31 replies to this topic

[Jon937]

What would be the best length crank with KADs Road spec 16v head? I have read all your comments so far and such think 84mm would rev to slow but deliver max torque. Would the 81.3mm be okay to deliver max torque or would it be better to go for a destroked 1275 crank to make more use of the 4 valves per cylinder?

[mini13]

all the strokes will work well with good prep, there are 1460 engines (86mm stroke) out there that will rev to 8500, depends what you want to spend really...

 

in terms of short cranks... the way to do it is to use 6" rods ( 1/4" longer) SC now do a rod and piston set for this, also the BMW head will go in with no bonnet mods apart from a nibble on the x member

[nicklouse]

What would be the best length crank with KADs Road spec 16v head? I have read all your comments so far and such think 84mm would rev to slow but deliver max torque. Would the 81.3mm be okay to deliver max torque or would it be better to go for a destroked 1275 crank to make more use of the 4 valves per cylinder?

It does not really matter.

What can you afford? Go for that and use it.

[Dusky]

What would be the best length crank with KADs Road spec 16v head? I have read all your comments so far and such think 84mm would rev to slow but deliver max torque. Would the 81.3mm be okay to deliver max torque or would it be better to go for a destroked 1275 crank to make more use of the 4 valves per cylinder?

It does not really matter.

What can you afford? Go for that and use it.

If it doesnt matter, why not pick the cheapest and save cash?

[nicklouse]

What would be the best length crank with KADs Road spec 16v head? I have read all your comments so far and such think 84mm would rev to slow but deliver max torque. Would the 81.3mm be okay to deliver max torque or would it be better to go for a destroked 1275 crank to make more use of the 4 valves per cylinder?

It does not really matter.
What can you afford? Go for that and use it.

If it doesnt matter, why not pick the cheapest and save cash?

The reason it does not matter is that as what he says he is planning on doing has been done by one man, and that man is supposedly making the front subframe for him so that is really who he should be talking to.

So far we have a KAD 16v head and a turbo running on standard ten inch wheels and no arches.

Just like another poster on here give all the info. Unless you have decided that going the turbo line is too expensive.

[Jon937]

How does the 86mm crank rev to 8500rpm? Surely that would put a huge amount of strain on the crank. Would Med engineering cranks be okay if running a crank 84mm or more at such a high rpm, if not where sells a crank to do so?

[Jon937]

How does the 86mm crank rev to 8500rpm? Surely that would put a huge amount of strain on the crank. Would Med engineering cranks be okay if running a crank 84mm or more at such a high rpm, if not where sells a crank to do so?

[Alex_B]

How does the 86mm crank rev to 8500rpm? Surely that would put a huge amount of strain on the crank. Would Med engineering cranks be okay if running a crank 84mm or more at such a high rpm, if not where sells a crank to do so?

The rev limit of rotating components tends to be governed by how well balanced the unit is, providing the crank, flywheel etc are balanced well then the crank will see less strain on it. But yes a longer stroke will put more strain on the crank around the big end journals. It also depends on the materials used in the crank. 
Best people to ask about that question would be MED considering they make the cranks and could tell you how well they will perform at that engine speed.

These questions that you're asking can't be answered with a simple yes or no, in fact you could write an engineering dissertation on some of them. However if you get yourself a copy of David Vizards tuning the a-series book you will be able to see the limits of what is achievable with the engine. 

[Jon937]

I have read the yellow Bible and am in the process of reading it again. I asked the question as I didn't know if anyone had done anything like this before.

[mini13]

one way of making a pretty bomb proof 1460 is to go with large journels, its detailed in the yello book, billet crank with over size journels and ford bearings. also engine life needs to be factored in... you cant expect 100,000 miles from a stroked lump that rev's and revs...

 

I know SC have built a 1460 BMW headed engine, dunno the specs though, but it had some serious head work.

 

for a 1430 on the road, i would use a 7k rev limit, which means using fairly docile cams in terms of 16v, if you want a rever go for a std stroke, or maybe pick up a south african 1100 crank.

[Jon937]

I have had a look on SC's website and found nothing about the 1460 engine you are talking about. Please could you comment with some more details about this, a link and what pages to refer to in the yellow Bible?

[mini13]

i thnk the 1460 bit was at the end of the big motors chapter, but i'll check tonight,

 

it was on SC's facebook page, interesting now I look at it again as it appears that they are using long con rods and short deck height pistons form the mention of no max psiton speed increase...

 

https://www.facebook...?type=3

 

https://www.facebook...?type=3

 

https://www.facebook...?type=3

 

https://www.facebook...?type=3

 

also interesting...

 

https://www.facebook...56335284&type=3

Edited by mini13, 06 July 2015 - 12:35 PM.

[Jon937]

86mm stroke according to the first image comments

[mini13]

er.. well yeah its a 1460....

[Jon937]

Med do a 88mm stroke that I think I read somewhere that fits in a 1275 block with no mods