Going from 3.2 to 3.4, some questions.
 

I am planning of doing an engine rebuild in the very near future.
The engine is a ROW 3.2 from 1986, 915 tranny.

I would like to go to a 3.4 with S-cams. I would also like to keep the Motronic engine management (but maybe with custom chip).

In Wayne's rebuild book the 3.4 upgrade is one of his top engine picks.
And it says it is a bolt on solution.
So if I buy a set of cylinders and pistons (98mm Mahle), do I just swap them with the ones I will be removing????
Or are there special things to pay attention to???
Things I have to change, adapt, modify??

Any guesstimates on how much hp I will gain compared to the stock setup?

If more info is needed, let me know. ;)

Thanks for the feedback guys!

The P&C's are a direct replacement for the 95's. I am not sure about using an S cam on a Motronic engine. Talk with John at Dougherty Racing Cams about what you want from your engine. The cam will determine the personality of how it drives. Do you want more torque with less high end or do you want the power to come on at higher rpm's? John can guide you on this. Another question is what compression ratio are you wanting to go with? That will determine if you need to twin plug the engine. Many variables based upon what you want from the rebuild. You will need a chip to take advantage of the 3.4 upgrade. I did the SteveW custom chip as this is needed for anything other than a 3.2.

If you are looking at Mahle P&C's I would consider using the Nickies from LN Engineering Nickies The Original and Genuine CNC Billet Aluminum NSC-Plated Cylinders and going to the slip fit 3.5 P&C's. From a price perspective I don't think there is much difference in price and JMHO a better choice. If I had the budget it is what would be in my car. A true 3.5 upgrade as the 3.4 is not really 3.4 only close.

On my rebuild I used QSC/JE 3.4 P&C's, DC-22 cams, performance springs, ARP rod bolts, I was looking for more performance and am happy with the outcome. Using a Dynolicious app on an ITouch I recorded 258 hp. I had SteveW set the redline for 7200 rpm since I was hitting redline at 6800 all the time. Now it feels natural to shift by 6900 to 7000 and there is very good power until that point. Dyno next spring to actually see where the most power is being made at.

Biggest thing I learned is to figure out what you want from the engine, where do you want the power at. Talk to people like John@DR Camshafts and SteveW about it. They will be able to answer your questions about what works the best for what you want.

There is a thread here at PP which I haven't been able to find that shows the build of a 3.5 engine and all that was done. Will find and post later.

I have been very satisfied with the 3.4 upgrade and would recommend it anytime. Just know what you want from it, use the knowledge from the many people (both pros and and the rest of us) to what works and what fits in the budget to achieve it.

A shot of 3.4 P&C's installed
http://forums.pelicanparts.com/uploa...1258236494.jpg

Let's see... 3.4/3.2 = 1.0625

so you get about 6% more hp for a LOT more $$ (unless your P & C's are so worn they need to be ash canned anyway.

Porsche rated the engine at 217 and I am pushing 260. Definitely more than 6%. HP on Porsche is not cheap. The driving experience is considerably different than before the rebuild.

CC= cubic cash on Porsche

I'm happy with my 3.4 - and I have a new engine. With high lift cams I'd recommend you replace all the rocker arms.

I'm getting a little more then 6%

This is part of what concerns me about building a 3.4 vs just dropping a 3.6 in my '86. I've had my car dyno'd on a very conservative Dyno Dynamics machine (known locally as the heartbreaker because it debunks lot of high hp claims made by some parts purveyors) and it put down 202 whp. If you use the 15% assumption, that's 230 at the crank. Stock 194K mile 3.2 with George Narbel headers, Ben's 911R M&K muffler, and a 15 yr old Autothority chip. Going from my KS pistons to JE 98mm 9.5cr, if I apply the 6.25% displacement I'd get 245hp, maybe 250 if you consider a slight increase in CR. Add a mild 964 grind cam, extrude hone the intakes, and a fresh rebuild, perhaps 255-260. 25-30 horse for $7500 in parts and machining costs alone seems to be darn expensive horses. I can take an off the shelf stock 964 3.6, put my headers and muffler on, retune the software and get 265-275 hp, with lots more torque.

If I factor in selling my current 3.2, I can do the conversion for less $$ than building a 3.4. More power, more torque, potentially more reliable, twin plug iginition, less $$. Hmmm. What's the purpose of the 3.4 single plug conversion? Not trying to downplay the 3.4 since it's still under consideration. But for a track car that sees maybe 500 miles a year on the street, help convince me why a 3.4 is a better value than dropping in a 3.6. Even if they cost the same.

