348 or 355 ignition timing curve info needed

Does anyone know what this is? I'm to the point where I need to pre-program a timing curve to my ignition software and believe a 348 or 355 guideline would help. Obviously the 2v 308 combustion chamber is not as efficient as the 348 or 355 but the cams I am using will cause similar peak pressures at high rpm.

For those who don't know, I have installed a 360 crank to a 308 block bored to 83mm for a total displacement of 3413cc. I'm using 10.5:1 compression pistons and brank new cams with 248 duration @ .050 and .425 lift. I've also ported and flowed the intakes with a 2mm larger intake valve. Ignition is via a 36-1 crank trigger wheel I custom made and installed to a 308 damper which I cut down a bit and of course a ECU. The project is nearing completion so I need to start thinking a bit further about the above timing curve so I can at least get it to the dyno to really smooth things out.

 

I know these cars having timing/fuel all lumped into the motronic brain but someone must know the figures

 

Factory 360 crank. Compared to the 308 crank, the bore spacing is the same but the flywheel end is .049 shorter and the opposite end where the timing gear mounts is .110 too shallow thus a spacer with a keyway has been fabricated to make up the difference. Spins by hand. Very nice.

Computer program modelling is telling me 332bhp with 268lbs tq and that only 32 degrees total timing is needed under full load. That figure is based on stock head flow as I have yet to change the figures to what the heads flow now, which is about 9% above stock. So I'm thinking I might just touch 350bhp. That total timing figure sounds awfully low though which is why I am wondering what total figure the 348 and 355 run. I have the quench and piston design about as good as they can be for this terrible spherical combustion chamber (pistons are almost completely flat except for the valve pockets). T

 

I would also really like to know how much the 348 or 355 motors can pushed 'pushed' with timing and still make power. I know there are 'chip' kits for 348s but I wonder how much more timing and fuel the chip is actually pushing in

 

And it weighs 2800lbs! She will move well.

 

You can use a 355 crank I believe. Just 1mm stroke difference to a 360 crank. I will actually have one shortly. With Ti rods.

 

The difference between that 1 extra MM is probably no more than 10-12bhp, so in other words it would be difficult to 'feel' any difference. The piston mean speed would be about identical which is where the torque comes from anyway. The 355 crank comes from a 355 fire motor but the crank and rods are of course a-ok. The 360 crank I am currently using came from a similar fire motor and was of course perfect.

The 348 engine with a 355 crank would see a very decent boost in Bhp. Those 348 heads already flow very well as-is. A 308QV engine with heads flowed to stock 348 head flow made 347bhp at the flywheel with 267 torque. It was also using electronic electromotive injection but with the stock plenum. I'm sure with a better intake it would have made 25-30bhp on top of that.

 

The 348 inherently flows just incredibly well right out of the box essentially punching above its weight class. I'm surprised no one has thrown a 355 crank in one before I guess. Well, it is a big job.......

 

There is a 3mm stroke difference between the 348 and 355 crank. It's 75mm stroke vs 78mm stroke. The 360 crank stroke is 79mm which is where the 1mm we were discussing before came from. Regarding 348 skirt clearance I cannot be sure. 3mm difference from the 348 to 355 is not a whole lot and I cannot imagine there would be that little room to begin with in a stock configuration. I have plenty of additional room even with the 308 block.

 

Still waiting to hear from No Doubt. If you're reading this, I sent you a PM! thanks all