How easy it is to cause confusion with cam numbers?

[Stan Weiss]

Pumaracing said:

Do you mean specifically from an A series engine?

Dave,
Yes, since you talked about duration changes at the valve at different lifter raises because of changes in rocker arm ratio. I would like to get a better idea of the profile on which you are basing these statements.

Stan

[Pumaracing]

Stan, I've tried to find a way to extract text values from my old DOS program I have all this data on but failed miserably. I'm sure I used to be able to do it many years ago. Anyway, I'll just have to type it all out. I won't say whose profile this is but it's a full race cam of similar lobe lift to the MD310 mentioned above. Values are in thou every 5 cam degrees.

0
2
4
6
8
10
17
33
60
92
125
158
190
220
247
271
292
309
321
329
333
332
327
318
304
286
264
240
212
183
151
120
88
56
32
18
12
10
8
6
4
2
0

[Stan Weiss]

Dave,
Thank you very much. What would the lash be with 1.5:1 rockers. That has a nice long constant velocity lash ramp. So getting the lash to tight would add a good number of seat-to-seat degrees of duration.

Stan

[Pumaracing]

The lash on that particular profile with 1.5 rockers would be 15 thou. Not quite as much as the MD310.

[PeterBurgess]

Hi Dave

I cannot help but feel you are getting more and more distant from engine building and head modding and resort to trying to put down others efforts but heyho if you get a buzz from that that is your prerogative. You carry on and enjoy rejoicing in your typing trying to put folk down and belittle them and we'll get on with our race stuff and carry on sharing power curves etc with those on ph.
I put the video link up so folk could see that, yes, the power was very good from the 1380 engine with the correct rocker/cam arrangement as it took the rest of the cars in its class and went on to nip at the heels of the mG Z wotsit class which I guess is a bonus when you've already taken the gunfighters in 'your' class, the driver got a good buzz from it anyway

Peter

[Stan Weiss]

Pumaracing said:

The lash on that particular profile with 1.5 rockers would be 15 thou. Not quite as much as the MD310.

Dave,
Thanks. That is what I had guessed. The seat-to-seat duration of 320 degrees is what had me questioning myself.

Stan

[Pumaracing]

Pete, by all means just keep on posting your impossible torque per litre claims and I'll keep knocking them out of the park. I thought maybe you'd have learned something from the 96 ft lb per litre Ford Crossflow fiasco we had from you last year but nope. Now you double down with a 93 ft lb per litre Mini engine of all things FFS. At least the Crossflow has one port per valve but you now seriously think you get more torque from a siamese port small bore long stroke 2v boat anchor than most people can manage from a modern 4v engine?

It seems that the filter most people have inside their head that makes them at least think "Hmmmm, that looks a bit unlikely" when impossible power figures appear on the printout simply doesn't exist in your brain. Apparently the data bypasses this area and goes straight to the "Yeahhhhh, yippee, I'm a tuning god" button inside your head, releases a big dose of endorphins and you're as happy as a little clam for the rest of the day.

Then when someone calls you on it all your inbuilt defensive mechanisms kick into action rather than any shred of real scientific enquiry. Posting videos to show "oh boo hoo, look it's really quick so my dyno must be accurate", trawling the internet for any other power figures from even wildly different engine types, playing the "so when was the last time you built a race engine Dave?" card because of course that's really relevant to the laws of physics and finally the "you're such a hater" ploy.

Yes Pete, I'm just so bitter and twisted that you can get 20% more torque per litre out of a 2v engine than I ever did. You must read Dave Vizard's books on the Mini engine and think "pah! what a loser" at his puny torque results. If only either of us could finally learn the secrets that would let us climb that last step up onto the "tuning god" perch from where you loftily survey the poor mortals who trail in your wake.

[Stan Weiss]

Since I do not know what the ICL is I may have it off a little.

