Spurious Duplex gears.

[mk1]

As they say. . . . .

When the flag drops the Bu**sh*t stops.

I realise that outright bhp figures are very meaningless, but wondered about a comparison as it was such an interesting spec.

Thanks for your reply.

[aquamini]

Hi they were made by kent nothing missing except the chain they use same chain as motorbikes never wear out or stretch,they are not available now disscontinued because of cost i have these on a few motors never had a problem no chain stretch cam timing always spot on,it might be worth ringing kent to see if they have a chain?Minisport used to sell them aswell but think you might get a better answer ringing chester zoo.If memory serves i think they were called (silent mini adjustable vernier timing gears)if no joy i will look on my spare engine to see if their is a part number on chain hope this is of some help.

[dutchacme]

The 970 has of course a semi bullet proof bottom, however the combo of a short stroke and a five port head do hinder getting mixture into the combustion chamber. In hindsight it is better to have a longer throw crankshaft in combination with longer con rods to get mixture into the combustion chamber.

The racing 998 Seven engines, with their longer throw, higher gas speeds, would be just shy of my 970 on the dyno. However they would need a check (tear down) every race where as mine would easily do one years of racing (< 40 hours running time).

I always wondered whether Arden did realize this handicap of the 970 and went straight away for an 8 port.

All credit to my engine builder, who has a kind of the stig thing.

[Tulka]

The Morse Hy-Vo type of chain that Mini13 refer to was used in Bmc 1800 auto transmissions.

Tulka

[ivor badger]

The 970 has of course a semi bullet proof bottom, however the combo of a short stroke and a five port head do hinder getting mixture into the combustion chamber. In hindsight it is better to have a longer throw crankshaft in combination with longer con rods to get mixture into the combustion chamber.

The racing 998 Seven engines, with their longer throw, higher gas speeds, would be just shy of my 970 on the dyno. However they would need a check (tear down) every race where as mine would easily do one years of racing (< 40 hours running time).

I always wondered whether Arden did realize this handicap of the 970 and went straight away for an 8 port.

All credit to my engine builder, who has a kind of the stig thing.

Since there was quite a performance advantage in having a 999 s over a 998 in the 60s and 70s. I fail to see any advantage in going for the 998 bore/stroke. The fact that 998s have their current power outputs is probably a reflection on 40 odd years of competitive developement as there is a class for them to race.

A years racing of 40 hours from a 970 S engine without a strip? I know Sedric Bell used to throw away the valve gear on his every 3 races. What revs you actually running?

[dutchacme]

What I tried to express is that the five port head lets in relatively more mixture on top of a long throw crank than on top of a short stroke. The five port head is the limiting factor for a 970.

Although my 999 will rev safely 9000 rpm, it is interesting to see the rpm histogram from the data logger, the majority of the lap-time is spent between 5000 rpm and 7500 rpm. And this agrees, confirms with the torque curve which we engineered (ended up with).

The torque curve makes that it is not beneficial to hang on after 7500 rpm in the first, second and third.

970 racer

[Vegard]

I guess there is also a limit to the valve gear. No matter how short the stroke and big the bore, you cannot rev 14000rpm with a pushrod engine. This sort of ruins the possibility that could be had with the 970. Look at KAD's 999 engine...No pushrods. LOADS more power than any 998 could ever achieve.

[dutchacme]

What do you guess a stage 4 KAD on a 999 would make? 137 – 140 hp and 86 – 89 lbs.feet ?

[Vegard]

I seem to remember that the black KAD car had closer to 150hp. I guess your torque guesstimate is close though. There would be no low down torque.

[littler]

what about the 850 they did 73.5 mm bore, 50 mm stroke with a 16 valve head.... 150 bhp

[ivor badger]

What do you guess a stage 4 KAD on a 999 would make? 137 – 140 hp and 86 – 89 lbs.feet ?

That being about the power output of a 1lt Coswoth SCA!

[Vegard]

What do you guess a stage 4 KAD on a 999 would make? 137 – 140 hp and 86 – 89 lbs.feet ?

