What would you do to build a 3.0L Race motor?
 

Well if you've read my other post, you'll know that it's time to build that 3.0L motor that I've been dreaming of..

I am looking for input on the best horespower bang for the buck with the following contraints:

1. Must use 93 octane.
2. Must be reliable
3. Nothing exotic or impossible to replicate
4. Must be in the "Vintage Spirit"
5. This is not an unlimited budget project...

That being said, here are the primary things I want to do:

1. 46mm Webers and Exhaust (alreay own)
2. Pistons and Cams (though not TOO radical in case I zing it again)
3. AASE titanium valve springs and keepers
4. Raceware rod bolts
5. Valve guides, new valves (what kind?)

Now, what else? I've heard all kinds of high HP numbers thrown about by vendors, what can I honestly expect? WHat should I budget (including splitting case and replacing bearings)

If you intend to drive it on the street 91 octane, early S cams, 10:1 JE pistons, 1 5/8 headers, 38 mm intake ports, and choke those 46's down so they have some air velocity. That will make a decent tractable motor that puts out about 260-265 hp with open exhaust/ corrected jetting at the track.
EBS has a good thing going with their piston packages and their springs/retainer kit is very good as well.

Track only, more radical cams- these move your effective horsepower range/ when the cam comes on- up the rpm scale, so around town driving sucks. Elgin can recommend some grinds. Then you can go with 1 3/4 headers, taller manifolds, 11.5:1 JE pistons, twin plug ignition (electramotive is good bang for the $$),100 octane, more headwork and you can expect 300-305 hp

After this it gets even more expen$ive

Seems like you have things pretty sorted out. I would cross drill the crank, and modify the bearing so you dont get oil starvation at the 2&5 rod bearings.

Why are you limited to 93 octane? that kind of restricts you to 10.5:1 CR

46s are a bit too big for a 3.0 with anything but RSR cams (in my opinion...)

-Wayne

This is a track only car, never dips below 4000 RPM (except when exiting pit lane) so bottom end isn't a concern. Would like to have the power band from 4000-7000RPM, no need for anything outside of this.

The 93 Octane requirement is for on-going cost essentially. Would save on average of $750 per year... Is it worth it?

Well, all other things being equal how much horsepower would be gained by going from 9.8:1 to 11.5:1? Is it worth an extra $2250 in fuel costs over 3 years? Would $2250 invested elsewhere get just as much horsepower and remove the hassle of having to get race fuel?

3.2 P/C's would put me in a MUCH higher sub-class for that extra 150cc displacement. The cutoff is 2999cc

At what racing organization and class are you aiming this engine?

-zuff

VSCDA and MidWest Council

You have to replace the pistons if you want more cam, so you should think about the 98mm ones (for 3.2 litres) that Noah is talking about.

I have 270hp from a 10.3:1 c/r 3.2 with S cams and standard exhaust. I have left horsepower on the table from my cam choice and exhuast but have fancy MoTeC control which probably picks me back up a little.

(edit) just saw the stuff about 3.0l limit. Ooops.

You need twin plug.

Chris;
First I'd start with the rule book. Then I'd read the rule book again (are you sensing a theme?). Then I'd ask how many HP do you want? From that you can work back to a cost. Or you can do it the other way.

Here are a few conceptual ideas to consider.

Can you change the stroke? Given a 3.0 liter engine capacity, a shorter stroke (like 66mm) would allow you to rev the motor higher which would equal more HP assuming that you have the cam to match.

More CR is a good thing as long as you can get the fuel to match. It will move your torque curve up across the board. This often will give you more room to use a wilder cam without making the off cam torque disappear completely. Race fuel, twin plugging and a mappable ignition system are all ways to get this accomplished. While Porsche has generally used 10.3:1 as a max for their air cooled, engines, I've heard of IMSA and SCCA engines running closer to 11.0:1 or 12.0:1.

As far as ignition is concerned, distributor type ignition systems are pretty blunt instruments. If you can go to a mappable system, you will most likely pick up a little HP, but a lot of flexibility by making the engine run more efficiently across the rev range.

You might want to think of it in terms of an engine strategy. What sort of engines are you competing with? Where are they better? Where is the Porsche engine better? Where is the Porsche Chassis better? Where is it comparatively behind the pack? Then pick out the facit that you want to fix or maximize and figure out what that means to the engine.

Or you can just go the well tried 3.0 Porsche club race motor route that others have already blazed. A lot of it has been done before. If it was me, I'd try to do something different.

I think that you have the right idea though, speed is a function of money -- how fast do you want to go? So what's the rule book say is legal?

To get maximum power you have to raise the CR, to safely run a higher CR, you have to use racing fuel (or higher octane than pump premium).

Its a catch-22,if you want to play you have to pay.

Twin-plugging will help you run lower octane fuel with higher CR pistons. but then you have the $2000 cost to get your heads machined, and a dual ignition installed. So the $2250 in fuel costs is a wash with the twin plug mods..

If you cross drill your crank, and build a bullet proof bottom end. and get 10.5: pistons with GE-80 cams you will have a rock solid screamer. You will have to feed the engine the 104 just to be on the safe side

Ah, okay. I knew 3.0L wasn't a good fit for PCA GT rules. Shame, too, 'cause it's a great engine size.

