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Discussion Starter · #1 ·
who does custom cranks, can they be made as standard cranks
as iv heard of steel items being as much as £1200
advantages of steel cranks?
also, when measureing up for the stroke, how much tolerance
should be give for the piston skirt/crank web distance;
i.e. how close can the length of the big end journal
to the centre of the crank be to the length between the centre of the big end of the con-rod to the bottom of the skirt...
if anyone understands that?
TIA
 

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Discussion Starter · #4 ·
cheers Rob, i dont intend revving that high, just want a crank to my dimensions.
Any ideas on that clearence i tried to describe above?
thanks for any help
 

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I've talked to Doug Kidde a few times. Very helpfull bloke.

TBH a one off crank is gonna cost you a lot who ever does it.
Do some searches and ring around is all I can suggest.
I found a few that would do a 'cash' price but that mostly involved just dropping the VAT value.

They'll also be able to advise on dimensions etc as they are the experts.
What are you trying to build that needs a special crank?
 

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Discussion Starter · #6 ·
im trying to build a big CC engine using a VW small block,
i can go to 1700cc at least, then as far as possible with a custom
crank/con-rod/piston set up.
Any guide on the prices that you got?
TIA
 

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If you are just lengthening the stroke, then you can get the crank welded, ground and straightened, then just get the custom rods.. much cheaper, but you won't be able to rev a long stroke engine very well.
 

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If this engine are VW AP code, is the engine most tunned here in Brazil. Here have crankshaft with 86, 94 and 100mm of stroke. And you can re-bore the cylinders to 83.5mm pistons with security. Much here put GM 86mm piston, but is only for race and aspirated engine, because the walls of cylinder can crash easy.
This block have extra cam to active the distributor and oil pump?



Cheers!
 

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Discussion Starter · #9 ·
Never knew you could do that Brian, but i was wanting to keep my OE crank for
something else, i also know about the restrictive revs, i was thinking
of limiting it to 6700rpm?
Matheus, im not sure what the AP is, but looking at that bore it will be a big block,
most people use a diesel crank in those to raise the CC, but they are phisically
longer ans taller than my small block, so this is what i have to do
if i want over 1.7L and not to use my OE crank.
So has no one tried to get the con-rod length as close to the stroke length before?
Too risky?
Thanks
 

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Hello friend.
Do you have one picture of your engine bay? I can tell if your engine is AP in some seconds. If is AP, is much more easier to give tips for you. I worked in AP engines in all of my life, i know all things from this engine.
About you put higher stroker crank in your standard bock, you will have the problem of the lenght of block. You can correct it modify the rods for less lenght, but it will provide to your badder angular vibration(r/l relation), and its so danger for high revs. The better solution in my opinion, is you keep your standard rods, and modify the top of yours pistons, remove material from top area. In aspirated engine, can do it, only need care about detonation, if it detonates, you can have a hole in piston like hot knife in butter. In this situation the r/l will be badder, but not so much like you modify to smaller rods.
Do you have the specs of your engine? Bore, stroke and lenght of yours rods? If have, i can calculate to you the r/l, and know what r/l will be with new crank. The limit of ideal r/l is 0,30, but much engines with 0,31, 0,32 work in high rev without problem, only give more vibration(and less durability to rods bearings), but can survive.



Cheers!
 

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Discussion Starter · #11 ·
The 1.6 crank is out of a AEE engine code, its an 8v small block with 86.9mm stroke
The 1.4 16v , engine code AFH which is the small block im building has a stroke of 75.6mm
both have a bore of 76.5mm and are almost identical blocks bar the pulley arrangement.
Sorry i have no pictures of them, but as they are small blocks as found in the VW polo hatch backs
i know they wont be the same as the AP you have mentioned, also, the largest bore
possible is circa 80mm, i know the big blocks like the KR(1.8 16v K-jet), 9A/6A(2.0 16v K-jet) and ABF (2.0 16v digifant)
can all use the larger strokes you have metioned above, and go to circa 83mm bore.

As regards using a shallower piston and standard rods, wont this increase ovality wear in the bores,
since the piston with less side to it will slide up and down the bore less square
than a deeper piston with longer skirts? Sorry for the poor explanation.
Is this a similar problem to the angular vibration(r/l relation) you have explained above?

I was going to layout the 1.4 16v crank, with standard rod and piston,
accurately measure the length from the piston crown to the centre of the crank (centre of the main journal)
then with this length find the shallowest pistons available to me, and with the remaining
length, share it between the new cranks stroke and the new con-rods length.
I just was not sure how close the piston skirt could come to the crank web before it
became risky?
Any further guidence much appreciated
 

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whitie said:
The 1.6 crank is out of a AEE engine code, its an 8v small block with 86.9mm stroke
The 1.4 16v , engine code AFH which is the small block im building has a stroke of 75.6mm
both have a bore of 76.5mm and are almost identical blocks bar the pulley arrangement.
Sorry i have no pictures of them, but as they are small blocks as found in the VW polo hatch backs
i know they wont be the same as the AP you have mentioned, also, the largest bore
possible is circa 80mm, i know the big blocks like the KR(1.8 16v K-jet), 9A/6A(2.0 16v K-jet) and ABF (2.0 16v digifant)
can all use the larger strokes you have metioned above, and go to circa 83mm bore.

As regards using a shallower piston and standard rods, wont this increase ovality wear in the bores,
since the piston with less side to it will slide up and down the bore less square
than a deeper piston with longer skirts? Sorry for the poor explanation.
Is this a similar problem to the angular vibration(r/l relation) you have explained above?

