build a 3.0 into ???

Jeff Alton · 02-26-2010, 03:05 PM

I have a 3.0 SC motor that I want to build into something with big HP for my race car. I already have a fairly strong (315hp) 3.4.....

What can I build using the 70.4 crank?

1) SS 3.2 using 98's
2) SS 3.3 using 100's
3) SS 3.45 using 102's

Or use the 74.4 crank and make:

1) 3.4 using 98's (already have that)
2) 3.5 using 100's
3) 3.7 using 102's

The motor would be race only. Twin Plugged. Likely using my twin plugged 3.2 heads unless can get the 3.0 heads modified for a reasonable budget.

I would like to be able to retain my 48mm Jenvey ITB's, but would consider a switch to larger ITB's or to 50PMO's if required.

Have two sets of 1 5/8 headers already, but would go to 1 3/4 if required on a bigger motor.

High CR is fine, race fuel and twin plugs....

How about a cam for the different motors.

Not looking to spin it more that 7500rpm and 7250 will likely suffice.

Cheers

DUK · 02-26-2010, 04:34 PM

No replacement for displacement. I know you've heard that, but oh so true.

Trade some of the things you have and get bigger.

Jeff Alton · 02-26-2010, 05:00 PM

No need to trade, I have it all in stock available.

But was thinking of something a little different from the norm.... Maybe a 3.7 using the 74.4 crank, should get lots of bottom end with that motor.....

Cheers

DUK · 02-26-2010, 05:13 PM

Maybe a 3.7 using the 74.4 crank, should get lots of bottom end with that motor.....

Now were talkin'. lol

Jeff Alton · 02-26-2010, 08:10 PM

That was the original plan, still use the current 3.2 heads and maybe get away with the current 48mm throttles...... Bigger cams and headers and off we go!

Cheers

pu911 · 02-26-2010, 08:26 PM

I have a 3.5, great motor!
Phil

aws · 02-28-2010, 11:14 AM

Jeff: By limiting the project to 7200-7500 RPM you are answering your own question. You are negating the benefit of the shorter stroke crank by using that RPM Redline. The 74.4x100 is a good combination with a fair rod ratio. Using the new JE SRF (X box) piston at 12/1, a 149i Webcam (modified RSR Sprint), the 3.2 twin plug heads (should flow 260-265cfm out of the box) and 1 5/8 headers I would expect 330 FWHP at that rpm number. Stock rods with ARP bolts would be adequate at that number if no mistakes are made. The reason for the JE X-box forging is there have been complaints about the old 100mm forging failing.
Other choices are stroking the 74.4 crank to 76.4 and using the 102mm cylinders, (3.8) but I don't have direct experience with that configuration. I would certainly be wary of the cylinder spigot skirt thickness at 102mm in a intermediate stud spacing case.
aws

Jeff Alton · 02-28-2010, 01:04 PM

Thanks,

I am not too worried about the cylinders, they would Nickies from Charles and I trust he did his homework.

I will check out the cam you mention, but usually deffer to John D for my cams.

Cheers

kenikh · 03-07-2010, 07:20 PM

For a race motor, I can't imagine using a lazy feeling crank like the 74.4. The 70.4mm is as long as I consider viable for a race car unless you happen to find a GT3 crank, which is a whole different story than the Carrera crank, POS 964 crank or (the admittedly much better) 993 crank. Nickies and JE FSRs all the way.

I say do the 70.4x102 and have John build you a custom DC90, maybe on 102 lobe centers, which is basically a higher lift RSR Sprint Cam.

*EDIT - saw you want to limit the motor to 7500...boring. Wanna be different? Spin it.

Packy · Packy's Garage

I say do the 3.7L. I always wanted to see more of those "experimental" motors but I heard they require a lot of work to get the large cylinders and pistons to work with that case. If I had the time and money that would definitely be on the top of the list for a cool/unique race motor.

