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Location:
Brisbane, Queensland
Registered:
May 2002
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 compression depression
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Thu, 29 August 2002 09:08
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ok I'm still toying with how to build my 2tg 3t hybrid, I'm getting more to the point of just bolting it all together and not moddifing anything, if this is the case can someone tell me what type of compression I would get by using the 3t block and crank with 3t rods and pistons and the 2tg head thrown on top?
see I sold my Bimmer and now I have $7000 to spend on my baby.
anyone?
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Location:
New Zealand
Registered:
May 2002
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Re: compression depression
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Thu, 29 August 2002 11:01
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I've heard 10.3 and 10.5 banged about.
Also, read other posts.... valves will hit pistons.
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Location:
Brisbane, Queensland
Registered:
May 2002
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Re: compression depression
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Sat, 31 August 2002 03:02
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thanks for that mate
well I will bolt it all together and see how she goes
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Location:
Tasmania
Registered:
May 2002
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Re: compression depression
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Sat, 31 August 2002 15:33
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Why not do the math? You passed grade 6 right? You can calulate the volume of a cylinder, understand ratios, convert different units?
The 3T head chamber is 68cc I am told.
The 2TG head chamber is 62cc.
Assume the compression ratio of a 3T-C is 9:1.
The swept volume of one cylinder of a 3T motor is:
78 x (pie x 85^2) / (4 x 1000) = 442.6cc
For a 3T-C motor:
compression ratio 9/1 = (442.6 + 68 - piston top) / (68 - piston top)
Therefore, the piston top area is about 18cc or something like that.
Compression for 3T-G motor:
Compression ratio = (442.6 + 62 - 1 / (62 - 1
= 11:1
This is not the real result, because I made up a few of those numbers. Work it out properly, but also calcutate for a 1mm head gaskit, and you will find that the result is actualy about 10:1. The higher the better I guess. Also remember you will be taking some material off the piston for the exhaust valve clearance. Its best to measure your combustion chambers yourself, with oil or clay or something. Don't just reley on figures floating around the internet.
10.5:1 is more like what you will end up with if going with aftermarket 89mm forged pistons.
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Location:
Brisbane, Queensland
Registered:
May 2002
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Re: compression depression
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Mon, 02 September 2002 09:09
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ok first of all showing my nievity, what is the difference between a 3T motor and a 3T-c , I always thought that to be californian emissions control crap, please tell me if I am wronge.
ok next, I thought that I wouldn't need to worry about flycutting into the pistons because I'm not changing the profile of the cam, even if I do get them reground they still won't poke any further into the chamber.
I've got a set of pistons coming up from melbourne.
they will either be Hasting's, grant or ACL, they are the 3T oversized pistons by 40thou.
the guy on the phone told me that 3T and 3TC pistons are the same.
I am also getting chromed rings and pins with the pistons.
so all up around the $230 mark.
but..... are the 2tg and the 3t rods the same???
I've got a set of each,
also one more thing, the 2tg head that I picked up is the 882200 one. what are the good and bad things about this head????
I understand it isn't the yamaha head.
I'm sending the head away this week to get checked over and maybe new valve stem seals just to be on the safe side.
 which brings me to another thing I just thought of, will 2t valve stem seals fit in a 2tg head or will I have to get the right ones, afterall the ones in it at the moment might be perfect, I just don't know.
thanks
Benny
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Location:
Tasmania
Registered:
May 2002
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Re: compression depression
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Mon, 02 September 2002 11:31
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3T, 3T-C, 13T, 3T-EU, they are all pretty much the same. The C does not mean Californian emissions, but does refer to basic emission equipment.
I think you still need the exhaust side cut in the pistons. Even if you have lower lift, a regrind cam with longer duration will keep the valve open for longer when the piston is at the top.
2TG and 3T rods look the same I think, same dimentions. Either can be used but its rumoured that 2T-G ones are stronger.
Don't get hung up about wether its the "Yamaha" or not. No the 88220 does not say "Yamaha" on it, so what. The 88220 head has smaller valves, also has less webbing in the head, and the exhaust studs are smaller. You can change the exhaust studs to bigger ones yourself. If you realy wanted to, you could get the valves and seats changed as well, only if you have the money.
I think the 2TG stem seals are different to the 2T ones, maybe I forget.
