How Much Can I Shave A 3k Head

[TheHeadShaver noob]

Hi

 

I have a 3k engine i wanna shave the head off just a little, the car is a daily driver so I'm not looking for anything extreme, just need it flattened and I'm gonna take a bit more off just to get a lil more compression.

 

How much can i safely shave off without compromising the engines life or having to do any other mods to the head? a 1mm?, 2mm? i don't know how that will translate into the compression ratio, but like i said i don't want anything extreme, what would u reccomend?

 

I also wonder how i can identify a 3k engine from the numbers stamped on the block, i need to find out when its made, and preferably wich kinda car its from, corolla or starlet.

 

thanks in advance for all ur help :D

[jason12]

I've heard about 20thou, but you may wanna double check

[maxyboy55]

my 4k had a static compression ratio of 8.5:1 (from stock) (measured)

i shaved it 40 thou (1mm) and ended up with a static compression ratio of 10.7:1

 

i would say to measure the volume with a pipet and piece of perspex and calculate it from there,

shave it 20 thou or 30 thou and see what you get

[Redwarf]

Have taken anything up to .125 (3mm) off one. When the leverage holes disappear from the side of the head, that's about it.

 

Take .040 to .060 (1-1.5mm) off it and you'll be fine.

[altezzaclub]

A 3K I don't know, but I do know how to measure them!

 

If you just tell the head shop to mill 20thou off, you're assuming it has never been touched before. If you measure the combustion chamber volume you can easily calculate how much to shave off to get any particular compression ratio.

 

All you need is a flat piece of plastic sheet with a hole in it, of a size that covers the combustion chamber face, and a pippette or burette or syringe. You need the valves in place (if they're not on springs I stick them in with grease) you tip the head upside down and put grease around the edge of the chamber. Fill the syringe with turps, press the plastic sheet onto the grease and fill the combustion chamber with turps. You need to measure this fairly accurately, so a pippette is best, just like in the photo below. I took that after I'd done it and lifted the perspex, that's why the grease doesn't seal completely.

 

The area of the combustion chamber is measured off a piece of graph paper- just push it gently around the edges of the chamber, then draw around the shape. Count the squares inside and work out how many sq cm it is.

 

Now you're a race engine expert!

 

If the piston is flat there is no combustion chamber there, the gasket has 5ml in it, and the head has what you measure. So the biggest volume is when the piston is down, 1/4 of the engine capacity+head gasket 5ml+head volume, and that compresses into the smallest colume at top dead center, head gasket 5ml + head volume.

 

Work out how many ml you need to drop off the head to get 10 to 1 compression and work out how many mm to shave off from the area of your graph paper.

 

Its not hard, its something you can use on all your engines for the next thirty years and it puts you in control!

[Redwarf]

Or the cheap and nasty method, measure the leverage depressions. On an unmolested one they should be around .125.

[TWF#14]

the heads come out different sizes tho we had a 3k that had been shaving 81mm then a mate bought a brand new one never been used 79mm?????

[Redwarf]

I'm not talking overall head size, I'm talking about the leverage holes in the face.

[TheHeadShaver noob]

Thanks a lot for all ur answers!

 

i always wondered how to measure the combustion chamber volume, thanks for the lesson :D

 

if my head is a virgin and never been shaved before, i think i will settle for just a 1mm, if that gives a ratio of 10,7:1 on a 4k, then i should get about the same or maybe a lil better on a 3k, right?

 

To measure the leverage holes, what/where exactly are they? I'm a lil noobish when it comes to technical terms and my english aint that great either ;)

 

Last question, i have some air tools, should i polish the intake and exhaust ports, or is it just a waste of time? the carb and everything is stock. if i should polish it, or maybe even make the ports bigger, do i need to be real carefull or is it not much chance for me to polish/port too much so i get into some water channels or anything?

[Taz_Rx]

On the spark plug side of the head there is one or more little indents in the bottom face of the head. They're there so when removing the head you can remove the bolts and stick a screw driver in the leaverage hole to 'level' the head off the block.

Have a look and you'll see what we're talking about.

 

You can go pretty big with both inlet and ex ports before you'll grind through a water jacket. Be aware that's there's not a lot of point in increasing the size of the ports without also increasing the size of the valves though.

[altezzaclub]

...and very little point in doing anything apart from a polish and port matching if you're using the stock carb.

 

Save the cash and get better carbs & a set of extractors then do the head, matching the three units up to each other.

 

Add a cam grind and you have a much perkier K.

[TheHeadShaver noob]

Thanks again for all ur great answers.

 

well no reason for me to port the head then, but maybe i will polish it a lil while its off anyway.

 

I prolly get some more questions when i start working on it tho :abuse: