3.0 SC HP Expectation - post modification
 

I was hoping someone could provide some clarity on some mods I am planning.

I've looked at various options but one that stood out (largely based on $$$) was to do the following:

1. Maintain cylinders so therefore retain as 3.0
2. Switch CIS to Weber 40mm
3. SSI's (or early headers)
4. Sport muffler
5. Cams (not sure which ones at this stage)
6. JE Pistons (10.5:1)

What is a reasonable HP expectation out of this?

The car is to be used for street driving only. Ideally I am hoping for around the 260-280FWHP. Any ideas on what torque I can expect?

Do I need to do anything else (ie. porting) to get these sorts of HP numbers?

What is the HP limit of the 40mm carbs? I would like to know at what point should I consider the much more spendy option of 46mm PMO's.

Thanks.

That seems a little high. remember there is no greater HP mod than more CC's. Adding dual plugs would help with higher compression, bigger webers, headers, a better ignition/ curved distributor. That would bring you closer to ~260. The list is endless!
If $$$ are #1, than stick with ROW stock pistons (9.8:1?), good carb cams, weber 40,s, headers/no heat and lighten up the car.

Thanks James. What sort of HP do you think I would expect with that combination?

I am not totally governed by the cost but I do try and think about cost/benefit.

My 3.0L was dynoed on a MAHA rolling road last week.

It features 10,5:1 JE pistons with single ignition (ROZ 100 gas is available at German gas stations), cams similar to GE60, early 'big port' SC heads, Dansk 1 5/8" headers with dual pipe 'barrow type" exhaust and 40 Webers with 36mm venturis.

We came out at @241 HP at the flywheel at 6,7k RPM - power started to drop of at 6,9k RPM. Torque figures were at @214 ft-lbs at 3,8k RPM.

With twin plug ignition and some additional work to the case, cylinder mooning etc to reduce windage losses 250FWHP MIGHT be reachable here.

Best,
Christian

Be careful...With today's pump gas, 10.5 CR will lead to detonation if you don't twin plug. Also, 40mm Webers will be too small if you have any head work done.

Here's some results from my 10.5 CR 3.0 twin plug.

http://forums.pelicanparts.com/porsche-911-technical-forum/246563-another-rsr-clone-project-dyno-day.html

Thanks Christian - just the sort of info I was after.

That's a great result. I was wondering if 40mm were too small. I guess I need to firm up my HP expectation and go from there. It seems that I can get 240 with 40mm. If I want more then 46mm is the answer.

I retained the stock Mahle 95mm cylinders for my build with JE 10.5:1 pistons. I used GE 60 cams, 46 mm Webers that I bought for about the same price as a good set of 40s and twin plugged the heads. The only dyno time is seat-of-the-pants. I was told that this combination would be "peaky" and hard to drive on the street. I was also told that there would be little difference in power under 4,500 rpm.

This motor is a torque monster and will rev to 8,000 like a light switch. It's a blast to drive. It's very, very streetable and cruises at 70 like a stocker. I have one issue I haven't sorted yet with the just off idle to 2,000 rpm stumble. There's a transition that the current carb set-up doesn't like but I'll get it fixed.

I don't think you'll like 40s with GE60 cams; they run out of breath too early. Save your money and get the 46s and for sure dual plug your heads.

Lindy

The 3.0L with 40 Webers and the modifications mentioned above does pull very strong from 2k RPM in 4th gear all the way up to 7k RPM. The cams do kick in additionally at around 3,9k RPM but it is definately very driveable from idle.

With ROZ 100 gas available here in Germany 10,5:1 is reasonable with single-plug and taking the relatively low dynamic compression due to the profile of the GE60 cams into account.

Best,
Christian

Christian,

You're right about single plugs and 100 octane fuel but the biggest benefit to twin plugs is being able to add lots of advance and still have the motor live. If you run stock timing it's not an issue but this combination likes lots a timing (36 degrees total in at 3,500 rpm). The difference between 36 and 26 (stock) is incredible. You can't do that with single plugs except for about 30 seconds.

Lindy

LOL love it Lindy! BTW, love your engine build.

Thanks Lindy. I have been watching your rebuild with keen interest. I'd say you have confirmed the need for 46mm and twin plug. If you get some more carbs at that price let me know :D

...and it makes a lot of fun to drive ;)

This may not help but this is what I have...

3.0 79
Ported heads,
SSI's Blended to heads + 2/1 Monthy
10.5:1 JE's
Dual plug
ITB's
EMS ECU
GE80 like cams,
Raceware springs (stock retainers)
ARP rod bolts,
spinning to 7,200 ( built for 8k but for street longevity reasons limited )
Lightened flywheel/ race clutch

204 RWHP......great to drive on the street...heaps of torque low down but all the power after 4k. Only issue is the flywheel makes it a bit jolty in traffic.

