Thinking of building a Frankenstein 69S 2.4 engine

[Mark Henry]

First and foremost, I'm another damn 914 guy who could care less about being “numbers correct”. I'm also on a bit of a low budget, basically I have to sell my cool VW bug and T4 stuff to get cool 911 engine stuff.
I other words I'm really another cheap VW bug guy. (not TOO cheap though)

Second, this is a street fun car, maybe I'll do a DE or AX someday. Nothing more.

Here's the dogs breakfast I have so far collected, the good, the bad and the ugly;

75 2.7S core, bottom end “looks” good, Cali engine that had reactors, alusil cylinders, damaged piston (reason for tear down) and pretty beat heads. Case has case savers, but is suspect due to reactors, small end of the rods are tight, STD crank, fan and shroud.

69 2.0T core,, OK condition, case has been case savers, but has a non-CW crank that needs grinding, 69T heads and cams, pistons shot.

69S "clone" heads, cut to 84mm spec, real nice, good guides, ported and polished and matched (thought one was real, it's not), suppose to been built by Peter Dawe. They are reworked and ported 67S heads. everything is 1mm smaller than a 2.7 head, 45x39mm valves, no MFI ports. I think I would replace the valves, pretty sure you can rework 46x40mm valves to work.

67S cams that I may try to trade for something more drivable...but I do live in the country

new 2.7 rebuild parts, almost complete, came with the 2.7 core, no head studs, items were bought from here.
80mm birals, heads have been cut, so these don't fit. Trying to trade for 2.4 in the classifieds (Came on the 2.0 core)
40mm IDA webers, 30mm chokes, good for break-in, but I'm serious about twin plugging it with megasquirt and future upgrade to FI is likely.
69S dizzy,
75S dizzy
69 flywheel is good for the 914 conversion.
Hydro tensioners, also have used 930's, new lockkits


If I can sell my big type 4 914 engine parts I might be able to swing some fancy P&C's, but I'd like to keep a 2.4 biral set and custom JE's in mind if I can't... If new P&C kit I would get off the pro's not ebay. I'm cheap not stupid.

The only concern for using 90mm cylinders (if I went 2.7) is the smaller '67 head outer "mating" surface would get milled off, I don't think it's an issue as the inner surface is the real mating surface. I can get 5 nikasils cheap and local, group 6.

I do have a bit of a clue and Wayne's book is in the mail, In the early 90's I built 3 stock engines (first one a true basket case) and I read Anderson's book. I've replaced seats and guides in VW heads and have built high end engines. Most machine work is no problem, twin plug looks doable, lots of 69T head practice cores for set-up and I'll get it balanced.
I've used aftermarket FI and nickies (type 4) in the past, lots of time to play and scrounge.

160hp I'd be a bit disappointed but OK, 180hp would be great, 200hp and I'd be dancing a jig.
I really don't want over 200hp as I don't want to be breaking other stuff, adding extra coolers, etc.

So any thoughts, ideas and advice would be appreciated.
I have many questions, but Wayne's book is on the way and that should answer many.
These are ones that might not be covered;

WTF would you do with this combo?
Is either case OK with mods?
What is the case hole size with 2.4 cylinders?
The 69S heads is the 46x40mm modded valves OK? I realize the shims and stems will need extra care.

Thanks Mark

L to R: 2.7 head, clone 69s head (7/66 casting) and real 69S head. 2.0S cylinder, but heads are cut for 84mm

[Mark Henry]

more pics

[chiroracer]

Wait for waynes book ,but you should consider using the 2.7 stuff with je pistons and 2.7 heads and the 67s cams the 69 stuff has smaller valves. good luck and dont cut corners. Steve

[kenikh]

Wow, that's a great bucket of parts. First, I am required to say that you will be far better off selling these parts and buying a used 3 liter. The reason is simple: pretty much all magnesium cases need to be line bored once they are disassembled, the 3 liter aluminum cases don't. The exceptions are the '69T case and the CIS 2.4T 7R case.

The '69T case is the least stressed of any 911 motor, as they barely made 130HP and didn't rev high; if you are going to find an early case that hasn't distorted, this is the one. It is also the lightest case for a 911 ever made, so the weight balance of any car using this case will be very good. The downside is that these are the weakest cases Porsche ever made and are not great for performance builds. They also don't have piston squirters, so the dollars needed to build one of these will quickly eclipse the value you extract.

The CIS 2.4T 7R case on the other hand, is similar in that they were very unstressed and additionally are the only small spigot case that is of the stronger 7R type. FWIW, I am using one of these cases for my motor and still resized and line-bored it just to be safe. Your 7R case is the larger 2.7 case, so doesn't fall into this category and is almost assuredly out of spec since it has the thermal reactors in place.

