Plus one for the TTR fast road system fitted to my 1700cc TC. Mine is now approx 10 years old I had it ceramic coated inside and out. The difference to the car when first fitted is astonishing when compared to the standard sytem. The engine breathes properly especially further up the rev range and gives the improved mid range torque you are looking for. No requirement to modify anything it fits out of the box.

I had the entire system off the car for a recent gearbox change and it is still in great condition after 10 years.

the full system I have has the added advantage of sounding great.

Martin

[S2Jay]

Thanks everyone for the comments & analysis work.

@StressCraxx
I did get the sense from your first post that the Bean Header was the best solution.
It did seem that most if not all of the headers I had seen were the 4 into 1 design, and I also thought that this was either for a performance benefit, or just b/c it was easier/cheaper to fabricate. I had not checked with Bean & did not know they offered 1 of their own design. So thanks for showing that.
I have been more familiar with old iron lump V8s. One of the early header designs was what was called a “Tri-Y” design, which is the 4 into 2 into 1. It was said to improve mid-range torque, which is also true of the longer collector lengths.

@Frogelan Thanks for all of the math work on the design elements.
Agree that “very large primaries do not help torque.” It makes sense that at lower rpm, there is not as much actual gas flow being generated & the goal is to create/maintain as much velocity as possible & the smaller diameter helps do this. This is why I was wondering if I should stay with the original 1-3/8” primary that is the “original” port size, even though this make mean losing a few hp [how many?] at the top end. The 1.5” primary seems reasonable, although the 2.0” secondary seems too large, but this is just a layman’s opinion based only on observation & limited experience.

@MartinH Thanks for relating your experience with the TTR system, especially since it is with a 1700 cc like the one I am trying to compete [waiting for head work from machine shop]. And appreciate you posting the dimension of the primary pipe [and congrats on the Ducatis!].
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Without controlled direct comparison the question remains about potential difference in lost hp or torque with the 1-3/8” primary pipe vs the larger tube size primary. I would expect strong mid range torque with the small pipe, with perhaps no noticeable loss & perhaps as strong, or even stronger than with the larger primaries, and then seeing some loss to restriction as the rpm climbs.

I have done some further checking, and here is what I have found so far.

I called D. Bean & I was a bit surprised when Ken said that they do not offer the Stainless Steel version of the Elan Header, only the mild steel version now, and it is only $395.
It is made as one piece in the 4-2-1 configuration and includes the collector pipe, which had been sold as a separate piece [at least in my old D.B. catalog]. It is what I am calling the “standard” size diameter, meaning original port size of 1-3/8”. Ken quotes 1.365”, which I am guessing is the Tube I.D.

Doing some further searching, I was again surprised to find that SJ Sportscars offer a 4-2-1 system in Stainless of 3 pieces; the 2 separate manifold sections and a separate collector piece
It is also of the 1-3/8” primary size.
They further offer the complete exhaust system, but I am less interested in this as it would require shipping the 1 long car length piece at an extra cost adder for length.

They list the 2 piece manifold set at $339.15 usd [their site does the conversion to usd when prompted in checkout], plus $49.88 for the collector, so $389.03 for all, all stainless.
Their site also provides a shipping cost to the U.S. of about $100, although I have not checked if that is just to a New York P.O.E., for example, or to my door.
Even if there is an additional shipping cost this seems like a decent deal for stainless parts. It is still the small primary pipe size, not the 1.5”, but it is Stainless, so always trade-offs, it seems. Which is really where I began this project.

Ray @RD Ent shows a 4-2-1 in mild steel with 1-3/8” primaries & 1-3/4” collector, appears to be coated, for $345 usd.

The TTR header is a 1.5” primary “Big Tube” version and is also 4-2-1. In their pic it appears to be mild steel that has been coated black, but I saw no description to confirm that.
It is listed at 450 uk.
TTR is the only source for a “Big Tube” version of the Header that I have found or know of. If anyone knows of another source for this, please advise & I will check on it.

Although the question remains about relative torque in the mid range rpm, Martin’s post did provide an insight into the TTR system “Big Tube” system. Since I do not know Martin, or his engine, cams, tuning, etc, or his previous experience, he does provide a reminder about 1 thing. That is that one of the changes/improvements/benefits of the stroker 1700 cc engine is that it makes stronger Tq just b/c of the longer stroke. So regardless of the relative gain or loss of maximum potential tq, that combination is making enough tq to make Martin [& most likely me] very pleased with the performance. He also mentioned no flat spots or sluggishness that could be attributed to the [slightly] larger port size. So now I am back to thinking that I should go with the larger Tube header.
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[S2Jay]

Here is a Summary of the manifold features I found.

All use the 4 into 2 into 1 configuration
2 are “1 piece”, 1 flange
2 use Individual flanges @ each port
3 are small/original size primaries
Only 1 is “Big Tube”
3 are mild steel
Only 1 is Stainless

Elan Exhaust Header/Manifold offered

Dave Bean Lotus Config Material Primary Diam. Price
4-2-1 Mild Steel 1-3/8” $395 usd
1 piece, w/collector
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RD Enterprises 4-2-1 Mild Steel 1-3/8” $345 usd
1 piece, w/collector
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SJ Sportscars 4-2-1 Stainless Steel 1-3/8” £255.00
3 piece, incl collector separate $394.88 usd
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T Thompson Racing 4-2-1 Mild Steel 1.5” [1-1/2”] £450.00
3 piece, incl collector separate 589.18 usd
Individual flange @ each port
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[S2Jay]

Here are pics of some of the Headers available.

