View PostKENut, on 07 October 2010 - 06:15 PM, said:

Seems most high power turbo K's use pretty big cams. True?

 

 

Not necessarily , big cams have big overlap and boost will push straight out the exhaust port.

 

High lift and big duration is possible, lobe separation is the biggest difference in a turbo cam important to prevent this^ from happening.

Yes, from what I've been reading people are using large cams (ie camtech 609 etc) but lobe separation isnt ideal?

And a couple have gone for custom jobbies, but there isnt much info on those!

 

So for a turbo application would you go for a smaller lsa?

So for a turbo application would you go for a smaller lsa?

 

Correct. Reduce valce seperation to reduce blow-by.

 

 

 

Edit: Brain fade, sound of said INCREASE VALVE SEPERATION.

Edited October 10, 201015 yr by Taz_Rx

higher lobe seperation, 114 for turbo grinds usually, na cams are usually approx 108.

My 5k going into my ke20. >from sump to carbs.

 

• 1988 liteace 5k block
  
• 4k sump
  
• shimmed oil pump
  
• 4k crank
  
• 5k conrods
  
• ACL bearing kit
  
• ACL dished pistons
  
• 25/65 278' mild cam
  
• Powerdrive twin timing chain
  
• holden solid lifters
  
• A12 pushrods
  
• 4k rocker assembly
  
• 5k valve springs
  
• 4k valves
  
• 4k head with heavy port/polish/manifold match
  
• hurricane short 4-1 tube headers
  
• redline inlet manifold
  
• twin 40mm Solex carbs
  
• Racer water pump
  
• electronic dizzy
  
• Bosch high energy coil
  
• top gun leads
  
• NGK plugs
  
• 4k flywheel
   
  

....it's built, just waiting for the car to come home to me. No idea what the output will be. I will likely bolt the sc12 up in the future....

 

hey mate, we used 5k valve springs on our bigport head running 10:7:1 compression and bent all the push rods as the valve springs closed up to qucik so we put holden ones in, just thought illd let ya no

hey mate, we used 5k valve springs on our bigport head running 10:7:1 compression and bent all the push rods as the valve springs closed up to qucik so we put holden ones in, just thought illd let ya no

That may have had something to do with the lift of your cam.

Edited October 8, 201015 yr by GJM85

That may have had something to do with the lift of your cam.

 

Could off, chucked out a brand new set of valve springs haha

i blame the massive hp of k motors lol

Correct. Reduce valce seperation to reduce blow-by.

 

higher lobe seperation, 114 for turbo grinds usually, na cams are usually approx 108.

 

To be precise, turbos run reduced valve overlap by increasing lobe separation...

 

Which must reduce the duration for each valve too.

Tight Engineering recommended the 104 cam for my set up as I would be running a low boost application, but would also be suitable of a NA set up.

How possible is it to run 5k crank, rods and pistons in my 3k block? Purely as my block is 1970 pre emissions :)

4K Crank into a 3k block would require removing material to clear the counterweights on the crank due to the longer stroke.

 

I asked this same question a long while back and that was the general answer i got.

 

5K pistons wont fit due to the bigger bore of the 5K over the 3K/4K.

 

Id just stick with everything in a 5K block. Newer, more than likely less corosion, possibly stronger and less hassles.

Edited October 9, 201015 yr by SLO-030

Sick of hassles with the law, would be nice to have an engine with no emissions laws, efi with a haltech would be a dream not to be able to be touched for that

How possible is it to run 5k crank, rods and pistons in my 3k block? Purely as my block is 1970 pre emissions :)

 

As with most K motors the majority of combustion occurs in the cylinder head. Adding the extra 12mm to the 66mm stroke of the 3k would see your piston top leaving the cylinder bore. You would need shortened pistons or conrods or both.

Ok thanks for the answer