2TG head porting! Need a quick answer to save the Chop!

[BrianGT]

I'm cleaning out the ports on my 2TG ...I'm not trying to enlarge it as I am a novice and don't want to ruin it!
I am just removing the casting ridges and taking away the rough surfaces. I am not altering the shape except for the inevitable loss of material through de-burring.

Is it ok to cut down the valve guides as they stick out quite a long way in to the ports? There seems to be enough guide left in the head to support the valve but if anyone of you Tech guys can confirm it would help me from maybe making a mistake!
Cheers guys!

[Celica RA45]

a lot of guys leave the inlet guide as is and take out as much on the exhaust guide.they were never really that good a head to begin with .if i remember we only picked up 4hp by doing clean up etc ,valve angle made it hard to get heaps of lift

[71TA22]

Brian,

Leave the valve guides. Even better take them out and replace once you are done.

Just debur and smooth the tracts.

Best thing you can do is port match, particularly on the inlet side.

You should also consider some grinding/shaping work on the carb manifold - have a look at the mating surface and its easy to see what needs to be done.

[BrianGT]

Thanks guys!

I never thought of taking them out but it's a great idea as they really are in the way.

The ports are all matched with the manifolds and gaskets and the butterflies on the carbs are in sync with the manifold openings.
I just feel better about cleaning up the ports. If i get 2bhp it's a bonus!

[MorGo]

Do not remove the quides;to this day seen a one with worn quides (and then you MUST have seats cut;never going to get back to same centerline if you remove/change quides).Yes,you can grind the quides when porting but then again,it's something to leave to those that know what the are doing.
Most flow increase is in the shape of the seats/valves.Port itself don't need much enlargening unless going to be high rpm race engine.
And then the moot point of -G engines;are the valves straight? I have put a X on the wall every time there comes in G-head with all straight valves.There is 2 X in the wall..
So get the valves ground true and have a 30º back cut done.

[BrianGT]

Thanks Morgo.....I actually remembered after my post,from my mechanicing days, that when you fit new guides you have to have the seats recut. So they will stay in place!

Would you advise cutting the protruding length down a little?

It's obvious that I am a novice at this so I want to learn as much as I can. I am willing to do as little as needed not to spoil the head so if you tell me to leave it alone I will take notice!!

[MorGo]

You can grind the quides thinner and even shorten them little but that is not the first thing to do;the flow will not increase without other port and seat work.
Most anything you do is just cosmetic and maybe worth a 3 hp.

[BrianGT]

Cheers Morgo.....I think it will have a nice placebo effect when I put it back on the block!

[BrianGT]

Second question!

My block is bored out to 89mm which is obviously a lot wider than the std. block. I have left the combustion chambers as original which means there is a mark where the new gasket has made which is wider than the original bore.

Should anything be done to smooth that step out of the way? I know that by removing any of that lip I would be lowering compression so any thoughts would be really appreciated.

[MorGo]

First:when the block is unassembled get the deck ground flat!! Worst I have decked was over 0,3 mm sunked between the bores..
The -G heads rarely are warped and since you are using bigger bore gasket there is no need to mill the head.Certainly it don't hurt and some 0,5 mm from head rise compression slightly (I advise against it;it's easy to mill parts down but there is a limit on that and adding the material back is damd difficult!)

["Z" UTE]

Briamn, my 2cents worth, deburr the exhaust side, but leave the intake side rough. The rough surface on the intake side cause vortices and eddys' to occur, these are extremely important in ensuring thorough mixing of the air and fuel.

[BrianGT]

Briamn, my 2cents worth, deburr the exhaust side, but leave the intake side rough. The rough surface on the intake side cause vortices and eddys' to occur, these are extremely important in ensuring thorough mixing of the air and fuel.

Thanks.... but I've already done the inlets! I have left them unpolished though and the surface is matt and not too smooth.

I'm realising that it's only going to be cosmetic but I just feel better giving the head a really good clean and lapping the valves in. Maybe it's just a placebo!

[BrianGT]

Third question!

Are there two types of shim that sit between the valve spring bases and the head? One for single springs and another type for double?
My head is an 88222 and came with single valve springs.....I think there must be a different shim to take double springs........hmmmmmmmmmm!

[MorGo]

Ehh.. must admit that I don't remember 100% sure but I would say that the shims are same in all -G heads.No matter what version be it 18R-G or 2T-G all the same.
At least during all these years I haven't seen but one kind of under spring washer.

[BrianGT]

Ehh.. must admit that I don't remember 100% sure but I would say that the shims are same in all -G heads.No matter what version be it 18R-G or 2T-G all the same.
At least during all these years I haven't seen but one kind of under spring washer.

Thanks Morgo! My friend who has built many 2TG's says the same so I suspect it's correct.

The thing is that the outer spring sits nicely against the upturned lip on the shim but that means that the inner spring actually sits on top of that very thin lip. From an engineering viewpoint it doesn't feel right and hence my question.
I have one shim that has the lip broken off and also on that valve the inner spring had broken....made me wonder why.