So what is it ? (engine question)

[John Fusco]

My car is a 67 normal with a 901/05 engine with increased displacement to 2.2 liters.
The records are not clear as to what type pistons, heads were used. I assume the cams are the originals - the distributer is #0231 159 002.
I notice I am listed in the latest Esses as a 67 T.
From B.A.'s Perf. Handbook I realize that increasing the disp. will lower the compression ratio.
A 2.2 T with a compression ratio of 8.6 :1 has 125 hp. Does that mean my engine with 2.2 liters has less power than the stock 2.0 ?
If so - what are the advantages of the increase ?

I plan on getting a dyno in the spring ( new seats and rear shocks come first)
But am curious to know what I might have now.

Is this answerable on the info I have given?

Thanks
John

[911pcars]

John,
All other things being equal, increasing displacement usually increases torque and horsepower. Not knowing what pieces you have in your engine makes it difficult to know the approx. power range. The main variables for a higher compression ratio include:

- larger bore
- larger stroke
- smaller combustion chamber volume
- higher dome on piston top

A big factor in engine power is how much air can pass through it. This is a function of the valve timing; namely how long and how far the camshaft opens the valves as well as valve and port size. An S camshaft keeps the valves open longer and opens them further to allow more air (and fuel) to enter the combustion chambers. A factory 2 liter S engine should be in the area of 170-180 hp.

Hope this helps,
Sherwood

[LeafGreen]

Another key factor in producing power is to keep the cylinder pressure that the engine sees while running as high as possible; this is a function of the static compression ratio and camshaft timing. A standard cranking compression test is a good reality check for the proper piston and cam combo. Here are some examples: 1) A stock 72T with 7.5:1 CR will crank 150 PSI! How? By not keeping the intake valve open too long and blowing down the cylinder. 2) My jet boat with an 8.5:1 455 Olds wouldn't rev over 3800 RPM, and took its sweet time getting there, until I installed a smaller cam designed to work with the low CR. This little change netted me about 80 HP, and it now gets to 4500 RPM almost immediately.

As previously mentioned, getting more air in and out (improving volumetric efficiency) is the recipe to increasing RPM and HP, but it must be backed up with a high CR, or you will have a very unhappy engine.

[John Fusco]

Thanks guys;

The 901/01 (and 901/05) cams have the same valve timing as the 70/71 901/09 911 E - So shouldn't the comp ratio be the same 9.1:1 ? or is it reduced by 4/10ths of a point ?
Would it be a "67 something between a T and an E " ?
I notice the 67/68 901/30 rally engine had, along with 46 ida's and S cams (and certainly higher comp pistons ) it had valve and port openings the same as for the 911 normal.
My comp test came back all in the 170's - bad idea to change just the cam grind ? would that make an unhappy engine ?

Thanks again
John

[pwd72s]

Took me a while to figure it out...in the esses, T means Targa, C means coupe.

[John Fusco]

Except it's not a targa. Also it is listed as
67 T (c)

Which is cool - if thats what she is. But what is she ?



John

[pwd72s]

beats me then, because I never heard of a '67 911T... mea culpa...

[John Fusco]

Me neither, though I believe it may be an equivalency thing.
If the thing that is equivalent is the thing I got.

John

[LeafGreen]

John,

Wow! 170 PSI - That definitely makes for a happy engine from a performance standpoint, but my guess it's probably unhappy if you run 87 octane.

I'm kind of new to P-cars, so bear with me on the details. Now let's see if I have this right. A 2.2 is a bored out 2.0, and a 2.4 is a stroked 2.2. If the orig. 2.0 was rebuilt using a 2.2 crank and rods, and that was the only change, then you would have an increase in CR because the cyl. volume was increased without increasing the combustion chamber volume. This assumes that the 2.0 and 2.2 pistons are the same (i.e. have the same deck height). Are the 2.0 and 2.2 heads different in terms of chamber volume? 2.2 being larger? I can see abnormally high cyl. pressures resulting from someone using the short "T" cams with something like an "E" or "S" spec. CR.

Do the early cars require the use of premium gas? Remember: 91 RON = 87 RM/2, not our currently available 92 premium.

[roblav]

A few things here:

- The 901/01 and 901/05 engines do NOT have the same cams as the 911E's. The 911E cams are somewhat milder.
- The early cars generally require high octane fuel, especially the 2.0 liter versions because the piston dome height does not provide very good flame spread.
- Your 901/05 with 2.2 liter pistons is probably putting out about 160HP.