2,2 engine "powered"?

[Max911]

Dear Gentlemen

As usual I trust on your suggestion.

My 911 T 2,2 my 1970 ex USA before I bought in his first life was a track day car
Following picture will make you understand


Terrible in my opinion...(de gustibus...)

So I restored it to mint original specs


Engine was running good so I apart from common gaskets and oil seal, exhaust and tear and wear parts I decided not to fully rebuild it

But I am curious to understand which kind of preparation the former owner could have done to engine...

Compression is 10,5:1 vs std 8,6:1
Air intake trumpet 46mm vs 40mm on original zenith 40
My local porsche workshop told me that cams were set on E model specs vs T specs but cams are the correct T cams: The car seemed well maintained so I think it was not an error...

Now set as a T the engine runs well pulls and revs good: no smoke and regular, no rattles nor clacking sound.

My local porsche workshop told me that the engine is a little bit too much "metallic" in sound through the revs ...
Maybe stainless steel exhaust enhance metallic notes...personally I find maybe too intrusive the fan noise up to 3000rpm...but I have no experience of other 2,2 T restored to compare with...

Waiting to get it run on dyno to find the hp output if anyone of you know what were common "recipes" to transform these cars in track days cars please help me in understand which modification could my engine have

Thanks
Max





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[yoda]

Sorry Max, I can’t help you with your engine question but the car looks fabulous!

[Bootsy]

A stainless exhaust does have a metallic sound even more pronounced if you have SSI exchangers on it?

[Max911]

Thanks @yoda
@bootsy: yes I have SSI stainless steel exchangers+muffler kit


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[fetuhoe]

The 'trumpet' diameter on a Zenith 40TIN is normally 46mm at the carb side which is the same as those fitted to a 40IDA3C or one of the derivatives.

If you measure he top of the carb you will find that they are 46mm diameter where the auxiliary venturi fits into the top cover and only reduces to 40mm in the main body of the carb at the manifold end.

A 2.2T will have reduced power compared to the E and S models for three basic reasons.

a. Compression Ratio is lower as 8.6:1 compared to 9.1:1 for a 911E and 9.8:1 for a 911S

b. The cam used in a T is 'softer' than either the E or the S cams

c. The port sizes are smaller on T engines and won't tend to be as effective at higher engine speeds.

If your cams have been timed to a E specification then in real terms the cam timing has been advanced and this will tend to increase the low end/mid band torque at the expense of top end performance which seems a bit odd when using a T cam which is already quite limited in terms of top end performance.

With a 10.5:1 Compression and advanced T cams I would be a little concerned that under heavy loads that the engine may be prone to pinking.

Do you know what type of piston has been fitted and what cyilnders you have?

[Nige]

Judging how the car originally appeared to showcase a part from each historical stage of an aircooled 911 I bet the engine is the same.

[Max911]

@fetuhoe thanks for your consideration: cylinder are original(according to code on them) as I presume pistons: engine has surely received a "head" refurbishment considering the oil chain tensioners installed.
I think that no other rebuilding have been made. Mileage is 86.000 and seems correct.


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[fetuhoe]

It would be difficult to have a compression ratio of 10.5:1 with a 911T piston as you would have to reduce the combustion chamber volume by around 20%.

If you reduced the deck height to zero you would only gain about 50% of the required volume and run the risk of the valves touching the piston.

By advancing the cam you will have already reduced the intake valve clearance so reducing the deck height isn't a great idea.

If compression is 10.5:1 it is likely that the pistons have been changed.

[Max911]

Thank you for your supposals @fetuhoe

Now my concerns are:

If my engine got a sort of "tune up", with specifics set cams phase set up... (E model or similar to E model or simply "unique"...)
but my local dealer porsche that follows only original specs phased it as an original one but guessing a "not normal engine tone"...

What is the best check to do?

According to my personal driving feeling the engine is good and pulls strongly... But I fear I'm compromising anything while running with original specs on a not original set up...

I mean: I hope that setting the cams on T reference they would be able to find anything not properly good...

I hope my explanation is good enough


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[neilbardsley]

Sounds like you are trying to guess what tricks the previous owner will have done? I think that is going to be very difficult without taking it apart? Also sounds like you are happy with the engine's performance so is your question about how to tune if you don't know the spec or do you have another concern?

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[Max911]

@neilbardsley thank you for your question.
My concern is if the car is really properly tuned with a std set up on a not properly std engine


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[Max911]

Dear all Gentlemen

Today I rolled my car on a dyno and results are pleasently a confirm of standard power (123 hp) although at 5200 rpm...less than 5800 that Porsche declared...
Torque 18,48 kgm at 4200 rpm with a constant level at almost 18kgm from 3000rpm to 4500rpm

I'm happy with these results cause I like as the car go...pulls and revs strongly

I still continue to ask myself if the engine has been prepared or not...
The only thing I don't understand is the quick drop down of power after 5200rpm

When you drive the car passing 5000rpm you immediately feel that the engine is lowering power and that's better to shift gear up...

Following power and torque diagram

Gentlemen as always your considerations are welcome








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[Ashley James]

I drove a 2.4T a lot in the day and rather liked it, but although it was a nice docile flexible motor, it wasn’t particularly fast. What it was was an excellent fast touring car in the it handled beautifully, had enough power to get past dawdlers and was comfortable. It was slower accelerating than the DB5 I had at the time, but much faster cornering and more grippy.

I imagine that the same applies today, but I wouldn’t have thought it would male a good track car because the power is more mid range than top end. A bit like the current MX5 say.

[210bhp]

Sounds like the modifications might be in the gearbox ratios rather than major engine work.

Fantastic looking car by the way.


Regards
Mike

[911hillclimber]

My 73T had a 2.2 on Weber S in it when I bought it 30 years ago.
I drove it for a year on that engine and it was exactly as Ashley describes, I remember how rounded it was on the road, very much like the MGB GT I had before it.

Engine went to a young lad who was going to put it in a 914 even back in the early 90's