I was going to layout the 1.4 16v crank, with standard rod and piston,
accurately measure the length from the piston crown to the centre of the crank (centre of the main journal)
then with this length find the shallowest pistons available to me, and with the remaining
length, share it between the new cranks stroke and the new con-rods length.
I just was not sure how close the piston skirt could come to the crank web before it
became risky?
Any further guidence much appreciated

Hello friend.
Yeap, your engine are not AP, your engine are know here in Brazil with the code EA-111, here is a picture of this engine in a Golf bay:


i have full specs of this engine, see below if its beats with your engine:

Bore and Stroke: 76,5 x 86,9 mm
Cubic capacity: 1.598 cm3
Lenght of rods: 138 mm
r/l relation: 0,314
Compressio ratio: 10,8:1
Max power: 101 bhp at 5.500 rpm
Max Torque : 14,28 m.kgf at 3.250 rpm
Rocker arms with bearings


This specs is of the 1.6 engine, here in Brazil don´t have VW 1.4 engines, but if the block are the same, you only need change the cranshaft and rods(maybe the pistons, if the pine postion are diferent). The r/l relation of the 1.6 engine are not so good, but is not critical too, 0,314 can survive easy in high revs.
About your teory of r/l relation are wrond. R/l relation is the intensity angular work that rod will be, more angule, will have more stress with vibration. The pistons don´t enter in meter for r/l, only the lenght of rods and the half stroke of cranshaft. See the pics below of two situations, one with better r/l and other with badder r/l:


BAD R/L(small rod and big stroke):


Good R/L(big rod and small stroke, this are perfect for high rev):





Cheers,
 

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Discussion Starter · #13 ·
that picture is the 2.0 8v, and the spec you have is for a 1.6 8v, but it is the big block
as found in the polo saloon/estate and mk3 golf. As it is the big block its is possible to take that engine to 2.1 litres,
but i have the small block 1.6 8v, it has 75bhp and not 100bhp like the big block,
the CR is also lower at 9.8:1 . Sorry if I sound a little patronising, i work at VW and have
tried the cranks from the big block to see if they fit, but they are longer(horizontally) than my OE crank.

Your explantion on the r/l relation says the longer rod is better and the depth of the piston does not come
into it, so does that mean i wont be risking ovality of the bore with a shallow piston?

im away on a course this week, but back on the net next week end, if i get you
my rod length,piston depth and the complete length from centre of the main journal to the crown of the piston would you be able to advise me on the ideal stroke/rod length?

Many thanks
Tom
 

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If the engine is gogin to be this tune'd then it's rebuilt intervals will be shorter anyway surely? the increased lateral wear due to the increased stroke is the trade off, on a one off engin eno one can say how bad it would be though.
 

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that picture is the 2.0 8v, and the spec you have is for a 1.6 8v, but it is the big block
as found in the polo saloon/estate and mk3 golf. As it is the big block its is possible to take that engine to 2.1 litres,
but i have the small block 1.6 8v, it has 75bhp and not 100bhp like the big block,
the CR is also lower at 9.8:1 . Sorry if I sound a little patronising, i work at VW and have
tried the cranks from the big block to see if they fit, but they are longer(horizontally) than my OE crank.
well, then, i don't know what engine is that. Your engine have eletronic acelerator and inlet manifold variable? Maybe your engine is the same of Audi A3 1.6. Is not common here in Brazil. Other information, your block is iron or aluminum?
But, what you think in change your small block for a big block one? Because AP block is not heavy, is a compact block, is made primary for only 1800cc. The AP equipped standard really small cars like VW Gol here in Brazil. Don't will make bad weight distribution for your car.



Your explantion on the r/l relation says the longer rod is better and the depth of the piston does not come
into it, so does that mean i wont be risking ovality of the bore with a shallow piston?
You make a confusion. The r/l relation is only the value of angule that rod will work in engine, not more thant it. And the lenght, bore, any things of pistons, don't will interfer in the r/l relation.
Your care about ovality i understand, but is not so danger, because the lenght that you will lower in pistons, is not so much, don't care about it. You need do more attention in resistance of tops of pistons.






m away on a course this week, but back on the net next week end, if i get you
my rod length,piston depth and the complete length from centre of the main journal to the crown of the piston would you be able to advise me on the ideal stroke/rod length?
Yes, no problem. But you need have in mind, when you stroker a engine, you will have badder r/l relation. Its a fact. You need only know if the new r/l will be critical for the revs that you want to run.
You see the C16XE engine, have a litle bad r/l relation, and SBD have kitts for it run 10.000rpm. The problem of bad r/l is the resitance of rods and bearings. Then, if you can put forged rods, don't need much care about r/l.



Cheers!
 

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Discussion Starter · #16 ·
After talking to someone thats been working on VWs for 15 years iv decided not to stroke it, but just to bore it to 1700cc.
As for the AP being compact, the smal block(the blocks i have) are even more compact
and the weight distribution is the reason im keeping it.
The Audi block will be the same as the AP.
It would be interesting to know what you would come up with if i give you the OE dimesions as i said i would in my last post.
I will try get them tomorrow and hopefully you can have a look

many thanks
 

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whitie said:
After talking to someone thats been working on VWs for 15 years iv decided not to stroke it, but just to bore it to 1700cc.
As for the AP being compact, the smal block(the blocks i have) are even more compact
and the weight distribution is the reason im keeping it.
The Audi block will be the same as the AP.
It would be interesting to know what you would come up with if i give you the OE dimesions as i said i would in my last post.
I will try get them tomorrow and hopefully you can have a look

many thanks
Nice. But what you will do with this 1.700cc? You will put turbo or will make only N/A mods?
If you only increase the bore, don´t need calculate nem r/l, your r/l after this mod, will be the same, don´t care. Only becarefull if the wall of cylinders are much fragile, any detonates can make a runner in the wall.
Is much common here in Brazil we put 86mm pistons in AP, and its common to happen.


Cheers!
 
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