2.4 Build
 

Hello All,
It‘s been quite a while since I‘ve posted. Life has gotten in the way of my Porsche pursuits.

I‘m now ready to focus a bit on increasing the torque on my 2.4 Motor.

Aside from the odd Autocross or PCA track day, the car will not be tracked. My core objective is a reliable motor with strong low end torque pulling well from ca 1500rpm.

Current setup:
- [ ] PMO carbs 40
- [ ] Bore: 74mm OEM Mahle 911s piston and cylinder
- [ ] Stroke: 70.4mm
- [ ] Compression Ratio: 8.8:1
- [ ] Valve sizes: 46mm intake / 49mm exhaust
- [ ] Port sized: 32mm intake / 32mm exhaust
- [ ] Camshaft specs:
- [ ] intake duration 270/ exhaust duration 254
- [ ] Exhaust opens at 36ABC/ closes at 20ATC

I‘m considering a PMO EFI system to improve everyday useability; meaning sure cold starts, minimum sputtering across rpm range, slight increase in fuel mileage, etc...

What would you build with these objectives and current setup in mind?

Many thanks in advance for your thoughts!

Best... Oliver

It's always how far you want to take it and of course your budget.

If it was me I would go to a 92 or 93mm bore for a 2,8 or 2.9 with a CR around 9.5 - 1 and a mod S cam.

Easy to open up the ports to 36mm

Next step would be more compression and dual plugs....

Thank you Trackrash. From my perspective the build to achieve reliability and strong torque at the wheel (225+?) starting at around 1500 will dictate the cost. Would a 92/93 bore and mod S cams get me there? Would E cams be better given their mid range capabilities?

A local mechanic I know has a 2,9 and he claims it is bullet proof. Maybe others will have info on the latest cylinders that are available in that size.

As far as cams go, I would use a mod S. If you want more midrange, go with a mod solex grind or something like a DC 35. The trick is to match all of your components. More compression likes more cam, for example. I'm running a custom GT-2 102. Similar to a DC 35 in my 3,0. Starts pulling around 3,000 RPM. IMO, you will want more cam than the factory E grind.

Look here for good cam choices. Dougherty Racing Cams Porsche 911, 930 and 964 camshaft profiles

My last motor was a SS2,5 with E cams. I originally had T cams then went to the E grind, due to my car's classing. I would have liked to have even more cam than the E even in that motor.

What Trackrash said. Higher compression with Mod S or DC 30 cams is a bullet proof application. Don't know why Porsche did not make it.

I had a 73 E... ran out of breath at redline 7300 RPM.
Upped the compression to 9.5....big difference
reground the E cams to DC30's....holy cow...screamer.

Combination of compression and cam with the right VE is the recipe you want.
9.5 CR and DC 30 cams on MFI 2.4 was an amazing engine.

Chris
73 E

""Aside from the odd Autocross or PCA track day, the car will not be tracked"".

Some of the most dangerous words you could have chosen.

If you will use the car for any sort of off road event, chose the one that will put the engine at its greatest demand and build the engine to this. Even if its a 1 time use only. The number of times a customer has said to me, ""if only I had built my engine for ...……. It is my fault, I was at the track and wouldn't slow down""!!!

My advice is to go EFI. Don't bother with anything else. A well tuned EFI system will be hands down better all around. Most EFI systems today are all very good offering control well above that of any mechanical system or Carburetors. I hate carburetors. If only they would remain in tune and change for different conditions???

We are currently building the first of our 2.9L kit with new rods and Pistons and newly designed camshaft. A more modern take on these older engine upgrades. Budget will be your limiter here. Figure out exactly what you want to spend in total and work backwards from there.

Thank you Neil, Chris and Trashrash. Sound advice on building for track/ autocross. I will work to that.

I am currently thinking PMO‘s EFI system for the exact reason you mention plus the reliable/ sure starting.

So I’ hearing:
- EFI
- DC 30 or similar cams (what is the list here?)
- 9.5 CR

Which P&C’s should I opt for here?

Rough budget would be $20k max.

Am I in the Range?

Are you doing the work?

