Short or Long stroke

[edmayo]

You're correct Raj, engine didn't move, just the wheels moving further back in the chassis, trans didn't move either, CV's just ran at a greater angle. They proved the CV angle would work when they did the Sportomatics.

[Bert]

Andrea, The shop that is building my car has 901 and 911 transmissions in use with 2,8 engines with close to 300hp. You must use an aftermarket sideplate for strength and avoid hard launches in first gear. For the transmission, they say that an external pump and cooler are unnecessary for sprint races and only become required for endurance events of 4 hrs or longer. For the crank, I think you might like a long stroke configuration for some added torque exiting slow corners at the Targa and limit port sizes to no more than 38mm to keep port velocities at low revs adequate for sharp throttle response.

Great info here.

But who makes the best reinforced sideplate?

Thanks,

[Flieger]

From what I hear, Wevo is good. I have no experience with this, however.

[andrea70]

Interesting comments...

About Varunan's questions:

remeber that my 3d is about Targa Florio and SWB chassis...

1) Why Alu Case? Simple. In 1970-1971 the alu case was stronger than all the mags cases (we have to wait the 7R to see something really strong)

2) Why twin spark? because all the racing engine had it in those days.

Now i understand that some of you say that the 2,5 LS is better than 2,5 (or 2,3) SS even if the LS have some problems with flywheel vibrations.

Why?

Thanks
Andrea

[andrea70]

Raj, i always known that alu case is far stronger than all mag case but 7R.

It's uncorrect?

[a911s]

The early aluminum case is stronger than any of the mag cases including the 7R. It's what I would use to build any race motor under 3L.

[Mr9146]

The early aluminum case is stronger than any of the mag cases including the 7R. It's what I would use to build any race motor under 3L.

Strong but significantly heavier. Plus, the added machine work needed to "make it work" gets pretty pricey.

You can pin a mag case and do the rest of the machine work and be perfectly fine at reduced cost.

Andrea, do a search on the forum for "twin plug" and you'll find a lot of helpful information from guys like Steve Weiner at Rennsport Systems. This topic has been covered in extreme depth numerous times here on the site. I think there's even a reprint of Steve's very good article on twin-plugging that was in Esses about a year or so ago.

[Bert]

From what I hear, Wevo is good. I have no experience with this, however.

I checked with WEVO and they only make a stronger sideplate for the 915 transmission.

[Flunder]

Andrea:

If I was going to build a good strong 2,5L engine for the Targa for your 68S I would use an aluminum case for the sake of correctness and do the following:

1. machine the spigots for the 2,5 barrels; do the oil bypass conversion and and install piston squirters
2. use 66mm short stroke crank that you already have in the engine
3. buy a set of 70T heads to benefit from the better combustion chamber shape and the larger valves. Machine the heads for twin plugs and open up the ports for 36mm intake and exhaust ports. The heads will need to be chamfered for the bigger bore. The T heads have no injector holes and will look like the 68S heads. When machined to the 36mm intake port size, they will match the port size of your S intake manifolds and mate up nicely.
4. 10.3 Mahle Sport 89mm pistons and cylinders
5. Marelli 12 spark distributor with Pertonix conversions for upper and lower circuits to avoid problems with the points (I think you already have one; if not an aftermarket equivalent distributor)
6. Use an SC four line dry sump pump
7. Weber 40 IDS carbs if you already have them and block off the high speed enrichment and re-jet; or 40 IDA and jet to suit (46s only if you go for 906 cams and tall 906 manifolds - which I would not go for personally - maybe for Nurburgrring, but not the Targa where there are many slow corners
8. S cams will be torquey for this combination and provide surprisingly good mid range - will still come on the cam at 5,000 but will provide better flexibility than the same S cam in a 2,0L.
9. Heat exhangers are fine - but use a twin outlet sport muffler for 10-15 more horsepower
10. This would provide 210 plus DIN and plenty of torque too for good acceleration out of slow corners.
11. Fit late Turbo chain tensioners and after market guards so you can use your 1968 cam towers, chain boxes and rocker covers for the correct appearance of the engine.
12. You will need an external oil cooler with this much compression and horse power, so to control all that heat, fit a '73 thermostat and external lines to a good radiator type fender mount cooler
13. Check the rules to make certain this engine would be "Targa legal" in your model year car for the historic class in which you plan to compete.

Finish it off with a 901 transmission with a forged side plate cover and load it with airport gears and a limited slip.

Carefully rebuild you brake system and install hard brake pads.

Fit a roll bar.

Do not use Nadella axles.

[a911s]

Again, great advice from Flunder!