1984 3.2 Euro engine - Crank swap?

[JonoUK]

Hello everyone
I’m in the UK and new to the forum having just started to clean then dismantle
my 3.2 European engine.
It is to go into a Beck GTS so very much on show
and I want to make an engine just a bit more exciting
than standard. I’m happy to spend a sensible amount of money
but not a race engine!
Can I please ask for recommendations on
what changes to make.
I have not done this before so I would appreciate
some guidance from those who have.
In summary
1. I want the engine to manage up to about 7300rpm
with a very light flywheel and to feel very ‘sharp’.

(Power is not a big thing for me - about 250 is fine)
2. I like a ‘cammy’ Engine - the Beck is very light.
3. I will use new PMO carbs - injector cutouts to be filled in.
4. I expect to have to use a 3.0 crank - am I right?
5. This route means that the rods need changing - recommendations
please.
6. Should I change the cams ? - which ones are recommended?
7. If cams changed are there clearance issues?
8. There are no emission issues to consider.
9. Are there any obvious

I hope this gives a clear picture of the sort of engine I’m after
but happy to reconsider if you think I’m on the wrong track.

I’d love to hear from you and it’s great to be in your forum

[Trackrash]

I could be wrong, but I don't see why you can't spin a Carrera crank to 7300 rpm. The problem is what crank and case mods, oil pump, rods, pistons and valve train will you need.

I'm sure the experts here will chime in with their experience.

[JonoUK]

Thanks Gordon
That’s an interesting thought.
Maybe the crank is OK and it’s about reducing the weight (or increasing strength)
in piston/ rod / valves?
Jono

[faapgar]

A nice combo would be to use a 3.0 SC crank and a set of earlier Pankl Titanium Rods.Used come up for sale and not that costly.Some CP Pistons and an early 911S style cam.With your PMO carbs a nice 250 hp. with some nice 1 5/8 headers.Ciao Fred

[Jeff Alton]

Lower your RPM goals a bit (200rpm), keep the 74.4 crank and 3.2 (95mm) or 3.4 (98mm) displacement. 10.5:1 CR, Use a mod S cam (of which there are many varieties. PMO carbs and get 275+ HP easily.

Plus as a 3.4 you will enjoy a fair bit more torque over the 3.0.

[Walt Fricke]

Why do you expect to have to use a 3.0 crank? The issue with the longer crank of the 3.2 is the fact that Porsche reduced the rod bolt diameter by 1mm, because the crank rod journal was increased (?), which meant that there wasn't much of a margin in rod bolt strength at high RPMs.

The solution for that is to use stronger aftermarket rod bolts.

I gather you like the looks of carbs? Because EFI is better.

[faapgar]

I had built one of these in the 80,s.You do not need torque.My suggestion to use SC crank with light rods was because of my build experience.250 -270 is all the world in a car of this weight.Less torque opens up your gearbox options as well.914 is perfect if you do not do hole shots when you exit Cars & Coffee.Strong side cover that takes 930 bearing and you are fine.Have fun.Ciao Fred

[Jeff Alton]

If you have a 3.2 now, I just do not see the need to go buy a 3.0 crank. Sure, you could sell the 3.2 crank for more than you paid for the 3.0 crank, but.... Anyways, regardless of which way you go, a 3.0 or 3.2 with good CR and cams will make you happy.

Cheers

[JonoUK]

Hi Fred Jeff and Walt
Thanks for taking the trouble to help.
Had an issue here but now sorted and back in garage so sorry for slow reply.
(No going back now - just made 2nd payment on the body)

Crankcase now at Headshop Warrington UK so they are asking questions.
3.2 Crank / rods / barrels all perfect so they stay - with the bigger rod bolts.
Should they be changing all barrel studs or just Dilavar ones?

Plan:
Throw out pistons - (bad shape for twin plug and heavy) and fit set JE 10.5:1
This should give me space for cam choice and make the 2nd plug actually work.

I am right to be choosing from 3 -
Standard pair from 964?
DC60 ?
S cam which a lot of people seem to like. The original has a bearing less - Is this what you mean by a Mod S cam Jeff? ( An S profile but with the extra journal ?)

And yes Walt 😂 I just want to have the PMOs (and they may suit my cam change) but if you think there is an advantage I could use throttle bodies? - very happy to take advice

Best wishes
Jono

[cmcfaul]

Mod S is a DC30 cam. Not as aggressive as the DC60. Will breath well past 7500 RPM's and have more torque then the DC 60 but not as much top end. Term comes from the original 911 S motors from the early 70's (somewhere between an E and S cam profile...mod S).

Chris

[JonoUK]

Hi Chris and thanks.
I’m trying to get an engine that feels just a bit different to a modern engine.
it’s a fun car after all!
Maybe a little lumpy on tickover is OK but an engine that feels like it sharpens up when it gets to 4500-5000
Any suggestions?
reds
Jono

[Walt Fricke]

You can't use "bigger" rod bolts on the 3.2. The rod journal's OD was increased, and to keep the overall width of the rod big end the same (or at least small enough to avoid interference with the case or oil pump etc) Porsche reduced the rod bolt (and hole) diameter one mm. So you use stronger bolts than stock for a modified or high RPM motor and call it good.

EFI is nearly infinitely adjustable, and you don't have to mess with jetting - just tweak the programming. Easy to do on a chassis dyno - make a run, adjust a map, make another, etc. For street cars, guys ride around with a driver with the laptop in their laps, filling in and optimizing the rows and columns on the maps which determine spark timing and fuel injection amounts.

This also makes possible independent throttle bodies - where all six sit right atop their ports, not like with carbs where only 2 and 5 have a straight shot. A friend once measured the difference in flow between the center and end holes. It was at least measureable with fairly straight forward pressure wands, which means there is a VE difference. Might not be oodles of extra or lost HP, but real if you want to optimize. VE optimization is good overall, even for a street motor where you aren't looking for that last foot pound so you can pass someone on the straight on the track.

But at somewhat of a cost - like about everything.

[JonoUK]

Thanks Walt for such a clear explanation.
Is there any knowledge on taking weight out of JE Pistons?
The stock 3.2 pistons look very heavy so I can only guess the JE’s are lighter anyway but I really don’t like the idea of anything that big going up and down so quickly.
At my target rev limit of about 7200/7300 what changes would be made to the valve spring and cap or are standard OK.
Weight here - especially in the cap can’t be a good thing?
Kind regards to all who are guiding me
Jono

[Jeff Alton]

Call JE and ask them the weight of their pistons in the bore and CR you require. Then ask then why they are not lighter. Report your findings...