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Question to all those who have a 3.2L Short Stroke W/46mm PMOs??

I am in the process of rebuilding my engine that started life as a 3.0L 911SC.
Over the years I have made modifications and finally I am now taking the it a step further by installing the 46mm PMOs and a set of DC-40 Cams. I will stay single pluged for now @ 9.8:1 CR

I had a some questions to those folks that have already built their 3.2L Short Stroke Motor and have a set of PMOs as well.

1. How responsive is the motor below 4,000RPM?
2. What can I expect in terms of HP?
3. What if anything did you do to the cylinder heads?

Thanks !

GM
Old 03-03-2009, 07:08 PM
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I am running 98mm Mahle PCs on my 3.2SS with DC40-108 cams and 46mm ITBs (EFI). It is 10:1 CR and twin plugged. The car feels much like the 3.0 that was used to build this motor below 4K. Above this value its a whole 'nuther ball game. yeah, its a rocket ship above 5K and will pull hard through 7300 redline. I did nothing to the stock 78 SC heads. I have not had it on a dyno.

Jamie
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Old 03-03-2009, 07:58 PM
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Jamie,

Thanks for the info.....
Your 78 Heads have 39mm intake ports versus my 34mm.
My plan was to enlarge the intake to 40mm but I may consider a smaller size to maintain better low end power. I just hope someone else has done this on a single plugged motor so I can get their feed back....

Thanks again !!
Old 03-04-2009, 05:33 AM
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In my opinion the 34mm ports are just big enough for a 3.0 with CIS. For a Carbed 3.2 they will severly limit your top end power. I'd suggest 39mm ports for that engine.

-Andy
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Old 03-04-2009, 10:01 PM
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I am in the process of putting together a similar motor
3l case
79 heads, single plug, race springs
DC C2 grind
9.8 JEs/98mm

However, running MS EFI through larger 79 manifold cause it's what i had, plus it will allow easy tuning. I'll let u know how it goes. Should be together in a month or so.
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Old 03-05-2009, 03:47 AM
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Port shape is more important than port size.
We recently built a 3.0 MFI with DC80 cams, MFI 10.5:1 Twin plug that made 305 DIN @ 7200 and flat torque curve from 3200. These are 3rd party turner numbers not our numbers. This engine runs Supertec Venti-port 36 mm intake ports.
Some ports will restrict high RPM but truly how often are two valve Porsche engines turned much higher than 7200-7400.
The DC 40 cams will be well done before 7000rpm.
Stay small and enjoy the derivability.

A quick note: We recently built a 4.0 liter with DC40 cams that spins the tires in third gear. This engine runs 3.6 C2 heads with ports reduced to 40 mm from 43 mm. At first we thought the clutch was slipping.

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Old 03-05-2009, 05:27 AM
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I have the same setup except mine started from a 79 which has the bigger heads and I dual plugged it using the JC racing dizzy. Henry did the head work. Steve Weiner supplied the PMOs and invaluable knowledge. I would highly highly recommend using Steve as your dealer and advisor in all aspects of the build.

To answer your questions, response is excellent in all rpm ranges. I ditched my megasquirt which I could never get working right, it would often die at idle during off-throttle, the PMO's are a blessing for me.

Don't know the hp numbers yet, and no special head work was done except a rebuild with dual spark.
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Old 03-16-2009, 11:07 AM
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I had a motor very similar, 3.2 short stroke with 78 SC heads, GE40 cams and Weber 46's. It had extremely excellent torque down low, no issues.
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Old 03-23-2009, 12:44 PM
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Thanks for all the replies on this issue..... I will post pictures and HP figures once I am done....

GM
Old 03-24-2009, 08:31 PM
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carb setup

I do not have pmo but I have a 3.2SS with twin plugs, large port SC heads, Ge 60 cams and weber 46's. Not certain of CR.

Anyone have venturi and jetting experience? For what it is worth, I have always driven small bore stuff. I am more of a horsepower guy. A 3.2 has a ton of torque and I would sacrifice bottom end for top end..
Old 03-27-2009, 04:07 PM
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I am resurrecting this thread as I am getting closer to my rebuild. (finally after the credit meltdown). I am upgrading my 3.0 for mostly street and autocross duty. I have the later 3.0 heads with 36mm intake. I want to maintain the low rpm response of my engine while giving me the adrenaline rush to 7000. I currently have PMO 40s and Electromotive crankfire installed with a set of 98mm on the table. I have read about Jeff Higgins who has successfully built a 3.0 MFI using a custom DRC ground cam with a bit less duration than mod S but more than a Solex grind and 484 intake lift. I like the idea of keeping power band from 4700 to 6100. With that cam, I used Jluetjens formulas to determine an intake port size of 37.5mm.

Now, my engine builder has me rethinking the cam. Since stock valvetrain should be able to support 7000 rpm, he recommends a mod S cam. This will raise the powerband up another 300 rpm or so without affecting the low rpm and I wonder what this does does to my head size/shape? Should I go with the early style heads? or stick with reworking smaller heads and promote better flow? I don't want to loose the response of higher velocity at lower rpms. hmmm

My P&C choice now would be Max Moritz at 9.8:1 but I can easily go 10.5:1 with another Electromitive coilpack dualplug setup.