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by kenikh

For a race motor, I can't imagine using a lazy feeling crank like the 74.4. The 70.4mm is as long as I consider viable for a race car unless you happen to find a GT3 crank, which is a whole different story than the Carrera crank, POS 964 crank or (the admittedly much better) 993 crank. Nickies and JE FSRs all the way.

I say do the 70.4x102 and have John build you a custom DC90, maybe on 102 lobe centers, which is basically a higher lift RSR Sprint Cam.

*EDIT - saw you want to limit the motor to 7500...boring. Wanna be different? Spin it.

Short stroke with the longest rods viable by design and spin the crap out of it.
If you want to use a 70.4 crank I have a 935 70.4mm crank. What's the difference you ask? the 935 70.4 crank has full counter weights. It looks much like the 74.4 crank. This 935 crank with 996 GT3 Pankl gen 2 rods (130mm) would allow you to twist the engine to close to 9000 rpm.
Now if 9000 rpm is not enough, we also have a 66mm crank.
Add 105 Nickies and either crank an wow!!!!

Jeff Alton · 03-11-2010, 06:59 PM

Quote:

Originally Posted by kenikh

For a race motor, I can't imagine using a lazy feeling crank like the 74.4. The 70.4mm is as long as I consider viable for a race car unless you happen to find a GT3 crank, which is a whole different story than the Carrera crank, POS 964 crank or (the admittedly much better) 993 crank. Nickies and JE FSRs all the way.

I say do the 70.4x102 and have John build you a custom DC90, maybe on 102 lobe centers, which is basically a higher lift RSR Sprint Cam.

*EDIT - saw you want to limit the motor to 7500...boring. Wanna be different? Spin it.

I am not married to 7500, but figured getting a cam that peaked out there would still give me some torque, which I need from 4K....

Jeff Alton · 03-11-2010, 07:04 PM

Quote:

Originally Posted by Henry Schmidt

Short stroke with the longest rods viable by design and spin the crap out of it.
If you want to use a 70.4 crank I have a 935 70.4mm crank. What's the difference you ask? the 935 70.4 crank has full counter weights. It looks much like the 74.4 crank. This 935 crank with 996 GT3 Pankl gen 2 rods (130mm) would allow you to twist the engine to close to 9000 rpm.
Now if 9000 rpm is not enough, we also have a 66mm crank.
Add 105 Nickies and either crank an wow!!!!

Ok,

What bore would you run with the 70.4 crank?

What do I get with a 66mm crank and 105's in terms of power/torque curve? 3.4L, are my current 48mm throttles enough? Exhaust? cam?

Cheers

kenikh · 03-11-2010, 07:14 PM

A 66mm stroke 3.4L...could you get the valve train light enough to make it feasible to spin it to 8K?

Jeff Alton · 03-11-2010, 09:21 PM

Well, dunno?

Have Ti retainers and race springs, depends on the cam I guess?

Cheers

efhughes3 · efhughes3's Garage

All of a sudden, the excitement I have on my bump is tempered.

Packy · Packy's Garage

I say supercharge or turbo. you can never have too much horse power, just too little traction or braking.

kenikh · 03-14-2010, 08:51 PM

One thing about a 911, though in terms of power...it is very easy to have too little transmission. Big turbo power = big turbo "BOOM" on anything not a 4 speed (ick) or a G50 ($$$$$).

Jeff Alton · 03-15-2010, 09:47 AM

For the track I prefer the drivability of a NA motor. Yes, turbo = more power and I have thought about it, but like Kenik says, transmission issues would soon await...

Cheers

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by Jeff Alton

Ok,

What bore would you run with the 70.4 crank?

What do I get with a 66mm crank and 105's in terms of power/torque curve? 3.4L, are my current 48mm throttles enough? Exhaust? cam?

Cheers

Sorry it took so long to get back.
I have no idea what kind of power/torque 66 x 105 would produce but what a hoot to build it. I will say that 8200-8500 rpm would be possible and given the correct port and cam configuration I would think you could produce good power from 4500.