If you're stuck on using high CR with 93 octane gas, I agree. But considering how much it costs to go twin plug (and they money's not in the head work--it's in the ignition system), you would save money by just buying the race gas. My father and I ran a short-stroke single plug 3.2L race engine for several seasons. The engine made great power (dyno'ed at 305HP) and was very reliable. Of course, it required race gas. My point is that you can have a great single-plug race motor even with a larger bore that what you're building.

-zuff

How about start with a 3.2, replace the crank with a 66mm crank, get some longer rods to move the pistons back up in the barrels (and restore some of the CR) and some GE80 or 906 cams. You'll have to pull close to 8000 RPM, but you most likely won't have to touch the heads since that is about the limit of the 3.2 heads. The short stroke will keep your piston speeds under control and reduce the forces on your bottom end. The top end will need some good valve springs though. Ballpark: 300 HP on street fuel, more on race fuel with extra compression.

the motor I planned (but never built) by talking to some engine gurus was

3.2L 74.4mm crank
98mm or 100mm Mahles (that makes 3.4 and 3.5L respectively)
3.2L heads
twin plug the heads
talk to rennsport systems about a 964 dual dizzy
steve can get a SC donor dizzy and a 964 dizzy and make you a 12 lead dizzy that works with MSD boxes and coils
carillo rods if you really want to be safe

to do 3.5L you would have to bore the spigots on the case which is pretty cheap...you may want to do the shuffle pins...boat tail

the heads would need to have double plugs drilled which is cheap...port and polish is up to you...you could get by with a mild polishing

since it is a race motor a wild cam would make you GOBS of power with the 3.5L

and if it is race you can get really high CR + the twin plug...

check out www.andial.com site...somewhere they ahve a list of all the pistons they sell and they have marked whether it is for the street or for the track...


BTW I had some parts I was gonna buy from the now defunct paul weir...he had some cool 3.5L motor parts...the carillo rods...some good pistons and cylinder...an engine case...etc...he posts them on ebay once in a while if you want his contact info let me know

I have a 3.2L crank and rods...and 3.2L heads which I had for this engine, but I have been distracted by karting and my targa project...

let me know

MJ

I might have to retract the "you need twin plug" :D :D :D

Yep... I've spent 2 years looking through the rules... Problem is, they keep changing the thing and making exceptions...

However the overiding rule is:

Displacement. Must be under 3.0. THe divisions are 0-2.0 2.0-3.0, 3.0-5.0, 5.0+

I would like to see about 270-300hp for under $5k while still having a motor that will last 3-5 years. (Of strictly on-track driving, approximately 3-5k miles per year)

Chris,
I for one would love to squeeze that kind of juice out of a 3.0 for 5K. If you find the path, please keep us in the loop. If it turns out to be a streitable[sic] motor, I bet lots of people will follow.
Good luck,
Mark

ahhh to dream...
 

Twin plug, Ti valve train with bigger valves, forged rockers, Ti/Carillo rods, cams, raceware, 11+:1 C/R, lightweight Flywheel, headers, megaphones, etc. etc. Also, selll those Webers, in favor of a high-butterfly slide-valve injection system! Man, I have to go take a cold shower now. :D :D

That's a near impossibility when Nikasil pistons and cylinders run around $3K...

-Wayne

Wayne,

I realize that this is impossible if I start the rebuild with Mahle. J&E would be more economical but I've gotten mixed reviews on their longevity.

My initial though is to invest in the hardware like Mahle's and a set of cams, raceware rod bolts and crossdrilling the crank. Basically doing the bottom end as long as I'm splitting the case...

Extras like polishing, etc.. might be able to be put off for a time...

Sounds a lot like an engine I'm thinking of building. ;) As above but I plan to use 3.2 heads and twin plugs. Cams will most likely be custom grinds once I get airflow numbers for the heads. Look into ARP studs as well. If 4000-7000 is most important to you stick with the 46 webers and use 1.75 inch headers. Do you need to run a muffler? Reason I ask is within the next few weeks I'll be dyno tuning my headered 3.0 with both a 2 in 2 out 2.5 inch Flowmaster and a custom X pipe exhaust I just completed (like and hour ago, to late to test drive LOL) For the X pipe exhaust I used relatively quiet turbo mufflers but could easily incorporate drag-race sytle mufflers to keep within track limits but would be to loud for street use. I'm hoping to get another one built with race mufflers before my dyno session. As the others mentioned this motor will be somewhat sluggish down low but that's the sacrifice you have to make in order to make big HP without larger displacement or forced induction. One thing to keep in mind, it has been my experience with drag race engines that longer duration camshafts allow incrementally higher compression ratio due to bleed off, I see no reason why the same wouldn't be true for a 911 although they don't have the superior cooling that water provides for the heads (typical V8 can run a half point higer compression just by switching to more efficient cooling aluminum heads over stock cast iron) I've been able to run as much as a full point higher compression on my large cammed drag motors with the same octane fuel. In fact some really large cams just don't run right without increase compression. I'll keep you in mind when I find a good cam grinder. I know Crane is making 911 cams again, they only charge 10-20 dollars more for a custom grind vs. a standard grind but I don't know if their tech reps would be any help in selecting a 911 grind given their obvious primary market. I'd also recommend polishing at least the combustion chambers, you can do this yourself with a Dremel tool and a cylinder head cc'ing kit.