Need info: 3.0 RSR/IROC fender and flare vents

[kenikh]

Does anyone know the details regarding 3L race cars and the inclusion of venting at:

the rear of the front fenders and
the front and back of the rear flares

I always thought this was an IROC thing, but early IROC pictures show otherwise:




These are the flares/vents in question:





Can anyone shed light on when they were introduced and the context as to the reason?

[al lkosmal]

Kenik,
I think that may have been early (74 or so) RSR (but I've not seen it on the IROC cars) bodywork and used for brake cooling.
Al

PS: others far more knowledgeable may chime in now.

[HelmetHead]

IROC cars were 9"/11" flares (close to turbo flares) The wider flares with vents are later RSR flares which I believe are 11" front and 13" rear

[wayner]

I've never seen a real iroc car with vented flares. Every one that I have seen has the same rear flare as the 73 RSR ( but with 74 bumpers),

Later RSRs had the vented rear flares.

I always thought the vents appeared later in 74 on the RSRs (after the IROCS), since the Irocs were transition cars between the 73RSR and the bigger engined wider impact bumper era 74RSR

[jackb911]

The IROC cars were based on the RS 3.0, not the RSR which had wider flares and the vented fenders.

[wayner]

The IROC cars were based on the RS 3.0, not the RSR which had wider flares and the vented fenders.

Jack, not many people talk about the 74 RS 3.0.

Do you know if the 74 RS3.0 was the same width body as the 72RS 2.7, or did its flares also grow by1974?

I think everyone on this board seems to agree that the factory vented rear flares were wider than the factory non vented 1973 RSR flares, but I have no idea the relationship between the earlier cars and the 74 RS3.0

Thanks

[Flieger]

RS 3.0 flares are essentially the same as Turbo flares I believe. They certainly are wider than 2.7 RS flares - closer to 2.8 RSR flares but with a different profile. The front flare profile might be a bit more organic than the front Turbo flare, though.

[jackb911]

Originally Posted by wayner

Jack, not many people talk about the 74 RS 3.0.

Do you know if the 74 RS3.0 was the same width body as the 72RS 2.7, or did its flares also grow by1974?

I think everyone on this board seems to agree that the factory vented rear flares were wider than the factory non vented 1973 RSR flares, but I have no idea the relationship between the earlier cars and the 74 RS3.0

Thanks

I don't claim to be an authority on the RS 3.0, I've only seen one "real" one in person (at Rennsport reunion III) but here's my observation...

The flares appear to be the same size/shape as what was on the 1973 RSR. The side profile on these is not as symmetrical as what was used on the later 930 and M491 cars but the width appears to be about the same. Both types are referred to as "9 and 11 inch" flares.

Here's a good RS and RSR site that contains lots of photos of these cars: slidevalve911rsr's Photo Galleries at pbase.com

And a photo of a real RS 3.0:

[wayner]

So it seems that the 74 RS 3.0 is the missing link!

Regarding flares, visually the 73RSR (plus 1974 bumpers) appears to have became the 74 RS 3.0, and formed the basis for the 74 IROC?

And the wider vented rear flare, offset front vented fender RSR was a different beast that evebtually lead to the 935...

I like that explanation

[wayner]

I think what adds to the confusion is the number of project cars that have been built using aftermarket vented flares that are narrower for street use

[jackb911]

My ex-'87 that was converted to resemble a RS 3.0 / IROC. These are 930 flares, note the difference as compared to the correct original ones on the white RS pictured above.

[rsnodgrass]

Does anyone know where this photo came from? I've never been able to find it in any books, nor figure out who might have taken this photo. Thanks!

[enzoducoing]

Hello
I believe the picture above is of the cars arriving at Riverside just as they left the factory with RS ducktails. Later the ducktails were deemed without enough downforce for the 3.0 engines for the Riverside track and they were retrofitted with solid lightweight 930 turbo-size tails before the start of the '74 IROC series. The turbo tail had been already designed by Mobius in planning for the development and fitting of the '75 turbo, they were wider and made of aluminum/fiberglass.
The vented wider flares were used also on the late '74 3.0 RSR to accommodate 12in and 13in rear wheels. The vented flares were never raced on the original IROC cars.
Cheers
MD

[kenikh]

^ An epic knowledge drop!

