Just another 26R replica build attempt

[Famous Frank]

Roy,

What a wonderful and terrific project! And your explanation of the engine build is wonderful. Thank you!

I have a real 26R in a million pieces waiting for me to start the restoration. It's been apart since1967. Although it would make a terrific race car, I'm too old now to start racing again. As such I'm going to drive mine on the street. I think they are beautiful and should be seen by everyone, not just those going to the races. As such, a pure FIA engine was not in my cards. After doing some research I too want to go the John McCoy Omni route as you did. I've purchased his 1950 crankshaft. And was looking for a new tall block also. Impossible to find here in the states unless you want to pay full retail plus. Mine is on order from Summit racing with an anticipated delivery date of Mid Feb.

Since mine will be street driven I want overdrive and a five speed. I've decided on using the Ford T5 Five Speed that is used in a million Mustangs and other vehicles.

Prior to making that decision the Ford Lotus 4 speed with the Close Ratio Dog Gear Transmission would have worked well. As such I have one purchased from TTR in 2016. Complete to convert a standard Lotus Elan 4 speed to the Dog Gear Trans. Although all the parts came from TTR, the box is all marked Quaife.

The parts are:
Dog Gear Kit Close Ratio 1060 pounds
Gearbox Service Kit 105 pounds
Competition Layshaft 53 pounds
Heavy Duty Selector Forks (pair) 196 pounds
Reverse Idler Gear 62 pounds
Steel Front Seal Housing 93 pounds
________________________________________________
Sub Total 1, 569 pounds
times 1.36 to US Dollars
Total $2,133.84

I will sell them for the 2016 prices I have listed and I'll pay for the shipping within the Continental USA. I will not break apart the parts. They are all or nothing. This is a chance to get the Dog Gear Transmission Parts at the 2016 prices, brand new, without paying the shipping from the UK.


In the meantime, I want to hear more about your engine and the rest of the build.

Did you use the converted Stromberg head or a CNC machined Weber head or a brand new weber head?

Are the carbs 45 DCOE or 40 DCOE?

Do you know what size valves are fitted? Standard Lotus Big Valves or ???

Did you have to use a larger diameter header to flow that much air?

Do you know the jet sizes?

And as asked already, what cams are being used?

John talks about using Carrillo Rods. Did you use those also?

A Johnson Oil Pump?

Oh my, .................too many questions but do you have any idea what that will feel like with over two hundred HP? UnGodly with the Devil on your shoulder!!!!

All the best and again, "Thank You!"
Frank

[45DCOE]

To Stu, Tim, and the legendary Famous Frank….. Sorry for the late post but been on an Omicron high the last few weeks (very intoxicating).
THE SAGA OF THE ROY E. JOHNSON OIL PUMP
Since Stu and Tim already have one and Frank was enquiring, let me relate how this may be the single most critical component of John McCoy’s higher horsepower engine builds. When I first talked to John (October,2020) about ordering an engine, he was lamenting that he was stuck and could not finish a 1950 engine ( for a customer from Wisconsin—-a member of this board?) because he could not get ahold of Roy Johnson to order more of his Stage 1 pumps. It had been 3 months since the engine was done and the only thing holding up completion was installing a Johnson oil pump. The owner was getting antsy (understandably). All calls to Johnson went unreturned and John was seriously thinking of flying to California and visiting Johnson’s factory in Santa Clarita to find out what was going on. That’s how important these pumps were to his high horsepower projects.
As luck would have it, I live in Santa Clarita just down the street about 10 minutes away. So for the next 3 weeks, I drove past (sometimes twice a day) until one day the man was in! I suggested he call John (they are longtime good friends) and the hookup was made to send some pumps. Johnson is the nicest guy and real smart (a lubrication genius). Unfortunately personal issues beyond his control forced him to close his factory but not before we were able to finagle some pumps (one of which was to be mine).
After long conversations with John, I could not believe how much importance he placed on oil lubrication for this particular engine. Trying to run 190+ horsepower under racing conditions with a Twincam at the upper limits of feasible displacement requires a pimp with exact tolerances of impeller, gear, and housing bore. Thus the Johnson pump with precise tolerances and heat sinking comes into play. It reduces cavitation and therefore aeration of oil to run at a cooler especially with the newer thinner synthetic oils to actually increase horsepower. He had blown a few engines while racing his Escort and Lotus Cortina using other pumps until he discovered Johnson’s pump. None since then.
The bottom line is….if you have one, hold onto it….. there will be no more. Actually John may have two more left from that last batch. He has not yet come up with a Plan B to find a similar pump. Trying to contract a machine shop for even a minimal production run would be expensive.
Buying a Johnson pump from OmniTech required a lip-seal oil sump modification and discouraged a lot of people who call because of the high cost. John believes this is the only wet sump system that can rival a dry sump. I think with stock engines and maybe up to a Stage 3, a good standard (not high pressure) oil pump and modified gated oil sump would be fine. Just that extra HP of more built engines will create wear and tear that a Johnson pump nicely addresses. The name of the game then becomes lubrication!
Let me get back to you Frank, Stu, and Tim in a little bit.

