4g61t.org

If I remember right didnt ColtR already build such a motor? Did he not have to deck the tops of the pistons to clearance the valves because the piston sat too high? I know this was discussed somewhere on this board already.
I believe beserko asked alot of questions concerning how the motor was setup and the compression.

Um, the 4G61T DOESN'T use 1G pistons. Funny how the bore's are 82mm and 85mm, respectively.

The difference between the 1.6, 2.0 and 2.4 are BORE and STROKE and DECK HEIGHT. The reason the deck height changes is because the stroke changed. AFAIK, they all use the same 1G rod (150mm).

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Darin
1986 GMC 3/4 Ton 4x4 Diesel (soon to be Greasel)
1993 Colt GL

I still do not understand. Lets forget completly about the engine size. Suppose you put the 61 piston beside the 2g63t piston, which one would have the least dish? Or which one when installed in a cylinder at tdc would hold the least volume?

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89 Mighty Max 2.6. Lookin for side drafts 89 Colt turbo. SOLD
91 Galant GSX, waiting for 2.4

Normally the 4G61T has 82mm pistons and the 4G63 has 85mm pistons which affects overall static CR.

However, if we assume for ease of argument that they have the same size pistons, then with the increased stroke of the 4G63, it would require a deeper dish over the 4G61 to maintain the same CR.

So to compare the two, which one in its properly sized bore at tdc would hold the least volume?

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89 Mighty Max 2.6. Lookin for side drafts 89 Colt turbo. SOLD
91 Galant GSX, waiting for 2.4

are the turbo/non-turbo 4g63 intake manifolds the same? what about the 4g67? I already have a non-turbo TB for my 4g61t project, I am gonna port what I can before the motor goes in, but if the 63/67 manifolds are the same, that will help me out.
and is it at all possible to fit 61 pistons in a 63, for a small bore/long stroke combo. if so, then one more step would be to get 61 pistons in and 64 crank (the anti-rev motor!). can sleeves be made? or is that more of an entire-custom-block sort of thing?

I'm new to the world of 4g6x-series motors, but I am an apt pupil.

~joe

All I know is if you want a motor that has the same stroke as a 4G63 but smaller turbo pistons then you will have to hunt down a G62T. G62T is found in a Tredia and Cordia Mitsubishi, not many around anymore and it was SOHC, the block crank and rods are basically the same as the 4G63. The bore is smal like the 4G61. So that is what you want it already exists just have to convert it over to a DOHC setup using the timing belt and tensioner from a 4G63 if possible. I am just going off what I read months ago about this motor on this site prior to the info purge that occured.

I actually know where one of those is, but its in one of those teeny, as.hole, i-would rather-crush-it-than-sell-it-cheap yards.

more importantly, what is the bore? does it bolt up to a 4g6x tranny? any machine shop work required to accept DOHC head, like the g4cs/4g64?

I will watch this thread with interest...

~joe

I think the whole piston topic that I started is pretty interesting as well.
Some one please help, my engine is all apart and I want it back togeather. I just want to know which pistons to put in?

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89 Mighty Max 2.6. Lookin for side drafts 89 Colt turbo. SOLD
91 Galant GSX, waiting for 2.4

The 4G61T (82mm) piston has a smaller dish in it than the 4G63T (85mm) piston.

_________________
Darin
1986 GMC 3/4 Ton 4x4 Diesel (soon to be Greasel)
1993 Colt GL

smaller as then less.

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89 Mighty Max 2.6. Lookin for side drafts 89 Colt turbo. SOLD
91 Galant GSX, waiting for 2.4

Does anyone know what the C/R is for the N/A 4g61's. Maybe you could use a set of N/A 4g61 pistons and use a larger 1.2 mm head gasket to bring the compression back down to a good turbo range. If the C/R of the N/A's are around 9.5...this would probably work, but I'm lacking all the information to validate this.

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Turning a 4g61t into 1595 cc's of FURY!
10.995 @ 134.44 - http://www.youtube.com/watch?v=bZXvcvzuWGQ

SOLD to the fastest shifting hermaphrodite in CO

I am not sure if the piston are stout enough.

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89 Mighty Max 2.6. Lookin for side drafts 89 Colt turbo. SOLD
91 Galant GSX, waiting for 2.4

The standard N/A piston for the 4G61 is domed and produces a CR of 9.2:1 which is probably a bit too high for the stock cast piston material to handle.

If I was in the US and building a strong 4G61T I would be looking at the Magnus 4G63 10:1 flat-top forged pistons which in a 4G61T would give a static CR ~9:1 mark.

I agree with XLR8. I'm using Magnus 9:1's to drop the compression ratio down to ~8:1, but more deisrable would be the super stout 10:1 flattop's from Marco.

And yes, smaller dish means less volume, means less dish.

_________________
Darin
1986 GMC 3/4 Ton 4x4 Diesel (soon to be Greasel)
1993 Colt GL