How about a gear ratio change for a little more get up and go? I assume it would be somewhat cheaper, simpler and perhaps as effective. Anyone have any experience with this for comparison? I'm assuming most people are looking for increased acceleration rather than top end.

a lot of the discussion about buying a 3.6 and it being lots cheaper than rebuilding a motor into 3.4 circles around a pretty large assumption: that the 3.6 you bought is in great shape. Of course its a testament to Porsche reliability that many of us have installed used motors, chipped, headered, and raced them for long periods of time. But you have to assume the risk of that gamble too. You could just end up buying something that was neglected or has a huge amount of miles. How old is the newest 3.6 at this point? If the owner had covered 3k miles per year, you could be buying a worn out motor.
I agree that its always much easier to buy , plug and play. And posters are also correct that the larger displacement gives you more hp right out of the box. Just be heads up on what you are purchasing when you consider buying a used engine compared to rebuilding

Another option to consider would be 100s with JE pistons from LN Engineering. I run them in my TRE-built ROW SC (now a short-stroke 3.3) with just about everything else stock and it makes a mountain of torque in the mid-range and keeps pulling until the tach needle is pegged.

http://www.lnengineering.com/911.html

When (if) I need a top end rebuild of my 3,2 I was considering this modification. Modifying for power and rebuilding due to wear are two different scenarios. Do the 3,4 L conversions pass smog in CA with the modest increase in compression and still single plug? Is this even an issue with a small displacement increase?

Although putting a 3,6 in is perhaps cheaper, it would be more fun for me to build up a 3,4.

Technically speaking, any modification other than stock, has to be California Air Resources Board approved. And there are precious few porsche performance items that pass those regs.
BUT, can they see inside your engine for the mods? Nope, but you are responsible to have the car tuned correctly to pass emissions, so a larger displacement motor can have the chip tuning that will meet the tailpipe standards and yield more hp and torque while meeting your moral responsibility

Does the throttle body or flapper box arm need to be modified?

In terms of morals...

mor·al (môrl, mr-)
adj.
1. Of or concerned with the judgment of the goodness or badness of human action and character: moral scrutiny; a moral quandary.
2. Teaching or exhibiting goodness or correctness of character and behavior: a moral lesson.
3. Conforming to standards of what is right or just in behavior; virtuous: a moral life.
4. Arising from conscience or the sense of right and wrong: a moral obligation.
5. Having psychological rather than physical or tangible effects: a moral victory; moral support.
6. Based on strong likelihood or firm conviction, rather than on the actual evidence: a moral certainty.

I might argue it is my moral obligation to resist such emissions legislation that are not effective and detrimental...but that's another discussion.

Hey TRE-
You're absolutely correct on several fronts:

The 3.6 could also need to be freshened up. Always a risk. But before installation I could pull the heads, install ARP rod bolts, 993 head studs and be reasonable certain that the engine would hold together for a few seasons.

I don't need to worry about emissions in IL on my '86 especially for mostly track.

With proper chip tuning, the 3.6 will make good torque.

My goal was to consider alternatives. My 3.2 needs a top end at least. At 194,000 miles and with completely unknown history, it's time. When I had the headers off last winter, oil dripped from cylinders 1 and 6 past the guides and seals. And it still have one piece oil return tubes on it. But I still have between 4 and 6% leakdown and the engine doesn't use any noticable oil in an entire weekend at the track. But every morning it smokes enough to kill all bugs within 50 yards. I've run this engine for two years (probably 40 days) on the track and have done nothing but a healthy diet of Brad Penn every other event. I don't want to tempt fate and have an exhaust stem break because of the slop in the guide.

I like the idea of a 3.4 because of the shorter stroke and freer revving nature of the engine. But the 3.6 just makes so much more torque and with twin plug can get away with the higher compression on 93 or 94 octane pump fuel. There are turns at some tracks I'd like to take at 4500-5000 in 4th rather than 6000+ in 3rd because I just run out of revs too soon at track out. So it's a catch 22- which way to go. The 3.4 would be fresh, and happy at up to 7200, but the 3.6 can be driven using lower rpms and taking advantage of a healtier torque curve.

ZAMIRZ- the 100's would require more work (ie $$) to work with Motronic. Charles Navarro is local to me and we've shared thoughts. The good news is that he can bore my Alusil barrels to run the 98 J&E's. Saves a boat load. If I went with Nickies, the parts and machine shop bill would quickly reach $10K and for that I can pull a 3.6 apart to freshen and install for less $$. I'm one of the 10.2% who got "retired" by this crappy economy so I've got to watch the 911 $$$ carefully for now. I need to rebuild the 3.2 but think it would be a shame to just rebuild stock just to save a few dollars.