Dave Bean Engineering & Authorized Lotus Parts Supplier[pic in catalog, no website pic] http://davebean.com/
4-2-1 Configuration, Mild Steel, 1-3/8" Primary, 1-3/4" Collector Outlet

TTR
Tony Thompson Racing https://www.tonythompsonracing.co.uk/parts/
Big Tube Header by Tony Thompson Racing

Big Tube Header, 1.5" Primary Tube, 4-2-1 Mild Steel

TTR Big Tube Header -300x300.jpg (16.78 KiB) Viewed 578 times

RD Enterprises http://www.rdent.com/
RD Enterprises Header, 4-2-1, Mild Steel

SJ Sportscars Header, 4-2-1, Stainless Steel

RD Ent Header 50s01.jpg (34.7 KiB) Viewed 578 times

SJ Sportscars https://www.sjsportscars.com/parts-and-accessories.htm
SJ Sportscars Header, 4-2-1, Stainless Steel
Collector as a separate piece.

[snowyelan]

From the pics only TTR has equal length primaries. Did Ken mention if the Bean header was equal length primaries?
The SJS pics appear to be from Falcon. I have an older Falcon system. Its been ok, but the pipe into the muffler cracked and I had to re-weld it. The header itself has held up.

[The Veg]

I've got the one from RD. 1558 Engine, Stromberg head built to DBE Stage II, which I understand is similar to Lotus 'big valve' spec, with DBE 112 cam. Haven't done a dyno or anything else scientific, but it runs well enough.

[S2Jay]

@snowyelan
Yes, it is a bit tough to see from the small pic, and because of the angle – its just a copy of their online web catalog listing – but it is similar in layout to the SJS, with port 1 & 4 run together into a secondary pipe, then cyls #2 & #3 run together. The 2 secondary pips are sitting “on top” of each other in the pic, and then the separate 2 pipe collector mates them together into a single pipe exit to the exhaust pipe.
The pic on their site is larger & clearer, and it is easier to see the layout.

Ken @ D. Bean said their system was 4-2-1 & that matches the pic I have in an older catalog of theirs that I still have. I did not ask about the lengths of the primary pipes. A few years back, when my catalog was printed, it shows the collector as a separate part, but it apparently now been incorporated into a single piece header, with a one-piece flange that bolts to the Head – as opposed to having 4 separate flanges as with SJS & TTR.

Stainless can have problems with cracking, depending on how it well it was welded & may also need to be properly “quenched” to reduce the probability of cracking at the welds.

@The Veg
Sounds like a really solid engine build with well planned enhancements from the original.
The RD piece does look like a good item from the pic, & Ray has a great rep for offering quality products, whether ones he has made, or vendor purchases.

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[StressCraxx]

@S2Jay - Yes, the Bean 4-2-1 header has the equal length primaries that two primaries each merge into one tube. The collector is unique with the two inlets blended into a long tapered flat oval into a 1-3/4" outlet. The collector is about 12" long. Dave Bean did a lot of dyno time with multiple iterations of collectors making a good strong street header that made good torque with little sacrifice of top end power.

If I had the car with me, I would take some photos and post for you. I'll look to see if I can find a photo and scan it.

The important thing to do here is the engine math before you start throwing money down. Treat the engine as an entire "power system" from the airbox to the tail pipe. Any change you make will have a positive, negative or no effect at your expense.

On my Formula Ford Kent motor, the header flange opening was centered to the exhaust port for the first dyno runs. My engine builder raised the header flange so the bottom of the opening was flush with the bottom of the header which resulted in two more HP at 6600RPM. Adjusting the relief valve in the oil pump to 35 psi down from 40 gave me one more HP. The power is in the details.

The distributor must be in perfect condition with no timing scatter from mechanical slop. Same with the carbs. The low speed circuit drives most people nuts with off idle stumble or the dreaded "flat spot" from going lean. Leaky throttle shafts and manifold gaskets can make you crazy.

Talk with your engine builder, particularly if he is Twincam conversant. In SoCal, Tony Ingram is excellent for race or street, Frank Monise Motors in Montclair is also very good for race motors. Start with the head and porting the intake runners to get them cleaned up. Avoid much bigger intake valves because the seat is already too close to the spark plug threads and subject to cracking. Cam lift, limited duration and overlap are crucial to drive-ability on the street. Higher cam lift also required careful preparation to avoid coil bind.

[661]

I would thoroughly recommend a slip joint system, like the ones sold by TTr and Kelsports. The headers can be removed without any engine movement.

[TWebb]

I have a TTR header that has not been used with which I am willing to part. $250 plus shipping.

I'm located in Tulsa, OK.

Feel free to contact me if you are interested.

Tim Webb
coopers66 at aol dot com
479.236.7606