[Updated on: Mon, 02 September 2002 11:34]
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Location:
Brisbane, Queensland
Registered:
May 2002
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Re: compression depression
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Tue, 03 September 2002 10:24
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thanks for that jonny,
I made a few more calls today after I got my pistons (shiney)
they look exactly the same as the stock pistions cept that they are 1mm oversized, they still have the reliefs cut into them for the valve to clear.
I was also told that a possible 15% power increase is obtainable if the cams are dialed in correctly, needing a dyno to do this.
does the 2tg head have adjustable cam gears or do i have to buy them?
thanks once again.
I think I will give both sets of rods to the shop and they can pick what ones to use.
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Location:
New Zealand
Registered:
May 2002
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Re: compression depression
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Tue, 03 September 2002 10:32
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I have "adjustable cam gears", basically stock ones redrilled all over the place. The holes in the cam gears of exhaust and intake have slightly differently drilled holes so you can get odd amounts of overlap..... have a look closely to understand this.
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Location:
Tasmania
Registered:
May 2002
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Re: compression depression
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Tue, 03 September 2002 11:12
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3T pistons do have valve reliefs, but the exhaust one is not big enough. You need to make it bigger for the 2TG exhaust valve. That is me comparing it to a 2TG pistons at least.
2TG cam gears are adjustable, with different holes and a pin.
With standard cams, you should only have to set them up as in the book, with both notches pointing up. If you have regrind cams, you will want to dial them in to the specs that come with the camshaft. No dyno work should be required if you are buying a proven cam grind profile. Maybe you would experience a 15% loss if you did not dial it in right?
Bill Sherwood has a bit on cams on his site. Something about setting the lobe centres to 100 degrees if the duration is over about 280 degrees? Otherwise at 110 degrees? I would think it be easier to set them up going on closing and opening times, but I have never done this before. I think you need a dial gauge and a degree wheel.
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Location:
Brisbane, Queensland
Registered:
May 2002
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Re: compression depression
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Wed, 04 September 2002 08:58
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that is one wierd way of setting up cams 
there are notches in the cams for a reson, anyway.
I gave my head to the head shop thismornig to be crack tested and the valves vacumed tested, I later rang him up to tell him to strip the head for me because I want to port and polish it without getting crap in the valve stems.
he told me in the morning that matching the ports does a good job, porting can be risky buisness.
but then I was told later in the day that I just should ought to do it myself with a die grinder.
Now I am confused, will I really gain that much more power from a port and polish job on this 2tg head , it looks like it flows well now?....or will matching the ports be enough?
secondly, I started to have a closer look at my carb's and inlet manifold this arvo.
can I get Solex rebuild kits?...
also the sleeve that is on the outer side of the throat, I have removed this and god damm that throat is a lot bigger now, is it a good idea to leave it like this??
I plan to get trumpets and unifilter socks.
thanks.
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Location:
Tasmania
Registered:
May 2002
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Re: compression depression
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Wed, 04 September 2002 15:28
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I don't know why, but I think that sleave should stay. It could be need for something. The main venturi already limits the flow a bit, at 32mm. I don't think removing the sleave will make any difference in flow, except that it may upset it a bit. Not sure about this one.
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Location:
Brisbane, Queensland
Registered:
May 2002
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Re: compression depression
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Wed, 04 September 2002 21:06
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hehehe, lets try it
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Location:
deloraine tas
Registered:
September 2004
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Re: compression depression
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Fri, 15 April 2005 12:44
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i no this is an old post but can anyone tell me what valve steam seals i can use in the 2tgue head? like from a 2tc or somthing? please help i need this info i cant find any 2tg ones and the head needs to go back on my 3t block. thanks
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Location:
Tasmania
Registered:
May 2002
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Re: compression depression
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Sun, 17 April 2005 00:53
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You can get a 2T-GEU head gasket kit off e-bay fairly cheap, I forgot if it comes with valve stem seals or not.
Go to a decent engine rebuild shop and they should be able to look it up and order. Or, get them to measure the valve stem and valve diameters and I am sure they can match it up. It is different to 2T-C from memory.
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Location:
deloraine tas
Registered:
September 2004
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Re: compression depression
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Sun, 17 April 2005 02:12
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you wouldent have any new ones lyeing about would you jonny?
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