R8 1100 Extractors and Inlet Manofold WTB

A 40 with 34mm chokes should work OK. I have vague memories of setting a 40 up on both of your manifolds on a motorkhana special over 20 years ago. I remember staying with the two pulse manifold as the owner liked it better. I do think twin 40s with 30mm chokes would be the best solution, and may clean up the idle and low down somewhat as well.

The A6 Cosworth is a very large duration camshaft that is just not going to make a lot of torque down low. In a hot street type engine I would be looking at less duration so the engine is nicer for the 90% of the time you are under 4500 rpm. An A3 Cosworth would drop 30 degrees out of the duration at 50 thou and wouldn't be throwing so much fuelled up air out the exhaust at low revs. I used an A3 Cosworth in a 16TS engine many years ago with twin Webers, and was very happy with the idle at 1100 rpm and the power delivery. It came in quite hard at 3500, but was nice enough below this.

Road cars are always a compromise.
 
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Manifolds !!!

KB, the biggest problem with your test is the exhaust manifold. Running a A6 cam with ability to bring in lots of air (carb and inlet) and then trying to force it out a cast iron manifold, will never give any kind of true result, The cam requires extraction to fill the chambers properly, and if you have no exhaust pulse it will not work much more than a 32 twin choke carb. And will require a lot more tuning, choke tubes, emulsions, and jets.

Sorry, bad test !!!!
 
geckoeng said:
KB, the biggest problem with your test is the exhaust manifold. Running a A6 cam with ability to bring in lots of air (carb and inlet) and then trying to force it out a cast iron manifold, will never give any kind of true result, The cam requires extraction to fill the chambers properly, and if you have no exhaust pulse it will not work much more than a 32 twin choke carb. And will require a lot more tuning, choke tubes, emulsions, and jets.

Sorry, bad test !!!!
Click to expand...

Agree! This may not be the ideal thread to post in but the importance of a decent extractor should be priority no 1. KB, you said that the cam started working well from 4500rpm and up, that figure could drop as low as 3000rpm with a good extractor.

Some facts. HarryA can support this. I did a calc for him and he had the extractor made accordingly. When he collected his car and tried it on the way home he experienced instant fuel starvation from 1st gear and up. Ie, not fuel pump, but real under fuelling that had to be corrected by bigger main jets. That is on a G motor that had a 4 into 2 into 1 as original extractor.

On the 1800 TS motor for the A110 Targa car I got 175 hp at the FW. I did a calc for him too and the extractor was made accordingly. A test on the same dyno with a detuned motor 1) 98 pump fuel instead of AVGAS. 2) Less advance to prevent knocking. 3) Rev limiter lower to 7200 instead of 7500.
The Dyno test turned out 185 hp.

My race car in ZA with 1480 G motor made 155hp at 7800rpm with 45 Weber SD's. I doubt if it would be that much without a decent extractor or be able to handle 45s.

Ross might have something to say about his old Dauphine and its abilities.

The formula I use is that from Alexander Bell in one of his books and if anybody wants it I will pass it on. I have made it into an EXCEL spreadsheet so it isn't 2 pages of calcs anymore but just a few blocks to enter your figures in and it will pop the dimensions out.

The above might be completely off the topic but keep it in mind for future mods.

Regards
Frans.
 
The key word here I guess is "Decent extractors" where you do the calculations and custom build a set. I have an old set of Lynx or Lynx copies tucked away in the shed (sorry to the original poster but these are not for sale), but Colliers maintain the R12 exhaust manifold are just as good if not better than that particular Extractor set - "all it adds is more noise" I think was the comment.
KB
 
If you can post the camshaft specs of this A6 cam (or I can get it form the web) and tell me where would you like the optimum revs to be (suggest 4500 -5000) I will do the calc and attach it. I think it is very easy to buy a few mandrel bends and tack something together and have it welded if you can't do it yourself. It is just a matter of jigsaw puzzle the pieces together. If an extractor is going to cost you in the region of 400-500 dollars then an ideal one will cost you less.

Regards
Frans
 
Difficult to find specs, but I found these off a UK website. Hopefully Alan can comment on the validity - I won't pretend I understand them all. It is referred to as a Cosworth A6 grind. Your Rev recommendations seem sensible.

