914/6 Conversion Project, Identifying Engine Specs Options

[Dugo16]

I recently picked up a 914/6 conversion project car. I am in the process of trying to figure out what is in the engine without fully disassembling it since it appears to be in good shape. Engine is out of the car. Here is what I know so far.

- 1972 911T Case (911/07)
- 90mm Cylinders (90zn2)
- K1819n heads (one is a K1819g)
- 40IDS3C carbs

Trying to figure out what cam and crankshaft are in there.

Valve lift measurements below where measured with a dial gauge placed on the valve retainer.

- Intake lift .402
- Exhaust lift .376

Stock cam?

I figure the crank is a 66mm but it could be also be a 70.4mm from what I have read. Anyway to figure that out without disassembly?

Thanks in advance for any info. I appreciate the massive amount of knowledge the 914world community has!

-Doug

[brant]

72 year would have come with a 70.4 crank

I think with 90cylinders
Most likely a 2.7

But that’s a guess
On my part
Could be otherwise

[Dugo16]

I recently picked up a 914/6 conversion project car. I am in the process of trying to figure out what is in the engine without fully disassembling it since it appears to be in good shape. Engine is out of the car. Here is what I know so far.

- 1971

911T Case (911/07)
- 90mm Cylinders (90zn2)
- K1819n heads (one is a K1819g)
- 40IDS3C carbs

Trying to figure out what cam and crankshaft are in there.

Valve lift measurements below where measured with a dial gauge placed on the valve retainer.

- Intake lift .402
- Exhaust lift .376

Stock cam?

I figure the crank is a 66mm but it could be also be a 70.4mm from what I have read. Anyway to figure that out without disassembly?

Thanks in advance for any info. I appreciate the massive amount of knowledge the 914world community has!

-Doug

Apologies for the typo. It is a 1971 911T Case (2.2) and not a 1972.

[930cabman]

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Great way to start off with a /6 conversion.

Is it a running engine?

Rust issues? Pics

[infraredcalvin]

I’m going through this on a heavily modified 3.4, there is no way to tell until you take it apart. When measuring at the spring you have to take into account the rocker arm ratio… apparently this can vary with a reground cam….

If its a runner, get it tuned best you can, dyno it, compare to stock numbers, if you’re happy enjoy it, or go down the rabbit hole…

[burton73]

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Please post some pictures

Best Bob B

[targa72e]

for early cranks 2 plugs on flywheel end is 66mm one plug is 70.4.

john

[sixnotfour]

https://www.drcamshafts.com/911profiles.htm

[sixnotfour]

might want to price check IDS webers...

[brant]

might want to price check IDS webers...

I saw that...
might be the motor was built up with those carbs
or they used what they had.
but nice carbs!

brant

[930cabman]

might want to price check IDS webers...

I saw that...
might be the motor was built up with those carbs
or they used what they had.
but nice carbs!

brant

AFAIK the differences are mostly cosmetic

is she a running engine?

[brant]

That carb has one difference though that makes it better

It’s able to add enrichment through an extra circuit at red line
Unlike all of the other 3 barrel webers.

A functional upgrade. Not cosmetic

So great for high rpm applications over 6-7000 rpm
One year only
And originally on the last carb’s 911S
So valuable carbs

[Dugo16]

for early cranks 2 plugs on flywheel end is 66mm one plug is 70.4.

john

Thanks John. It is has two plugs so 66mm crank. That confirms a short-stroke 2.5.

[Dugo16]

If its a runner, get it tuned best you can, dyno it, compare to stock numbers, if you’re happy enjoy it, or go down the rabbit hole…

I agree with you, the specs don't really matter since I won't be tearing it apart. It just kills me not knowing exactly what is in there...

[Dugo16]

[quote name='930cabman' date='Aug 18 2025, 08:40 AM' post='3219964']
[quote name='brant' post='3219962' date='Aug 18 2025, 09:21 AM']
[quote name='sixnotfour' post='3219933' date='Aug 18 2025, 07:35 AM']
might want to price check IDS webers...
[/quote]

is she a running engine?
[/quote]

IDS webers were a nice surprise on this one. I am rebuilding them now.

Engine was running before I pulled it. Idled was really bad and had some popping but sounded great at around 3500rpms

[Dugo16]

Moving on to the clutch and trans.

Clutch disc only shows wear on the outside half on the flywheel side. Is this normal? Normal for a new clutch disc?

Clutch disc measures at 9.7mm so thinking it is pretty new based on new ones being around 10mm. Flywheel surface looks good and appears to be flat using a small straight edge.

-Doug

[porschetub]

for early cranks 2 plugs on flywheel end is 66mm one plug is 70.4.

john

Thanks John. It is has two plugs so 66mm crank. That confirms a short-stroke 2.5.

I wasn't aware you could run 90mm pistons with a short stroke crank, seem to remember 86mm is the largest short stroke kit available ? think the the 86mm kit gives displacement over just over 2.3 litre .
Regardless of that sounds like it you a good motor, mine is a 71 2.2T motor and with a few mods it is a fun drive , but changing cams apparently wakes up an otherwise tame engine as many have done.
Good luck in your build, cheers.

[porschetub]

Moving on to the clutch and trans.

Clutch disc only shows wear on the outside half on the flywheel side. Is this normal? Normal for a new clutch disc?

Clutch disc measures at 9.7mm so thinking it is pretty new based on new ones being around 10mm. Flywheel surface looks good and appears to be flat using a small straight edge.

-Doug

You can most likely reuse that clutch disk but not with that flywheel without getting it ground and resurfaced, post some pics of the flywheel and pressure plate would be handy to help you further, cheers.

[sixnotfour]

for early cranks 2 plugs on flywheel end is 66mm one plug is 70.4.

john

Thanks John. It is has two plugs so 66mm crank. That confirms a short-stroke 2.5.

I wasn't aware you could run 90mm pistons with a short stroke crank, seem to remember 86mm is the largest short stroke kit available ? think the the 86mm kit gives displacement over just over 2.3 litre .
Regardless of that sounds like it you a good motor, mine is a 71 2.2T motor and with a few mods it is a fun drive , but changing cams apparently wakes up an otherwise tame engine as many have done.
Good luck in your build, cheers.

90mm into a 2.2 case is done by boring out the case.. has been done alot , usually crack behind cyl. #3 case is weeker that's a 4-5r and 7r 2.4...2.7..
Nice about 911 engines the rods and cranks go together..to make combos possible..

[Dugo16]

[/quote]
You can most likely reuse that clutch disk but not with that flywheel without getting it ground and resurfaced, post some pics of the flywheel and pressure plate would be handy to help you further, cheers.
[/quote]

Certainly. Here is the pressure plate and the flywheel. Thx.