Regarding both of the above options, rebuilding a mag case is BRUTALLY expensive since unlike in VW land (I have a Type 3 hotrod), oversized bearings are unobtainium and priced to match. The only other option is to resize the case and line bore to standard, which costs about the same as line boring and buying oversized bearings ($1000, to start, without the other "nice to have" options). For context, I spent almost $3000 rebuilding my 2.4T 7R case to take the stresses of 300HP.

That said, if I haven't scared you off and you still want to use a mag case, here's the spec that will get you where you want to be with your parts:

Case:
Have the '69T case evaluated. If the mains are in spec, you can use it, but you will need to do some additional work to shore up its reliability. This would include doing the oil bypass mod and adding a bearing to the intermediate shaft saddle (if not already done by a previous owner), adding piston squirters and adding shuffle pins. You are very fortunate it has case savers! Given that the motor sounds like it basically grenaded, I would also have the galley plugs removed and the case flushed. For a good price list of all of this work, look here:
"Competition Engineering - Expert Porsche machining for 44 years - 6 cylinder case, case savers & cam towers"
Competition Engineering line boring - Expert Porsche machining for 44 years
Competition Engineering - Oil Systems - Expert Porsche machining for 44 years

Heads:
From the pic at bottom, your head are a mish-mash. Look at the casting dates and you will quickly see that they don't match. The far right head, BTW, is not a real '69S head - it is a '69T head that may have been rebuilt to '69S spec. The part number supports this.

Casting numbers and heads - clearing the confusion - Early 911S Registry Bulletin Board

Another point to note is that any head with a '74 date and beyond will almost assuredly be cut for 90mm P/Cs. If you post pics of the '67S heads, I could easily tell you if they are indeed what you think they are.

Pistons and Cylinders:
Are you sure your 80mm are Biral? The '69T came with cast iron cylinders, while the E and S are the only ones that used Biral. A magnet on the fins should answer the question quickly. Cast iron are not good. BTW, 2.2 and 2.4 cylinders are both 84mm, so you could source either. FWIW, for ~$200, you can buy an adapter kit from Supertec that will allow you to use the earlier cylinders with alter heads, versus replacing them.

Other:
Use the '69S dizzy - great advance curve
The Webers are a great choice
'S' cams get a bad rap - they are totally streetable and a blast to drive. Use them.
Tensioners - you can use either, I prefer the 930 tensioners w/ collars due to simplicity.

So the basic spec I recommend:
Use the '69T case with the recommended upgrades - DO NOT OVERBORE
Use the '67S heads (cut for 84mm)
Use the 2.7 crank (if good)
Buy some QSC/JE P/Cs @ 84mm and 9.5:1 CR (on 70.4mm stroke) - I recommend Supertec since they inspect every set.
Use the 'S' cams
Use the '69S dizzy
Use the oil pump from the 7R core motor

This will yield a nice 'S' spec 2.4 motor which will get you to between 190HP and 200HP with a nice, surprisingly torquey delivery, with an eager top end.

[Mark Henry]

Good stuff, cool!

The head set is one real 69S (edit I guess it's not, looks like a 69T head) and the other 5 (looks like 67S heads) have been ported, most likely new bigger seats and matched. 36mm intake ports and 45X39 valves

for sure biral 80 mm jugs

[Mark Henry]

Originally Posted by kenikh

First, I am required to say that you will be far better off selling these parts and buying a used 3 liter.

As if I haven't been told that

[stownsen914]

Hi,

One other thing to consider is that the 2.0L heads have a steeper combustion chamber and more prone to detonation, especially when used on larger bore engines. You might be better off with some 2.7S heads, which you should be able to find a set of those pretty cheap.

Scott

[Mark Henry]

Better pics of the heads and intake ports, only one head has the plugged MFI port. The 66 date heads are three 6/66 and two 7/66, same part number.

[Mark Henry]

Originally Posted by stownsen914

Hi,

One other thing to consider is that the 2.0L heads have a steeper combustion chamber and more prone to detonation, especially when used on larger bore engines. You might be better off with some 2.7S heads, which you should be able to find a set of those pretty cheap.

Scott

That's not the first time I've heard this said....

You know I have a set of 2.7 75S heads from the other core, I really having hard time seeing the difference in the chamber's between the two. (I see the plug relief is a bit different)

Like see though ports...I can see through the 2.7 heads, maybe a hair more on the 2.0 heads.
Chamber looks real close...same depth,

yes the flycut is different and I haven't CCed the heads...yet. Valve angle is slightly different, not much.

Cheers

[304065]

Mark, the 66 heads should measure 72cc, the 75 heads will be 68. This means that among other things, the piston dome volume will be lower for the same compression ratio (even notwithstanding the reduction in dome volume caused by the larger bore). Generally speaking, the smaller the bump on the piston, the less it divides the combustion chamber in half, which tends to increase the propensity for detonation. (Gross oversimplification). So you're better off going with the later heads, if I didnt' do concours that's what I would do.

[Mark Henry]

Mail call! I got Wayne's book yesterday....processing...processing... please stand by.... processing...