Modifying a 3.0 turbo to 350 h.p.

[gumba]

Still researching a 3.0 turbo motor. A stock or aftermarket i/c is not going to work in the stock location, but a i/c will be used. The goal is 350-400 chp. I know the basic mods, bigger turbo, i/c, better exhaust, sc cams, better w/g, but would like some more specific information. Starting with a stock 3.0 motor with 6.5 c/r. A few questions:
Can the stock intake/fuel head be modified to handle the power, or move up to a 3.3 intake, or something else.
Can the heads be flycut to bump the compression up to 7.1
Are the aftermarket parts interchangeable between a 3.0 and 3.3, such as the turbo, and heated headers like the 930 SSI's. If not, which system fits.
Will the K27 bolt up and work.
The goal is a nice street motor. For now, it will be bolted up to a '84 915 trans w/7:31 r&p and early 5th gear, Sachs sport clutch.

Also feel free to list your mods and h.p.

[RarlyL8]

Mods do 3.0L are similar to 3.3L as stated. There are a few differences.
The fuel head is fine as-is but the WUR may not be able to keep up. Verify if you have the -022 early WUR.
K27 bolts up with only a bracket mod. Up pipe is fine if stock.
The 7:31 915 will drive you nuts with 350hp. 8:31 is even a bit short.
Headers will bolt up direct no issue as well as muffler.
These engines really respond to mods, you're going to love it!

[quattrorunner]

Everything sounds great till you get to the 915 w/7:31. Not only is it too short but too week as well. From what I understand, you would want a turbo and system that would hold off power/torque till the higher rpms to help with the weekness of the 915 with those power levels.
It's best to plan on using a stronger gearbox before wishing you had. I've gone through one and feel I'll use up this one as well.
BTW, my 3.0 is stock with the 6.5/1 pistons but I have an inter cooler and this engine is great. Such fun.

[pkabush]

I would stick with your stock w/g unless it needs replacing. My understanding is that they perform at least as well as a Tial. IIRC that info came from Chris at Turbo Craft.

[quattrorunner]

Run 964 cams for more power up top.

[gumba]

How much h.p. will the 915 tolerate? I'll be starting with the stock to sub 300 h.p. at first. I may need to live with this trans until I can up grade. The 350 h.p. would be my goal. How long it takes to get there is based on the condition of the motor.

[sjf911]

Originally Posted by gumba

How much h.p. will the 915 tolerate? I'll be starting with the stock to sub 300 h.p. at first. I may need to live with this trans until I can up grade. The 350 h.p. would be my goal. How long it takes to get there is based on the condition of the motor.

I suspect that the age and associated wear plays a role as much as the relative weakness of the tranny. I'm doing fine with mine so far (over 400hp) but would not be surprised to see it fail suddenly which is why I have a short bell 930 waiting in the wings. I did reinforce mine with a billet side cover, one piece bearing retainer, LSD, and WEVO main case modification after fixing the loose pinion race. IIRC, your '84 should not be as prone to pinion race issues.

[quattrorunner]

Steve had all the little bits that really help from my reading. And they're not cheep so my idea is to just go through 915 gearboxes till I can get a g50. Those parts add up quickly and combined with installation it makes no sense to me for me. My 915 broke the second gear into three complete parts. It didn't look warped which suppressed me. Looked pretty great other than the second gear(I dis assembled it and sold it to some guy in Puerto Rico that way).
But it was a mag box. The aluminum have the ovaling/warpage if I'm not mistaken. It is possible I'm mistaken.

[jess p]

I would stick with the 8:31 ratio. Many people put down the 915 for strength. I
have a late aluminum 915 with 8:31 behind a SBC putting out 400 hp and
350 Torque. I can't use 1st gear but let me tell you I have out paced a
super bike on one occasion. I ran a centerforce dual clutch from Patrick
motorsport and after a year that thing started slipping and it's Kevlar on
one side. Yet the 915 held up.

[gumba]

Doesn't the G50 use a hydraulic clutch? Are you converting to a hydraulic clutch or is there some way to retain the stock cable?
Is the trans the same length at a 915?
I'm leaning towards selling me 915 w/7:31 and getting a 915 w8:31. Also checking to see if the 915 needs the Wevo mods mentioned above.
The motor & trans will live an easy life, no tracking, banging gears, etc.

