Interesting Conundrum
 

Guten Morgen Pelicans,
I have an interesting one on my hands. We recently got a motor in for rebuild that was done by a very respected shop back in the mid-90's. (They are no longer around to ask questions).
Anyway, it's a 1970T motor with a 66mm crank and 93mm Mahle Motorsports Ps and Cs. Stock 2.2L heads with standard size ports and valves.
A few of the elder statesmen in the P car engine builder community have really frowned on this combination.
I'm looking for solid alternatives that would make good, street able power and be reliable. The preference is to reuse the components because everything is still in great shape. But is this extremely over square motor limiting its own potential? The motor currently specs out at 9.79:1 and is running webers, 104/102 cams and a stock single plug ignition. Kinda thinking out loud here and hoping to get a few opinions...

That should be a great motor. . . if you spin it. The advantage of the oversquare design is its ability to rev-- but with stock 32mm ports in the heads (valve sizes are the same for 2,2 T E S) you will run out of air.

Spend your money on the heads and twin plug, sport muffler and drive it like you stole it.

T and E that year had 32x32 ports. The S had 36x35 ports. Port the heads to the S spec. The S motor had 9.8:1 compression that year, so maybe no need for twin plug.
Bob B

66 x 93 sweet 2.7 short stroke. I did this 5 years ago with MFI twin plugs GE-60 cams 10:5 compression on a 7R case. Still running great and pulls strong from 3500 to 7500.

I'm wondering just how much benefit the twin plug would add in this scenario assuming with port to S head spec.

Twin-ignition would improve mid-range torque and throttle response quite noticeably. At 9.79:1 on pump gas, one cannot use as much timing as such an engine needs for best performance so twin-ignition with 25-26 degrees provides the "Full Monty". :)

Andial did a number of these with those thin-walled 93mm cylinders. The only issue with them is they tend to ovalize over time and create more blowby, even though power is not appreciably affected.

Thanks for the input Steve! Since I was unable to get dyno numbers before tearing the motor down, I am having a little struggle with being able to quantify the "full monty" of gain from the twin ignition. I'm estimating he was at around 60-65hp/L (somewhere around 170hp). I think the bigger ports will get us closer to 70-75hp/L (190hp). Not sure if the twin plug will let us dial in enough advance to hit the magical 200hp or not. It's a ton of C/R though so maybe those old stand by rough guesstimates are SNAFU.

JB,

No question that the T ports constrain the engine's potential. :) They do enhance low-end torque, but that can be restored with twin-ignition and optimal advance, should you decide to modify them.

Those cams (solex) provide excellent mid-range power and are all done by 6700-6800 in a 2.7. If you want the engine to make 200BHP or more, you will need something like Mod-S cams and S-spec heads. Remember, more cam makes it a little peakier so close-ratio gears should be considered.

FWIW, we can CNC those T heads to S spec if you wish.

Bottom line,..it really depends on where you want the power curves, but this one has potential to do 210-220BHP with good heads and more cam. :)

The objective is to be done making power around 6800-6900rpm. Since this is a spirited 40+ year old street car, I can completely understand why the customer is hesitant to spin it past factory redline even with a full balanced and setup motor. I was thinking the twin plug would buy us back some of the low end torque plus make the motor a little happier to run around town at close to 10:1 but the cost of the period correct looking twin plug systems requires a lot of empirical data to prove its value.
Steve, can you PM me your details please.

PM'ed as requested.