I though the HP would be higher but I am not prepared to do any more work at this time.

Mark..........

Tom Sch helped a lot on tuning my 3.0L (thanks again for that!) - and was one of the first who actually drove it. Check out his awesome 3.2L build!

@lindy 911
With dual plugs you can of course advance timing to the numbers you have mentioned. Considering the somehow 'budget' orientated approach this would have fetched another $2,5-3,0k for the subject build and it runs very well on single plugs with the high octane fuel available here in Germany.

Best,
Christian

Dude the oil prices are down because they want us to buy their christmas retail and day after thanksgiving crap-once the x-mas rush is over-hello 3.00/gallon

Anyone car to guess at what Jhon Smitch is talking about?

Lindy

D911SC,

There's a set of brand new DC 60 (GE60) cams for sale here for $500. Here's your budget start. Jump on them and we'll start looking for carbs and other parts. These are $900+ new.

Lindy

Thanks Lindy, I saw that and your comment convinced me to go for them. I am not sure if seller is willing to ship to Aus but I have asked anyway. Fingers crossed!

Maybe but with a similar build, twin plugging and LOTS of EFI tuning I topped out at 240 fwhp. Good luck.

here's mine. dead solid dependable and pulls like a truck. nothing exotic, but it works. don't get to focused on big HP at high rpm's. torque is what get's it done. I've got stock 34mm ports and 34mm venturis in weber 40's.

http://forums.pelicanparts.com/porsche-911-technical-forum/502996-3-0-dyno-day-pleasant-surprise.html

That's a great looking dyno sheet haycait911. Any hints on what that 'secret cam grind' is???

details here:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/449608-dougherty-racing-cams-my-experience.html

the engine pulls amazingly. I've done some more accurate 0-60 times and they're in the low fives. could shave a little yet but I'm unwilling to dump the clutch at launch.

YouTube - 004.AVI

also went drag racing:D

http://forums.pelicanparts.com/porsche-911-technical-forum/540300-took-my-swb-drag-racing-today.html

Tried to buy them but seller won't ship to Aus. I'll keep looking - thanks for the heads up.

FWIW D911SC , I would be inclined to put together the rest of your package, pistons, crank, heads, induction, before buying the cam. the cam can be tailored to whatever setup you come up with. it has the most flexibility compared to everything else.

I wonder if these twin plug heads are still availible they would make a nice addition to your build, plus they have the beefier springs and retainers allready installed with your euro pistons and the shaved heads it is likely you will end up with around a 10:1 CR. Or you can order custom J&E pistons once you measure everything.

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/524010-fs-3-2-cylinder-heads-twin-plug.html

Shane

Thanks Shane. I'll have a look at these.

Thanks again haycait911. It does make sense to do it this way.

Just took delivery of Wayne's book today - no guessing which chapter I am reading first!!

These may or may not be the optimal cams for your set up but they are in Australia and are new billet web cams 964 grind. At 600 bones you may be able to barter and get them down to 500. At least you will save on shipping. SmileWavy

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/514305-sale-billet-cams-suit-2-7-3-0-3-2-a.html

Shane

I managed to get these ones. Despite advice to get cams last I have read alot of good things about these - not the least your own comments Lindy.

At this stage I have revised my build to be:

1. 3.2SS using JE 98mm 10.5:1 (purchased)
2. GE60 cams (purchased)
3. PMO 46mm (what the heck, I'll just go top shelf!)
4. SSI (ordered today)
5. Dansk 2 in 2 out
6. Upgraded rods (not sure which ones yet - open to advice)
7. Single spark (researched this and in Aus we have the fuel to cope with 10.5:1)

No doubt they'll be a few extras.

If anyone has any spare PMO's or 98mm cylinders floating around I'd be interesting in hearing from you.:)

I know, as soon as you have dual plug you then need all the bits to drive it again the price goes up. Even with higher octane fuel without a knock senor you may be risking the whole engine. Dual plug is insurance, admitedly not cheep, but worth concidering....or put an ECU in there with a knock sensor to retard the ignition if needed.

Otherwise spending money and building a motor that you can not get all of the benefit from is a leaving a lot on the table.

Mark........

D911SC,

Your motor will be a rocket but the omission of the twin plug, I believe, is a mistake. If you sourced a used set of 46 Webers you could use the saved money on a Rennwerks 12 wire distributor and MSD ignition to fire it. 100 octane fuel is marginal with 10.5 : 1 and you need a safety buffer at high RPM.