As far as P&C go, look here https://lnengineering.com/products/aircooled-cylinders-pistons/porsche-911-1965-77.html?p=3

and here https://www.pelicanparts.com/cgi-bin/ksearch/PEL_search_2016.cgi?command=DWsearch&description=c ylinders

Boring out a set of 2,7 cylinders may be an option, but I'm not experienced there.

BTW, this ^ is why I started with an SC motor for my last build. I found a COMPLETE 3,0 SC motor with MAHLE cylinders. All I needed, beside a basic refresh was JE pistons and Doughtery cams to build my new motor.

I liked the JE pistons, they are lighter and have deep valve pockets. Your heads will likely be milled as part of the rebuild process. This will add a little compression. It's important to keep temps down and fuel mixture not too lean to avoid detonation. A fender mounted cooler would be recommended.

Chris

Thank you for your input.

My builder is recommending boring the case spigots and going with 93 mm pistons and cylinders and 10.3 –1 compression ratio. This will require twin plug, which I‘m told will help with low speed response.
The heads will need to be modified for the twin plug, and the port sizes would be 36 intake and 35 exhaust with GE30 cams. Front mounted cooler will also be needed.

Is the added expense of twin plugging and boring the case spigots worth it in terms of low end performance?

Would a 9.5:1 CR and one plug per cylinder be close to his recommendation?

That high a CR seems to me may stress the motor too much?

Am I off base here?

I‘m looking for a reliable bullet proof motor with good low end torque.

9.5 CR is about the max for single plug.

93mm, 10+ CR and twin plug is a race motor. Will need highest octane gas and a cooler to limit detonation (not an option). NOt the direction I would go, just too far from stock in my opinion.

Chris

Thank you Chris.
I‘m not looking for a race motor rather good low end torque for a fun spirited driving car.
Perhaps the brief I‘m giving them is too tall for my needs.

Do I really need 190/200 ft lbs for this?

... Oliver

Ask anyone who builds these for a living. The motor you want is a 9.5 (below 10) CR with DR 30 cam. It's the engine Porsche should have built. Will pull harder down low than an S and scream past redline unlike an E.

I had an 73 E with this set up and got there incomentally. Only change I would make is it wants to rev beyond the 7300 RPM redline (its full on powerband at redline). If you can lighten the top end to allow more revs before floating the valves I don't know where it will run out of breath. On the track the only cars faster were turbos. Very reliable setup as well.

As part of the process I did Case Savers (7R case), ARP rod bolts, JP pistons (deep valve pockets and lighter), ARP flywheel bolts and the rests of the stock stuff. None of these mods are budget busters but recommended.

Good Luck and enjoy the process

Chris
73 E

Thank you Chris,
I‘m on a steep learning curve with this build. I understand the some of the basics though get lost in the details.
What are the benefits of ARP rod and flywheel bolts?
Is there a lightweight flywheel I should be looking at?
What about the clutch?
Did you mean JE pistons? I haven’t heard of JP pistons for Porsche motors.
Can your set up with with a 7O.4 stroke?

Apologies for the myriad of question. I want to make sure I get this right.

Many thanks... Oliver

Also... what would you estimate the max torque be for the engine you describe with EFI?

Sorry. JE pistons. The ARP bolts are just stronger than stock. My research told me with increased HP and RPM's to go with the stronger bolts in these two locations.

Chris

Thank you all.
I too believe twin plug may be overkill.

What are the board‘s thoughts on:
- PMO EFI w/ Clewett mgt.
- 93mm bore w/ JE p&c‘s
- keep 70.4 stroke
- GE 30 cams
- remain Single Plug

What torque would this motor generate in the 1500-4000/ 5000 rpm range?
Would this be a cost effective build?

Best... Oliver

You're definitely in territory where an outside oil cooler would be needed to handle this rig. Overall BHP as described would likely be in the 230-240bhp range. Great street engine. PMO w/EFI is $$$. If you're doing the build yourself you're in the $10-12k range for parts, but I am probably a bit low.

Great thread for a fellow Noob - thanks to the OP for starting - and thanks to the collective brain trust for responding.

There is some harmonic issue with the flywheel bolts and it is recommended to upgrade those to the ARP. I look at as why not...Cheap insurance. Same goes for the rod bolts....why not.

These magnesium cases get brittle with age and heat cycles. Recommend casesavers all around. Again cheap insurance.

