914-6 engine choices

[speedo]

My 914-6 is in paint and it is decision time for the engine build. I have the original engine on the shelf, and will probably not touch it for now. I have a 65 aluminum case that has been opened to 90mm and has the MFI pedestal studs added. My thought was to build either a 2.3 or a 2.5 short stroke MFI on the 66mm crank. However, I am missing the P and Cs and the heads, and I'm not sure how much "operating" room in the engine compartment I would lose with MFI. My easier option is to start with a decent running 2.2 T that I have and consider stroking to a 70.4 crank, adding 2.2 S P and Cs, and swapping out the cams for E cams or possibly S cams (or maybe something in the middle). This would give me a very satisfactory 2.4 S spec engine with a slightly higher cr due to the 2.2 S pistons. I have all of the parts to build this. The valves T-S are 46/40 so those are fine. My questions relate to the ports. Porting the heads to S specs 36/35 will give me better flow (especially with the higher cr 2.2 S pistons. How much should porting cost...and/or is it worth it to make a template and do it myself? What will I gain by increasing the port sizes from T to S specs. I will probably run a pair of Weber IDAs that I just rebuilt.

Not trying to do the engine build on the cheap...but there is something to be said for keeping rebuild costs within reason by using what I already own.
Suggestions are appreciated.

[racer]

Do you want HP or TQ? I love nice peaky engines.. at the track.. but trudging along in traffic, nearly fouling plugs cause running at 5K+ isn't an option, isn't any fun. The flip side is a 911T spec engine that runs out of fun at 5K... Given your elevation, how much elevation change do you drive through? How often would you have to change plugs/re-jet? An injected car might be an easier option

So.. I guess I am asking, how will you be using the car?

[Catorce]

I have a 2.7 with Webers in mine. Feels like the perfect engine for the car.

[speedo]

Did some detective work. Found a machine shop in CO Spgs Martin Willis, seems knowledgeable and reasonable price-wise. Anybody have any experience with the shop?
His turn-around is going to be a lot quicker than Ollies.

[speedo]

Originally Posted by racer

Do you want HP or TQ? I love nice peaky engines.. at the track.. but trudging along in traffic, nearly fouling plugs cause running at 5K+ isn't an option, isn't any fun. The flip side is a 911T spec engine that runs out of fun at 5K... Given your elevation, how much elevation change do you drive through? How often would you have to change plugs/re-jet? An injected car might be an easier option

So.. I guess I am asking, how will you be using the car?

This will be a fun driver. No track time. Just want a bit more hustpa than the factory 2.0 without going crazy. I don't live in, or drive in city traffic. Not a lot of stop and go, mostly open roads.

[speedo]

Originally Posted by Catorce

I have a 2.7 with Webers in mine. Feels like the perfect engine for the car.

Kind of what I was shooting for...170-180 hp. In fact when I bought the car it came with a 2.7 and the original 2.0 engines. The 2.7 became an RS MFI engine and went to a new home. An E cam would more closely replicate the 2.7 CIS cam...something to consider.
I have a 74 911 with a 2.7 normal engine and it is very pleasant to drive. Is your engine a normal or 2.7 S? My normal is 140 hp and I believe the S was 165 hp? With Webers I guess you add a few more hp but less fuel economy?

[Catorce]

Originally Posted by speedo

Kind of what I was shooting for...170-180 hp. In fact when I bought the car it came with a 2.7 and the original 2.0 engines. The 2.7 became an RS MFI engine and went to a new home. An E cam would more closely replicate the 2.7 CIS cam...something to consider.
I have a 74 911 with a 2.7 normal engine and it is very pleasant to drive. Is your engine a normal or 2.7 S? My normal is 140 hp and I believe the S was 165 hp? With Webers I guess you add a few more hp but less fuel economy?

Mine is pretty hopped up with electromotive ignition 964 cams, and some other stuff, makes ~220 HP or thereabouts with every trick in the 2.7 playbook used

[jmz]

Unless you are using the aluminum case for something else or planning on selling it to fund the project then I would build either a 2.5 or 2.7. I'd likely go carbs simply for cost and timeliness of the build but if you've go the $$ and the time then an MFI 2.5 or 2.7 would be pretty special.

[Matt Monson]

I’ve got a new set of RS MFI p&C out in the warehouse Lars. Let me know if you wanna chat.

[targa72e]

I have a 65 aluminum case that has been opened to 90mm and has the MFI pedestal studs added. My thought was to build either a 2.3 or a 2.5 short stroke MFI on the 66mm crank.

With the bores opened to 90mm it would be a 2.5. This would be good start if you wanted something with bigger cams that would rev to 7500-8000rpm. If you don't want to rev that high replace 66mm crank with 70.4 and build a 2.7. 9.5 to 1 compression and mod S cams would be a nice motor.

However, I am missing the P and Cs and the heads.
2.2-2.7 heads are same casting and can be purchased at reasonable price.

I'm not sure how much "operating" room in the engine compartment I would lose with MFI.
MFI doesn't take up much more space than carbs. The engine sheet metal needs to be modified to fit over the MFI drive.

My easier option is to start with a decent running 2.2 T that I have and consider stroking to a 70.4 crank, adding 2.2 S P and Cs, and swapping out the cams for E cams or possibly S cams (or maybe something in the middle).

You would want at least S cams. The higher compression using 2.2S pistons on 70.4 crank on pump gas might be a issue. E-cams might have way to high a dynamic compression and bigger cams would help this. Better option might be to use 86mm P&C which are the largest without machining spigots and make a 9.5 to 1 long stroke 2.5.

I have a 914-6 conversion with a 2.4 MFI engine. It has 2.4S pistons and Ecams. I also built the gearbox with shorter 3rd KA and 4th S gears. I live in Littleton if you wanted to come down and see what MFI in a 914 does to engine access. You could also go for a drive and see if E cams on a 2.4 would meet your needs.


thanks,

john

[speedo]

Thanks John! I just sent you an email. Now that you mention it, I may have some aftermkt 86mm P and Cs. I will go out this afternoon and take stock of the piston, cam and crank inventory.

[AskewRSR]

I have a Real 914 6 engine case if you are interested. PM Me. Thanks

[speedo]

Originally Posted by AskewRSR

I have a Real 914 6 engine case if you are interested. PM Me. Thanks

I appreciate the offer but I have the original engine for the car. Another 914-6 case to build up is probably the opposite direction I want to go as with a bigger build I would want a stronger case...ie aluminum. And bigger jugs would mean I would have to violate the spigots on the 2.0 case.