‘73 T 2.4L MFI engine help

[OC73Targa]

Hi, I recently purchased a ‘73 targa T with matching numbers 2.4 L engine and MFI.
Engine is running ok but I would like to do a refresh/rebuild to stop the leaks and upgrade performance. Looking to keep it as a street car. Would prefer mid range torque to high end power.

Couple of questions as I’m new to Porsche cars
- what would be the forum experts recommended performance upgrades that are cost effective and maintain “originality”?
- I live in Orange County CA. Any recommended shops / mechanics to do the work?

Probably unnecessary but pics of the engine attached below

Thanks!

[Major Dad]

How bad are the leaks, can you live with them ? A rebuild will be $20,000. if it runs ok why not running for a year or six months and enjoy as is next summer ?

Do a leak down test, replace all plugs and points , filters and oils. New brakes if needed, a professional valet / detail and drive it.

[OC73Targa]

Thank you MD!
The car is getting stripped down to go back to original color and redo the interior... so I think it is a good time to at least refresh the engine, stop the leaks and add some HP

Any suggestions and recommendations from the forum experts?

[targa72e]

recommended performance upgrades that are cost effective and maintain “originality”?
I was in the same place a number of years ago. I added 2.4S P&C to get a little more compression and E cams. T and E engines have the same port size. I was able to make this combo work well with the stock MFI pump and stacks. It did require quite a bit of tuning of the MFI pump with a wide band to get the mixture correct across the RPM range. Dyno sheet (Dyno jet) with power at the wheels below. Power was just a little better than E (probably do to more compression).




If you are willing to have the heads ported, MFI pump redone, bigger cams and have stacks bored larger then you have more options. If I were to do it again I would probably go with 86mm P&C (these do not need case machining) to get more displacement (2.5L) and something like Mod S cams. MFI would need custom space cam to fuel properly.

john

[Henry Schmidt]

Most of the long hood MFI engines we build are what we call "2450".
With or without MFI it's a nice configuration.
86mm, 9.5:1 compression, 36 mm intake ports and mod-Solex or mod-S cams.
The intake Throttle bodies will probably need to be re-bushed so enlarging them at that point is a low cost upgrade.
With Mod-S cams these specs yield close to 200 HP and look stock from the outside.

[OC73Targa]

John, Henry, thanks so much!
Looks like you are both playing on the he same sheet of music.
Would these mods require additional cooling?
What should be the expected cost of these solutions?
Any suggestions regarding heat exchangers and muffler?

[Trackrash]

Henry's solution is a great upgrade. Jay Lenno does something similar in this video. https://www.bing.com/videos/search?q=youtube+jay+leno%27s+911+porsche&docid=608035917814039842&mid=EFA21E6D806960787E65EFA21E6D806960787E65&view=detail&FORM=VIRE

For my money, I would bore out the cylinders to 92 to make it a 2.8. Will look the same outside but great horse power potential. Only with a small price increase over the 2.5.

Some have quoted ~$20K for a complete rebuild with all the WINTs when a qualified aircooled Porsche specialist does all the work.

Exhaust is easy. Either headers, if you don't mind no heat, or SSIs and a sport muffler of your choice.

BTW. You may want to get BRUCE ANDERSON'S PORSCHE 911 PERFORMANCE HANDBOOK. It is a great source of information on building and modifying these motors. Our host has it, but they have "updated" their catalog again and I give up trying to find it.

[OC73Targa]

Thank you Gordon!
Would 98mm cylinders require extra cooling?
If yes, is there a middle ground solution between 86 and 98mm that would not require extra cooling and case machining?
What is the stock intake and exhaust port sizes for this engine?

Any recommendations about shops that can perform the work near Huntington Beach?

I’ll get the book, thanks for the suggestion

[Henry Schmidt]

Originally Posted by OC73Targa

John, Henry, thanks so much!
Looks like you are both playing on the he same sheet of music.
Would these mods require additional cooling?
What should be the expected cost of these solutions?
Any suggestions regarding heat exchangers and muffler?