With more HP comes more heat. Heat and higher CR is a bad combination (detonation). Now or down the road an external oil cooler could not hurt.

Chris
73 E

A local builder actually stopped having mag cases dowel pinned at each and every main journal as the lack of 'give' was causing stress cracks in blocks completely trashing the reusability of the block, so now he has them pinned at only 2 or 3 of the main webs. Mind you, this is only for motors starting to push above 240-250.

Hello all,
Back on this again after too many weeks of COVID-19 crisis management.

Planning for Automotive Associates of Canton, CT to start the build soon.

At the moment we are thinking the following:
- stroke as is at 70.4
- bore 92 mm Nickies P&Cs
- Mod S cam (or DC 30?)
- CR 9.5:1
- Existing PMO 40 carbs (keep costs down)
- single plug (keep costs down)
- front fender mount oil cooler
- case savers
- ARP rod and flywheel bolts

The estimate is that this set-up would bring torque to rough 175 with good low/mid range power and roughly 20ö-210 HP. This seems to be close to RS specs (being a bit generous here).

Are their any other watch outs I should be considering to increase either lo/mid torque or reliability/longevity?

Best to all. Stay safe and healthy.... Oliver

Mod S and DC30 are basically the same. I used DC 30s and could not be happier. Anything you can do to lighten the top end will help. Mine was at full power band at 7300 redline. Would have loved to let go further. Will be a great engine! Keep an eye on temps and mixture. Lean is fast but can eat a piston.

Chris
73 E MFI

DC30 are mod solex, this is the most aggressive that can be ground on E cams with out welding. DC40 are modS and require S or higher cams to start with for regrind. DC40 has a little more lift and duration than DC30. I just built a 2.7 with RS pistons and DC40 cams and 40 webers. I could not be happier with cam selection, great midrange with surge at top. Will be taking to Dyno once things open up from CV19.

john

My $0.02. Check the link here for cam choices.
Dougherty Racing Cams Porsche 911, 930 and 964 camshaft profiles
Look at DC35, my choice. A little less duration than the Mod S (DC40), but more lift. Meaning better midrange, you may give up some at 7k rpm, but over all good power. Dougherty Racing Cams Porsche 911, 930 and 964 camshaft profiles

Your specs basically the same as the engine I’m building .. other thing to consider is inlet sizing .. port heads and inlet trumpets to S specs, (maybe a little larger if you’re chasing hp) clean up throttle bodies to match 36 to heads, 38 to inlet trumpets.

Should be good for ~230hp, more tq across time rev range.

Thank you all for the continued advice. This will be a journey. I’m mirroring this thread with EarlyS as not all are on both.

The engine will be pulled from the car in a few weeks time. Having other bits worked being done while she’s sitting idle (wiring, trim refinishing, making sure all the switches and lights work, LEDs all around for better night vision, etc...) as I plan to drive her much more frequently than in the past. Tear down is planned for the summer with the build over winter. Goal is to be finished by next spring. This should provide ample time to get it right. The builder at Auto Associates is great and has done some relatively minor work on Phoenix before.

The engine is unfortunately not the original. The infamous MotorMiester took care that many years ago by “misappropriating” the 7R case without informing me. (There’s an old thread on this here or on Pelican.) Took me a while to find that out. I also believe they were the fundamental cause of the engine fire. The current case is from a ‘72t. After the fire, Farnbacher Loles rebuilt the engine again which I got back just after they closed up shop. This build should purge all past sins.

I want this engine to be “right” (fun spirited drive w/ low end torque) and last a 100k (reliability/ bulletproof/etc..). I’m still working on the build sheet which is continuously evolving based on what I’m learning here and on Pelican from all you fantastic experts. The current build sheet is as below. I would like to make this sheet as detailed, transparent and thought through as possible to ensure the builder and I are on the same page. Any advice on filling in the specifics is VERY much appreciated. Of course all must stay in budget which is good but not unlimited.