Thanks for all the thoughts everyone.

That's the beauty of our cars, we have choices.

When you start getting power out of a 3.4 you end up with a motor a fair bit different than a 3.6, at least I did.

Going bigger cams, ITB's and twin plug (10.5cr) I got a motor that made peak HP at 7000 and was flat from there to 7400. It has an amazingly flat torque curve as well starting at 3200. Not the sort of torque one may get from a 3.6, but still plenty. With the ITB's you get major league throttle response.

I built the 3.4 more for its character (like a big early "S" motor) than outright power, even though it makes lots of HP. I had rebuilt a 3.6 longblock and sold it to build the 3.4.....

I think if you are staying with the 3.2 intake, the BIG reason to go 3.4 would be if you needed a set of P/C anyways. Then it is the same money. I would go a little more cam than a 964 (which I really like in a 3.0) and would maybe look at a DC20 or even a bit more.

If you have SSI's now (already a bit small on a 3.2) you would need to consider moving up to 1 5/8 headers (or maybe 1.75 if you ditch the intake and go with a big cam and more compression).....

Cheers

I expect that you have done other things to the motor, or do not have accurate hp measurement (say, a road dyno - which is a notoriously inaccurate way to measure hp). Also P AG rates hp very conservatively, so your motor likely p[ut out more hp than that originally.

Geronimo,

What are your goals for the car and do you have to deal with certification or smog concerns in Belgium?

A stock long block 3.2 can make up to 270hp. Even with the stock intake in place.

For me, a well tuned 3.2 Carrera with a good suspension set up, proper wheels, and some lightening is a great car. Anything much past that is a lot of dollars chasing marginal improvements.

Having said that, it would be cool to basically build a 3.2 911S. Lighten the car to 2300 lbs w fiber bumpers + lids, run a cam aggressive enough to make it act like a 2.2S, new rods that can turn to 7300rpm, and carbs. Add close ratio gears and it would be a major blast to own and drive.

Back to reality, 3.2 Carrera's respond very well to exhaust and chip changes. If you can get to a 1 3/4's equal length header system w a proper sport muffler, aftermarket rod bolts, and a chip tuned to use your euro compression / fuel, and turn to 7k rpm, you will have a great motor that can make up to around 260hp.

Thus, if your euro P&C's are still in spec as they should be if you are under 200k, keep the $3500 for other goodies like suspension, light weight interior, track fees, and leave the contents of the front trunk at home to save another 50 lbs.

With 260hp pushing 2500 lbs you will have a wonderful car.

Adding 5% more power over a well tuned euro 3.2 by making it a 3.4 would just be and extra spoon full of gravy. ;)

Biggest thing is to decide what is important to you from the engine. A 3.6 may be a better way to go. When I started I expected to put new studs in and do a valve job. Not really anything else. Ended up doing a full rebuild, new P&C's, high lift cam, many things refreshed and set up to be able to handle rpm's well over 7000. I learned a lot and my engine is what I imagined it would be, just took a little longer to get there than I planned. (rookie mistake).
JeremyD's engine has 20 more hp than mine as I believe he (Jeremy, correct me if I am wrong) flowed the intake and opened up the throttle body plus his exhaust allows better flow as well. The exhaust mods are on my list of things to do.
I spent around $6500 for my rebuild. The budget for me was a limiting factor but did all the right things if I want to more performance later on.
No budget I would have done the 3.5 Nikies/JE since they would handle high lift cams, not so sure the Mahle's will.

The car drives much different as corners that were taken in high RPM are now in the next higher gear in the 4500-5000 rpm range. I am learning to use the new power that I didn't have before.:D

Here is the thread I was looking for on Ralph's Carrera3.5l rebuild. I think there was even more power to be had if you aren't worrying about emissions. Pretty conservative of what you could get from this engine. Here are the links.
http://forums.pelicanparts.com/porsche-911-technical-forum/186906-3-2-3-5-part-ii.html

Dyno results, remember this is with 91 octane pump gas.

http://forums.pelicanparts.com/porsche-911-technical-forum/198971-3-2l-3-5l-dyno-results.html

Dave - how many 3.6's have you opened up that haven't needed valve guides? When I asked my local wrench that question - out of 100's he could only name a handful. How many have you opened up that haven't shown layshaft bearing wear? - That number was also pretty small. I sleep better at night knowing I have pretty close to zero oil usage, I have new bearings and rockers. I have six new valves and new guides. You roll the dice - sometimes you come out ahead, some times not so much.

from my dyno

BTW - just came back from a day at sebring and my car ran like a friggin top - I passed a few full out D and E full race cars - even with my extra weight the performance is good. Yes you have to drive in the upper rpm's - but what Porsche can you drive (or want to drive at 3,000 rpms's anyway?)

