Author Topic: g40 or gt Crank and conrods. and oversized piston rings??  (Read 5040 times)

Offline Oily Fingers

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g40 or gt Crank and conrods. and oversized piston rings??
« on: August 08, 2009, 10:27:06 pm »
Right after speaking to a fellow CP member.  I have been informed that i can use my spare GT block adn fit the G40 crank,conrods and pistons.   But could i use the crank as well, and use the g40 conrods and pistons???

also i am planning to use the 1272cc bores and hone them out a weee bit.   Would i benifit from getting a set of slightly oversized piston rings, instead of using stock ones???


joel

Offline Tommo

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #1 on: August 08, 2009, 11:37:12 pm »
Just the pistons that differ AFAIK. Everything else is the same. I wouldnt reccomend 'honing it out', if the bores are a bit glazed then a quick brush over with a hone will freshen it up. But you only really want to do it enough to rough them up a bit, as too much honing will mean your pistons could slap a little. Over sized rings fit oversized pistons and oversized bores.

To be fair I have never really seen much wear on modern engines bores. I would be surprised if your bores are beyond the VW wear tolerances.

Offline Oily Fingers

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #2 on: August 10, 2009, 01:50:51 pm »
kool,  so i'll just need a set of g40 pistons.   

the block i will be using is from a GT i recently broke,  it had done 150k,  so an uber quick run round with the Hone will be ok to freshen it up then?

btw wats does AFAIK mean???  i have forgot lol


Offline Yoof

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #3 on: August 10, 2009, 01:59:51 pm »
AFAIK= As Far As I Know  :)

The dimensions of the GT and G40 cranks are the same, although having seen turnings off each crank after them being lightened, I'd suggest they're slightly different, without taking the turning to a metrology lab I don't know how- be it a slightly different alloy, they're both still cast then machine finished though.

The webbing on GT blocks is different to that of a G40, this is only external (from memory) but must add strength, I don't think anyone running a 3F block has had problems though- although you will have to take into account the oil return feed for the charger, and the knock sensor boss at the rear of the block.


Offline Oily Fingers

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #4 on: August 10, 2009, 04:22:30 pm »
AFAIK= As Far As I Know  :)

The dimensions of the GT and G40 cranks are the same, although having seen turnings off each crank after them being lightened, I'd suggest they're slightly different, without taking the turning to a metrology lab I don't know how- be it a slightly different alloy, they're both still cast then machine finished though.

The webbing on GT blocks is different to that of a G40, this is only external (from memory) but must add strength, I don't think anyone running a 3F block has had problems though- although you will have to take into account the oil return feed for the charger, and the knock sensor boss at the rear of the block.



yeah was speaking to a mate who's got philJ's old capri green g40 yesterday.  We were chatting about the oil retrun and knock sensor.  Soon get round it some how.   Just gathering infomation atm still.

Offline randombadger69

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #5 on: August 11, 2009, 04:17:43 pm »
yeah was speaking to a mate who's got philJ's old capri green g40 yesterday.  We were chatting about the oil retrun and knock sensor.  Soon get round it some how.   Just gathering infomation atm still.

Thinking about it the oil return line shouldn't be a problem. Weld a 10x1.00mm nut to your sump and that should suffice. The Knock sensors the bit that has me miffed ??? How does this work and how can it be improvised?

Offline Nick_S

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #6 on: August 11, 2009, 04:30:19 pm »
The 3F block should still have a stump cast onto it on the back of cylinder 2. All you need do is drill and tap a hole into it to mount the knock sensor on.

Offline hayesey

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #7 on: August 11, 2009, 04:32:27 pm »
look at this thread:

http://www.polog40.co.uk/forum/index.php/topic,2551.0.html

the mystery hole he's talking about is where the knock sensor bolts to.  I think that stub is still there on non-g40 blocks but you'd just need to drill and tap a thread into it for the sensor to bolt to.

Same goes for the charger oil drain, the stub should still be there I think, you'll just need to drill and tap an m10x1.00mm threaded hole through it into the crankcase.  Or your suggestion of doing the same into the top of the sump would also work.  I'd have thought just drilling and tapping the block would be easier if you've got access to a big enough drill press or milling machine.

Offline Oily Fingers

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #8 on: August 11, 2009, 07:36:53 pm »
quickie.   if i was to get it rebored to 1341cc.  using the gt crank and conrods.  Where can you get the larger pistons from to suit the 1341cc??

toying with the idea now as there seems to be abit more options open if i do bore it out.

Offline randombadger69

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Re: g40 or gt Crank and conrods. and oversized piston rings??
« Reply #9 on: August 12, 2009, 01:51:38 pm »
Phil had some Accralite 77mm pistons for sale recently. Obviously they can supply these or another option would be Wossner (G-werks do these iirc) I expect many people make them, try Ebay.de for price comparison. You know you should go 1w though ;)...