Thanks,

Roy

[45DCOE]

Ha,ha….. Typo Pimp should be pump. But then again if a pimp knows oil pumps, I just might hire him.

Roy

[elansprint71]

H Frank,
If you have a genuine 26/R in a million pieces why would you want to make it into something which will end up as just another hot-rod, rather than a 26/R? Can you tell us what the identification of this car is, please?

[TWebb]

Famous Frank,

I sent you a message as to the gearbox parts. You can reach me at:

coopers66 at aol dot com

Tim

[45DCOE]

Here is a link to the definitive article on the JohnsonOil Pump as written up in Lotus ReMarque from 2010.


https://omnitech-engineering.com/images ... p10-11.pdf


Roy

[45DCOE]

Hello Rohan…..
In response to what kind of cams John McCoy uses for his 1950 builds, I have not spoken to him yet but on his billing invoice gives a description :

Cam Blanks/Grind OM 490 Intake 267 Duration

OM. 460 Exhaust. 262 Duration

See if this makes sense to you.

Thanks,
Roy

[rgh0]

John normally quotes his cams at 50 thou lift duration so inlet is a 0.490 inch max lift with 267 duration at 50 thou lift and exhaust 0.460 max lift and 262 duration at 50 thou lift.

I am surprised he is using the 490 lift cam on the inlet I have always believed it has to long a duration for anything except a 8000 rpm race engine in a light open wheeler based on my experience with Johns modified heads and 1600 cc engines . Maybe it works in a heavier car with 1950 cc but I would expect you to be loosing a lot of mid range torque for top end power.

John would know better than me and i am sure he has done the research and dyno work but I would ask why such a long duration inlet cam in a road car even if its 1950cc.

Spring, cam and follower life with 490 lift cams is also limited as you are pushing the springs and cam / follower interface loads to their maximum stress limits. OK for a race engine but a risk with a road engine and their longer operating hours even if its at lower revs. John quoted to me at one time a 16 hours spring life with the 490 cam ! maybe he has found a better spring since then ?

cheers
Rohan

cheers
Rohan

[45DCOE]

Hello Rohan,
I have enclosed the dyno curves done on Portland, Oregon Twincam engine builder Arnie Loyning’s Superflow WinDyn:

Horsepower and torque curves

Horsepower and torque curves

Looking at the torque curve, it seems to peak at 5700RPM but stays pretty flat till around 6900RPM. It starts decreasing but at the peak horsepower of 208.9 at 7300RPM, torque is still a respectable 150.3 cranklbs- ft.
Would you interpret this curve as a significant loss of mid-range torque in keeping with what you expected from the 490 lift cam?

Thanks,

Roy

[stugilmour]

Thanks for posting the curves. Excellent question on the torque curve.

I must say that I find the engine torque to be great in the Plus 2.

Another question. What would you folks expect for fuel economy at cruise? My car cruises at 80 mph at 3,500 RPM.

I got a reasonable tune on the Webers prior to onset of winter. Don’t really have definitive mileage figures yet, but during tuning runs I was apparently rarely achieving more than 20 mpg. I asked Keith and he said to expect lower mileage, which makes sense. What range would be as expected?

[45DCOE]

Hello Stu……
Yes you and Tim would be the ones to ask about how this translates into real time torque as your engines are installed and working…. I am sure we have the same cam profiles. The dyno curves are a good predictor but what is delivered at the wheels and the driver’s subjective analysis must also be considered very important.
Also Stu, will be posting on John’s improvement on the MSD ignition systems….very significant but frustrating at the same time.

