Building a 2.9 Long Stroke

[914obsession]

I'm looking into building a new engine, and so far it seems like a 2.9 long stroke is my best bet. This egnine will be going into a relatively lite weight 914-6. I'd like to autocross the car but also be able to take some long weekend trips. I don't really care to rev the engine any higher than 7k, so I wouldn't be planning on putting in titanium keepers and race springs. I'd like to use a set of Webers that I already have, they are 40 IDAs, I figure I'll need new 40mm venturies and jets. Has anyone gone this route?

I'm sort of partial to the "E" Cams, but open to suggestions. What P/C would you use? Can you bore out a set of 90mm to 93mm or is that causing the walls to get too thin? I plan on using a 7R case with case savers and shuffle pins, any other case modifications other than opening up the case for 93mm cylinders? What sort of power and torque should I expect with this setup?

Thanks

[kenikh]

I am curious why a 2.9 vs a more robust 3.0?

[914obsession]

I have the ability to buy a 2.7 pretty cheap, I haven't seen any cheap 3.0 recently. What would a 3.0 long block needing a rebuild cost me? With the 3.0 I'll probably have to make the upgrade to 46 IDAs or PMOs.

[Steve@Rennsport]

Hi,

A few suggestions,...

1) Don't go bigger than 92mm; they are already thin and anything bigger doesn't yield proportionate results due to ring sealing issues.

2) 40mm venturies in 40mm carbs is a no-go. First, they would never even work and second, no such things,.... Stick to 36mm ones, especially with E or Solex cams. Even 38mm ones are marginal in a 40mm carb.

3) Anything over 9.8:1 will require twin-ignition or race gas. Budget for that.

4) Your case mods sound fine. Using your 7R, install case savers, shuffle pins, do the oil bypass if its older than a '75 one. No spigot machining is needed (thankfully).

[914obsession]

Thanks Steve!

I'm not committed to this build yet. I'll look into the 3.0 liter option. Does anyone know someone selling a 3.0 core pretty cheap?

[914obsession]

Well, I bought a 3.0 liter last night, now it looks like I'm committed. What cams should I run with this engine assuming that I plan on using a set of 40 Webers and am not planning on running this thing at real high RPMS- "E", Solex, "S"?

Also, does anyone have any experience with the GT3 coated rod bearings? Would the 9.5/1 JE pistons be a good fit? What do you do for a distributor? Do I need to get the original CIS distributor re-curved? Does anyone have an extra set of 930 tensioners?

Thanks!

[kenikh]

If the Solex cams will clear the pistons, I'd go that route. They are LOTS of fun on a big motor. Steve, any thoughts?

[Henry Schmidt]

Over the years I have installed 8 or 10 engines in my 914/6. In the day I would build a cool engine and once a year sell that engine to go on vacation. The car was basically restored about 5 years ago and sent where cars go to rest but before the restoration I built it's last engine. After years of swopping engine I finally installed a 2.7 RS spec engine. The only changes were the Weber carbs and Solex cams. 8.5 compression ratio to suit even the worst fuel and believe it or not this engine was the best all around driver the car ever got. Absolutely the most fun to drive.

As I remember : Started w/ stock 2.0T, 2.0 S , 2.4S MFI, 2.8 carbs 906 cams, 3.0 carbs, high compression 2.7S, CIS 3.0, 2.4 E, 2.5 SS carbs 906 cams, 2.7 RS w/solex cams. From the 2.8 w/carbs the trans was swopped to side shift and A,F,M,S,X.

The stock engine and trans are still setting in the shop.

[911st]

SC cams are a good cam.

Besides, w the 40mm carbs and big cams you are going to run out of air at the upper rpms.

A stock SC motor w headers and carbs is a nice motor if tuned right and should be good for 225-240HP with good throttle response.

After that is gets expensive.

Here in Nthn Ca we have a race class known as the Toyo Cup or now the 911 cup. The main spec motor is a mostly stock SC motor w carbs. They are very fast!