What say thee.
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Old 11-28-2009, 06:40 PM
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I looked at the Mod S grind for my cams, and decided they simply do not have enough lift for a warmed over 3.0 liter, and way too much duration for the rpm range in which I wanted it to make power.

The Mod S runs .470"/.440" lift on intake/exhaust, and 266/249 degrees duration @ .040" lift. This profile is meant for a smaller, higher reving motor, and works quite well in one. It also requires (according to John Dougherty) racing valve springs with higher seat pressure than stock. Once you go with the heavier springs, you must also go with stronger aftermarket rocker arms. The stock ones are meant to break in any valve/piston contact, saving the rest of the works from greater damage. They will also break if rev'ed into the mid 7,000's with a high lift cam.

After speaking with John Dougherty, we settled on what he calls his "GT2-102" grind for my motor. Specs are .485"/.470" lift, and 254/238 degrees duration @ .040" lift. One of the key aspects of this cam's design is its gentle ramp angles, which accelerate the valves more slowly than the Mod S and similar cams. So, even though it has more lift than the Mod S, the valves actually open and close slower (they spend less time all the way open), allowing stock springs to control them just fine. The ability to run a stock valvetrain (other than the cams) was important to me.

These cams make peak power at 6,000 rpm and peak torque at 5,000. Mod S cams will make peak torque and horsepower much higher; peak hp will probably come at whatever you decide will be redline. In other words, hp will climb as long as rpm's climb, well above where it sounds like you would like to rev it. It will feel slightly peaky, and give up a lot of mid range punch - I disagree with your builder on that point. Yes, the Mod S will give more mid-range than a stock 3.0, but there is so much more to be had...

My horsepower numbers are nothing to write home about - somewhere between 245-250 at the crank. It's the torque that makes this motor, peaking at 230-235 foot pounds, and laying down over 200 foot pounds from just 3,000 to over 6,000 rpm. No Mod S cam will do that; no way, no how. The 3.0's I've seen chronicled here with Mod S, normal S, 964, 20/21, GE or DC 40's or 60's, etc., are lucky to make 210 foot pounds peak.

I started out with the later SC heads as well. I had the intakes opened to 38mm, or 1mm smaller than the early large port heads. That's pretty close to what you came up with John's formula. This port size does seem to work to help make some monster torque numbers, as long as intake velocities are kept high enough through the mid range. I don't think the Mod S will do that.

I typically shift somewhere between 6,500-7,000 rpm. That shift point is not determined by where the power is, but rather by where the next braking zone is. With ARP rod bolts, and the lower end carefully balanced by Monty at Redmond European, I'm sure it is mechanically safe to go several hundred rpm higher than that. There is simply no reason to, though, with peak power at 6,000 and such a flat torque curve. Shifting at 6,500-7,000 neatly splits its peak power in each gear; in other words, that's just about as much above peak power rpm-wise as it drops below, rpm-wise, when I shift. And if I find myself in the "wrong" gear, it can certainly grunt its way out of a corner from quite low in the rev range. I think that would be an advantage in autocross - it certainly is on the street, and on the track.

Anyway, those are my thoughts. Call John Dougherty, or email him, and talk cams. He was a huge help to me, taking the time to understand what I wanted, and finally making an outstanding recommendation. He even custom ground these for me (I'm not sure, they may even have been the first set), and since then, at least two other Pelicans have built or are building 3.0's with these cams. I love 'em - they give this motor its personality, one with a surprising amount of punch.
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Old 11-30-2009, 07:29 PM
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3.2L S/S dyno'd 240hp at the wheels

To answer the original question pretty much spec for spec. Hope this helps.

I thought my build was conservative and was surprised at the outcome. I know others have bigger numbers, but I was only hoping for 250hp at the crank.

Specs 3.2S/S:
PMO 46mm carbs (running a little rich with 38mm vents)
J/E 98mm 9.5:1 pistons
DC40-106 cams (thanks John these rock!)
Single plug with non-recurved SC distributor (at about 15 degs intial to get 33-35 fully advanced, need to send in for recurve...)
Big port SC heads (stock)
MSD Ignition
L/W alum pressure plate (stock steel flywheel)
Stock valve springs/retainers (I know...)
Early smaller 1 1/2" headers, dual in/out M&K R-type muffler

Wish I could scan the sheet, but here is the basics (dyno dynamics dyno?):
239 rwhp (280+ at the crank depending on your math, dyno guy said about 300hp) HP peaks at 6500-6900 rpm (perfect, wanted a 7k redline)smooth curve all the way up

200-205 rw torque peaks from 4500-5800 rpm (240 or so at the crank?)
Torque is above 175 at the wheels (or 200+ at the crank) from 3500 - 7000 rpm Plenty of torque starting at under 3k to move a 2200 lb RS Clone.

