incarnus

I'm planning on running an entirely new rotating assembly and using 6.00" rods either way (unless you guys can think of any major reasons not to). The car will function as a daily driver and get about 100-150 miles a week. I'm planning on about 10 pounds of boost, but my goal is 700 to 750 rwhp and I'll do what it takes to get this. The car doesn't have to pass emissions, but I don't want it to wake the neighbors either. I'd have no problems with 383, but from what I've been told I don't really need the extra cubes with the turbos, and I'm concerned about longevity. I'd like the car to have good street manners. Cost is not a huge concern, speed costs money and I'm not trying to be a cheapskate.

Also, I'm not building the car specifically for drag (although it will definately see some time at the strip), but for road racing. The project should begin in May. Any input you guys can give me would be great.

BTW the car is a bone stock 94 Forumla hardtop with an A4 that I'll be changing to a T56 at the same time as the engine work. Planning on the Star stage III clutch.

Thanks!

94z'sson

well i would go with a 355 because it can rev higher and turbo has everything to do with exhaust moving out to turn the compressor so you would need rpms

Monty

For a street car, I'd go with the extra ci's, it'llbe more powerful when not under boost and will help spool mthe turbos up quicker. In street applications, even with forced induction there's still no substitute for ci's. With a turbo engine, you don't need to spin it very high to make huge power, you do not need a high rpm screamer to make chassis twisting power.

For road racing and street use, you want the broadest power curve possible, the most area under the torque/power curve, and the extgra displacement will help provide that.

incarnus

Cool, thanks guys.

89ProchargedROC

i would also suggest a 5.7" rod too on either motor....

with the power you are wanting to attain the longer rod is going to push the pin in the piston up higher which i personally dont like with boost motors

just something that doesn't sit right with me

94SLUG

Depending on turbo size i would go with a 355 for the rev factor. If you use a 6 rod i think you save weight from pistons ? I like smaller stronger moving parts i vote fully forged 355.

stewmeistr

I've had a turbo on both a 383 and a 355 in my car and I can tell you that the 383 did have a little more off idle but overall with the 355 I was happy and really couldn't tell the difference between the two otherwise. I believe the 355 is a little more stable in its S/R ratios with th 5.7 rods and the 383 with 5.85 rods. I wouldn't go with 6.0 rods for the afforementioned reasons.

My combo was/is:
GM forged steal crank
5.70 CAT H beam Rods
and TRW -21 cc dish pistons
64cc chambers
8.3:1= good boost motor for 15#'s on pump gas.
My .02
Rob

incarnus

Wow, more input! Thanks a bunch! I really don't understand the issues with the rods other than cylinder wall stress. Although I was told that with a shorter rod the piston spends more time closer to TDC? Is this true, and does it mean anything?

Also, if you're dead set against really long rods, how about a 5.85 in a 355?

Thanks again!

sleepybu

if you go with a 355 use 6" rods...the pin won't be in the ring pack like on a 383 and you'll have a better r/s ratio

joefreeland

I would go with the 355. Turbos will give you plenty of torque that traction off the line will be an issue. The extra torque from the 383 off idle will not be benifitial. Also all things being equal the 355 should be stronger. The 6"rods will put the wrist pin closer to the top of the piston but i dont think it will be an issue with that stroke.

Brad