SPA 6hours

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Migge
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SPA 6hours

Post by Migge »

Saw the yellow MGB GT V8 at Spa again. A very fast car and a very good driver. 3.9 with 4 Dellortos DRLA 48.

The winner of the SPA 6h was a GT40 with Wright/Gans/Wolfe best lap time 2:47

The winner of the British Sports and Saloon car comp. was Russel McCarthy with his MGB GT best lap tim 2:47!!!!

BTW he has a special crank/cam combination and has a firing order 14527638. Normaly it is for Buick/Rover 184356572. He says less vibrations and better gas flow.
On the dyno 390 BHP!!

Never heart about that. Just know that you can choose 2 different firing orders on Ford depending on the cam but with the same crank.

Okay so now the experts.
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catsx11
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Post by catsx11 »

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Last edited by catsx11 on Wed Aug 23, 2017 4:20 pm, edited 1 time in total.
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Migge
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Re: SPA 6hours

Post by Migge »

The crank and the cam gives you the firing order. You can easily test that if you just change the leads on your sparks and recognize that "something is wrong". Just change 2 of them and you will "hear" the misfiring.
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Paul Blore
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Re: SPA 6hours

Post by Paul Blore »

Alan,

Most, but not all, Ford, Chevy and Rover/Buick V8's have the same firing order, but they number their cylinders differently, so the firing order also looks different. Ford number the cylinders 1-4 down the right side, front to back and 5-6 down the left side, front to back. Chevys and RV8s are numbered on alternate sides starting a #1 on the front left, #2 front right, #3 second left and so on to #8 right rear.
If you renumber the Ford cylinders to match the RV8 and Chevy, or vice versa, you will find that the firing order is the same.
Chevy & RV8 - 1-8-4-3-6-5-7-2
Ford - 1-5-4-2-6-3-7-8
These all use 2-plane or cross-plane cranks with the big-ends mounted in pairs at 90 degrees to each other. Therefore each cylinder can be in one of two places within its 4-stroke cycle and that is dictated by the camshaft. Cross-plane cranks tend to be smoother, but require heavy counterweights to offset the primary imbalance.
A Ferrari V8 uses a flat-plane crank, with the big-end journals at 180 degrees to each other. Flat plane cranks tend to be lighter because they don't need counterweights to offset the primary imbalance and are generally used in racing and "high performance" engines.
Here's a link to a nice YouTube video that explains the differences in more detail:

https://youtu.be/_TssXF8yQek

Paul
catsx11
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Post by catsx11 »

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Last edited by catsx11 on Wed Aug 23, 2017 4:21 pm, edited 1 time in total.
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peterc
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Re: SPA 6hours

Post by peterc »

Alan,
You also need to take into account the differences in stroke of the crank and cylinder bore to achieve the same capacity. Then throw in the many differing cam designs and how the opening/ closing of valves overlap.
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Re: SPA 6hours

Post by Paul Blore »

catsx11 wrote:Thanks Paul
That has helped a lot
I have seen a lot of tutorials from that u-tube poster, very informative!
I also found this interesting…
https://www.youtube.com/watch?v=-Pz4dYuQK_c

so, why does the rhythm of a 289/302/427 Ford V8s sound different to say a Rover or Chevy?
For the most part, the "rhythm" will be the same. The exhaust configuration will make a big difference. One of the issues with a cross-plane crank is the exhaust scavenging. Because of the firing order, the exhaust pulses don't come out at regular intervals on each side, which accounts for the typical "American" V8 burble. A flat-plane crank engine fires alternately one side to the other, which means the exhaust gases follow at regular intervals.

Paul
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agnoraan
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Re: SPA 6hours

Post by agnoraan »

Hi Alan. here's a link to a crisp sounding, though a bit raspy, Rover V8

https://www.youtube.com/watch?v=Wt2DcRW6r-M
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Post by catsx11 »

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Last edited by catsx11 on Wed Aug 23, 2017 4:21 pm, edited 1 time in total.
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Re: SPA 6hours

Post by nikbj68 »

My Rover engine sounds quite authentically lumpy, although quite muted with the '98db' silencers! That'll be the 285 cam. :)
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