Inlet Valve Timing - Opens 62 BTDC; Closes 94 ABDC
Exhaust Valve Timing - Opens 94 BBDC; Closes 62 ATDC
Inlet Valve Lift - 0.400 inch
Exhaust Valve lift - 0.400 inch
Inlet Valve Clearance - 0.014 thou
Exhaust Valve Clearance - 0.019 thou

Notes - full race cam for pre-crossflow 997 - 1500. Not for Road Use.

The A3 is listed as the hottest cam recommended for street use as per Alan's comments.

I'll the invoice from the Engine builder but I don't recall cam specs on there.

KB
 
My info on the A6 Cosworth is Advertised timing Ex 86-54 In 54-86. 270 degrees duration@50thou and with 1.5 ratio rockers gives 435 thou lift at the valve. Clearance is 14 thou In and Ex.

A3 Cosworth is Ex 75-41 In 40-77. 240 degrees @50thou. Ex 90 thou lift @TDC and In 113 thou @TDC on overlap. 414 thou lift at valve with 1.5 rocker. 12 thou clearance In and Ex.

A8 is closer to what you have. Ex 96-76 In 76-96. 260 degrees at 50 thou. 414 thou lift at valve 15 thou clearance.
 
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That clearly is a fullrace cam! Looks like you mean bussiness. :headbang: I have attached a short analysis as well. To give you an idea, Your cam has an advertised duration of 336 deg. That means the crank rotation is 336 deg from when the valve opens at the suggested valve clearance, to when it closes. My race car has an advertised duration of 302 deg.

But that aside because now you have it so lets make it work. The exhaust calcs attached gives you 3 options of rev ranges 5k, 5,5k, 6k. You will see that because of this cam the lengths is very long and dia is small to get a higher velocity of exh gases and that in turn will allow good scavenging during the overlap period.

The 5000rpm one needs a primary of 29.2mm ID. Available pipe sizes in that range is 31.8mm OD or 1 1/4" pipe. the secondary will be 1 5/8"
The 5500rpm one needs a primary of 30.6mm ID. Available pipe sizes in that range is 35.0mm OD or 1 3/8" pipe. The secondary will be 1 3/4"
The 6000rpm one needs a primary of 31.9mm ID. Available pipe sizes in that range is 35.0mm OD or 1 3/8" pipe. The secondary will be 1 7/8"

The last 2 will use the same OD as can be seen. The pipe wall thickness has already been included. You might have a small problem to stick to the required length but seeing you have a R10 with a little longer backside, it should be possible.

The collector length is important as well. Because it is a "restriction" the ideal inverted ventury should be 7-10 degrees. that will allow max flow with least restriction. You can make a template on paper of the cone that is opened? (I don't know what it is called in English, maybe protraction?) Sheet metal workers use it a lot to bend something from a flat sheetmetal. There are good examples on Google to get this method. I have not included a 4500 rpm calc because it becomes too long. The secondary length is X or multiples of X. In our case it is short and doesn't need to run to the back so we will always use X.

I hope it makes sense.
Regards
Frans
 

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KB Cancel all the above. I see Alan has replied with totally different specs while I was writing this thread. Alan, can I use your specs?
 
Go for it. I got the specs from the TigheCams site, who have ground 90% of my cams in the past. Look at Ford 1600 pushrod cams.

I would make the primary 1.375" ID and go 4-2-1 as Frans is indicating. Most guys that make extractors make them too short, meaning that the resonant frequency when it all comes together, the rpm would be too high.

Actually looking a Frans drawings, he is showing a 4-1 system, which in general works better in the top end rpm, but can certainly be good in the rest of the range as well.

A friend has been experimenting with a N/A Nissan KA24 2.4L 16 valve engine in his Datsun 1600, finding that small changes in the exhaust are giving large changes in performance. Started with 250 Hp at 8500 at the wheels initially, but had lousy midrange. Now has gained 50Hp at 4800 and is still making 238 Hp at the wheels now at a reasonable 7600, by changing lengths, pipe diameter and collector venturi sizes about 5 times, and moving the cams around a bit.
 