Phoenix Engine rebuild:
At the moment the thoughts are:

- 93 P&C‘s nickies w/ J&E’s
- 9.5:1 CR
- 70.4 stroke (existing)
- PMO 40 (existing)
- Mod S cams
- ARP rod bolts
- ARP flywheel bolts
- ARP head studs
- Time-cert threaded inserts
- Case savers
- Keep current exhaust and SSIs
- Front mounted oil cooler

Still open and being discussed are:
- pistons: Mahle vs JE. Why not German made Mahle? Have JE really rectified there past reliability issues?
- Port Heads 36 (S specs)..?
- Port Inlet trumpets 38 (S specs)... ?
- Throttle body to match heads and inlet trumpets... ?
- Narrow the cooling deflectors/tins
- Lightweight Rods to match the lightweight P&Cs? (Pauter / Carrillo?)
- Pressure plate... lightweight?
- Clutch disc...? (I believe there is a Sachs in it now)
- Flywheel... aluminum? lightly shave OEM/ steel?, standard OEM?... goal is to balance free revving with Streetable. I heard there are stalling and chatter issues if it’s too lightweight.
- Engine mounts. Do we need to change these to help manage the increased torque?
- Steel/ stainless steel fuels lines wherever possible (reliability and to prevent leaks... anything to prevent a 2nd fire!)
- Case... Original 7R is gone. Would love to find another. Other obtainable / affordable options?
- Transmission gearing. Would there be a noticeable benefit to changing the transmission gearing to better/ best fit the new engine Dynamics? (It must be worth the cost as the transmission has already been rebuilt and now also has a LSD.)

I’m hoping to complete the build sheet by the end of next month or so to ensure there is plenty of time get parts and line up good machinists. The process so far has been enjoyable and I’m learning a lot from here, Early S, Bruce’s book, etc...

Thank you all for your support! I‘ve asked the builder to send me lots of fotos of the tear down and the build which I will post here. I will try an post a foto of the current motor. I suspect the final build won’t appear much different to the casual observer though what lies beneath will become a different story... a good sleeper.

Many thanks to all. Stay safe and healthy! ... Oliver

Oliver- great to see this thread pop up! I remember your sweet car from many years ago on one of the Palisades runs. Nice to see you still have it and the passion for it to improve it further.

I don’t have much experience with the N/A motors but I would pitch in the following few remarks from years of hanging around cars:
1. Find a way to make the EFI happen. Nothing you can do will be more of an improvement.
2. Don’t bother with a 7k-ish cam... you’ll be there .0001% of the time but have to life with it the other 99.9999% of the time you’re not. Especially with carbs
3. LTWT flywheels and pressure plates have a 50/50 love/hate track record with users. Save your money for the EFI
4. Talk to Len Cummings about custom fuel lines from tank to injectors. Peace of mind
5. Mahle. Why screw around
6. 2 builders I know like ARP for rod bolts but not for head studs. Canyon/Supertec/993s
7. Don’t do everything at once. Transmission mods and oil cooler additions particularly can be shockingly expensive and drag out a project into infinity. Hit it hard, and return it to service and enjoy it. Next winter you can take the next base camp.

I like AA. Ken and Scott helped me with a small deer strike / front half repaint. They specify their own clevite bearings for these engines and I’m sure they’ll use them here.

Maybe we can get back out for another one of these Palisades / Hawk Nest runs. My son is in his final year at West Point and they have a great vantage point of Cold Spring across the Hudson. We’ve visited there many times over the past four years. Beautiful area.
Good luck with your build!

OK, my $0.02.

If you want midrange torque and instant response, without twisting to 6,000 rpm, go with a DC 35 or similar cam. Yea, you may loose some HP at 7,000 rpm, but you won't miss it. It is much nicer to be able to hit the gas at 3000-3500 rpm and have the motor PULL than wait to 4500 rpm for things to happen.

Stick with a stock flywheel, they are already very light. However, use the aluminum PP. That combination is the best of both worlds. Nice response, but manageable.

Get the motor running with the PMOs. Then go to EFI on a later project if you think you need it.

Go with Mahle pistons, IF you can get the correct ones for your build. However the newest generation of JEs will work just fine.

Carrillo or similar rods are overkill, but nice if you have the $$$ to spend.

Do the porting.

If you go to stainless braided fuel hose, make sure you get Aeroquip or quality that is alcohol safe.

Those were some fun runs along the Palisades. Hope to get back into it all next year.

I‘m still seriously considering PMO EFI and the cam goals is the range your indicating. Would be perfect for the Bear Mt pkwy and Schawangunk Mt roads. I may as well complete all the work now as I will not have an opportunity to use the car this year anyway. Scott at AA will assemble over this Winter.

