4ag head question

**bmak** · 27-02-2006, 11:32 AM

Did a search on the old forum too but couldnt find an answer.

Any problems taking .5mm off a 4ag bigport head. The motor has never had any work done before.

**45aken** · 27-02-2006, 11:35 AM

i very highly doubt it.
very highly

**bmak** · 27-02-2006, 11:44 AM

Yeah i didnt think so but i thought i better ask as putting it back on is a bit harder.
All water galleries were perfect so i didnt even need to do any welding & the head is very straight. I cleaned up the combustion chambers & just want to up comp a little more.

How far can you go with them?

I'm use to taking 1-2mm or more off k heads

**Starfire** · 27-02-2006, 12:22 PM

Rather than shaving the head perhaps you should consider a metal head gasket that is thinner than standard. That should give you the required compression up.

Shaving the head shouldnt be a problem for that kind of clearance, but remember that a stock 4AG is non-interferance (the valves can never hit the pistons no matter what the timing is at or if the timing belt breaks). Increasing your lift, piston dome or compression may change this so if you do spit out a belt things could break.

I dont think that half a milimeter will be an issue though.

**TooF** · 27-02-2006, 01:40 PM

i would feel that 0.5mm should be ok.. but as starfire has said they are non-interference.. but i think the tolerance is pretty tight ? so if you were to put different cams etc that would all change...

**Biggo** · 27-02-2006, 02:57 PM

Stock HG's are 1.2mm arnt they? Why not get a TRD or HKS .8mm gasket? Or even better, shave the head AND get a lower profile gasket!

**myne** · 27-02-2006, 03:56 PM

lol the new rage - extreme low profile gaskets
next is chromed rods, LED injectors, and anodised pistons.

**45aken** · 27-02-2006, 04:04 PM

anodised pistons

gold..

**oldcorollas** · 27-02-2006, 04:42 PM

or if you are doing it to maintain a flat head surface, you could always use a thicker gasket to maintain the squish clearance...

squish is usually about 40thou = 1mm, so to take half that away may make too much squish... unless you relieve the head a little in the squish areas.

the other issue is belt length and tension.. while 0.5mm doesn't sound much, that 1mm extra belt length has to be taken up somewhere and it will change your cam timing also.\
just a couple of thoughts..

**Starfire** · 27-02-2006, 05:03 PM

The belt tensioner should be able to compensate for an extra 1mm of length. Shaving the head will effect the cam timing. Changing the cam timing will effect the ignition timing.

Both should be checked after modding the engine.

**bmak** · 27-02-2006, 10:03 PM

Thanx for the info guys.

I realize it will change cam timing a little(still cant be as bad as the ex cam being 1 tooth out as it was) & have already checked that there is plenty of belt adjustment.

No point going to a metal HG as i would need to machine the block & im only doing this cause the HG blew.

Engine has done 230k so it probably wont be long before it gets a conversion anyway.

This whole job has been a pain & i cant wait to go back to working on a rwd car with a K motor