Rocker Arm Ratio = 1.500 - Valve Lash = 0.0150

VALVE___Lift______Opens___ClosesDuration
_______________Deg_BTDC__Deg_ABDC___________Area
_______0.00000__40.00_|_100.00_|_320.00_|__44.64
_______0.00600__34.29_|__86.67_|_300.95_|__44.54
_______0.01000__30.48_|__82.22_|_292.70_|__44.54
_______0.02000__26.04_|__76.19_|_282.23_|__44.30
_______0.04000__18.64_|__68.06_|_266.70_|__43.75
_______0.05000__16.17_|__65.28_|_261.45_|__43.75


Rocker Arm Ratio = 1.300 - Valve Lash = 0.0130

VALVE___Lift______Opens___ClosesDuration
_______________Deg_BTDC__Deg_ABDC___________Area
_______0.00000__40.00_|_100.00_|_320.00_|__38.69
_______0.00600__33.41_|__85.64_|_299.05_|__38.60
_______0.01000__29.57_|__80.51_|_290.08_|__38.58
_______0.02000__24.76_|__74.73_|_279.48_|__38.39
_______0.04000__17.12_|__66.35_|_263.47_|__37.92
_______0.05000__14.27_|__63.14_|_257.41_|__37.92

Stan

[Pumaracing]

Wotcha wanting Stan? Marks out of 10?

[Stan Weiss]

Pumaracing said:

Wotcha wanting Stan? Marks out of 10?

Dave,
Are you feeling OK? Your posted seem to be more barbed than normal.

Stan

[stevieturbo]

Stan Weiss said:

Dave,
Are you feeling OK? Your posted seem to be more barbed than normal.

Stan

Must be his time of month

[Pumaracing]

Stan Weiss said:

Dave,
Are you feeling OK? Your posted seem to be more barbed than normal.

Stan

No barb intended Stan. Just wondering what exactly you were trying to demonstrate with the numbers you posted as you didn't explain any further. I thought perhaps it was homework you wanted me to check.

[Stan Weiss]

Pumaracing said:

No barb intended Stan. Just wondering what exactly you were trying to demonstrate with the numbers you posted as you didn't explain any further. I thought perhaps it was homework you wanted me to check.

Dave,
Unlike this and some of my other posts that one was not addressed to you. I was showing everyone what I got, which also included what the areas were for the cam with and without the higher ratio rockers.

If you want to act like a teacher and grade me that is up to you.

Stan

[PeterBurgess]

Thanks for the figures Stan, quite a percentage difference.

No one has asked why the power curves are so different when we have dynoed cars with cams which are not happy with high lift rockers. The graphs are all results of hours of testing not just run what you brung sessions. The massive torque dips are caused by overfuelling, however, if we reduce the fuel input to regain some of the 'dip' we run far too weak at higher rpms and lose power hand over fist. Once the cam/rocker ratio is 'happy' we get flatter fuel lines and can run better mixtures at all rpms. The dips do not respond to ignition timing only fuel. I suppose one could get the setup better with fuel injection but the area under the curve is way off the mark with wrong rocker/cam geometry. In 1987 and 1988 we won a good championship with a TR4 on sus and intermediates, it beat most of the full race cars on webers and slicks. For the 1989 season the owner fitted roller rockers that were high lift. Power was some 25 bhp down at the wheels. The driver blamed our tuning and we told him he had done something wrong with the build as we all thought (dumbly!) that high lift rockers had to be better. The rockers were swapped for the standard ratio ones and we won the championship again! Nothing like hard earned experience!

Peter

[spyder dryver]

PeterBurgess said:

... In 1987 and 1988 we won a good championship with a TR4 on sus and intermediates, it beat most of the full race cars on webers and slicks...

Peter

Hi Peter!
I remember it well.

Geoff

[Pumaracing]

Stan Weiss said:

Dave,
Unlike this and some of my other posts that one was not addressed to you.
Stan

I'm sorry Stan, we're clearly at complete cross purposes here. I thought as it was my cam data and you asked if you could check my statement that the high lift rockers only made a very small number of degrees change to the effective duration that you "were" addressing it to me and that the "I may have it off a little" part was asking me to check something. I also didn't know what you meant by ICL.