I haven't gotten the smile off my face yet.

Erik
Old 12-01-2009, 03:33 PM
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Interesting Eric,

The 3.0 RS engine peaked at 6100 RPM even with all that duration. Yours is 500 rpm higher. With 98mm slugs I would think it would be low 6s. The 106 LSA should widen/flatten the torque curve but never really seen it extend power upwards.
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Last edited by joetiii; 12-02-2009 at 07:15 PM..
Old 12-02-2009, 07:12 PM
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Joetii-

Sorry to add to any confusion...? I am no expert by any means, just offering my dyno results. I had found many builders but no real actual dyno results on the 3.2L S/S combo with carbs/cams on the board so I thought it would be beneficial for others.

Making pure assumptions on what others have said on the board in other posts, maybe the hp peaks at a higher rpm due to the cam timing specs? John listed to set the cam timing to 3.8mm of overlap if I remember correctly. I believe the typical S cams are in the low 5s (at least my Webcam S-grinds were on my 2.7L, factory S cams are 5.2 or so). I didn't question it. But that may have possibly moved the peak hp curve up in the rev range by a few hundred revs? The graph shows all 3 pulls peaking at 6700 or so, but it is within 5hp of that from 6500-6900 rpm.

Just a guess at this point. I couldn't be happier, that's for sure. Very driveable and plenty of top end, would pull through to 7300-7500 if I let it I would guess.

Erik
Old 12-02-2009, 08:19 PM
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Quote:
Originally Posted by kandhmfg View Post
To answer the original question pretty much spec for spec. Hope this helps.

I thought my build was conservative and was surprised at the outcome. I know others have bigger numbers, but I was only hoping for 250hp at the crank.

Specs 3.2S/S:
PMO 46mm carbs (running a little rich with 38mm vents)
J/E 98mm 9.5:1 pistons
DC40-106 cams (thanks John these rock!)
Single plug with non-recurved SC distributor (at about 15 degs intial to get 33-35 fully advanced, need to send in for recurve...)
Big port SC heads (stock)
MSD Ignition
L/W alum pressure plate (stock steel flywheel)
Stock valve springs/retainers (I know...)
Early smaller 1 1/2" headers, dual in/out M&K R-type muffler

Wish I could scan the sheet, but here is the basics (dyno dynamics dyno?):
239 rwhp (280+ at the crank depending on your math, dyno guy said about 300hp) HP peaks at 6500-6900 rpm (perfect, wanted a 7k redline)smooth curve all the way up

200-205 rw torque peaks from 4500-5800 rpm (240 or so at the crank?)
Torque is above 175 at the wheels (or 200+ at the crank) from 3500 - 7000 rpm Plenty of torque starting at under 3k to move a 2200 lb RS Clone.

I haven't gotten the smile off my face yet.

Erik
Damn, i gotta get a set of PMO's I used the stock large port manifolds on my (basically identical) build in the interest of time, $$ and so that i could use my existing MS EFI. The car was awesome in europe, but seeing your numbers, realize how much more is in the motor.

3.2SS with MS EFI dyno results
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Old 12-05-2009, 07:07 AM
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Dyno sheet scan

Finally got my scanner to work again. Here is the scan file of the dyno run.

Sorry for the coffee stain.

Old 12-06-2009, 09:12 AM
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New 3.2 Short Stroke from Norway

Old thread but I thought I would share info about my one year old 3.2 Short Stroke.

Engine spec:
3.2 Short Stroke.
3.0 SC engineblock, boattailed.
3.0 SC heads, 39mm. intake.
3.0 SC rods, 70.4mm original stroke.
3.0 SC camtowers.
3.2 RSR mahle Motorsport P/C, 10.3:1 CR
CAM: Web Cam Racing Cams
Grind: 120/104
Duration at 1 mm: 284/270 *Duration at 0.050": 264/248 *
Valve lift(inch): 0.476/0.450
Valve lift(mm): 12.09/11.43
Lobe separation angle: 100
Lift @ overlap setting: 5.2mm
PMO ITB's, 46mm.
Electromotive TEC3R sequential enginemanagement.
Twin plug.
Backdated exhaust: Dansk 2-1 muffler and 1.5" heatexchangers.

Power result: 237.2 met.hp and 290Nm / 213.9 ft.lbf at the wheelhubs. Calculated with 15% drivetrain loss it gives approx. 283PS and 341Nm / 251.5 ft.lbf. at the crank.
Dyno used was a ROTOTEST. Rototest dynamometers for true measurements (engine dynamometer / chassis dyno)
The car weighs 1220kg / 2689.6 lb and it almost keeps up with a 3.4 short stroke that is faster than a 930 0-62mph. My car with stock gearbox. The 3.4SS 911 weighs 1080kg / 2381 lb. and has a G50 gearbox.
Very happy with the result.
Here's the dynosheet of both my 3.2SS and one of my friends 3.4SS. Red curve: 3.2SS, blue curve: 3.4SS.
The last graph shows how similar in performance they are.



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