One thing to remember is that this combination likes timing and lots of it. 30+ degrees of total timing is not uncommon with the DC 60 cams. The timing really wakes the motor up above 4,000 RPM. You're almost there, but I sure would hate to see you melt a brand new 3.2 SS.

Lindy

Oh by the way, your stock rods with ARP or Raceware bolts are good to about 7,000 RPM. Have them re-sized then re-bush the pin end. I like Raceware because of the ease of installation; they do not require a stretch gauge and use a torque wrench.

A good source for most of this is Arron Burnham @ Rennwerks in Camarillo, Ca. 850-240-6931

Here's my 3.0L rebuild.

81 3.0L ( small ports)
John Dougherty GT2-102 cams
JE 9.5:1 pistons
40mm webers
Heads drilled for twin plug
European headers
M&K 2 in 2 out sport muffler w/baffles

On J&B Racings engine dyno it made 245hp/228lbs torque on twin plugs.
With single plugs it made 233hp/217lbs torque.

This was turning the engine to 7200rpm. HP peaked around 6800rpm torque around 5600rpm.

Actually, the advantage of twin plugs is in running much less advance and still getting the charge to burn completely. That's the whole idea of lighting it from both sides. Most of us run around 25-26 degrees total with twin plugs at about 10.5:1 to 11:1 compression.

Cranking the total advance on a twin plug motor up to 36 degrees will soon ruin it through severe detonation. You probably won't even hear it until something expensive lets go.

Thanks for your comments - Lindy, Mark Kent and Jeff. As the response is to twin spark I will need to consider this. I can't ignore good advice. I am not rushing this rebuild so I can save up the extra $$ and do it then. The last thing I want it to leave a pile of bits on the road as I destroy my new motor.

I have a couple of questions. For twin sparking I need a new 12 wire distributor and MSD ignition. As well as drilling the heads is there anything else to do?

Also, is it also worth considering new rods rather than stock? With the DC60 do I need to try and get more than 7000 RPM's? Again the last thing I want to do is break something due to bad planning. I am trying to make a fast but strong/reliable engine.

Nothing else to do on the ignition. Don't forget to drill the lower valve covers as well.

Depending on the angle of the second plug, it may interfere somewhere. Some guys drill and tap for the smaller plugs to avoid this. I drilled and tapped for standard, full size plugs, and mine interfered with one of the head stud nut. Replacing the barrel nut at that one position (per cylinder) with a hex nut solved that problem pretty easily (the barrel nut was tall enough to hit the plug, the hex nut is shorter).

I fire mine with an Electromotive set-up. It's just matter of personal preference - the cost is about the same as a dizzy. I like the lack of moving parts and programability. No one can argue with the "cool factor" of the dizzy, though. Just two different approaches; both work quite well.

Like Lindy says, Your stock rods are fine for 7,000 rpm (or more, actually) even with stock bolts. ARP or Raceware provide that insurance factor for over-rev, and a lot of peace of mind. Stock rocker arms are the limiting factor in these motors, not the rods. You'll be fine. I've been running my stock rod / ARP rod bolt combo for a couple of years and dozens of track days. I'll usually shift at 6,800-7,000 rpm, but have been known to take it to 7,200 on occasion. I pulled the top end off after about a year or so, and the rod bearings looked brand new.

Jeff,

Why do you say the stock rockers are the limiting factor versus the stock rods. I think this may be the first time I have heard that one. Stock springs yes limiting. With good springs and Ti retainers I do not see the rockers being an RPM limiter. Please expand on the thought.

Regards,

PFM

The stock rockers are designed to break in the event of piston to valve contact, like if a tensioner fails and the chain skips a tooth, or in the event of a serious over-rev (the infamous 5-2 downshift, missed shift, or something like that).

High lift cams with abrupt ramp angles that accelerate the valve very quickly, coupled with the heavy springs required to keep the whole works from floating under those conditions, will sometimes exceed this designed-in yield strength. With a big enough cam and heavy enough springs, this happens before rod bolt strength or rod strength becomes an issue.

Jeff,

Thanks for that bit of input. I have had the miss fortune of testing the break away design you speak of in a friends car. The reason this has me scratching my head is the lack of aftermarket rockers for these engines to overcome this problem. My cams are not that radical nor spring pressures that high. I would like to hear from CamGrinder on this thought as well. I did detail the rockers and sent them out for cryogenic treatment. If the pistons and valves kiss in this build something else broke first.

With a well prepped set of Porsche rods and Raceware bolts what RPM do you think they are good for?

Regards,

PFM