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MG Midget and Sprite Technical - Re Torquing Heads

I am finally about to put my 1430 'A' series engine together. The bore size is 73.5mm.

Has anyone got a handle on how to keep the gasket integrity up to scratch for a reasonably high mileage, say 20K miles (32.2K/Km for Arie!)?

Is a re-torque of help?, if so technique to use, back off fully and re-torque, or, just re-torque. Any difference hot or cold.

Road rather than race use, ( but,occasional forays into the 'red mist' area when necessary!)

CR 10.5-ish,gasket Metro Turbo, 11 stud.

Any comments most welcome.

Peter
PJ HOBSON

Are they standard studs or ARP?
Gary Lazarus

1430cc with a 73.5mm bore????

Are you sure you dont mean 1380cc or did you stroke the crankshaft and rods?

sorry I have nothing to add to the re-torque question

Prop
Prop

Prop, 1430 is acheived with a 73.5 bore - and a Morris (BL) Marina crankshaft (which had meatier mains bearings than midget crank), with mains offset-ground down to Midget size. With the original conrods, gives a small increase in stroke (can't remember the numbers) - to give an overall capacity of 1430.

Building one myself next year.

Saw a V-reg 1.3 Marina on the M3 this morning!
Steve Clark

Gary, Standard studs only.

Prop, the crank is stroked to 84mm.

Peter
PJ HOBSON

1426cc actually :)

Run the engine up until it gets to running temp, switch off, leave it for a few minutes then retorque the head while its still warm - the 10th and 11th stud needs less torque than the others and don't forget to reset the tappets, then leave it alone until rebuild time... As long as you use an AF460 gasket or similar you shouldn't have any problem

JB
J A Bilsland

go for arp studs(or high tensile) i did not at first and had (have) lots of trouble with the std ones
it might have something to do with the 12:1 compression ratio :P

check minispares for good but cheap high tensile studs
Onno Könemann

Thank you for that bit of info...Sounds like an interesting build, I certianly wasnt aware that something like that could be done.

Prop...HHHmmm, Ya know i bet it would take anther $5000 to convert my 1330 to a 1430...Prop
Prop

Not far out Prop, $100/cc ... it's the most expensive cc gain that last 50cc!

We have done a few of these. If using the Marina crank you should also cross-drill to match the original Midget crank, and also nitride to prolong the life of your efforts.

We have had no reliability issues in 000's of road miles with the head gasket, even with other gaskets than the Payen/"Turbo" one and CR of 11.5:1.
Paul Walbran

JB: Do you back off the torque fully and then re-torque, or, just check it from where it is?

Thanks,

Peter
PJ HOBSON

Peter,

I think that Keith Calver's article on head gaskets is worth a read:

http://www.calverst.com/cc110f.htm

Then follow links for Cyl Head and Head and gasket Issues

Guy

Guy Weller

Just retorque from where it is - usually you will get 1/2 turn or so on most studs.

JB
J A Bilsland

"Do you back off the torque fully and then re-torque, or, just check it from where it is?"

The nuts should be backed off about 1/8 of a turn, then torqued to spec. This is necessary to get away from what is termed "stiction". More torque is required to get a tight nut to turn than to keep it moving. All torque reading should be taken as the nut is still moving. Cheers - Dave
David DuBois

Hi All

Dave is correct in saying back off each nut and retorque so you are getting a 'fresh' torque and keep moving the torque wrench, no jerky movements. It is common practice to allow the engine to cool to retorque which usually means overnight. We only retorque copper gaskets, the black gaskets we leave well alone after initial fitment.

Peter
peter burgess

Hi Everyone,

Thanks guys for all your input, it's much appreciated. Once I get my bad back sorted I'll crack on with the job.

Peter
PJ HOBSON

This thread was discussed between 04/11/2009 and 09/11/2009

MG Midget and Sprite Technical index

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