3.5 Liters upgrade for 308/328 (303 HP)

Poking around Carobu’s website last evening, I found this price list:

http://www.carobu.com/catalog/assets/applets/308_RR_engine-exhaust_pricing_2009-1-2.pdf

Note that a set of 85 mm pistons plus a set of eight (8) matching liners carries a price of $6,280.00, which personally strikes me as a bit overpriced.

The “3.5 liter” comments are slightly misleading, as the use of these custom 85 mm pistons with a stock 71 mm stroke 308 crank yields 3.2 liters. With a stock 73 mm stroke 328 crank, you end up with 3.3 liters. In order to end up with 3.5 liters, you would also need to fit a 77 mm stroke crank, sourced from another engine.

Also, here’s an interesting video: http://www.carobu.com/html/308_qv_3_5l.html

Enjoy - DM

 

Why not just put a 355 motor?
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Possibly that crank is from a 360( not sure what a 360 stroke is) . If I have a chance tomorrow I'll try and drop a 360 crank into a 308 block .
I like what rifledriver is saying , just a torque boost and not trying to turn the car into something it isn't .
The 360 liner is shorter to the oring land than the 308 , so to use a 360 liner you would need some sort of spacer on the OD ?
Ok , read the Carobu website and it says it a 355 crank modified ??

 

That is cool.

Doesn't look like a bolt in swap, though. How much work was it?

355 motors probably aren't found in every wrecking yard, either, though I am sure they are available.

Doug

 

Questions for you:

It looks like you use a 89 MM bore and the stock 71 MM stroke, and Carobu uses an 85MM bore and longer 77 MM stroke.

Now, generally, longer stroke=more torque (or at least Tq peaks at a lower RPM), and Short stroke motors get peak Tq at higher RPM.

Are you claiming a higher Tq attained, or higher Tq at lower RPM, or larger ave Tq across an RPM band of say 2500-7500 RPM, or any other RPM range?

Street use, in my mind, equates to your Tq being maximized at a lower RPM,and higher ave Tq across the typical usage band of say 2500-5500 RPM, or 3000-6000 RPM. Though my definition of street use may be different from others.

Thanks,
Doug

 

Hi Doug, a longer stroke will make more torque at lower RPM, that is a given. I wanted to develop the 3.5 liter with Steve Demirjian with 2 VALVE heads FIRST as we knew when we were to use a longer rod & a set of 4 VALVE HEADS along with a 360 crank that it would make some serious torque & HP.

I do not know about you but when I drive my Ferrari's I am usually in the 4500 RPM - 6500 PRM range when shifting, so to have a good amount of torque in that area makes that car fun to drive for me. My peak torque on the dyno was 269.7 at 5500 RPM as you can see by the sheet in the link below the curve is pretty flat with the bore & stroke that we are using, I am happy with the results. To re cap, Nicks Forza Ferrari 3.5 liter is a 89 mm bore x 71 mm stroke which makes 3.53 liters & when we go to 89 x 79 it will make 3.93 liters.


Here is a link to my peliminary dyno sheet that was done at Tate's, those results were a basic baseline for this 3.5 liter 2 VALVE street engine.

http://www.nicksforzaferrari.com/forzaferrariwebsite1_085.htm


http://www.youtube.com/watch?v=8GbeoqQreTI&feature=channel_page


http://www.youtube.com/watch?v=fqWjwMC2de4&feature=channel

 

I don't see where you would get the wrist pin into the oil ring groove with a stroked 308 unless you used a much longer than stock con rod.

The 4 liter uses an 82 mm crank, 138 mm rods and I still have enough compression height with larger than stock diameter wrist pins to keep the pin out of the oil ring groove. The L/S ratio is 1.68 with this stroke, rod length which is quite good.

My custom liners are longer than stock to better support the piston at BDC. I left enough clearance for enough over stroke for honing. The liners are honed in the block with deck plates to ensure they will be as round as possible in service.



Steve