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1969 T Racing pistons and cams

Sirs,


We are planning to build 1969 T according to European FIA rally rules. We are going to use Weber Carburators, sport exhaust and original T heads with original valves and port size.

I was planning something like 906 was. 10,3:1 compression and 281/251 camshaft.

In my understanding 1969 T cylinders are iron ? Is there oversize high compression pistons available if we overbore it. Also interested to here comments if someone have used more "modern" camshafts than 906 with this kind of compression. We are planning to rev this engine up to 7000 rpm but shift it about 5000rpm. Gearbox will be very short.

You may also send me an email or reply here in this topic or PM.

vm.lankolainen@gmail.com
Old 12-20-2009, 02:50 AM
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My suggestions;

J.E. or any other piston manufacturer can supply you with a piston of your needs. I believe 81mm is about all you can get without modifying your heads. Check the FIA rules as to how much overbore you can go.

I would look into a twin plug distributor and go for more compression as well unless rules limit this

Your valve/port size is too small to run anything with a 906 cam. Stick with a lower lift and duration cam to balance your package.

I would look at either E, Mod solex, or Mod S as my cam selections based on your rev limit.

Look to improve torque as a 2 liter needs all the help it can get.


Here is a 2.0 liter build I did for a client recently.
It is very close to the 901/26 engine, which was the 914/6 rally engine with 40 IDA carburetors.

a number of teams went to 901/26 engine at the end of the season and improved their lap times over the 906 webber engine(901/20)


1965 heads port matched to S manifolds
1965 aluminum case
66mm counterweighted crank
stock 2 liter rods with ARP rod bolts
1967 911S Piston/cylinders (customer was determined to use these)
twin plug distributor
Mod solex cams
Webber 40 IDA carburetors.


This engine pulls very well and runs up to a 7500 rpm limit. The only change I would have done is more compression to take full advantage on the twin plugs.
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Last edited by BURN-BROS; 12-20-2009 at 08:04 AM..
Old 12-20-2009, 08:01 AM
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Thank you Burn Bros for your comments. I just found this old story from here and it really helps me more.

What is difference between S and ModS cams ?

2.0 port size
Old 12-20-2009, 12:07 PM
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The Mod S has a wider lobe center, giving more dynamic compression and giving a bit more top end as well. It has a bit more lift.
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Old 12-20-2009, 12:52 PM
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Thank you again, One question more. Is there any reason why should use counterweight crankshaft in this kind of engine. I mean will non counterweight have possible balancing problems if rev up to 7000 rpm ? Non counterweight seems to be much more light and that's why it is interested.
Old 12-21-2009, 12:49 AM
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Quote:
Originally Posted by velimake View Post
Is there any reason why should use counterweight crankshaft in this kind of engine. I mean will non counterweight have possible balancing problems if rev up to 7000 rpm ? Non counterweight seems to be much more light and that's why it is interested.
I perfer to use the non counterweighted cranks for street duty. If you really want to run it, I can't see that it would be a problem for the rpm range. It will only help in acceleration, not in creating additional power.
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Old 12-21-2009, 08:01 AM
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Who is selling or manufacturing these Mod S cams ?
Old 12-21-2009, 11:32 AM
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Dougherty Racing Cams

John does a good job, and as a result I send my cam work to him.
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Old 12-21-2009, 11:35 AM
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I think building a car to compete in the European Historic Rally Chapionship is quite complex.

There are two different types of event that need to be considered.

The FIA European Sporting Rally Championship allows cars to enter in three seperate Categories.

Category 1 allows road legal cars that were homologated between 01/01/1958 and 31/12/1969 BUT it limits the eligible cars to either Touring or Grand Touring types.

This means that in the case of a Porsche 911 the car would need to comply with the Group 3 Homologation Form No. 607 which covers the 911T.


Unfortunately Appendix K does not permit any modification to compression ratios, pistons, camshafts etc and Appendix Vlll is very clear in this respect. Rebores are also limited to 0.6mm.

It is possible, of course to use a 911T in Category 2 which covers 01/01/1970 up to 31/12/1975 as this category permits cars which can run as a GTS and hence use any Group 4 Modifications permitted in the homologation papers and Appendix J of the relevant period.

It does mean, however, that you will have to compete with 911STs of either 2.3 or 2.5 litre capacity.

If you do run the car as a GTS Appendix lX does allow all of the changes to pistons, cam profiles etc, you have listed and allows a maximum re-bore of 1.2mm. Appendix J would also allow Twin Plugging hence the 911ST.

Category 3 is for cars dated from 1975 to 1981 and is not appropriate.

The other concern is that the 911S was also homologated into Group 3 in 1969 and is eligible to be used in Category 1 in this form and will, I am sure out perform a 911T in a Group 3 specification. The relevant Homologation Form is No. 608.

I am sure you could obtain an HTP for a car that has the engine mods you have outlined but if you run this car in Category 1 and the car is successful then Post Event Scrutineering is sufficently rigorous to find these modifications and you are likely to be taken through the 'Black Dot' procedure.

In general terms FIA Historic Sporting Events outright wins in Category 1 are usually taken by a Porsche 911S and Category 2 outright wins are commonly won by a 3.0 RSR.

If you are considering FIA European Historic Regularity Rallies then cars from either GT and GTS categories are both allowed and the class of the car is not taken into account in the overall results as they are not considered to have any influence.

Cars must however comply with their HTP and you would need to produce this document so the car is a GTS and it is probably best to specifiy it a G2 Historic Category Vehicle as this would give most scope for the mods you are looking to carry out.

If you are going to compete in the Sporting Championship I would run it as a 911S as the individual registration doesn't matter for Appendix K, it is only the specification of the car that is of concern.

Last edited by ix0ifan; 12-22-2009 at 09:59 AM..
Old 12-22-2009, 09:48 AM
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Yes it know it is complex.

I already have full FIA paper Group 3 GT26 1970 S (original factory S) and now wish to have another car for 60's. I like to have LWB car if I going to update this new car for 70's group 4 some day. That's why only forms 607,608,609 are possible to use. (1969 T,E,S). Now if you want use caburators only 607 is acceptable. Here in Finland maximun overbore for these 60's group 3 GTS cars is 1,2 mm and pistons and camshafts are free just like there were 60's .

Last edited by velimake; 12-22-2009 at 12:00 PM..
Old 12-22-2009, 10:38 AM
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I assume that you've got a copy of the factory booklet on preparation of the 911 for competition use. Is this correct?
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Old 12-23-2009, 01:39 PM
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Hello John,


I have early 70's booklet but if there is also late 60's available interested to see it .
Old 12-24-2009, 01:28 AM
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Old 12-24-2009, 01:28 AM
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