That being about the power output of a 1lt Coswoth SCA!

What's the valve sizes on an SCA? I guess there shouldn't be much difference between a 1 litre Cossie and KAD engine. Yes 3 vs. 5 mains, but that does only affect longevity, not outright power I'd imagine.

[ivor badger]

What do you guess a stage 4 KAD on a 999 would make? 137 – 140 hp and 86 – 89 lbs.feet ?

That being about the power output of a 1lt Coswoth SCA!

What's the valve sizes on an SCA? I guess there shouldn't be much difference between a 1 litre Cossie and KAD engine. Yes 3 vs. 5 mains, but that does only affect longevity, not outright power I'd imagine.

I would think there is more to engine power outputs than simply valve size.
An SCA, being an F2 engine and of much more advanced design was vastly superior to an MAE F3 engine. Although the F3 was limited by use of a single 1.5" carb. After 1964 and the moving on to F1 of JYS, the 999 S engine never won a top line F3 race again being completely outclassed by the MAE. The F2 developement of the 999 with a twin overhead cam head failed miserably.

[Vegard]

As long as the valve sizes are the same, port sizes are the same and everything else being equal, the engine does not care about what's under the piston crown. If KAD had made a head in 1969, then the world would have been completely different.

[sandman]

Hi they were made by kent nothing missing except the chain they use same chain as motorbikes never wear out or stretch,they are not available now disscontinued because of cost i have these on a few motors never had a problem no chain stretch cam timing always spot on,it might be worth ringing kent to see if they have a chain?Minisport used to sell them aswell but think you might get a better answer ringing chester zoo.If memory serves i think they were called (silent mini adjustable vernier timing gears)if no joy i will look on my spare engine to see if their is a part number on chain hope this is of some help.

Took me some minutes to understand this... 'punctuation would be of good help
Anyway, I too remember reading about this setup.... 'was in a catalouge or something. Considering the price of belt-setups (or even decent duplex chains), they should have upped the price and keept the production going - if the kit was as good as you say...

[Tulka]

Mark used to have a picture of some transfer gears with a chain like this
in the CLASSIC TUNING section. Also some cam gears from Mr Stewarts Cooper.
Deleted now.

Tulka

[dutchacme]

As long as the valve sizes are the same, port sizes are the same and everything else being equal, the engine does not care about what's under the piston crown. If KAD had made a head in 1969, then the world would have been completely different.

The engine does not care; the driver and or owner will care. A long stroke will generate higher gas speeds (along the opened valves) where as a short stroke will suck the mixture in with lesser gas speed. A short stroke will have benefits (better volumetric efficiency) from a multi valve head.

[Vegard]

As long as the valve sizes are the same, port sizes are the same and everything else being equal, the engine does not care about what's under the piston crown. If KAD had made a head in 1969, then the world would have been completely different.

The engine does not care; the driver and or owner will care. A long stroke will generate higher gas speeds (along the opened valves) where as a short stroke will suck the mixture in with lesser gas speed. A short stroke will have benefits (better volumetric efficiency) from a multi valve head.

Yes obviously, but I was commenting on that a 999 KAD engine would make potentially the same power as a 1000cc Cosworth.

[ivor badger]

As long as the valve sizes are the same, port sizes are the same and everything else being equal, the engine does not care about what's under the piston crown. If KAD had made a head in 1969, then the world would have been completely different.

The engine does not care; the driver and or owner will care. A long stroke will generate higher gas speeds (along the opened valves) where as a short stroke will suck the mixture in with lesser gas speed. A short stroke will have benefits (better volumetric efficiency) from a multi valve head.

Yes obviously, but I was commenting on that a 999 KAD engine would make potentially the same power as a 1000cc Cosworth.

From 1964.

[Tulka]

Lots of bar talk in here.Anyone remember the original tread?

Found Marks picture on the transfer chain.Seems simple enough.
Wonder what the drawback is? Anyone?

Tulka