This ought to be good...

[speedo]

Stock 2.2 engine numbers matching to car. Needs to be refreshed, so it is going to be completely rebuilt. The options I am exploring...to spice the engine up somewhat are as follows...
1) replace the heads with some reduced combustion area heads and run the T pistons. I will need to determine how much of the combustion chamber has been filled and machined. Determined that there is no way S pistons can be run. Stock T pistons and 66mm crank with increased compression due to heads.
2) use existing heads and run a 70.4 crank. The 2.2 T pistons were an 8.6 vs the 2.4 being a 7.5 CR...this will give me an automatic bump. So 70.4 crank with stock T pistons and increased CR due to 70.4 stroke.
3) run the 70.4 crank and the T pistons and the high compression heads.

The car is a numbers matching targa with a soft window. IE...flexible car. I want a spirited engine, which is why I am not using the extra set of 2.2 S pistons vs the T pistons. If this were a race engine build...story would be different. FWIW, I am going to run E cams with the setup and most likely port the IE to 35-36mm.
Thoughts?

Speedo

[speedo]

Lists the 2.4 T pistons at 7.5 CR. Wow...that seems low. So simply replacing the 2.4 T pistons with 2.2 T pistons bumps the CR to 8.6, so what does that do to the nominal hp with the 70.4 crank? Anybody done the lowly T replacement or are all the swaps focussed on E and S pistons?

Speedo

[gestalt1]

I think swapping the crank and rods is a great idea. You also get the displacement increase. For the heads i would just have them flycut to increase the CR a little.

[speedo]

So with the 2.2 T P and Cs, which had 32-32 ports, with the higher compression T P and Cs, should I open the ports up for better flow? I have a nice pair of E cams that I could add to the mix. Remember that I am going to run "tweaked" zeniths. I guess if I am going to flycut the heads, I will need to cut down the chain housings also to keep the cams centered in the towers?

Speedo

[304065]

Flycutting the heads is a very bad idea.

When you do that, you're basically reducing the deck height, which will give you a compression increase, but you also decrease the piston to valve and piston to head clearance.

On the other I hand I think the idea of using heads where the combustion chamber is smaller is a pretty interesting idea. Unclear the impact on the heads when they are welded up, and I assume from he budget that you aren't talking about Xtreme Heads.

The T pistons are not that exciting, but they do have the benefit of a fairly small dome volume. So if you did use the reduced volume heads, interference might be manageable.

Anyway, if the reduced volume heads aren't an option I would either stroke it or leave it stock.

[HawgRyder]

If in doubt about cutting the heads...try the old Plasticine method first (will save you a ton of $$$).
Assemble one rod..piston..cylinder unit on the crank...place a piece of Plasticine on the top of the piston...revolve the crank once...take the head off and check for thickness of Plasticine.
This will give you a start point.
The valves have remained closed because the cam was not in stalled.
Next...put the head back on and as the crank gets to top dead center....push the valves open ( I use weaker or just the inner springs at this point) and note the depth of travel (how much the valve opens) before it hits the top of the piston.
If you know the lift of the cam...and the ratio of the rocker..you can subtract that figure from your measurement to get the clearance of valve to piston (this would be the ideal number) the more worn the cam or rocker will give less lift.
Safety first...and you will collect a great deal of info for the next engine.
I'm sure that somebody here knows the amount of material to remove for each point of compression.
This method BTW allows for lots of experimentation with different pistons...both Porsche and aftermarket.
Bob

[gestalt1]

I do agree that flycutting the heads is not good due to the piston to valve clearence problem. However your cams are mild and keep in mind that when the piston is at top dead center the valves are not at there max opening, you really need to pre- build the top end to check clearence. An alternative to milling down the chain housings is to get shims to put between the cam tower and the heads- i think Henry sells them. I was only suggesting to flycut a small amount as to not cause the above problems.

[haycait911]

FWIW I'd be inclined toward component swapping over any machining. mostly it's a headache that creates other problems. lots of swapping options with these things.

also, big ports might just kill the bottom end of what is a very nice torquey motor. on my 3.2 stroker I'm going 35mm intakes for just that reason.

