Would You Start With a 3.0, 3.2 or 3.6?

[jamesjedi]

I am trying to decide about which engine case to start with. I am going to build another track car, starting with the engine. After hours of research I have not decided on where to start. The 3.0 case is winning from a cost perspective, as I have found one (a Euro case) that is a very good price. I am debating the 3.2 engine case, as it could be made into a 3.5. I like the idea of a 3.5. What case would you start with?


This engine will be a track/autocross, and street car (coffee, fun etc.). Ideally 275-300 hp at the crank would be super. Would this be a stressed 3.0. 300hp is such a NICE number, perhaps a little optimistic as I do not have unlimited resources.

I am looking forword to hearing from others experience. THANKS!

James

[Steve@Rennsport]

James,

The VERY first question I ask my clients when discussing engines is: "Whats your budget"?

That, after all, frames whats possible to do and what isn't.

A 300 BHP 3.0 is somewhat stressed.

A 300 BHP 3.2 less so.

A 300 BHP 3.6 is not stressed at all (some 3.6's need additional preparation to the bottom end for reliability).

Your performance and engine longevity will be somewhat proportional to your budget.

[brads911sc]

another factor on a track car is weight. HP can easily feel greater if you are lighter.. you may not feel a difference between 275 and 300 if you add extra weight by doing the 3.6. in addition to weight, you also want to consider other things in building a car that is rated for 33% more HP such as cooling, brakes, transmission, suspension... There are plenty of 250 hp cars that will likely blow your 300 hp off the track if they have the right weight savings, suspension, tires, and driver skill... Need to focus on the whole picture not just HP.

[jamesjedi]

What about 275 HP (I am assuming that we are talking about "at the crank"). A 275 HP 3.0, sounds like it would be mildly stressed???

Thanks for the insight.

James

[Steve@Rennsport]

Originally Posted by jamesjedi

What about 275 HP (I am assuming that we are talking about "at the crank"). A 275 HP 3.0, sounds like it would be mildly stressed???

Thanks for the insight.

James

A 275 HP 3.0 is mildly stressed and with close-ratio gears, runs VERY well,......

Again, its your budget that really determines what you do,...

[PFM]

The other question is what trans do you want to push this through? If the answer is a 901 the 3.2 or 3.6 has enough TQ to hurt the 901 even on a fairly mild build.

A 300 HP motor could be a long stroke deal making 260 FT/TQ at 6100 RPM or 210 FT/TQ at 7100. The first will kill a 901 gearbox, the second not so bad.

Just something else to consider.

PFM

[jamesjedi]

It is a good point, I will be using the 915.

[PFM]

James,

With the 915 I would think a 3.6 as a base would be a solid start. What are you planning for induction? Injection? Carbs? If injection the 3.6 manifold is very good, if aftermarket EFI / EMS then a little cam on a stock 3.6 will be a solid 300 HP.

PFM

[jamesjedi]

I like the 3.6, but it considerably more expensive to acquire the basics. The 3.0 is priced much less. The 3.0 can be made into a 3.4,3.5, or even a 3.7, but I think that this is where it could be comparable in expense to a 3.6.
I do love the idea of having an engine that is not stressed.

As for induction; that will depend on what is available on the market. I will be patient. Carbs have a great retro quality, and they are not over the top expensive.

Just a thought...is the 3.6 engine heavier than a 3.5, or is the weight negligible?

[PFM]

James,

Something to consider on the cost front, every thing for these engines carry a premium price. The reason I said the 3.6 in near stock trim is the cost. If you get your hands on a good running 3.6 it starts off about 270 HP as delivered. You should not need new pistons or cylinders for it, replace the rod bolts, bump the cam up and do something like a MegaSquirt on the great factory manifold and go have fun. No not as retro cool as carbs but will run well. The pistons stock are over 10 to 1, the oil pump is very good.

I have been collecting and recollecting my 3.0 Euro motor for too many years now. The 30 year old 3.0 case you buy will likely need help to get it all ready to go, best budget $1K just for that. Recon the rods, heads, valves, big cams, possible port and polish etc. Remember the 3.0 maybe had 220 to 240 to start you are looking to ad 60HP to that and will need to RPM it to make 300 HP. You are rebuilding a 30 year old motor here everything needs to be checked or replaced to turn 7000 plus RPM.

My build is for a 914, I have a great 901 box, the 3.0 Euro is the piece for my build but would have done a 3.6 if I was doing a 911 / 915 or better box.

PFM

[jamesjedi]

As I am learning about this, wouldn't your 3.0 be less stressed if you bumped up the displacement? It looks like the 3.0 and 3.2 case are very similar, and were designed for some very high HP factory race cars. Perhaps a 3.4, or 3.5?
I agree about the 3.6 being strong in stock form. In an early/mid-year 911, would that extra weight of the 3.6 create a balance problem? That is a allot of weight hanging over the rear axle.

[Steve@Rennsport]

Originally Posted by jamesjedi

As I am learning about this, wouldn't your 3.0 be less stressed if you bumped up the displacement? It looks like the 3.0 and 3.2 case are very similar, and were designed for some very high HP factory race cars. Perhaps a 3.4, or 3.5?

More displacement will increase torque and thats precisely what you want.

I agree about the 3.6 being strong in stock form. In an early/mid-year 911, would that extra weight of the 3.6 create a balance problem? That is a allot of weight hanging over the rear axle.

The 3.0-3.2-3.6 engines are all within 20 lbs of each other so the weight issues are negligible.