Thanks,

Roy

[rgh0]

Yes the dyno curves shows it does not really develop good torque until around 5500 rpm which is what I would expect. The engine would be terrific from 6000 to 8000 rpm but you are not really getting the benefit of the potential torque in the 2000 to 5000 rpm range which is where you spend most of the time in a road car.

The Des Hamill book "How to Choose Camshafts" is a good reference

i.e.

for two valve twin overhead camshaft engines
the durations below are seat to seat durations effective power bands
270 degree 1000 - 6500 rpm
280 duration 2000 - 7500 rpm
290 duration 3000 - 7500 rpm
300 duration 4000 - 8000 rpm
310 duration 5000 - 8500 rpm

Now the Lotus twin cam head especially a well ported one like Johns conversions loves high lift to get the flow for maximum power but the trade off is high lift requires a longer duration to keep the valve acceleration within acceptable ranges. The longer duration required for a high lift cam lifts and narrows the power band.

Across the board Johns cams get the highest lift possible in the selected duration but even with his cams if you go to 0.490 lift you get into durations around 310 degrees seat to seat. Using a shorter duration lower lift exhaust cam helps a bit with mid range torque ( I do that in my 1600 cc race engines) but the loss of torque in the 2000 to 5000 rpm range cannot be totally avoided which you see in the posted torque curves.

For a road engine I would use Johns 0.440 inch lift 285 degree seat to seat duration cams in both inlet and exhaust. For a race engine you can go to higher lift and longer duration cams depending on the car and tracks you race on. For my Elan I use Johns 0.460 lift 300 degree seat to seat duration cam on the inlet and the 0.440" lift cam on the exhaust . With the right carb settings and a 1950 cc engine you could potentially use the 0.460 and 0.440 combination in a road car if your preference is top end power. The 0.490 / 0.460 combination looks a step to far for a road car in my opinion and the torque curves seem to back that up.

cheers
Rohan

[45DCOE]

Hello Rohan,
John admits he has always been a bit of a maverick when trying to conform to tried and tested parameters of engine building. He says that through trial and error there have been successes but probably more failures. His “thinking outside the box” has culminated in engines unlike any other Twincam builder. Thus the 1950 engine has the components of an outlier in that it can be driven on the street and function great on the track. I don’t know if anyone has raced one yet. Let’s break this down.
He uses the 490 lift and 267 degree duration inlet cam calibrated at .050” (50 Thou). Rohan, you figured with 490 lift you get into durations around 310 degrees sea to seat, definitely race car territory. I don’t know if there is a formula to convert measurements from .050” (50Thou) to seat to seat, but I think his cam has a shorter duration, about 296 degrees converted to seat to seat. Regardless, from previous conversations the heart of the engine build is a bespoke 86 mm stroked 8 weight steel crankshaft (cost about $3,000USD). He has these specially made by Marine Crankshaft in Santa Ana, CA. With CP forged pistons, special rings (turbo,low tension gas nitrated), Carillo
Rods, 711 M 6015 BA Tallblock ( essential) bored to 85mm, 10.5 compression ratio, and lots of overlap all combine to increase piston speed to new levels. More stroke…more horsepower. Speaking to John previously, he does not consider these cams to be detrimental to torque in the normal street range revs from idle to 5500RPM.
Rohan wrote…..”The 0.490/ 0.460 combination looks a step too far for a road car in my opinion and the torque curves seem to back that up”. If we look once again at the previously posted (scroll upward) Corrected Torque and Power Curve and Data Sheet, we see the dyno calibration start at 4600 RPM due to dynomometer limitations. Even at 4600 RPM the torque is 137.3 club-ft (pretty high) so extrapolating downward to 3000- 3500 RPM would still give a way above average torque reading. As we increase revs to 4700 RPM (132.6 clb-ft), 4800 RPM (131,5 clb-ft), and 4900 RPM (132.6 clb-ft) we see a dip in torque but only about 5.8 clb-ft at the lowest but that still is a lot of torque. When you start to accelerate to 5000 RPM the torque and HP really comes on with max torque of 164.9 clb-ft at 5700 RPM and the HP peaking at 208.9 CHP at 7300 RPM.
The engine is not mounted yet in the car (far from it) but if all we have are the Torque and Power Curve and the Data Sheet, overall this thing can pull fairly smoothly over a very broad band. This is not to say Rohan is incorrect because all the previous data and charts point to this being more of a race engine that needs high revs and would have tractable problems on the street. I plan to run a 4.12 CWP (Burton Power) differential with Quaife ATB LSD so that will increase the revs also.
Looks like John McCoy has confounded us all and created something from “Planet Claire”! We need Stu Gilmour, Tim (My72Sprint), and an unknown engine customer from Wisconsin to chime in with their input on low end torque as they have similar 1950 builds.
Also, Rohan, John does use special valve springs. He derives state of the art springs from Indy Racing League Spring Wire! I hate to think where he gets his valves from.
Thanks,