[RarlyL8]

My signature line seems to be missing. If it were there you would see I ran a 350whp 930 engine in my widebody SC for about 15 years. Went through 2 trannies, the first broke with 300whp at the drag strip. Don't do that. Rebuilt that one with WEVO retainer and found an '86 with factory oil cooler and built that one strong with custom gears. It went with the car when I sold it. The 915 will not hold up to abuse even with the WEVO and side plate. Use the turbo not the clutch and all is well. No speed shifting or you will shuck 2nd gear (Quattro?)

I think it is a good idea to sell the 7:31 to an early 911 guy and get an 8:31 later model 915. I still have that repaired 915 under my bench if you decide to do that and need one.

[quattrorunner]

Originally Posted by RarlyL8

Use the turbo not the clutch and all is well. No speed shifting or you will shuck 2nd gear (Quattro?)

.

Sorry this is old news. Just found this older thread looking for something else and felt compelled to answer.
No I wasn't shifting. I was under boost at just over 3krpm just after straightening out a bend. Full power .8bar boost. Kaboom.
My turbo really pours power on at 3krpm. That trans just didn't take it.

[Robbbyg]

Which Engine type do you have also counts in equation on how much hp to get to 350.

Theres 930/53 with 245hp
And 930/52 with 260hp
both with same compression of 6:5-1


Im running around 350 on my 3.0 930 which was unintentional as the upgrades I did were done only with longetivety and reliability of engine in mind and the extra HP was a By-product so to speak as its a daily driver and I didn't like the engine running over 90 degrees in peakhour

I put on a 3.3 IC on top of a uppipe I made with silicone (20hp)
added 3.3 Inlet Manifold and diverter Valve housing (?hp)
Rotated my 3.0 Throttle Body but wasn't happy with gummied up linkages I had to make so am running a Throttle Body from a 3.3 also and fabbed a double spring inside the linkage for a smoother more direct feel and faster release when foot lifted off
Swapped out Muffler with a Monty one (20hp)
swapped out 8 pin Cdi with a MSD (?hp)
deleted the Decel
Also running a Porsche 5 speed with higher ratios so theres 50hp extra right there at the wheels over the 4 speed.
My engine doesnt have any running or starvation issues, and she seems to love the extra legs,
shes done 250000 so im aware and take note of all nuances.
She always starts on half a crank hot or cold, im happy with it.

[gumba]

A few things changed since my original post. The 3.0 long block was unusable and was replaced with a '79 3.3 long block. The 3.0 heads & cam towers are at Turbokraft for a valve job, porting, and match porting the aluminum blocks and 3.0 manifold. Will also be opened up for the 3.3 p&c's.
The cams were reground to SC specs by Elgin. RarlyL8 rebuild the euro fuel head & wur. I also picked up a used set of BB headers w/heat. Will probably stay with the stock turbo until I can up grade to a Garrett 35R.
I received the p&c's back and at least 2 of the pistons look dubious. I posted a description & photos on the engine rebuilding board and am waiting for some feed back. I will pack them up tomorrow and send them off to Ollies for further inspection.
After the engine assembly starts I'll send the trans out to get the 7:31 replaced with a 8:31 and add the Wevo bearing retainer & side plate.

[getz]

I make 345 hp at the crank and use a 915 (custom gears 2,3,4 and reinforced side plate) without difficulty. Agreed with all that 1st gear is worthless and have never launched the car aggressively. Have ridden second gear hard routinely into 3rd without a hitch.

[gumba]

So even with custom gearing there is no way to utilize 1st gear?

[onboost]

Originally Posted by gumba

So even with custom gearing there is no way to utilize 1st gear?

Yes, if someone is truly building a custom trans then that can be addressed too.. it just depends on what you want or what you're trying to get out of the trans.

A lot of people don't bother with a first gear change as they just view it simply for the purpose of getting the car moving.

Maybe Matt M. will chime in.. he's well versed in trans details.

[gumba]

I exchanged emails with Wevo about 1st gear options, his response:

There is only really one first gear for the 915, the AZ ratio, which I think
is 11:35.

Only alternative to that is the aftermarket shaft with a slide on first
gear, that gives some other taller options. Those are available form GT and
maybe from CMS.

[Das Schnell Ei]

Originally Posted by Robbbyg

Also running a Porsche 5 speed with higher ratios so theres 50hp extra right there at the wheels over the 4 speed.

[quattrorunner]

Also running a Porsche 5 speed with higher ratios so theres 50hp extra right there at the wheels over the 4 speed

Originally Posted by Das Schnell Ei