Engine Rebuild Decisions

[Fritz]

Hi all,

OK class, put your thinking caps on...actually, have a little fun with this.

Would you mind contributing your thoughts on my 73 E engine?

The goal is for the car to be a mild hot rod, "spirited" street/mountain driving, autocross and some DE events. No, I do not want to drop in a 3.0 or 3.2, I love the sound of the old engines with MFI. No, I really am not too concerned about PCA club racing and related rules.

2.4 vs 2.7
Any thoughts about bumping it up to a 2.7? Seems an easy (minor case mods) way to gain a little more power. 90 mm Nikasil cylinders are readily available.

8.0:1 vs 8.5:1 vs 9.5:1
If I go to 2.7, the euro spec 8.5:1 are readily available and cost effective. 9.5:1 are also available but more costly. I'm in the Denver area and the altitude robs some horsepower so high compression really helps here. What should I expect from 9.5:1 with todays gas?

S vs E cams
I kind of like the feel of the E coming out of corners. Given my driving goals, any thoughts?

B]Fuel/Air Flow[/B]
Considering all of the above plus opening up the heads/valves and throttle bodies to S specs, how would you treat the MFI pump. Would you rebuild the pump to S specs if keeping the E cams in the engine? Obviously if I go to S cams the pump will need the S specs.

I guess the two real decisions are compression ratio and cams so give me your thoughts.

Thanks,

[J P Stein]

I have done my 2.7L similar to the B. Anderson "hot rod" 2.7 in his book, more compression and Solex cams.....it's a hoot. I would go for the extra compression and keep your cams. Look at the dyno chart in his book. Just a tad less top end than the RS motor.

The only thing I can see that *may* be a bit of bother would be your case. If it's 7R, no problem. 5Rs have the wide spigots, but no internal reinforcement as in the 7Rs.They would *probably* be OK. 3Rs ....well, I wouldn't consider using them. An upgrade to the later oil pump would be a good idea, also, not to mention case savers, different head studs, yada,yada.

This is not a small project in both time and money for a DIYer.....or you could ship it and your Visa card to OTTO's

[my72911t/rs]

I did just that a72 t to 2.7 euro pistons solex cams mfi works great it has a sport exhaust very loud but I like it. Very quick seat of the pants feeling...Good luck to you... Matt

[StuttgartDavid]

For a street engine the S cams can be a bit much for smaller displacement, but they are the cat's pajamas in a larger engine. Since there is no substitute for ccs, I would go with the 2.7 - you will never regret the extra torque, yet it is a great combo with the S cams for both mid and high rpm power.

Higher compression may be tempting, especially at altitude, but compression and engine longevity are inversely related. Since it will be a street oriented engine and the 8.5 is a cheap combo as it is, I'd stay low here to keep the detonation demon away.

This leads into the answer for the cheapest, easiest, and most reliable combo for you to build. Why make a one-off combination that will require guesswork with the MFI (which will need to be recalibrated for a change in cc or cam) and other components, when the factory already did the R+D on the perfect combo for your application? The 210hp Carrera MFI engine had 2.7L with 8.5cr and S spec ports and manifolds. It was one of the greatest street/track engines of all time. The space cam for this will be a known quantity, rather than guesswork like other combos you suggested. Never reinvent the wheel when Porsche already did the work for you!

[skinnerd]

I'm in StuttgartDavid's camp. Go with the 2.7MFI factory spec engine. Although not inexpensive, all the parts are still available. My 73E was converted in the manner 10 years ago, and it's still an amazing powerplant. Great torque comes with the increased displacement. The engine was dynoed at 208hp at the rear wheels.... plus you get that incredible rush when the cams hit about 5000rpm. I'd probably opt for the 8.5cr for everyday use, as you can put any grade of fuel in you choose.... even 87 octane.

Just my 2cents... good luck.