Very much looking forward to it...

I think you and others have convinced me to stick with the OEM flywheel and go with Mahles. Will checkout the Aluminium PP. At the moment I‘m considering a Mod S cam. Do you see a DC 35 delivery more low end power band? I‘m not looking for a screamer and doubt I’ll be at 7k or more very often. I like the Carrillos as I‘m trying to reduce internal weight and get a more free revving engine. I‘m pushing the button on EFI as frankly I don’t want to go back later and do more. Would prefer to get it all done as I have the time and the funds. Hope to do nothing but regular maintenance and enjoy her once I get her back.

Many thanks!

The difference between the DC35 and DC 40 would be the DC40 will move the power band up the RPM scale. If you want a high RPM screamer, the DC40 would be the way to go.

With EFI there may be other options to consider.

You can contact John Dougherty, AKA camgrinder, at Dougherty race Cams and discuss your build with him.

Mod-S cam in 2.7/2.8 doesn’t create too much of a screamer .. improves tq over 2.7RS. Note 2 versions of Mod-S .. DC40 has more lift than WebCam 464/465 .. check this option too as might be a more driveable 2.7 cam.

Phoenix I just picked up my motor yesterday. Its set up with same specs. It was a 2.7. Now a 2.8 with 92mm J&E 9:5.1 pistons, MOD S cams,ported heads 41/35, aluminum PP and flywheel, 7:31 gear ratio on transmission, 46mm PMOs, Rarelyl8 1.5 OD headers and M&K GT3 muffler. Please let us know how your motor runs.http://forums.pelicanparts.com/uploa...1592099364.jpg
http://forums.pelicanparts.com/uploa...1592099364.jpg

Wow, complaining that your ‘73 E ran out of breath at 7300 rpm!

I am trying to get my stock SC, that runs out of breath at 5500 rpm (that’s a real let down, just when it’s starting to sound and pull good), to make it to 7,000 rpm!

As my goal is low-end torque, I won't be spending enough time at 7500+ to have any complaints. I'm getting my fill of high HP / high rev / high speed on the Autobahn while I'm here in Germany ;) This build will be for spirited rides in upstate NY and New England.

With the IMMENSE help from this board and working with Scott @ Auto Assoc. who will build the motor and we've pretty much landed on the following specs...

• 93mm Mahle Pistons (machined to 9.8:1 compression ratio compression from 10.3:1 to avoid twin plugging)
• LN Nickie Cylinders
• Existing 70,4 stroke
• Mod S cam (objective is for strong torque starting at 1,88/2,000 rmp)
• Pauter or Carola rods
• ARP rod bolts
• Port heads to 35mm Exhaust
• Port heads to 36mm Intake
• Oil pump…rebuilt by Glen Ye
• Throttle body to match /again… maximize low end torque)
• PMO EFI system (engine management system of your choice)
• Stainless steel fuel lines from tank to EFI: Aeroquip or other alcohol safe lines (want to do all I can to avoid another fire)
• High pressure fuel pump
• ARP head studs
• Time-cert threaded inserts/ case savers
• Shuffel pin case to reduce flex & movement
• Engine case… current ’72 case or ’73 7R case if locatable
• Aluminum pressure plate
• Stock flywheel
• ARP flywheel bolts
• Engine mounts… using club sport mounts


My only concern at this point is if it's worth getting the 93mm Mahle's and shaving them down to 9.8:1 CR or going with JE's and no shaving. (Trying to avoid the added expenses of twin plugging).

What does the board think?

Once I get past this, the difficult part starts... waiting, and waiting and waiting while resisting the urge to continue tweaking as this build won't be completed until Spring of next year. :(:(

Stay safe and healthy... Oliver

Sounds like a perfect spec. The JE's have deep valve pockets which help and give a margin of error (no experience with the aftermarket Mahle's) With cam change you may want an AFR meter to dial in the mixture. High CR + lean mixture= detonation. Plus it looks cool. had mine replace the cigarette lighter.

Chris
73 E

FWIW, my JEs ended up around 9.8 to 1 CR, from an advertised 9.5. Combustion chambers on my car were 89cc. So that may be the way to go for you as well.