[euro911sc]

James,

Review the cost of the parts to turn your 3.0 into a 3.5... last I checked it was more than a good 3.6 from filter to mufflers... It seems to me that the cost to build a really cool and neat motor like the 3.5 you mention will be a bit more than dropping in a nice 3.6.

Consider this plan:
If you buy a 3.6 you can, effectively, throw it in your car with very little work and have 80%+ of what you are desiring right away. Now you can take some time and recoup some $$ and plan the next stage of your adventure while driving the wheels off your car

Don't get me wrong, a 3.5 twin plug ITB race inspired engine is soooo much more sexy than a 3.6, but paying for sex is expensive... um... err... you know what I mean!

-Michael

[AlfonsoR]

James,

Make sure you think your project all the way through. I don't mean to be harshly critical, but I get the impression that right now, you are only looking at the cost of the case. That would seem to be "piece meal" cost analysis vs "big picture" cost analysis.

You mentioned carbs, what about iginition? Dual spark might be desirable, depending on how big you go, but even on a 3.2, dual spark makes a positive difference, according to what I've read. A 3.6 would already come with dual spark.

How about exhaust, a 993 3.6 would already come with pretty decent exhaust including heat. For a track-only car, this is probably not an issue, though.

Anyway, these are just my novice observations. Good luck and I hope you post with updates on your project.

[Steve@Rennsport]

Originally Posted by AlfonsoR

James,

Make sure you think your project all the way through. I don't mean to be harshly critical, but I get the impression that right now, you are only looking at the cost of the case. That would seem to be "piece meal" cost analysis vs "big picture" cost analysis.

You mentioned carbs, what about iginition? Dual spark might be desirable, depending on how big you go, but even on a 3.2, dual spark makes a positive difference, according to what I've read. A 3.6 would already come with dual spark.

How about exhaust, a 993 3.6 would already come with pretty decent exhaust including heat. For a track-only car, this is probably not an issue, though.

Anyway, these are just my novice observations. Good luck and I hope you post with updates on your project.

Thats some of the best advice I've seen here.

Figure out your budget: determine how much money you are willing and able to spend. Then,.......do your due diligence about what everything costs. Only then, will you know what you can or cannot do.

[KTL]

Originally Posted by Steve@Rennsport

A 275 HP 3.0 is mildly stressed and with close-ratio gears, runs VERY well,......

Again, its your budget that really determines what you do,...

I have one of those mild 3.0L engines that Steve speaks of, with the gears as well. I can say that it's a solid engine for a track car. Mine's as follows:

3.0 case with deep sump plate for 930 oil pump and oil bypass modification performed. I'd consider a 930 pump because they are very sturdy. Mine's got some sort of modification to it and it puts out very good pressure at all rpms.

Cross drilled 70.4 crank

9.8:1 Mahle Motorsport pistons

Upgraded rod bolts and head studs

Balanced stock rods

3.0 RSR sprint cams

High rpm valve springs and retainers up to 8K rpm

Carrera oil fed chain tensioners (not sure how I feel about these on a race engine)

Single plug Electromotive HPV-1 ignitiion. I like the Electromotive for its simplicity and reliability. However I would recommend twin plug for additional reliability, which I plan to do come next rebuild. Mine was built to run 110 leaded race gas.

Weber 46 carbs with 42mm throats and lightweight race clutch make for some crisp throttle response

Holcombe inconel headers with "straight" pipes (actually they're more like side pipes.... ) provides the howl

Short 2-3-4-5 gears (1.68, 1.33, 1.13 1.0) which really helps keep the engine on song.

On 110 race gas it was dynoed at 235 to the wheels. I've got it detuned to run on 93 pump gas. Still does well at around 220, so call it 260 crank HP?


So you can see there's nothing really super unique about it. Just most of the basic modifications for more power and reliability. However it all adds up to being costly. In the end, you have a solid 3.0 but I can say with certainty that the bigger engines in the class above me pull on me pretty good. Those 3.6 engines are quite torquey. However as Brad said, weight is an issue as well. A 3.3 also in a class above me pulls on the 3.6 cars very well since his 3.3 car is much lighter (8.5 wt/hp ratio vs. the heavier ~10.0 wt/hp 3.6 cars)

[ARCSinAK]

KTL-
Feel like sharing the $ involved in creating your motor? I too am considering adjusting my stock/SSI 80SC. Thanks to all for their time and knowledge.

Aloha-

Jed

[jamesjedi]

As for the cost of that motor....just look at the cams to get an idea.

[euro911sc]

I would think cams pale in cost to "Holcombe inconel headers" Woof!

-Michael

[KTL]

Well I could estimate costs based on checking current pricing. Translation: engine came with the car and I didn't have to put out the $ to build it. I obeyed the buying-a-racecar rule- buy someone else's instead of building your own bigger pile of cash

The inconel headers are nice but way overkill for my simple racecar. Not complaining. Just saying no way i'd spend that kind of money for them. They are very nice & light though and the flared band clamp collector connections are nice too. Probalby make changing from side pipes to Borla muffler very easy, if I ever have to do that. But mild steel or RarlyL8's new headers would suit me just fine if I were buying some nowadays.

Cams are just a grind from a cam maker like DRC or WebCams. They're not original RSR cams. They actually may be GE80 too. I have to check my records again.

My engine was built to run in PCA D class (which became E I believe) and then it went to NASA when he got away from the PCA scene. So it was a "stock" class and alleged to be a Carrera 3.0 build. How the engine could fall under a stock class using higher compression pistons, improved fastening, high rpm valvetrain and Weber 46s (Weber 46 are not a factory Porsche carb- they're racing carbs) is beyond me. Again, not complaining. Just explaining the intent behind how mine was built. Sounds like a cheater engine to me!