Roy

[rgh0]

Hi Roy

Yes I have a set of his indy racing springs and he told me to expected life with a 490 lift cam in racing was around 16 hours. The springs are also very stiff and when I measured them up in detail it is hard to set them up to accommodate 490 lift without excessive loads in a normal head. The excessive load they produce (over 200 to 220 lbs) at full lift can be managed especially in a race engine with a 16 hour life between rebuilds but more of a challenge in a road engine.

The torque curve down to 4500 rpm follows what I would expect with a 1950cc engine and the 490 / 460 lift cam combination. It will drop a little further down to around 3000 to 3500 rpm and may pick up a little again below that. With a shorter duration cam 440 lift the sort of torque seen on the dyno at 6000 rpm you would see all the way down to 2500 rpm I believe. The trade off would be a loss in power above 7000 to 7500 rpm as the torque wold be dropping quicker at that point

The torque curve can be affected by the carb chokes used. Smaller chokes help move the torque curve lower at the loss of some top end power. Not as great an influence as cam timing but a similar impact. I have 2 carb set ups for my competition elan engine one with 36 mm chokes for max torque circuits and one with 38 mm chokes for max power circuits. you can also play with cam timing for torque versus power also but i pick a mid range timing as its to much of a pain to change for individual tracks.

Their is no simple formula to convert 50 thou lift timing to seat to seat timing as the cam acceleration curve in the first 50 thou of lift can vary and cam acceleration above 50 thou can also vary but getting to 490 lift takes longer than getting to 460 lift and Johns 460 lift cam is 300 degrees seat to seat and the 490 will be at least 310. Most 490 lift cams from other well respected cam developers are even longer around 320 degrees. I have never got one of Johns 490 cams to measure up so I cannot be definitive.

edit - I did actually try a McCoy 490 cam a number of years ago and had forgotten about it - to many engines hahaha. See my post below about it

cheers
Rohan

[rgh0]

Hi Roy
I dug out the McCoy 490 lift cam I tried a number of years ago in 2009. it had the similar dyno result curve in my 1600 cc engine as in your engine with great power above 6000 rpm but not much below. its was a too narrow a power band for my racing so I took a step back in lifts and durations and have ended up with the McCoy 460 inlet 440 exhaust combination after many trials

I had the 490 cam measured at my local cam grinder with following summary data and it was a fairly conventional full race cam similar to what's available from others. Great in a 1600 cc Hart engine formula B open wheeler and a Hewland box where you can swap ratios to suit the track however the narrow power band not so good in my Elan for the tracks i race on even with its close ratio box .

334 degrees above 10 thou ( this is nominal seat to seat timing)
285 degrees 50 thou lift above above base circle

This cam may work better in a larger capacity long stroke block but it still drops its torque from 160 ft-lbs at 5500 rpm to 130 ftl-bs at 5000 rpm. a shorter duration cam will stop the drop and give the full mid range punch you expect out of a 1950 engine. 130 to 140 ft-bs is doable in a 1600cc let alone a 1950 cc engine

Maybe he has gone to high cam accelerations now to get shorter durations in 490 lift but I don't think he will get below 310 in a twink that has any life even with the lightest possible valve train?

I am sure this cam would work better on a 1950 long stroke engine but your own dyno curve says its loosing a huge amount of mid range torque with the large drop below 5500 rpm

While I have bought sets of valve springs form everyone to measure and assess I unfortunately cant afford to do that with all the cams out there

cheers
Rohan