** please note**

the above opinions are worth exactly what they cost, or maybe a little less.

[speedo]

And just stuff the 8.6cr 2.2 T pistons inside with the 70.4 crank and rods, will I end up with a true 8.6cr vs the 2.4 T 7.5cr? The heads are the same right? By going with the 70.4 crank...will I gain cr (and how much) or do I loose cr (and how much)? The type 911/03 was 8.6cr and 125 hp at 5800 rpm, while the 911/51 was 7.5cr and 140 hp at 5700rpm. So maybe...150 hp, and a nice torque curve with E cams? Getting close to what the specs are for a 2.2 E type 911/01. That would be a very acceptable bump without chasing myself around being worried about machining complications.

Speedo

[304065]

here's some math for you buddy

The first thing to do is backsolve the dome volume. These calcs assume a 1.0mm deck, and they assume the factory used a 1.0mm deck. The factory may have quoted their compression ratios at zero deck, however (that's another story).





and just stuff the 8.6cr 2.2 T pistons inside with the 70.4 crank and rods, will I end up with a true 8.6cr vs the 2.4 T 7.5cr? - no you end up with 9,1 just like the 2,2 E


The heads are the same right?right, 68cc combustion chamber volume

By going with the 70.4 crank...will I gain cr (and how much) or do I loose cr (and how much)? Think about it like this: with a longer stroke you have a greater swept volume. If you compress that into the same size head, using a piston that has the same size bump on it, then the compression ratio has to go up. And this in fact is exactly what happens, you can see how the math works

The type 911/03 was 8.6cr and 125 hp at 5800 rpm, painful

while the 911/51 was 7.5cr and 140 hp at 5700rpm. this had to make the marketing people cry

So maybe...150 hp, and a nice torque curve with E cams? (Hmm, if you use E ports, and you have the same compression ratio as a 2,2 E, and E cams, then you should be good for E specific output. 2,4E was 165 HP which is about what you should end up with. Except that the 2,4E used a smaller piston dome, it had lower compression. Horsepower for the factory motors is pretty linear with stock parts and normal aspiration.

[speedo]

This was exactly what I was hoping to find out. As soon as the car goes to paint I can break the engine down and see what shape the internals are in. This is all based on the assumption that the P and Cs are in decent shape...if for whatever reason they are not...I will go to plan B. And at this point, I am not sure what that looks like.
Thanks guys

[SWS911]

I would just stroke the engine with the 70.4 crank and leave the ports small and run the "T" cams. Should be a peppy, torquey very fun driver.

[speedo]

Sending of my 70.4 crank to get fluxed and polished and cleaned and replugged. My 66 rods were 9111031030R, and my 70.4 rods are 9111031050R. I did a search on rod lengths and didn't come up with much. Are the 66 and 70.4 rods different lengths? If not, the difference in stroke is 4.4mm so th 70.4 would push the piston into the head. The cylinder base gaskets for adjusting dome heights allow a max of 1mm...preferentially 0.5mm. So the 70.4 rods must be shorter than the 66 rods...unless I am missing something. The stroke is longer by 4.4mm so if the rods were the same...the overall stroke would be 8.8mm longer, and would hit the heads. This must be much simpler than I am making it out to be. I guess my real question is...with the 70.4 crank, what should my rod part numbers be?

Thanks

Speedo

[304065]

Originally Posted by speedo

Sending of my 70.4 crank to get fluxed and polished and cleaned and replugged. My 66 rods were 9111031030R, and my 70.4 rods are 9111031050R. I did a search on rod lengths and didn't come up with much. Are the 66 and 70.4 rods different lengths? If not, the difference in stroke is 4.4mm so th 70.4 would push the piston into the head. The cylinder base gaskets for adjusting dome heights allow a max of 1mm...preferentially 0.5mm. So the 70.4 rods must be shorter than the 66 rods...unless I am missing something. The stroke is longer by 4.4mm so if the rods were the same...the overall stroke would be 8.8mm longer, and would hit the heads. This must be much simpler than I am making it out to be. I guess my real question is...with the 70.4 crank, what should my rod part numbers be?

