Rennsport Art....

[72group4]

Attached are some pictures of a 1972 FIA Group 4 twin-plug engine being built for my vintage track / tarmac rally car project based on a 1972 911. The engine is being built by Steve Weiner of Rennsport Systems in Oregon.

Its nearing the end of the build and will be on the dyno shortly....is it just me or does the 911 engine in particular look like a piece of art?

Andrew

[cameron.arnott]

Art +1 + Herr Weiner Magic

What are the specs?

[e3photo]

Originally Posted by cameron.arnott

Art +1 + Herr Weiner Magic

What are the specs?

He does great work. He has a set of pistons from my 3.6 build, as he did the heads.


Cheers,
Emerald

[tadd]

What's the spacers under the carb manifolds for... Heat insulation? Air flow (is there magic porting)?

I gots me some of that sweet, sweet Steve CNC lovin myself .

t

[0396]

Great looking metal there!

[304065]

Nice fiberglass, is that Series900?

[356RS]

Steve's perfection at work. Can't wait for the dyno results.

[72group4]

The spacers under the intakes are to reduce reversion.

[tadd]

Thanks. Steve takes a lot of meat out of the top of the port - he says it turns the air better . It makes for a struggle to match the manifold though... I thought those spacers might be the solution.

Can you share specs? I don't have a clue as to what the rules for group 4 are... .

t

[Steve@Rennsport]

This is a 1972 FIA Group 4 spec 911 ST.

That requires a 2.5 litre, twin-plug, carbureted (or MFI) engine and the internal specs are designed for Tarmac Rallye's as well as track use.

Andrew can spill the beans on the rest if he chooses,..

There are some pics of the car in progress on the Early S forum; look at the "What the heck do you look like" thread.

[MBruns]

Looks nice, need a distributor for that one ?
Mike

[Turbo_pro]

Quick question:
I know Steve is a fan (fanatical) above 993 Dilivar studs and this engine appears to be using another type of stud. What are they?

[lucittm]

tadd,
I was looking at that too. I thought there should not be a gasket on the bottom of the block spacer insulators, just sealant?

[Steve@Rennsport]

Originally Posted by MBruns

Looks nice, need a distributor for that one ?
Mike

He's got one,...

[Steve@Rennsport]

Originally Posted by Turbo_pro

Quick question:
I know Steve is a fan (fanatical) above 993 Dilivar studs and this engine appears to be using another type of stud. What are they?

Hi Jim,

Those are factory steel studs which just fine for these small-bore engines with proper case preparation and strict oil temperature control.

3.0 and larger motors get the Twin-Turbo Dilavars.

[Turbo_pro]

Originally Posted by Steve@Rennsport

Hi Jim,

Those are factory steel studs which just fine for these small-bore engines with proper case preparation and strict oil temperature control.

3.0 and larger motors get the Twin-Turbo Dilavars.

I'm confused Steve
I thought you have consistently argued the issue of thermal expansion. We all know that mag cases expands more the aluminum cases and the Nikasil cylinders as opposed to Biral barrels is where the expansion difference exist.
At this point I must assume that you don't feel thermal expansion is an issue in this case and there in lies my confusion.

[Steve@Rennsport]

Originally Posted by Turbo_pro

I'm confused Steve
I thought you have consistently argued the issue of thermal expansion. We all know that mag cases expands more the aluminum cases and the Nikasil cylinders as opposed to Biral barrels is where the expansion difference exist.
At this point I must assume that you don't feel thermal expansion is an issue in this case and there in lies my confusion.

Its all about heat load and these smaller engines (2.0-2.5) simply do not produce the kind of localized heat that the bigger engines do unless they have a ton of compression or use forced induction.

Thermal expansion is always an issue but in this situation, the steel studs will work very well, based on past experience with this particular engine build. It has modest compression (to run on 91) so the case, studs, and Nikasil cylinders will not be highly stressed.

For an all-out race engine using CR's above 11.3:1, I would machine the cylinders for the fatter Dilavars since the expansion rates are higher.

Its VERY important to understand that each and every engine build is different so specified components aren't all the same.

[72group4]

Tadd,

The motor is built to the 1971 FIA specs (Federation Internationale de l'Automobiles) for Group 4 (Special GT) cars. Many of the factory 911 "ST or S/Ts" were built to FIA specs as were many privateer entries. These are build requirements allowing you to run in specific classes and are based upon modifications to production vehicles. Depending on the Group it dictates what you may or may not do to the factory motor as well as all other aspects of the car. Higher the Group number the more modified it gets. In this case we are allowed to make some modificaions - induction systems for example are "free" (but must be period - hence the Weber 46mm), cam profiles are also "free". In other areas they are understandably more restrictive. The car is being built to a "period in time" specification as the car will be used for vintage class racing in Canada and elsewhere....the '71 internationl FIA Group 4 specs (Appendix J) for my 72 911 were perfect for what I was doing. They are available from the FIA on their website.


Andrew

[tadd]

72group4:
Thanks for the reply... I was fishing for your choice on cams, ect. I understand if there are 'then id have to kill you', so no worries.

t

The motor is built to the 1971 FIA specs (Federation Internationale de l'Automobiles) for Group 4 (Special GT) cars. Many of the factory 911 "ST or S/Ts" were built to FIA specs as were many privateer entries. These are build requirements allowing you to run in specific classes and are based upon modifications to production vehicles. Depending on the Group it dictates what you may or may not do to the factory motor as well as all other aspects of the car. Higher the Group number the more modified it gets. In this case we are allowed to make some modificaions - induction systems for example are "free" (but must be period - hence the Weber 46mm), cam profiles are also "free". In other areas they are understandably more restrictive. The car is being built to a "period in time" specification as the car will be used for vintage class racing in Canada and elsewhere....the '71 internationl FIA Group 4 specs (Appendix J) for my 72 911 were perfect for what I was doing. They are available from the FIA on their website.


Andrew[/QUOTE]

[72group4]

Tadd,

Give Steve a shout - he will help you out.

Andrew