Need conversion advice 3.0 to 3.2
 

I am rebuilding my 78 sc motor and I have come across a set of 3.2 P's &C's so I figured I might as well do the upgrade to it. I would like to know if the crank and heads and wristpins on the 3.0 are the same as the 3.2 or do I have to do something more to complete the conversion. I will be running SSI's on it as well. I am wondering if anyone who has done a similar conversion can give me any feedback on the results.

Thanks,
Norm SmileWavy

in going from 3.0 --> 3.2

the factory changed the CRANK not the pistons.
this is referred as a long throw 3.2
the pistons were 95mm (same as the SC)
the throw is 74.4mm

what you are doing is making a short throw 3.2
the 3.2L conversion kit pistons are 98mm
the stock SC crank's throw is 70.4

Also the wrist pins of the 3.2 are different from the 3.0...i think 23mm vs 22

The 3.2L heads are also different. I think the valve sizes and ports are the same but the combustion chamber shape is different. The 3.2L are superior...also the early SC heads have bigger ports then the later SC heads

then the induction went from CIS to Motec

the short throw is supposed to be a little more zippy and high revving
the long throw will proabably have more low end torque



You need to give more details about the pistons and cylinders you bought. if they are STOCK off the factory 3.2L the pistons will not be compatible with your connecting rods. the cylinders are the same as the ones used on the SC (95mm)

to make a SC --> a 3.2L

usually you have to buy a Mahle 98mm p/c kit that works with your conrods
or
bore out your 95mm to 98mm...replate/resleeve and use custom JE pistons, use your SC con rods
or
replace your 3.0 crank with a 3.2 and the p/c from a 3.2L and the 3.2L con rods


so if you did buy 3.2L pistons off a 3.2L engine there is no way you can make a 3.2...you will end up with 3.0L (because of the diff in crank) with pistons that may not work with your CIS


More details please...

MJ

Thanks for the reply MJ, From what I gather I will be having a smaller diameter piston with a longer throw so I am actually not making any gains is that right?

I am basically buying the pistons and jugs from a stock 3.2 motor and I was hoping that the displacement increase would give me the boost I was hoping for but I see more clearly what you mean about the wrist pins and the crank throw so I am better off with rebuilding it stock and just stay mith my original configuration. Do you have any negative thoughts on replating cylinders at all?

your 3.0 throw is shorter then a 3.2
the pistons diameters are the same

so you either need to increase piston diameter or increase the throw

if you bought factory 3.2L p/c you have done neither

98mm Mahle kits go for about 3K
and they come in 2 flavors 1) CIS pistons 2) carb/MFI pistons

if you want more power it is proabably cost effective to buy a 3.2L engine and sell yours as a core...then you end up with a 3.2L with the superior Motec fuel injection

there are also minuses...you can search the archieves to help your decision

or do the ubiquitous 3.6L transplant for about 10K sell your engine for about 1500.00

rebuilding an engine is tough enough, but if you start making mods...they lead to other mods like compression ration...cams...distributor curves...etc...you need alot of planning

MJ


EDIT: yeah don't buy the pistons and cylinder they will do you no good...if you want a 3.2L the Mahles are the best way to go

search the achieves I know I have posted some combinations...you can/should talk to andial, EBS, Rennsport systems, etc...as well as this BBS

buy Bruce Andersons book, buy waynes new engine book

you need to do ALOT ALOT ALOT of research before you start buying parts...

good luck


Probably the most cost effective method:
if your p/c are reusable just rebuild, add 964 or Webcam 20/21 cams
add SSI's and carbs if emissions are not an issue

that will result in a pretty decent motor

also don't forget the mods like the pop-off valve, carrera tensioners, and not rubber centered clutch

Mark-

You may be confusing Motec with Motronics in this discussion. Two different animals. Porsche DME is known as "Motronics", made by Bosch. MoTeC is also a digital engine management system, but another manufacturer, and for Porsche, aftermarket only.

TT

oops...

I am gonna make a visit to SD one of these day...I think the element of surprise will help me wrestle those seats from you