stock 3.2 Carerra engine out

[sus911]

Looks like the clutch plate is at the end so the motor is coming out.

I already have a set of 993 HE's (flanges rotated by Ben M&K) and a new M&K 2/1 muffler to go in on this engine drop and I've just spent a few hours reading about cams for sock 3.2 motors.

My initial thoughts were that a 964 cam was a nice improvement on the stock cams but further reading indicates that more aggressive cams will see bigger performance improvements such as Super cup or 20/21 grinds.

My situation is that I will retain everything else stock on this motor ie. Motronic, single plug heads and bottom end for now. I am aware of the inherent restrictions of these motors due to the weak bottom end for revving and Motronic FI.

I propose to install as aggressive a cam as possible along with the new exhaust system to upgrade the engine performance as much as possible.

Obviously I will be rev restricted to 6250 so I assume I won't need to look at rockers or springs, or will I?

Also with regard to the cam profile in considering your opinion, remember this is an ROW car with 10.3:1 compression which needs to be considered for valve clearance.

In a nutshell, i am hoping to do this enhancement using the 993 HE's, a new cam profile, and Steve Wong to bring it all together.

THE CAR RUNS GREAT ON 98 OCTANE FUEL READILY AVAILABLE HERE.

Thanks and in anticipation of your advice,

Phil

[Eagledriver]

Phil,

I see nothing wrong with your plan. I'll let others advise you on the cam choice but regardless you'll have to check the clearances and be ready to machine your pistons for clearance. I would add aftermarket Rod bolts to your rebuild and replace the lower headstuds. Both can be done without spliting the case. Valve springs should be fine with the stock RPM limit.

-Andy

[sus911]

Thanks Andy.
I'm hoping someone will have had direct experience with factory 10.3:1 compression motors and camshaft profile compatability with stock pistons.
cheers,
Phil

[criv911]

I too am considering exactly the same rebuild [valve guide issues] I'm looking to replace my U.S. p/c's with euro spec 10.3 to 1 I have the 993 he's but I have to deal with 93 octane so I also have twin plug distributers ready. So I'm listening.

[JeremyD]

Here's my opinion -

If you go with JE pistons - they have a big relief cut for valves - no issues with a more agressive cam.

If you stay with Mahle - then you will probably need to gain some valve relief with anything over the 964 cam.

On my 9.8 to 1 3.4l mahle and 993 ss cams - I had to cut about a 3/4mm relief for the valves.

My advice would be to definitely do the rod bolts - definitely do the competition springs and retainers if you do any performance driving.

Definitely change out the lower studs (I would do both for piece of mind)

[anh911]

Phil,
Max revs are a function of cam and engine build profile. The cam profile and timing should be matched to where you want the power. (obviously within the engineering design spec of the motor) A good cam supplier will help out with selection based on your needs. With any and all cam changes P2V clearance must be checked during the build.
The motronic is more than capable of handling these cams. The problem is that the 3.2 has an air flow meter not hot wire. Big cams cause a lot of flow peaks at low and idle rpms. This can mess with the AFM, idle stabiliser and causes the flap to bounce, esp at idle so the system won't stabilise. Careful consideration and tuning can take care of it but if too radical a cam is used then you are will have to get creative with the intake system. the WC 20/21 grind is made specifically for the 3.2 and Dema (Elgin cams) makes several hot grinds for the 3.2 for up to about 12.5 CR race motors and will happily talk to you about all of them.

[sus911]

Thanks guys.

I've just had a baseline chassis dyno done and received a disappointing result of 155 bhp. Given the usual 1/3 drivetrain loss, the result suggests a rough crank hp of around 200.

Further investigation revealed that this test was done using "Real Time or Something” versus “Shoot Out” mode. Apparently most people use "Shoot Out” mode which averages out variables? I am advised that “Shoot Out” mode reads about 10% more than the other mode.

The following is my calculation:
155 / 0.9(allowing for the 10% lower reading) = 172. Divide by 3 then multiply by 4 as allowance for drivetrain loss = 229 is, close enough to the 231 stated hp.

At the track on Saturday, the car seemed to perform really well as it always has in the 20 years I've owned it - always strong and smooth. I was arm wrestling all day with a slightly modified '78 930 with a bigger turbo and RUF 5 speed box. He was understandably pulling away on the main straight but not shaming me by any means. I believe that the engine is probably putting out close to it's specified power.

