MA 10 crank compatable with CG series?

[Tony Perks]

Hi can some one tell me are the Ma and cg blocks basically the same? What I would like to do is put the Ma's 68mm stroke crankc into CG10 with some of Matt's forged pistons, to get a larger class 4 autograss engine is this possible???

Thanks.

 

[frank]

The ma flywheel is 5 bolt, but the shells are the same size eh, how about 72.5mm corsa pistons in a cg10 ?

 

[Tony Perks]

thanks frank that would give me 1039cc ish where as the ma crank would be around 1103cc somwhat nearer the 1130 class limit, or 1122 with ma crank and corsa pistons?

 

[frank]

The pre 98 1.0 k11 has the same clutch assy etc as the k10 eh, so maybe the ma crank and fly with 1.0 k11 clutch and g,box, and the corsa pistons (which. Have 4mm less compression height btw)

 

[Tony Perks]

That sounds like a good plan then Frank, with the corsa pistons being shorter they should with the extra length stroke of the MA xrank come about flush with the deck, the flywheel will be a steel jobbie, so I could make it fit any clutch i want really, thanks for the help Frank.

 

[frank]

Good luck tony the pistons have the same size pressfit wrist pin, and are the modern thin ring slipper type, and are anodised so hopefully will stand some boost, and they dont have the damn slit cut around the oil control ring groove like CG,s (that weakens the ringlands)
Hopefully you can make the oilpump drive fit ok

 

[Tony Perks]

Thanks frank engine will be NA so a revver, not sure what cam specs yet we will see how thw head flows then get some cams done to suit, Just got to find a Crankshaft now!

 

[Tony Perks]

Crankshaft now here thanks to Dave walker, Have done a dummy build with it using a 1275 block rods pistons, and using the 68mm MA crank this leaves the pistons 6.9mm down the bore, however the crank is too short for the chain/ oil pump so I may have to devise some clever extended crankshaft nose that bolts/keys onto the MA crank to adapt it. Pictures below show 1275 crank alongside 1348cc and MA 10 crank in Main bearing carrier:

The block showing the piston deck height.

The difference in crank seal size.

And the cranks oh and a lovely set of Matt H's Pistons, not mine a customers

To overcome the difference in stroke height I will be using a set of Vauxhall corsa X12xe pistons, which as Frank pointed out have the Gudgeon pin higher in the piston so the fact that the 998 rods are longer, and the piston pins higher I have worked out that I will have to shave about 0.050mm from the tops of the pistons and deckl the block the same amount.

 

[frank]

i,ve just re-assembled my corsa piston 3mm decked block one today too tony but with a 1275 crank this time (the 1348 crank gave too much c/r)
here,s tdc

 

[Tony Perks]

The one I am building is for a class 4 autograss race engine so I want as much compression as i can get 12.5:1 maybe a little more, still not sure what cam specs to go for yet as i have not put the head on the flow bench so may order custom cams to suit how the head flows, but I fancy something around 280degs inlet and 290ish on the exhaust, and if possible about 400 thou lift on inlet and about 350-360 exhaust, 2mm tdc lift, thats if things dont get a little tangled with those timings!

 

[frank]

sounds pretty hardcore the previous build with the cga crank and 2mm skimmed head was near 14:1 iirc and sounded like a diesel this one has slight dishes and less stroke eh, and 2mm @ tdc should be fine for p2v clearance eh

 

[Tony Perks]

Bit of an update after lots of measuring and fiddling I will now not be using the MA cranks as it would be just another thing to potentially go wrong so i will now be just using the CG10 cranks and .5mm oversize Corsa pistons, whch will give me 1087cc, a bit down on cc's but should be reliable, and high revving too, and still leaves plenty of Liner thickness on 1275 auto block, I will get some pictures up as soon as i can find the phone lead!