5K Head Cc And Cr

[springersrolla]

hey guys hows it goin, ive just picked up a 5k head thats been worked, i was told it was running all standard apart from aftermarket pistons. the motor apparently was running 11.5:1 :blinks: the head has the 2 tabs under the 1 and 4 spark plug tube so I'm sure its 5k head, its running standard 5k rocker gear, head was skimmed apparently 50thou, but comparing my 4k head to the 5k, it looks like about 5mm has been taken off it.

 

inlet ports have been opened and larger valves, ill have to check size, exhaust cleaned up, retaining original valves.

 

the bloke it bought it off reckons it went like a shower of shit, and said he had to retard the advance massively to compensate the compression ratio,

 

so now my question is.. if i run my 5k i just bought, lucky its had a fresh rebuild when i had bought it, if i cc the head, can someone tell me what the standard cc of the 5k head is?,

 

i'll have to get the head off soon to work out the pistons in the 5k, see what size dish they are, and figure out a cam and intake setup to suit. anyone with a bit of help would be good cheers

[springersrolla]

i measured the sizes and got 32mm from the inlet port, 33mm inlet valve, standard looking exhaust port, exhaust valve 25.5mm

 

this is what he told me. The inlet ports were opened up to the proper ratio for the larger inlet valves, the combustion chamber was reshaped for a quick burn, new guides and seats were fitted and it was shaved 30 thou. The standard k motor distibrutor needs stronger springs to slow the spark advance 'cause of the higher compression and quicker burn.. I did some research, picked the sizes for the inlet valves and ports and it turned out pretty good. head flows 139hp and should have 11.5:1 CR stock pistons.

[philbey]

Ports are definitely stock, combustion chambers look standard, maybe a little work but I don't reckon much.

 

Valves are standard looking.

 

Your increased compression most likely comes from the pistons, stock dished ones are 22cc and replacement new ones are about 9 cc, I ended up with way too much compression but got away with it by putting in a big cam.