My desire is to raise the hp to a reasonable maximum that the 915 transaxle will happily cope with, say around 280-290 crank hp. I would propose to do this with top end work only- cams, exhaust, motronic chipping, head work, valves springs etc. Power from 3,500 rpm upwards to a max. red line of 7,000 is desired.

I would be interested to know if this is possible without opening the case and getting stuck into the bottom end as well ie crank, rods, bolts etc. Obviously it would remain a 3.2.

thanks,

Phil

[JeremyD]

Originally posted by sus911

My desire is to raise the hp to a reasonable maximum that the 915 transaxle will happily cope with, say around 280-290 crank hp. I would propose to do this with top end work only- cams, exhaust, motronic chipping, head work, valves springs etc. Power from 3,500 rpm upwards to a max. red line of 7,000 is desired.

I would be interested to know if this is possible without opening the case and getting stuck into the bottom end as well ie crank, rods, bolts etc. Obviously it would remain a 3.2.

thanks,

Phil

Well, I have ...

3.4 mahle 9.8 to one jugs
extrude hone intake
993ss cams (Dougherty Racing Cams)
arp rod bolts
Supertech Head Studs
enlarged throttle body
competition springs and retainers (EBS)
LN 1 3/4" SS Headers
Dansk Dual in - Single out

For comparison my 3.4, in blue, compared to Ralph's 3.5, in red, compared to a bone stock 88 3.2 with a euro premuffler and stock chip, in green

[sus911]

Thanks for that interesting comparison Jeremy.
Just to clarify, where those dynos done on a chassis or engine dyno?
I have attached mine FYI.
I understand completely the suggestion about head studs and rod bolts to strengthen the engine for higher rpm. I'm not sure how much more work and expense this involves once the heads are off not having done it before.
I guess my main curiosity is how much to expect with just cams (provided I get the correct P-V clearances), chip, headwork and exhaust with an otherwise stock Euro 3.2.
If your dyno charts are engine tests, I think I know the answer. If they're chassis tests, it looks like I have a good chance to achieve my goal.
It looks like they are engine dyno runs by looking at the stock 3.2 curve (which I presume is a US 3.2) peaking at around 193 hp.
Awaiting your clarification on this.
regards,
Phil

[KTL]

I think your goals of that kind of horsepower with 3.2L from the heads out is rather unrealistic. Unless you're willing to add larger pistons and cylinders or a turbocharger, those numbers are out of your reach. The guys with more displacement than you're at, plus all the goodies above the pistons are just reaching those power levels.

Like anh911 said, the cams that work with stock pistons are not too aggressive so that will be another limiting factor. I'm installing DC20 "Super C2" cams in my 3.2 right now and i've not been able to set the spec for lift TDC overlap within the desired range- had to dial it back to 2.1mm vs. the 2.2-2.4mm range. Problem being piston-to-valve clearance. So you'll want to look into more accommodating pistons if you want to make the best of your induction system changes.

[Eagledriver]

I agree that your goal is unrealistic for a 3.2 especially with the stock airflow meter. That kind of power will require 98mm cylinders, cams exhaust, different airflow meter (hot wire). I don't think you need to do any headwork for the RPM range you are looking at. If you are going to rev past the stock RPM then you need to replace the rod bolts. This can be done without splitting the case. I see no reason not to split the case however as you are only talking 500 dollars or so more for a gasket kit and bearings. The rest of your mods will cost a bundle.

-Andy

[gtc]

Does anyone know how much power is to be gained by cam swaps?

I'm in a similar situation as Phil:
I'm planning the rebuild of my 3.2 and contemplating different bolt-on, motronic-compatible power adders, but ~$4,500+ for 98mm P&Cs adds too much to my budget for just a 6.25% power increase.

Cams (sounds like 964 or 20/21) and/or head flow work and/or intake and exhaust sound like more cost-effective alternatives to me.

[KTL]

Originally posted by gtc
Does anyone know how much power is to be gained by cam swaps?

Cams (sounds like 964 or 20/21) and/or head flow work and/or intake and exhaust sound like more cost-effective alternatives to me.

