Head skimming
 

1 do I need to do it ?

2 Where can I get it done?

3 How much to remove ?

Ive removed my heads the old gaskets were fine but I thought when the engine is out why not change the gaskets. Now im wondering if I will need to get them skimmed.

Cheers

I think the theory of getting the heads skimmed is that it changes compression inside the cylinder which gives slightly better performance.

Got my 1.4 SR nova done quite a few years ago at OD Cars facing Antrim Road RUC(PSNI) station. £35 back then.

I would say saying as you have stripped it get it done. They also do valve polishing which although is easily done urself, u can over do it. Polishing the valves is another good performance enhancer.

Neither off the two will see lots of BHP gains probably around 5-7(if that)but the car will run a lot better and might even give better MPG(especially the polishing off the valves).

the heads should also have notches in them to let you know how far they can be skimmed

be careful
 

its the one part of engines iv done a lot of work on and the one part of engines iv seen people make a balls of.
you dont need to do it per say,unless theres a warp in one of them,but in saying that it does no harm when your doing a full engine rebuild to check them for flatness.just get a plate of glass,clean the contact surfaces on the heads and cover them in engineers blue and rub them over the glass.thatl show up ant dips or bumps.failing that a good mill or surface grinder and clock them for flattness..

if they need a we skim only take whats needed to flatten them of and no more:nono: .

iv not used them but i know od cars on the antrim road do that type of work..i used to do my own and other punters but iv no access to a good surface grinder:(

my own on the old girl are done and 10 thou was removed.

any more and you could be running into pre ignition probs depending on the stste of tune of the rest of the engine:wonder: :wonder:


rab

OD cars, antrim road thats the name I was looking for!

Cheers Fabio

Cheers guys

no worries
 

if you get them done,,,just make sure your knock sensor is on the ball:Whatever_
performance wise the area you should see any improvment in will be at the bottom to mid revs..more grunt. high comp engines tend to not over rev as fast as an engine with lower comp....one of the race(bike)engines i had ran into a wall revs wise when the comp was raised but the grunt every were more than made up for it........mind you i had to buy shares in octain booster:lol1: :lol1:

why not get a we flow job done on the heads instead of the high comp route...it puts a lot less strain on the crank and big ends..

fabio

On a turbo engine you usually lower the compression to go for power, it's not the same as a normally aspirated engine which is what you're talking about.


Never heard of valve polishing ? but polishing does fuel atomisation no favours, porting does though depending what they are ported to suit.

No they don't

Clean them up and check for trueness as described above you will soon see any high/low spots.
If you do get them surfaced with the bare minimum removed.

Cheers

Vavle polishing probably isnt the right name 4 it!LOL. I am meaning getting the valves cleaned to get all the crap of them along with reseating to allow gasses 2 escape easier.

Reseating the valve improves the valve to seat seal in the head and can improve cylinder seal and compression if they are leaking too.

Multi angled valve seats can help improve flow when done with head porting to aid airflow into the cylinder.

Pete valve grinding is the name your looking for. It cleans the valve seats and makes sure there is no compression leaks. The whole point of having the heads skimmed is to make sure they are straight and true and seal properly with the head gaskets in the rebuild.
Performance-subarus advice is spot on especially on the compression front. You defo dont want to remove too much.........could end up with problems!!!

If you've got the heads off and were going to strip it anyway why not give it a good cleaning and renew valve stem seals, regrind the valves in etc.

If you're going to do anything that'll change or upset airflow too much you may need a remap.


Damien

Should have also said OD cars do a decent job....have used them in my distant past. To check the heads get a good straight edge like a metal ruler and lay it at different angles you will soon see if the heads warped. More likely if the heads exposed to high heat. How bad was that little flame out you had??????? OD could check the heads for you but it would prob be quicker cheaper easier to do yourself, and if in doubts about their condition leave them in.

mccomiskey engineering mahon road portadown are the best in n/i for head skimming most places send their heads to him anyway so why not cut the middle men out,does polishing and porting etc while your at it

i think there is a place beside opharmotors at nuts corner does it as well but i am not 100%