3.0 CIS to 3.5 ITB EFI
 

I'm building a stock 81 SC 3.0L CIS into a 3.5L twin plug motor using Tec-3r EMS with PMO ITBs. The car will be used for street and track and I'm retaining the AC, power brakes, heater and cruse control (if I can get it to work with this setup). Yea I know - I want it all. Would like to have a reasonable power band. Don't want a race motor, but respectable on the track.

What would be a good cam choice?
What size TBs would work best 46 or 50s?
What intake port size works best with the 3.0L heads?
I have SSIs/Monty - remember heater - so exhaust ports will match - ideas?
Are aluminum flywheels street-able or would an RSR be better?
Suggested clutch?
I'm concerned about oil cooling. I would like to retain the front valance. Suggestions?
Do piston crown and head/valve coatings work and are they worth it at this level?
Any other suggestions?


I already know I'm insane. Got that way with my first car. Don't need help in that area.

This is my first Porsche build and yes I'm getting professional help, but I want to tap a broad knowledge base.:confused:

I would probably use a DC60 or DC 42, probably 46mm TBs, around 41/38mm ports. I would have to say sell the SSI's, and make heater boxes around some 1-5/8" headers...SSI's are just too small for a 3.5

Aluminum flywheel with a steel face will be fine...or get a steel RSR flywheel.

Clutch...many options

Do you have a Carrera 3.2 radiator oil cooler? I would have a pull fan with a 3.2 Carrera cooler.

I don't often do the crown coatings (ceramic) but always do dry-film lubricant (kind of like Teflon) on the piston skirts. Dry-film lube is debatable on bearings but I like the extra insurance. Talk to Calico.

I assume you're using 3.2 Crank 74.4mm stroke, with 3.2 rods, 100mm Mahle P/C? Mandatory ARP rod bolts. If I were in your shoes I would consider getting a NEW GT3 crank (76.4mm stroke), 3.0 SC connecting rods (same big end size as GT3), and 98mm Mahle P/C. This is a 3.5L Long stroke, bada$$ stump puller with an unbreakable crank.

My 2c

Thanks for the excellent info. Yep - got the 74.4 Crank (930) and 100mm Mahle P/Cs - absolutely beautiful. Folks are telling me that the 3.2 rods (930 for me) need upgraded in this motor (insurance for a buzzz) to Pauter or Carrillo even if you use Raceware or ARP rod bolts. Please tell me it ain't so. Would save big $$$.

I've got a trombone cooler now. Didn't want to upgrade until I knew what would work.

Could I get your thoughts on scavenger oil pumps? Will my stock pump work with this setup?

Stock rods with a quality rod bolt will be fine.

Cheers

I am running a 3.5 with the following setup:
DC80 cams with racing valve springs
41mm intake and 38mm exhaust ports - ports will be opened further soon
45mm ITBs - toyota RXi with custom manifolds etc
High compression ratio
41mm headers

The motor is unbelievably smooth, even at low revs. Can be driven on the street, but torque comes on VERY strong above 4000 rpm. Peak torque is at nearly 5000 rpm and peak power is just over 6000 rpm.

I would possible go with milder cams for a street motor, and all other dimensions the same.

The current motor spins R rated rubber at 4000 rpm in 1st.

Fun to drive.

Always fun to dream.

jlmccauley. Hi, it sounds like you are getting a nice engine from what I have read so far about it. As far as an oil cooler, do you have a front valance that has the center opening? If so, I would recommend a front, center, oil cooler. I can't seem to find the Porsche factory part # for the one that my car has, but you probably know which one that I am talking about. If you have it mounted up front and centered, they do a really nice job of keeping the oil cooled, plus you can also add a couple of the small 12V fans, to help even more, if you get tied up in traffic, or have to go too slow to get a lot of air through the cooler. The fans would help a lot. Just a thought.

Sounds like a great motor. Always nice to see all th numbers coming in close from different perspectives. Excuse my ignorance, but what is a Toyota RXi? Are you using 3.2 rods? What CR are you running?

Nope, got the stock SC valance with external fog lights. But I really like the stock look. Also my driveway has a high curb which makes using the center opening with alot of front ovrhang impractical.

Is there any advantage in upgrading to Turbo Oil Squirters over my stock 3.0L?

As long as you are not going to rev the crap out of this motor... I agree.. stock rods with good quality aftermarket rod bolts....ARP

A Toyota RXi is a version of the toyota corolla. It is a 1600 with ITBs that are locally available as used units. They come in 43 and 45mm bores.

These are a cheep alternative to the ones available on your side of the world.

1meansc
Do you have any pics of the throttle body setup? What did you have to do to make these up?
sounds like a sweet setup

A few thoughts from a guy that recently did the 3.5 on a 3.0 thing:

1. Which Mahle pistons do you have? If they're the carbureted pistons then your cam options are numerous. If you have the motronic pistons, you will have to stay close to a 964 cam (ask me how I know)

2. SSIs are too small. I too wanted heat so I went with 993 heat exchangers (flanges flipped on one side) and a Triad muffler.

3. No way a trombone cooler will handle the heat of a 3.5. I started with one Carrera cooler in the passenger side fender and it wasn't enough. I ended up with 2 Carrera coolers in circuit. I rarely get above 220 on track days.

4. I just installed an RSR flywheel (from Patrick Motorsports) and have yet to drive the car, but I'll report back.

5. The 3.5 creates alot of torque, so consider going with stiffer engine mounts (I'm using Wevo).

6. I have a sachs power clutch which I just inspected (15 track days and about 2,000 miles of street driving) and it still looks new.

7. I went with ARP rod bolts (stock 3.2 rods) and head studs. I re-torqued the headstuds at about 1,000 miles and was surprised how far the bolts turned before hitting the proper torque. Some research on this forum revealed that this is a known problem with ARP. I would look into the Supertec and/or Raceware options if I were going to do it again.

8. As far as the oil pump goes, you're going to end up spending ALOT of money on this engine (trust me) and the oil pump is not a place to cut corners. I went with a new GT3 pump, but I think a 930 or even Carrera 3.2 pump would work.

And that's all I've got. Good luck with your project. Feel free to PM or email me for more info if you like.

Would a 964 or 993 oil pump be a fit and an appropriate upgrade for this application? My question is also for a build up on a 3.0 case with stock rods (but supercharged with a center-cooler in my case)