Why 180's?

[Kirby Schrader]

I was asked a question today that I couldn't answer...

Lola's and McClaren's did not have 180's.

Why did the GT40 have 180's?
Who decided it should have 180's?

Wondering in Texas,
Kirby

 

[Velez]

Efficiency and better sound.

 

[Randy V]

Like you, Kirby, I've often wondered why it was done on GT40 and many Indy / F1 cars and not the Lolas and McClarens. I am, however, glad that they did put them on the GT40 as it is one of the key things I've always loved about them.

Some people I know don't like the sound and say that it makes the V8 sound like a 6 cylinder.. I don't hear it that way - instead it is a sound at RPM that is intoxicating...

 

[Jac Mac]

A couple of things that might have influenced the choice...
Cam Timing Duration[ seat to seat] on the Race GT40's was ~ around 330°, when you factor in the max RPM of around 7000 on the SB & ~6500 on the FE the primary length ends up around 38/40 inches depending on where you want max torque etc so the ability of the crossover 180° design to 'soak' up a couple of inches would have been a +, ( nowdays with most people opting for shorter duration cams in the `~270/290° duration range along with higher RPM that means that most 180° setups are longer than ideal, but in header design longer is the safer option.)

The design of the rear of the tub & horseshoe also favours the up & over the transaxle setup, as getting the headers threaded thru the rear suspension links after exiting the engine recess would be an issue, also the height of the rear window plus need to get carb air from each side would prevent an 'up & back side for side' deal.
Interesting point, it appears the J-car that Ken Miles fatal accident occured in was tested with either eight seperate exh stacks or a short side for side system at one time, there is a photo of the rear body clip with cutouts that suggest such a system in the freidman shelby GT40 book.

 

[Jac Mac]

I should have added that the first engine choice for the GT40 was the pushrod 256cu in INDY Ford motor which already came with the 180° headers.

 

[Jim Craik]

Thanks Jac, thats the best explanation I have heard. Plus it looks cool and sounds cool!

 

[Randy V]

Good enough for me as well.

Thanks Jac.

 

[Jack Houpe]

A couple of things that might have influenced the choice...
Cam Timing Duration[ seat to seat] on the Race GT40's was ~ around 330°, when you factor in the max RPM of around 7000 on the SB & ~6500 on the FE the primary length ends up around 38/40 inches depending on where you want max torque etc so the ability of the crossover 180° design to 'soak' up a couple of inches would have been a +, ( nowdays with most people opting for shorter duration cams in the `~270/290° duration range along with higher RPM that means that most 180° setups are longer than ideal, but in header design longer is the safer option.)

The design of the rear of the tub & horseshoe also favours the up & over the transaxle setup, as getting the headers threaded thru the rear suspension links after exiting the engine recess would be an issue, also the height of the rear window plus need to get carb air from each side would prevent an 'up & back side for side' deal.
Interesting point, it appears the J-car that Ken Miles fatal accident occured in was tested with either eight seperate exh stacks or a short side for side system at one time, there is a photo of the rear body clip with cutouts that suggest such a system in the freidman shelby GT40 book.

I wish I knew as much as you have forgotten.

 

[EGLITOM]

Mhhmmm

Header length can be achieved with the standard setup as well ( space is there for it)
Up and over the horseshoe as well.
Think the only reason is Fords strive for the most power output they could get. The others didn´t care about this, they may have thougth that servicefriendlyness is an higher value ( you can take of one head / head/ collector/muffler without bothering with the other bank) in a long distance race than the last 2 or 3% of HP.

One thing i agree it changes the cruiser/muscle V8 sound to defenitely more exciting racer sound
None is believing you that this is an american V8 engine if they don´t see it.

TOM

 

[Scott Calabro]

I think a big part of it is that the Chevy powered cars would run into chassis/body/packaging difficulties due to the distributor being on the wrong end of the engine!

 

[Cliff Beer]

Here's my amateur/layman's explanation....

Back in the 60's, the LeMans race cars were required to run a muffler I believe (as I recall reading somewhere....) - straight pipe not allowed. And, with such compact spacing from the exhaust ports to the rear of the car, four headers going into one muffler on each side (ie. not a 180) would tend to encourage header lengths of substantially different lengths across the four. Not ideal. However, with a 180 header arrangement, it is easier to get more equal header lengths across all eight headers by virtue of being able to mix and match the configuration and arrangement of header pipes on both port and starboard. For example, on my 180 I've noticed that the header pipes associated with the rearward exhaust ports look to have roughly the same length as those associated with the forward exhaust ports, allowed primarily by virtue of being able to "cross over" in a configuration allowing it to be so.

Just my uneducated/non-expert opinion.

 

[Will Parker]

Good explanation here

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