Not much if you're sticking with original pistons, which limit cam selection (as does the original induction system). Cams shift the power band around but don't gain you gobs of horsepower. I just did DC20 cams (Dougherty Racing Super C2, comparable to the Webcam 20/21) and you'll want to be sure you check your P-V clearance if you do these cams, as they're about as agressive as you can get without changing pistons. The link below is my experiences. You'll see that I was not able to set my cams to the design lift measurement due to lack of P-V clearance.

Cam timing with DC20's

They feel more torquey than the stock cams (I had my stock ones reground to DC20 profile) but i've got nothing to substantiate that other than my butt. Plus my car was dormant for 7 months so of course it's going to feel fast today!

A big downside to 3.2 engines is their throttle response. A new chip, LW clutch & or flywheel and a flow meter replacement is where you'll gain some power and rev-ability on a 3.2 with stock induction. I have the cams, a LW clutch housing (25% weight loss) and a chip to match the two and it seems to be a noticeable improvement. But bang for the buck is not great at about $1K for the changes. I think the bottleneck is still the flowmeter but those don't come cheap so i'll have to do without unless a used one pops up somewhere.

I'm still babying the car while I break it in after reground cams, new springs, new keepers, new valves, new guides, new rocker shafts, reconditioned rocker arms,. So i'll have a better idea how well it goes when I do a track event this coming Friday.

As you can see from other peoples rebuild/upgrade experiences, you have to do a complete system to see substantial gains. A part here and a part there doesn't net much gain. Porsche designed a pretty solid package from the start.

[JeremyD]

I can't tell you how many engine builders I talked to - and I'm not sure who gave me the cake analogy - but it went something along the lines of building an engine is like baking a cake. you need to add ingredients in proportion. Just adding one doesn't make a good tasting endeavor.

[JeremyD]

Oh - and it was a chassis dyno - adjusted for engine specs

[sus911]

Thanks Jeremy.
When you say "chassis dyno - adjusted for engine specs" does this mean the dyno figure is actually an estimated crank HP figure or a true rear wheel measured HP and staeted as measuring that?
BTW, I adjusted my throttle linkage (I had never checked it) and dynoed again and showed nearly 15HP over last runs.

[JeremyD]

I am sorry- I am talking out my a$$ again. The 244.37 was adjusted for ambient temperature - but was the actual rear wheel hp figure.

[gtc]

Originally posted by JeremyD
I can't tell you how many engine builders I talked to - and I'm not sure who gave me the cake analogy - but it went something along the lines of building an engine is like baking a cake. you need to add ingredients in proportion. Just adding one doesn't make a good tasting endeavor.

I disagree. I want a small cake with LOTS of frosting.

What I mean is, if there weren't a valve clearance issue, what would be wrong with using the stock pistons and cylinders?

The rule of thumb I've heard from hot rod engine builders is to spend your money on heads, cams, intake/carburation, and bottom end, in that order (I'm not saying you should skimp on something like studs or rod bolts though). The reasoning behind this being that you may end up with a smaller engine, but it will breath very well.

[JeremyD]

I think Porsche did pretty well with the heads on the 3.2 - a few people I talked to said they will support 300hp without really any modification. Cams yes, incremental increases can be gained from extrude hone (really it just evens out airflow) increase the TB size and headers.

Porsche really doesn't leave a whole lot on the table...

The problem with the stock pistons - either US or Euro is the piston to valve clearance. Kevin discovered this - I even had it to a degree with my 98mm 9.8 to 1 p & c's. You can bypass this issue by either going to the JE pistons with the bigger valve pockets (and having a different expansion rate between the pistons and cylinders) or cutting a little relief in the stock pistons. I took less than a mm out of mine -

I do like how my engine came out. It acts like a little bigger than stock from 1000-4000 rpms. After 4000 it pulls like a train...

Look up user 911-32 - he has the euro 3.2 with 993 ss cams.

Link to Dyno run

[gtc]

Originally posted by JeremyD
... You can bypass this issue by ... cutting a little relief in the stock pistons. I took less than a mm out of mine -

That's what I was hoping to hear. Do you know how much material is available to remove? It sounds like the worst case scenario would mean removing 2mm from the pockets.

Edit: Oh, and your car sounds sweet by the way.