Thanks

Speedo

Lars, of course the rods are different lengths. The geometry of the engine didn't change-- when the factory stroked the crank from 66 to 70.4( a difference of 4.4mm) the rod had to get shorter by half that length (130mm - 2.2 =127.8mm)

If the rods were the same length you would end up with the piston 2.2mm above normal deck height, remember that the stroke is a circle with half the extra length on the top and half on the bottom, but for measuring deck only the top half counts. Now, normal deck is 1.0mm, which means you'd have negative deck of 1.2 (like a 964, where the piston actually protrudes into the head)

In practice you never have this problem because the way the factory stroked the crank in 1972 was by offset grinding the crank forging and making the big end smaller. To get back the bearing area lost by reducing the big end diameter, they made the bearing wider, and therefore the side clearance from 2,0-2,2 rods would be noticeably gigantic when you tried to bolt it up. See here for more: Two Inch NASCAR Bearings

Part numbers? I would have to check PET

[speedo]

Parts are deposited today to various shops for machining. The dizzie...should I have it curved for a 2.4 E? That would make sense as I will be running E cams, and the compression is bumped up close to a 2.4 E engine.

Speedo

[304065]

You have a 2,2 case so it takes the small bore aluminum body distributor.

What do you have, a Marelli?

I would try to find a 2,2E distributor and have it rebuilt so you have the right curve. As Ed Mayo says, they stopped putting gas in the gas years ago, so an advance curve like the 2,7 might be appropriate. You could even buy a new bosch distributor for a 2,7 and cut off the timing sector and turn the shaft down to fit, that would give you a brand new part.

Talk to Ed Fall at Vintage Werks.

[speedo]

The report back from the machine shop doing my heads and planning to hone the cylinders is that some water got into the intakes and rusted 3 cylinders. I have a few extra 84mm cylinders from a defunct 2.4 I acquired in a deal. Do I need to worry about height groups in matching these? I have a 2.2 E dizzie that is going to be "mildly" recurved. All my parts are at the machinists. I am ordering bearings, rings and gaskets. Th rebuild will start over the approaching holiday.
Thanks for all the help you guys

Speedo

[304065]

Yes, height groups are very important. Remember that if the cylinder height is different on the same bank you will have a hard time getting the cam to turn. Remember also that the cylinder height ultimately affects deck height which then affects compression, piston-to-head and -valve clearance as well as the geometry of the chains.

It's so easy to measure cylinder height that there's no reason this should be an issue. I suppose if you had a really bad mismatch you could use thicker base gaskets to compensate to get you back to stock height. Make sure the machine shop measures spigot height, the difference between the centerline of the crank and the seating surface of the cylinder.

[speedo]

I get the part number for the correct 70.4 rods to be 911 103 105 0R...this make sense? Went ahead and replaced the pin bushings as they were a bit worn.

Thanks guys.

Speedo

[speedo]

Case first...
Gently linebored. No oil bypass mod as I plan to run the 2.2 oil pump (not a race motor). Am I correct in that if I run a larger pump (2.7) I would need the oil bypass mod? For my purpose am I better to just use the 2.2 pump?
Also, it was stated somewhere that to run the larger throw crank that I need to clearance the case for the 2.2 T piston skirts...I can't find verification of this anywhere.
Finally, my carbs. I just did an extensive rebuild of my zeniths. Two questions here...I went ahead and reused the 27 zenith venturies as they were all that is available...and thinking they should flow fine with the stock ports. Now I read that weber 32s could be used with some modifications, but cannot find any discussion of what those mods might be. Last, the enrichment circuit should be disabled and apparently it was already as the little ports on the outside bottoms of the barrels are plugged. The device (diaphram) that feads these ports was included in the rebuild kit, so it got rebuilt. What are the exact steps to disable the enrichment circuit, and how do I check to see if this has been performed...or perform it myself?
Thanks guys! Ready to jump in, but better to ask these last minute questions now...vs when the long block is bolted up.

Speedo