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Thanks, I'll do it tomorrow. 23.30 here by us already.
Frans.
 
Cheers guys.

The engine builder has suggested a redline of 6 - 6500, so either a 5000 or 5500 may be the optimum to go for. I'm thinking 5500 has a nice ring to it!

I'll have another look for the correct specs in the meantime too.

KB
 
Expect to wind up your redline a bit. 8000 is closer to where your cam needs to be redlined. If it is all balanced and new, 7000 is not unreasonable for short periods. Your engine probably won't make peak power till 7500 with a cam of your duration.

I remember an R10 owner in Brisbane that played with his engines quite a bit, cutting a hole underneath his number plate to allow cam changes without pulling the engine out. The hole was covered by the number plate, so all looked as standard.

It isn't too late to change back to an A3, before a lot of effort is put into tuning and pipes.
 
Frans said:
Thanks, I'll do it tomorrow. 23.30 here by us already.
Frans.
Click to expand...

Frans - Hold off and I'll see if I can get the exact specs for this cam. Waggott don't seem to have a website and there are slightly different specs on the Wade Website for their version of this cam (although they are relatively similar to Alan's Tighe Cam info). I know the cam grinder started with a W, but not sure if it was Wade or Waggott. I do know that the engine builder has specified different valve clearances on Inlet and Exhaust whereas these are both the same for inlet/exhaust on the two websites (although the actual clearances are slightly different 14 versus 16) .

Let me see if I can get the true facts first, before you expend too much effort on my behalf. I'll go see them Friday Afternoon.
 
Waggots are in the Northern Rivers area of NSW. I always thought Waggotts did all of Colliers cams even way back in the Renault rally era of the 70's. I believe they were, and possibly still are the only certified company to regrind aircraft camshafts.

Wade are in Oakleigh, Victoria.
 
Could still be Waggotts as it was couriered off and back for grinding, but I'll find out for sure.
I couldn't find any website for them with specs, but I do seem to recall Dave mentioning Wade.
 
Waggott Cams

Back in the 70's there were 2 different waggotts grindig cams both brothers Ken & merv (father of peter at alstonville) ken died at toronto at a boat race meeting in the early 70's and graham the third brother continued his work , Merv did more in the bike and aircraft side and ken racemotors allthoe merv did the crossflow and twin cam heads for the holden grey motors all great minds and nice blokes to go with it.
Cheers Peter.
 
I confirmed today that it was indeed Waggotts in the Northern Rivers area, but they don't have a website I can find and Dave didn't have the specs easily to hand so I'm still waiting on getting the specs for you.

Frans - out of interest, does your calculation sheet enable design of 4:2:1 or only 4:1 designs?

What are the relative advantages/disadvantages of either?
KB
 
The 4:2:1 is supposed to give more torque low down but I think it is only noticeable in "laboratory" conditions. I don't think it will be a seat of the pants "feel the difference"!

But I do think that this will be a similar subject as women in a men's only meeting. 20 men and 20 opinions.

My calc sheet is only for 4:1.

Regards
Frans.
 
Frans - here are the official specs for my cam:

Advertised timings:
InOp BTDC 59 Deg
InCl ABDC 69 Deg
ExOp BBDC 94 Deg
ExCl ATDC 57 Deg

Timings @ .050
InOp BTDC 20 Deg
InCl ABDC 50 Deg
ExOp BBDC 53 Deg
ExCl ADTC 18 Deg

Duration:
Advertised In 308 Deg
Advertised Ex 330 Deg
@ .050 In 249 Deg
@ .050 Ex 251 Deg

Cam Lift:
Cam In 275.000 Thou
Cam Ex 275.000 Thou
@ TDC In 95.000 Thou
@ TDC Ex 88.000 Thou

Tappet Clearance:
In 20 Thou
Ex 22 Thou

Lobe centres:
In 105 Deg
Ex 107 Deg

Group A

Ps - here are the Extractors I have in the shed if people want to comment on those.
They are Sonic brand, but I'm happy to see if I can get a set of tuned ones made up to Frans' specs if possible:
 

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