5k Block With 3k Head

[Bigger Is Better]

Hi guys could anyone tell me what sort of compression i would be looking at running a 3k big port head on a 5k block and what other ways i can up the compression. ie different pistons, decking the blocke etc.

Cheers

[camerondownunder88]

Pends if it is a dish piston 5K or not.

 

If it is dished will drop CR if it is a flat top 5K should be same.

 

But hey put it on and a turbo/SC and hey perfect setup for boost.....

 

Cameron

[madrolla68]

Pends if it is a dish piston 5K or not.

 

If it is dished will drop CR if it is a flat top 5K should be same.

 

But hey put it on and a turbo/SC and hey perfect setup for boost.....

 

Cameron

 

 

thats exactly what i have 5K dish pistons,3K head with copper head gasket and shim and it comes out at 7. 8/ 1

[Hiro Protagonist]

Seeing as how the 3K head has a different bore to the 5k, how exactly is this possible without major boring? 3K head can fit on a 4K, but only because the 4K is essentially a stroked 3K

[anastasios]

hey mad rolla where did you get your copper head gasket from?

[camerondownunder88]

Hi,

The head on pretty much all K motors is the same apart from 7K and there are different styles between dished and non dished piston heads and XK-E head :D

 

The normal 3K head is a style for flat pistons so combustion is in the head. But From what I know all those heads it doesn't really matter on bore size as such as those heads on a for example a flat top piston 5K with a 5K gasket for the bore size as there is just a small flat section of head all the way around the CC now. And a standard K head has the D shape bowel so it has a section filled up anyway so no harm done. But for performance maybe this lip should be removed to say Fit the bore better.

 

But on a Dished piston 5K there heads were flat as combustion happens in the piston so when the head is on this motor and it has the combustion area in the head compression drops so this lip that will be there is mmm better as it could/might provide better air turbulence and more metal to take up space and lift performance so I would pretty much never worry about it here.

 

My explanations a bit crap but you might understand this is how I see it. ANd hey just try It is amazing what a K motor can take..lol I know :yes:

 

Cheers

Cameron

[Xany]

thats exactly what i have 5K dish pistons,3K head with copper head gasket and shim and it comes out at 7. :yes: 1

 

Also the same setup i am running....5K dished piston engine, with 3K bigport head...standard 5K headgasket (i do have a copper one when that one goes). Waiting on a few parts....then it should go even better :D

 

The Copper headgaskets were on ebay a while ago.....they were laser cut...can't remember how much i paid.

[Hiro Protagonist]

Once again I ask, how can this happen without serious boring out of the head (or does everyone like squish zones?). The 5K block has a bore of 80.5mm, the 3K has a bore of 75mm.

[Xany]

if you have a look at a 5K head then my 3K head......

 

 

5K

 

3K Bigport

 

not much difference eh?

[Bigger Is Better]

So what do you guys reckon that i should do i'm building the motor for a hill climber and i want the comp around 10.5-11:1. I know there is also variants in the 5k pistons. Which pistons are better to use compression wise or is there another piston i can use.

Cheers Josh

[camerondownunder88]

Hi,

Well you can use a 3K-B head and shave it to get compression up or also shave the block

 

Now pistons grab your self a set of 4agze pistons and 100Kw 4age con rods. These will fit in I think 4agze pistons like half a mm bigger so you will need a slight bore. The con rods are 3mm narrower than a 5K rod BUT you can weld them thicker mill em down if your worried, but that is work.

 

But from a tested and proven motor if not weld the oil pressure holds the rod still and well no damage after revving mm HARD as it was a rally KE rolla so for your use Id just install the rods no welding.

 

That will give u good rod and piston setup and shave block head and that will up CR and presto a pretty mean 5k.

 

Cheers

Cameron

[Bigger Is Better]

I also think i read somewhere on this site about using gemini pistons but i can't seem to fine it or am just imagining this. Don't 4AGZE have a diffrernt stroke asweell,

 

Cheers Josh

[camerondownunder88]

Hi,

4agze I believe have a different stroke YES. But your using there pistons so same bore so no problem but the 100Kw 4age has the right length rods and standard handle power and rev hard so no problems there mate.

 

Also gudgeon pin in 5K i believe is 18mm 4agze pistons 20mm so for easier build use 4age rods as standard ones will need tinkering to get them to meet up. Also 4agze pistons gudgeon pin is closer to the top of the piston so there you could say less top heavy so will rev harder and not as much free weight slapping around in the bore the weight is lower and can move better so Id use Toyota gear so 4agze pistons 4age 100KW version rods EASY..lol

 

Cameron

[Bigger Is Better]

Hi,

4agze I believe have a different stroke YES. But your using there pistons so same bore so no problem but the 100Kw 4age has the right length rods and standard handle power and rev hard so no problems there mate.

 

Also gudgeon pin in 5K i believe is 18mm 4agze pistons 20mm so for easier build use 4age rods as standard ones will need tinkering to get them to meet up. Also 4agze pistons gudgeon pin is closer to the top of the piston so there you could say less top heavy so will rev harder and not as much free weight slapping around in the bore the weight is lower and can move better so Id use Toyota gear so 4agze pistons 4age 100KW version rods EASY..lol

 

Cameron

 

So the rods are obviously longer on the 4AGE engines then but what is the style of piston like, are they flat tops or dished and what is the volume of the dish. I can get 5k pistons with a 3mm dish on the for $150 a set. If it is going to be the same volume dish or greater i would be better off getting these psitons to save the stuffing around.

 

Josh

[camerondownunder88]

Hi,

The pistons ill have to double check to see if i can get dish capacity of 4agze ones BUT on the pistons shape 4agze ones have a small dish smaller thana 5K 3mm one but it is a dish for the 4 valves to fit in pic at end of my post so these will prob up CR more with less shaving

BUT $150 for 3mm dish 5K pistons good price so if your not running boost get them a bit less stuffing around and in the mean time if your interested just play with 4agze ones and see if you want them one day as they will rev VERY hard when you blue print the bottom end and use them so recommended even if you don't run boost but want to rev hard.

 

But if you run 3mm dish 3K-B head you will still need to shave the head/block to up CR as I believe you can shave a stock 5K up to 5mm before it is to high and pings on fuel so you can take a fair chunk off. As they have combustion in piston bore standard so a 3K head it can happen there so the extra length a 5K bore had can be taken out.

 

Cheers

Cameron