But you used a different std rocker ratio than I did so I couldn't really tell if you were agreeing with me, disagreeing, asking me to check something or what.

Looking at it all again and allowing for me using 1.24 ratio and you using 1.3 we seem to agree that the effective duration change is small. Perhaps less than one might assume without doing all the maths I have to say.

Edited by Pumaracing on Friday 14th August 23:29

[Stan Weiss]

Pumaracing said:

I'm sorry Stan, we're clearly at complete cross purposes here. I thought as it was my cam data and you asked if you could check my statement that the high lift rockers only made a very small number of degrees change to the effective duration that you "were" addressing it to me and that the "I may have it off a little" part was asking me to check something. I also didn't know what you meant by ICL.

But you used a different std rocker ratio than I did so I couldn't really tell if you were agreeing with me, disagreeing, asking me to check something or what.

Looking at it all again and allowing for me using 1.24 ratio and you using 1.3 we seem to agree that the effective duration change is small. Perhaps less than one might assume without doing all the maths I have to say.

Edited by Pumaracing on Friday 14th August 23:29

Dave,
You are correct, I did ask for the data to be posted based on what you posted. I also have a short term memory problem as I use Peter's Rocker arm ratio and not your.

Rocker Arm Ratio = 1.240 - Valve Lash = 0.0124

VALVE___Lift______Opens___ClosesDuration
_______________Deg_BTDC__Deg_ABDC___________Area
_______0.00000__40.00_|_100.00_|_320.00_|__36.90
_______0.00600__33.09_|__85.27_|_298.36_|__36.82
_______0.01000__29.33_|__79.95_|_289.29_|__36.62
_______0.02000__24.29_|__74.19_|_278.49_|__36.62
_______0.04000__16.57_|__65.73_|_262.30_|__36.17
_______0.05000__13.58_|__62.37_|_255.95_|__36.17

Here is your 1.24:1 and now there is third set of durations and areas to compare.

Stan

[Pumaracing]

Stan, the nominal factory quoted ratio of stock Mini rockers was 1.245 as per both Vizard's books and also here (quoted rounded to 1.25) in Hamill's book.

https://books.google.co.uk/books?id=oqqhmgbXZkoC&a...

It usually didn't even measure up that high unless you picked the best possible rockers out of a bucketful or used offset bushes. Some could be as low as 1.21 or 1.22. I'm not sure where Peter's 1.3 comes from unless modifications were involved.

Anyway, we apparently agree 4 degrees duration change at 1mm net lift.

[PeterBurgess]

For playing 'what if' scenario number crunching games the numbers can be used from books, dangerous game extrapolating those figures as 'gospel' for the real world hands on tuning. Physical measurements and factory drawings are more important as mistakes can and do creep into workshop manuals and heresay writing, having said that, not always do the factory drawings exactly coincide with what was produced or even used during assembly/manufacture. I think the theoretical at 1.25:1 is just that, 'theoretical'.

Hi Geoff, saw Mick Richards recently and we had a good chinwag about old times! Tidying up my spare unit to install the SF901 engine dyno I found the prototype/flow bench head we used to develop the heads for Micks TR8 he dominated the race scene with after giving up on 'Kermit'. Things seem to go full circle as once again we are developing and improving our race SD1 V8 heads to work on three full race flat plane crank Rover V8 engines. We have also made friends with Ken Clarke who keeps us spellbound with stories of his hands on work on the TRW Race V8 SD1s! It is good to learn so much as all the knowledge disappears if it isn't passed on down the generations.

Peter

[PeterBurgess]

I have been looking at my records and I have mislead you Stan. We have had two sets of forged 'std' rockers measuring 1.3, these may have been cheated with offset rocker bushes for racing purpose. The forged rockers and pressed ones from early Minis are 1.28:1 as stated by both Piper and Kent in their cam catalogues. The sintered later Metro style are 1.25:1.
Sorry to have mislead you with the cheated 1.3:1s

Peter