Questions about my soon to be slow build...
 

In an earlier thread I had asked about buying just a case or an entire engine in order to build an engine to eventually end up in my car ('84 Carrera Coupe). I've decided to save up my pennies and buy a spare 3.2 engine and build off of that since I'm not in a rush to rebuild a working engine and would also like to have the Porsche running since it occasionally has to do daily driver work.

Now, realizing I'll need to find an engine, I figured now is as good a time as any to nail down some the specs on what I'm wanting to build. I'm sure there are things I haven't considered that I should or things I have completely missed that need to be done.

The engine will need to do double duty as a track day car and daily driver. I'd like to have enough torque in the low- and mid-range to make driving on the streets acceptable but also be able to let it rev high and freely with no issues. If I could hit 7k - 7.5k redline with reliability that would make me a very happy camper.

The new parts I've tentatively decided on are:

50mm PMO ITBs w/ TEC-3r engine management (twin-plugging the heads)
102mm JE Pistons 10.5:1 compression w/ Nickies Cylinders
Better Connecting rods
ARP/Raceware or some other quality brand head studs
1.75" Headers w/ heater boxes

Now, I don't know what to look for in a camshaft. I'm assuming a custom grind would be better than an off-the-shelf, but if an off-the-shelf would work well, that is good too.

These parts put me at a ~3.65L engine (using the 74.4mm 3.2L crank). Which should give me more than enough torque for daily driving along with really nice throttle response due to the ITBs.

In terms of machine work (other than what is described in Wayne's book).
-I know the heads will need machine work for the twin plugging and perhaps flow / porting.
-The case will need machine work to fit the new pistons and cylinders but what else should I do?
-Does anything special need to be done to the crankshaft?

What other parts should I factor into the equation? Better bearings? Springs? Valves?

The tearing down, buying and rebuilding of the engine is going to be my hobby / side project so I'm in no real rush to buy any of the parts, though I'd like to buy them from the inside of the case out. e.g. headstuds, pistons, rods and cylinders first, then camshafts, then the PMOs last.

As I said before, I doubt I'll be buying anything soon since I need to save before I start looking for the spare engine. However, the more information on the engine configuration to mull over and finally decide on before jumping into the project the better (and to know how long I'll need to save :)).

Thanks in advance for the advice. SmileWavy

The 3.2 rod bolts are smaller in diameter and combined with the longer stroke crankshaft, that leads to more stress and less structural integrity at higher rpms.

You will need stronger valve springs, maybe Titanium retainers. Titanium valves or Stainless Steel would help reduce valvetrain inertia and let it rev. The rod bolts will need to be in tip-top shape for the track.

JMHO.:)

cross drill your existing crank or consider the new supertec crank out now... make sure you are able to monitor the exhaust gases with a lm1 or 2 with a gauge on the dash... what hp are you hoping for?? i.e. you may need to help out the tranny w/ better side plate, possible oil cooling, possible lsd, gearing looked at...MUST address the ADDED oil cooling you will need... suspension upgrades to handle all of this new "go" you are planning on... brakes too... may need bigger wheels & tires for the brakes & aggressive handling it sounds like at the track...
If I were you, I would call 5 people from this board and get their opinion: Henry & supertec in CA, Steve weiner in OR, Dave at tre in CA, the boys at zuffenhausen in NC, Grady Clay in CO.
By doing this, you will establish 90+% of your plan in short order and with confidence from the pro's!
Good luck and keep us posted on how your project evolves!!
Bob

Hmm.. why does physics have to come and rear its ugly head?

I was figuring on stronger valve springs and retainers but if the stock ones could handle it no reason to upgrade.

Engines should always be in tip-top shape for the track :).

I'll have to look into these..

Yes, a wideband would be used for sure.

As far as HP goes, I think this should give me at least 360hp, but since I've never built an engine I couldn't really say.

