72 2.4, flat six Options

[CG-914]

Me and my dad are rebuilding a 72 2.4 engine.
They are some wired things going on with the parts in the engine so here are some facts and questions about them.

We are rebuilding the engine but also want to modify it.
Maybe different cams and make it a 2.5….

Engine Case
901.101.101.5R

Heads [Date?: 4x 72 + 2x 71]
911.104.306.OR [K 1819g]
Valve Intake 45 mm
Valve Exhaust 30 mm
Intake 37.5 mm
Exhaust 36 mm

The Intake ports are bored out. With that size are they even useable? also in regard of the plans? Are the valve sizes stock?

Cylinders [Mahle]
90 ZN 2 W6 [5x]
90 ZN 2 W5 [1x]
Diameter 84 mm
Total Hight 120 mm
Pistons [3 Piston Rings]
Hallmark 1: 83.95 [84 mm]
Hallmark 2: Sp 0,05
Are these the stock cylinders?

Cam Housing
901.105.111.OR
Stock?

Cam
left 901.105.183.OR [965?]
right 901.105.110.1R
Here it gets wired. With Wayne Dempsey's great book, I think this is a S and a L cam out of two different engines. Was that something a lot of people did?

Also the wear marks on them are pretty bad: See pics

Then the question about the 2.5 liter engine set up.
I understand, that they are two versions:
1: 2.7 liter as a high stroker
2: 2.4 liter with bigger bore.
With rebuilding a 2.4 what are our options to build a 2.5 exactly?
With what consequences? What needs to be changed/machined accordingly?

With that in in mind what cams are best?
As I read and heard the S cams are the best with now further consequences like taller intake manifolds?! Is there a great article about 911 Cams, they characters and consequences?

Thank you guys!

[Mike Bellis]

I don't know enough about flat sixes but those cams look NFG... (IMG:style_emoticons/default/barf.gif)

I'm sure there are better aftermarket cams than S, T or L.

[ConeDodger]

This is a question for Jeff "The Hammer" or sixnotfour to you... He will know what you have and which way you should go.

[Cap'n Krusty]

I think Jonathan at GPR is building a 2.5. Seems to me, FAR in the past, we used a 2/2.2 crank and rods with a 2.7 bore and special pistons. Betcha if you Google it you'll get all kinds of answers. BTW, a 2.7 is a 2.4 with a larger bore. You might want to go for that ............. The lobes on those cams can be welded and reground.

The Cap'n

[sixnotfour]

those heads should have 46 intake and 40 exhaust valves sizes.
the port size you have is modified.
the 90zn cylinders should be 90mm unless they have been sleeved.

more pictures

[sixnotfour]

2.7 with a 2.2 crank is a cheater 2.5 at 2519

[GeorgeRud]

If it started life as a 2.4, you already have a longer stroke crank (the short stroke 2.5 used the original 66mm throw crank). Using the 2.7 piston/ cylinder should give you a nice combination, just be sure to use case savers throughout so you are less likely to pull head studs. Are you going to be racing in an under 2.5 liter class?

You might want to check with Henry Schmidt at Supertec as he seems to know the combinations that work. He just rebuilt my 2.7 using the RS jugs and S cams.

[sixnotfour]

INHO the best autocross motor is a 2.4 S with solex cams cheapest and simple...SS motors you will need perfect gearing. You have not provided enough info about what you and you're dad intend to do upon completion..

[CG-914]

I dont know what crank and rods are in the case yet…

To the cap'n: they could be rewelded, the problem though is, that they out of two different engines… an S and E/L… so they dont fit or shouldnt?!

So the Jugs are stamped 90ZN which I guess now should be 90mm bore but they messure 84mmm I guess they are sleved, so 2.7 jugs to 84mm reduced, (= with a 66mm stroke that should be 2.3 or less…)

What confuses me is the Mahle diagram out of the Bruce Anderson book:
2.4 87.5mm bore 66.0mm stroke
2.7 90.0mm bore 70.4mm stroke

2.5 86.7mm bore 70.4mm stroke = long stroke
2.5 89.0mm bore 66.0mm stroke = short stroke

BUT:
The Wayne book says the 2.4 engines had a 84 mm bore and pistons…. (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif)

When the engine is done, the car is going to be a daily driver, but my dad and mom are canyon carvers and take no prisoners in the mountains every weekend or dont mind a 'sharper' engine everyday…

[sixnotfour]

looks like you may have a class specific built motor.. where did you get it ??
what is the case serial number ?? casting number on the bottom side of piston ??

[CG-914]

looks like you may have a class specific built motor.. where did you get it ??

Its a german car imported to LA in 2004.
It has factory fiberglass bumpers and fenders from the factory.
Factory recaro race seat on the driver side
The bad part is, that it has a welded shut oil cap on the right rear fender…

Any idea what motor?

[CG-914]

looks like you may have a class specific built motor.. where did you get it ??
what is the case serial number ?? casting number on the bottom side of piston ??

ID *6522038*
Pistion bottom is hard to read what we can make out:
4P8+

[sixnotfour]

84P8 are 2.2S pistons
Mahle for about 8yrs ? uses the 90mm casting and does the 84mm bore and they are Nikasyl coated inside, The old ones were aluminum fins with cast iron liner.Biral. Your piston and cylinder set is 4k

so if you have a 70.4 crank = 2.4

the BA 2.4/2.5 specs are for 2.5 race motors and are expensive and rare today.

factory 2.4 is 84 x 70.4



ID *6522038* is a 72 2.4 ,,like you said.

[sixnotfour]

http://www.elgincams.com/

http://www.webcamshafts.com/mobile/automob...1_sohc_12v.html

for a regrind or weld up.

look at the big end of the cams, grinders usually stamp the grind number on that end. no matter what the casting numbers are.

[totle]

I have kind of same setup.
Trying to figure out my engine spec.
I have same cylinders as you 90ZN2, but they are as well 84mm
2,2S pistons.

Do you have more info of the cylinders?

[JmuRiz]

2.2s in a 2.4 was an old hot-rod setup, because there weren't many options.
My brother is spec'ing out a 2.4 rebuild too. He talked with Henry at Supertec, he suggested his 2.45 engine build, I can dig up the specs later today if you like (or search for it on the pelican engine builder forum).

Edit: found the correspondence -
It is basically a 70.4 stroke x 86mm bore.
Slightly under 9.5:1 compression and use a DC "mod S" cam.
These engines make great torque while still producing 180 hp at the wheels @ only 6500 RPM.
The only other modification is a 36 mm intake port.

Btw, I think he strips and re-coats the pistons with nickasil

[sixnotfour]

I have kind of same setup.
Trying to figure out my engine spec.
I have same cylinders as you 90ZN2, but they are as well 84mm
2,2S pistons.

Do you have more info of the cylinders?

one more time;
Mahle for about 8yrs ? uses the 90mm casting and does the 84mm bore and they are Nikasyl coated inside