Stole the following well tuned 3.2 stock block dyno chart from 911Chips.com for referance of what can be done:

"The following is from a custom built '84 3.2 by TRE Motorsports on a Dynojet 248c. The combination of the engine build, TRE's race exhaust system, along our chip programmed for the engine package produces 234.7 rwhp at 6500 rpm. Factoring a 15% drivetrain loss, crank hp is 276 hp, a 69 hp improvement over the stock 207 hp motor. Not bad considering the entire intake and fuel injection system remains completely stock and unmodified due to POC class restrictions. Examining the torque curve, not only does it build smoothly to 5000 rpm, but doesn't stop rising until it it peaks out at 6200 rpm! Area under the curve from 4800-7400 rpm is what allows this car to fly. This car outruns track prepped Vipers and E46 M3s at the track as if they were driving Miss Daisy. (Motec? We don't need no stinkin' Motec!"

http://forums.pelicanparts.com/uploa...1258343607.gif

Enjoy.

As many have stated, buying a 3.6 is a crap shoot of sorts.... likely it needs the same sort of work your current 3.2 needs......

Cheers

Jeff's 3.4 build is another amazing one. Starts here http://forums.pelicanparts.com/911-engine-rebuilding-forum/267221-3-4-has-begun-part-1-a.html and continues http://forums.pelicanparts.com/911-engine-rebuilding-forum/361269-3-4-build-part-2-a.html
Ends up with 337 at the engine 997s territory:eek: and those 997 are no where near 2200lbs:cool:

Sorry Jeff couldn't help posting the links

Wow,
Guys, thanks for the many answers!!
You got me thinking again (pffff....:D)

What I am aiming for is a streetable engine since I will not be doing a lot of trackwork. (only on occasion)
Since I am doing the rebuild anyway, I want to squeeze some extra ponies out of it, who wouldn't.... I am hoping to find 50 HP over stock (280 instead of stock 231), but I won't be disappointed with 40hp over stock.
Modifications that require twinplugging will make it a bit expensive I guess, because of the added cost of twinplugging...
A 3.6 transplant is out of the question. 3.6's donor engines are rare here, so good ones will be even harder to find.

I thought I was pretty sure that I wanted to go to 3.4, but then I shouldn't have asked here, I suppose. (I do appreciate all your opinions though, so thanks already)

911st, if it is feasible to gain 40-50 hp without going the 3.4 route then I would certainly consider this as well. (That 270 with stock intake sounds very interesting!)

We don't have smog regulations here like in Cali, they are not nearly as strict, so I'm not worried about that.
Engine has 120000 miles on it. Tranny is going away to, so different gear ratios might be an option as wel!

Thanks guys, appreciate it!
More info is still welcome of course!

:eek::eek:

Wow, that is one awesome build!! (a bit out of my league, but very cool!)

Little bump to get some more info...


(sorry)

my engine specs:

3.4 mahle 9.8 to one jugs
~ 1MM taken out of pistons for valve pockets
Single plug
Magnecor Wires
Extrude hone intake
993ss cams (Dougherty Racing Cams)
arp rod bolts
Supertech Head Studs
Enlarged throttle body
competition springs and retainers (EBS)
993 Flipped Flange Heat Exchangers
MK 993 Bischof flange muffler
Steve Wong custom chip to pull it all together

My build thread here for ref: http://forums.pelicanparts.com/porsche-911-technical-forum/425027-3-2-3-4-top-end-rebuild.html

Dyno'd again recently (after 5k miles) on a different dyno at 272/243 bhp/ftlbs - so 270 ish give or take

Thanks Jeremy.

I assume you bought a set of cylinders and pistons, did you need to take 1mm out of the pistons, or did you do it just to be sure to have decent valve clearance?
How come you have a CR of 9.8 to 1? Did you change the crank as well?
I am looking at this set from FVD (mahle p/c kit 3,2 -> 3,4 (pin 23mm), FVD Online Shop )
This set seems to keep the same CR as stock (10.3 to 1), how will that be different compared to a lower CR of 9.8 to 1??
Will I need to twin plug???
Why did you opt for the 993ss cams?