The transmission is something I am going to address when the engine is ready to go in. An LSD was definitely on the list and I figured a tranny rebuild would be happening as well.

Cooling was going to be a wait and see. I'd run it one of the local tracks for a session or two and see what my temps were and then determine based on that how much more I need to go. I have a few preliminary ideas stirring around in my head and just need confirmation as to which way I go.

The suspension end of my car is already handled. I might have to go a bit wider on the tires than what I have already but I think they could be fine. The brakes are going to be another wait and see but like the cooling I have some ideas.

When the money begins to burn a hole in my pocket I'll definitely give them a call if they haven't chimed in on this thread.

The project is evolving so I'm just trying to get a good ground work on how $$$ and how much time I'm going to have to wait to make this come true. I'll try to keep this thread up-to-date with my evolving project (and eventually a started then finished project).

With your displacement and compression ratio, you will have plenty of torque throughout the powerband. You will not need to rev it too high to get lots of fun and propulsive force. Especially if you can match gear ratios to the power/torque curve, you will not need the very expensive modifications for high rpm valvetrains. That high speed, and particularly high acceleration of pistons, rods, valves, etc. is what puts major stress on engines.

Yep, but spinning it fast is always fun. If it isn't realistic or just too much money to make it spin at 7k safely I have no problem cutting back the rpms. I've still got plenty of time to decide and pound out the details, just it is nice to start figuring out what it'll all set me back in the end so I can start planning better... work + college means not a lot of time to spend dreaming about and building an engine.

Dump the shyte 74.4mm crank if you want 7500 RPM

I don't know if 102mm cylinders is even possible on a 3.2 case with the spigot spacing. Why not start with a 3.6 engine instead? You could easily build a 3.8 on it, and with ITBs and an aggressive cam you'd end up with with 400+ hp at near the same cost as your original 3.2-based plan.

So what is the problem with the original crank? Is it not build for higher rpms? Is it cast instead of forged?

For the 102mm cylinders I was just going off of what was listed on the LN Engineering website.

I'd never thought about going with a 3.6L from the 964 or 993 then just mildly modifying that. Good thing I posed this question to the Pelican brain trust. The more information I can get the better.

Thanks.

The 74.4mm stroke crank gererates more powerful vibrations as it revs faster. The amplitude of the vibration is greater than a short stroke. As the frequency increases, the stress on the engine, such as piston side loading, increases. The crank can start to vibrate and suffer fatigue, as longer stroke crankshaft geometries are less stiff than a shorter stroke, material and other variables held constant.

70.4mm stroke crank is better, 66mm stroke is better still. I think the Porsche 804 F1 engine used a stroke near 54mm and revved to 10,000rpm or thereabouts.

Thanks, I understood there would be more force based on the longer stroke but when kenikh said the crank was crap I was thinking it was bad due to the design of the crank e.g., cast vs. forged, some weird alloy, etc. not the overall design of the engine.

Yeah, I read somewhere that the F1 engines were highly oversquare designs with greater than 2 to 1 on Bore vs. Stroke.

#1 you'll have to change your "handle" if you are doing this yourself.

#2 if I was in your shoes I would try and find a nice 964 or early 993 engine to rebuild. Maybe even an early 964 (1990 or 1991) that has exhibited some of the dreaded head to cylinder leaking - Then do the LN Engineering Nickies (I like the JB Racing pressed cylinders too) They worn't be that much more money and probably a better basis for a rebuild with the twin plugging - etc...

Yeah, ChkbookMechanic was a nickname given in jest, so I just went with it. I don't mind tearing into my Porsche, my other car... I have limits on what I'll do since it can't afford to be on jack stands or out of commission for any extended amount of time.

Are there any good threads/sites that you know of offhand that give some good information on the 964 and 993 engines? If not, I'll just search the board. I know a decent amount about my particular engine (thanks to Wayne's book and some help from people more knowledge than me) but not much about the newer air-cooled engines.