Anytime you exceed 165 hp on an air-cooled 911 you should consider additional cooling.
Cost generally follows competence. 20K would be a minimum target for a properly built 911MFI engine.
Until you exceed the 240 hp range, stock heat exchangers will suffice.
Dansk makes a very nice stock replacement. Be careful to research any "sport" mufflers. One on the market that we used in the past had impressive construction but generally cost 10-15 horse power and a crazy harmonic at RPM.

As for increasing the engine bore to 90 or 92. The difference will be boring the spigots. If you have a 4R case I recommend against boring the spigots that far. Although it was a fairly common practice in the past it offers two challenges. The small spigot flange offers poor cylinder stability. If you have a 7R case, this issue is minimized. At this point you're now dealing with the standard issue associated with 2.7 cases. The spigot bore ends up very close to the head studs. The mag case needs all the material available to prevent stud pull-out. Even adding CaseSavers (recommended for any size mag case) only adds some reinforcement.
Second is the collectiblility of the matching numbers case. Once you've bore the case, there is no going back (sans sleeving the case). With the ever increasing value of these old Porsches the trade off for a few additional CCs seems short sighted.

[OC73Targa]

Thank you Henry. I agree with you, few additional CCs are not worth losing originality of the case.
Taking the “2450’ build you mentioned above as a baseline, what is the difference in HP and torque between the mod-Solex and mod-S cams?
I would like to replace/upgrade heat exchangers to stainless. What is the best exchangers/muffler selection to get the most power/mid-range torque?

[Henry Schmidt]

Originally Posted by OC73Targa

Thank you Henry. I agree with you, few additional CCs are not worth losing originality of the case.
Taking the “2450’ build you mentioned above as a baseline, what is the difference in HP and torque between the mod-Solex and mod-S cams?
I would like to replace/upgrade heat exchangers to stainless. What is the best exchangers/muffler selection to get the most power/mid-range torque?

Mod Solex offers better mid-range and the mod S will give you a higher rev range. Both cams offer nice drivability. There is probably 15 horsepower difference between the two.
Performance wise, there is very little difference (if any) between the SSI and Dansk replacement heat exchangers. Both are made of stainless steel. SSI are polished and use a unique stamping for the boxes.

I noticed that your injection system is not stock for a 73 2.4. The stacks are magnesium from a 2.0 or 2.2. 72-73 2.4 stacks are made of plastic. Better pictures could tell me more but that is where you start.

[OC73Targa]

Oh wow good catch. Just run out to the garage to check. My stacks are not plastic!
Why would anybody change them from the original?
Do I need to get them back to plastic? Any difference?
What other pictures would be helpful?

[manbridge 74]

Start with the engine serial number on right side of case behind/to side of fan. You can also post the type number directly behind that which looks like xxx/xx but is a number.

[Henry Schmidt]

Originally Posted by OC73Targa

Oh wow good catch. Just run out to the garage to check. My stacks are not plastic!
Why would anybody change them from the original?
Do I need to get them back to plastic? Any difference?
What other pictures would be helpful?

The engine is definitely a 2.4 type. Serial number is not necessary.
The plastic stacks had a propensity to catch fire and melt/deform. Maybe that is way they were changed.
The other reason why someone would change the stacks would be to fit a large id stack. If the engine was ever taken apart, there may have been performance upgrades that would benefit from a larger intake. The only way to tell is to tear it down.
The only pictures I would need to see would be close ups of the throttle bodies.
Sand cast are early 2.0/2.2, die cast are 2.4. The magnesium stacks had a different system for cold start injection which mean the air filter housing and bases are different.
As a collectible car the difference is significant. As a driver, what you have will work fine.

[OC73Targa]

See attached a couple of pictures of the throttle bodies and of the cold start system (I had it removed when I replaced the fuel filter)

[Henry Schmidt]

From the pictures, I believe you have 69 2.0 E or S throttle bodies and stacks.
I can't tell from the picture which. The is evidence that the TB were rebuilt so they could be just about any size....32mm all the way to 41mm at the intake port.
There are 6 distinctly different sand cast throttle bodies and four different stacks.
69 E & S TB and stacks, early 70-71 E & S TB, late 70-71 E & S TB and E & S stacks.

The fuel stations are all the same.