Thanks!




Shirish, thanks a lot for the link to your thread!!
Some very interesting stuff there!!
:)

I'll try and answer in order

With the 993 SS cams - I had to take less than a mm out of the top of the pistons for valve overlap clearance. Crank is original 3.2 crank

With the 3.4's (98mm) one of the Mahle options was 9.8 to one.

Twin Plug? I'm not sure on the quality of Gas in Belgium - here in the US we have 93 octane. I have not had an issue with detotantion - even at Sebring running hard with 115 degree on track temps.

I opted for the 993 SS cams because of their relatively flat torque curve - and because at the time they were considered to be about the maximum cam you could have and still keep motronic and still be able to keep an idle. This was about four years ago. I'm not aware if there are any better choices out there now - I'd contact Dogherty Racing Cams.

I was telling Ed in a previous email that my car is about on the edge of idle with the 993 SS cams and motronic. It's a lopey idle - every once in awhile it will actually stall if I have the AC on {i know, I know, the travesty} Actually it's much better now with a new AC compressor - the old one I had really sucked some HP from the engine when it was turned on.

Really though, I have a great motor. I have a few local Pelicans that I have given rides or let drive that covet my engine - I won't leave them alone with my car and a garage full of tools, that's for sure :)http://forums.pelicanparts.com/uploa...1258480236.jpg

After taking of 1mm of the pistons, how much valve clearance do you have?
Did you take of 1mm locally or over the entire surface of the piston????

Locally - just a 1/2 moon. Sorry I don't have a picture.

and my memory is not as good as it was - and this was four years ago (almost 5)

But I believe we needed 2mm valve to piston clearance. We were at about 1/2 that or 1mm. We relieved a valve pocket - localized half moon - ~ .8mm. That gave us 1.8 or so clearance.

Thanks so far, I am like a sponge absorbing all this info. It's great!
Is there a reason that you chose the 9.8 to 1 CR??
We have 98oct gas here readily available (I believe it is the same as your 93).
I'm not sure what the difference in engine characteristics will be between 9.8 and 10.3 but I think I would like to go with a CR of 10.3 to 1 since that is the same CR as stock. ( as long as I can avoid twinplugging, too costly)
Unless someone can explain/conince me why the lower CR would be better.

Thanks thanks thanks again!

It was recommended by my wrench who builds plenty of 3.4 engines for HSR. With the bigger combustion chambers (98mm vs 96mm) you start running into the limit of flame propagation.

He recommended that I keep it under 10 to one with regular gas (vs 100 octane race gas) and I'd have a safety margin in place. Over 10 - 1 and all it takes is excessive heat and/or a bad tank of gas and you could have some major heart ache.

Knowing that the stock CR of a ROW 3.2 engine is 10.3 to 1, does the problem of flame propagation become more prominent when the displacement increases? (3.2 to 3.4)

If it is, then twin plugging would be the right thing to do, I reckon....

yes, as the size of the combustion chamber increases - the effective safe limits for single plug decrease

Is there a difference in power, engine characteristics between the 10.3/1 and 9.8/1 CR????

Engine Horsepower (peak) is 287
# Old Compression Ratio is 9.8
# New Compression Ratio is 10.5
Computation Results:
# Computed New Engine HP is 292, a 2 percent change

In reality - building an engine is like baking a cake. Not only do you need the right ingredients, you need them in the right proportions. The net of a compression ratio - all things being the same may be only 2%.

But - if you twin plug, go to 11.5 to one, extrude hone, bigger cams, throttle body or ITB's you can have an even bigger impact on the net change.

If you read Wayne's engine book - you will see a few engines that he recommends - because they are good combinations.

:)

I have his book on my lap right now!
He recommends S-cams and 46mm Webers.
I'm not sure if I'll be using S-cams, I want a streetable, powerful but torqy engine, not a high revving race engine with only power on top.
Carbs are out of the question, motronic stays, with custom chip

Jeremy, thanks for your time and info!! I'm turning in, early day tomorrow!
We'll talk later, thanks!

Be careful with the 10.3 CR spec. Most original motors actually measure out at a much lower CR value. Plenty of wisdom in staying at a TRUE 9.5CR or less on a single plug 3.4.

Jeremy's and Michael's motors would be good and strong and likely have more bottom end grunt (maybe a by a fair bit?) than my higher strung motor does. That makes them excellent dual use motors, great on the street and great on the track.

Cheers