Cheap 2.0 build for track, engine build questions Options

[RFoulds]

To race in VARA D Production 2 liter class, I want to build a solid reliable motor. I am limited to the stock crank (71mm stroke), and stock piston size (94mm)

I have on hand a GA short block and a NOS set of Mahle 94mm P&C's, 8:1cr. I also have a nice pair of Italian Weber 40's. So my thought is, with the right machining and balancing, I should be able to build a solid reliable 2.0, that can produce 120hp . (wild guess)
Of course, what version of Webcam to use is still TBD, and heads.

questions I have:

am I kidding myself that the stock Mahle cylinders can handle continuous high rev's and heat?

will 44IDF carbs be significantly better than 40 or will the size of the jets matter most?

besides balancing crank, rods and flywheel, what machining should I consider? (Have not considered the heads yet.)

[ChrisFoley]

Sell the NOS set to a CW.
Forged pistons are lighter and make more sense for continuous high rpm use. Switch to CrMo rods too.
40s with 34mm venturis would work pretty good. 44s with 36mm vents might get you more top end, depending on how you build the engine.

Invest in the valvetrain. Use 8mm stem stainless valves for both intake and exhaust, CrMo pushrods, Porsche swivel foot adjusters, hd single valve springs.

The 86A camshaft is really easy to build around. It likes compression around 9.5:1.
Spin it up to 6500 rpm and with the right header you'll make 150 hp.

[infraredcalvin]

How competitive do you want to be? 120 hp will keep you at the back, no matter how great of a driver you are. It has been a while, but I used to run in that group with a 180hp 40 hr engine in a very well set up 912, I was still green but usually finished in the top 15 of a 40 car run group, and on the podium in my class. I always hated watching a “2.0” 911 pull away easily on the front straight at CA speedway.

i agree with Chris, bump up your target hp and you’ll have fun in midpack.

[mepstein]

How competitive do you want to be? 120 hp will keep you at the back, no matter how great of a driver you are. It has been a while, but I used to run in that group with a 180hp 40 hr engine in a very well set up 912, I was still green but usually finished in the top 15 of a 40 car run group, and on the podium in my class. I always hated watching a “2.0” 911 pull away easily on the front straight at CA speedway.

i agree with Chris, bump up your target hp and you’ll have fun in midpack.

I think 2.0 - 911’s are making 250-280 these days.

[Charles Freeborn]

I'd be happy to share specs of my Allen Johnsen built 2.0 if you're interested. Not sure of hp (haven't had it on a dyno yet) but guesstimate from others is 160ish.

I'm going to be on the hunt for a spare engine of similar specs this winter, so I'm following this thread with interest.

-C

[Charles Freeborn]

To race in VARA D Production 2 liter class, I want to build a solid reliable motor. I am limited to the stock crank (71mm stroke), and stock piston size (94mm)

I have on hand a GA short block and a NOS set of Mahle 94mm P&C's, 8:1cr. I also have a nice pair of Italian Weber 40's. So my thought is, with the right machining and balancing, I should be able to build a solid reliable 2.0, that can produce 120hp . (wild guess)
Of course, what version of Webcam to use is still TBD, and heads.

questions I have:

am I kidding myself that the stock Mahle cylinders can handle continuous high rev's and heat?

will 44IDF carbs be significantly better than 40 or will the size of the jets matter most?

besides balancing crank, rods and flywheel, what machining should I consider? (Have not considered the heads yet.)

Okay, here are the cliff notes on my engine built by AJRS.

94/71 Bore Stroke
"Euro" pistons
Webcam 86B
"Welded" heads 38/48
Balanced rockers - polished, etc
Swivel feet
Dual spring
Wedge Crank
Lightened Flywheel
Straight Cut Cam gears
Electromotive crank fired ignition
Half shaft driven alternator
Electric downdraft fan (there are no belts on this engine)
Weber IDF 44's (still working out jetting for sea level)

I am / will fill in details as I sort the jetting and dig through the stack of receipts from it's build. I'd provide cost numbers, but it was all done 15+ years ago so they will be way low.

In my conversations with the builder and other research the common theme with the T4's is headwork is where the horsepower is. Get it to breathe and it'll reward you well.

This is / was not a cheap engine, but boy howdy it pulls like a tractor. The S and X gears make it a very close ratio box that tops out at 120 or so, but if you don't mind shifting, there's a gear for pretty much any situation. Redline is at 6k. You can wring it out more but there's not really any power above that. Being a 914 you can shift mid-turn without consequence. If you're coming from a 911 (like me) this is a massive bonus. It's a big go kart. Dive into the turns, modulate throttle until it hooks up and then mash it. Huge fun.

-C