6 replies to this topic

[minilee94]

What CR should I be running for a 1380 road car has 7cc dish omega pistons head is a stage 4head polishe and ported , double valve springs ,11 stud and big valves and running a weber 45

Iv been told to run

By med 10.7.1
Swiftune 10.3.1

There is a big difference here so what one
Swiftune said they wouldn't let a customers car leave there building running 10.7.1

[phil hill]

On the basis that you've already asked two notable engine builders about it what can we, the great unwashed, possibly add ??

 

You've not really given enough information about the engine spec. to be able to comment, by which I mean what cam is it running and what use are you planning.

 

The compression ratio required for 1380 running a SW5/Kent255 would be different than say the same 1380 with a SW22/Kent296/STR930, as would it's characteristics, idle quality etc.

 

From the things you have mentioned I guess it's something of a road-racer/track-day/weekend-warrior type car, so do we assume a cam like a 286/SW10 ??

 

The reality is that there isn't much difference between 10.7 and 10.3, only a couple of cc's in fact, so be specific with your machinist as only a light skim of block or head will be required.

 

Phil.

[samsfern]

Id go for 10.7. On my old mini, 1330, piper 649+can, etc, i ran 12.2 with no troubles.

[minilee94]

The engine will be running a med xt cam kit

And it's a road car

Edited by minilee94, 14 August 2013 - 02:24 PM.

[phil hill]

In that case, and as it's MED's cam, I'd take their advice.  

 

Phil.

[Old Bob]

Paul Inch has just shaved my Omega pistons to drop the CR to 10.5:1  He suggested that anything higher would increased wear on long haul road driving (racing is obviously quite different!).  On that basis, either MED or Swiftune are sensible options but since it's a MED cam I would go with their recommendation.

 

Bob

[minilee94]

Yeah cheers spoke to them again today and they said 10.5.1 so that what I'm guna go for