[javadog]

Essentially, the '73 RSR, '74 RS 3.0 and '74 IROC cars all used the same flares. The flares on the '74 RSR were 2 inches wider. A lot of this had to do with homologation rules at the time. The '73 RSR was homologated as an evolution of the '73 RS and was allowed 2 inch wider fenders than that car. The '74 RS 3.0 was an evolution of the '73 car, to get it legal for FIA Group 3. The '74 RSR was based on the '74 RS. Got that?

The IROC cars were a mix of RS and RSR. Their engines were essentially similar to a late '73 RSR engine.

The ducktails were installed on the cars when they were shipped because the later style tails weren't ready yet. As it was, only 12 of the IROC cars made the boat. The last three had to be air-freighted.

All of the '74 RSR cars had the wider fenders from the beginning. They were also made of fiberglass, as opposed to the steel on the earlier cars.

JR

[JeremyD]

Have some pictures I've collected over the years -






and of course my car - an IROC wanna be

[gumba]

Our '75 Carrera based 3.0RS look. One with the ducktail, one with a modified Carrera tail.

[fryardds]

Ryan,

I seem to remember that Harvey Weidman was involved with the ducktails from the IROC cars. You might want to contact him for the entire story, but I think they came to him to be sold as he was involved with Porsche parts sales at that time. I think the photo of the cars on the carrier first appeared in a R&T article with the cars at Riverside Raceway.

[Bill Verburg]

In '73 Porsche wanted to compete in Group 5 w/ Ferrari, De Tomaso and Chevy so they took the '73 2.7RS as a basis for the '73 RSR which had a slightly larger (2806.53cc) more race oriented motor(type 911/72), trans, brakes and suspension. The rules allowed a 2" extension on the 2.7RS body w/ 9 & 11 x15 wheels, 230/600 & 260/600 tires. This size fender was later adopted to and standardized on the '74 3.0 IROC and 3.0RS and eventually the production 930s. The '73 was was the only use w/ the early bumper setup(not counting the 911S/T that used the 9" front and smaller 9" rear flare(2" extensions on the then std n/b car)

The IROC cars used the same 9 & 11" flares on the new '74 chassis w/ the bigger bumpers and new 3liter engines, these were base on the same RSR suspension used in '73 but w/ an aluminum block 3.0(911/74). The cars were delivered w/ the Burzel(ducktail) spoiler but received whale tails in time for the races. There were 2 version of the whale tail, long and short, the long was used on the race cars both IROC and RSR, the short whale was delivered on the 3.0RS which had the same fenders and bumpers and brakes as the IROC and RSR but use a detuned 3.0 liter al. block version of the motor. The long tail was delivered unmounted w/ the 3.0RS

The '74 3.0 RSR was used the even wider and vented fenders here the 2" extension was applied to wide body(9 &11) 3.0RS chassis to 11 & 13, the front fender rear facing vents were used to release air heated by the brakes, cooling ducts for the rear brakes were let into both the leading and trailing faces of the rear flares front wheels were 10.5 rear 14 x15w/ the same brakes as were used on the previous RSR, IROC and 3.0RS but w/ centerlocks instead of 5 bolts

'73 RSR


'74 IROC


'74RSR


'74 3.0RS

[javadog]

Porsche ran the RSR in Group 4. After enough of the Carrera 2.7 cars were built, that car became legal for Group 3, as well. The Carrera RS 3.0 was also homologated into Group 3, as an evolution of the previous year's car. Group 5 was left to the 935 in 1976, as it was a new category from that year forwards. The factory skipped 1975, more or less, and ran the 934 in group 4 in 1976.

JR