I'm been perving at a few peoples handy work and I have a question on gaskets. What size should the inlet cut out on a standard 1275 gasket be? The gasket I have hear has cut outs the same size as the ports on a stock standard 940 head, yet most pics I've seen show people enlarging the ports....so what do they do for a gasket...cut it? I am not making mine particularly bigger....just smoothing the way, but I'm curious.

Standard port holes are 1-3/8" from memory.
Those of us bith bigger intake runners use a `big port' gasket. Available from Karcraft and most Mini joints.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Well there you go then! Any idea how much bigger? Yes the stock head and gasket are 1 3/8. I haven't got it here but I think my inlet manifold is a bit bigger, so until now I would have had a nice step. I have no desire to open up the ports all the way through but a bigger gasket would a least allow me to blend it so there's no step on the way in.

Inlets on big port gasket are 1-9/16" (39.6mm for the Imperially challenged).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thank you muchly

hi, i find the std inlet gasket holes big enough at 35mm, but the exhausts are always too small & gasket needs to be opened up on a modified head.

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1275

Huh....lining up the gasket on the head I was thinking the opposite...the exhaust cutouts looked huge (compared to the head).

I had to enlarge all the exhaust holes a little yesterday on a BIG port gasket...
The ones they sell now have slightly smaller exhausts than the old red asbestos ones did.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Geez....that's a WHOLE lotta metal coming out of those ports

The standard port has something like 5mm clearance around it compared to the standard gasket.....

If you need to mod the gasket it's probably too big!!!

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Lillee - 1969 Morris Mini K

Exhaust ports in mine are Vizard standard...
If I didn't trim the gasket it would stick into the ports creating a restriction. Then I mightn't get enough power out of the 1412 to beat yours....

<edit> at GR's today I saw another of these later bigport gaskets with the exhaust holes seriously opened out, so it's a common mod...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

So how big are the exhaust ports on the the big port gasket?

NFI now, I only have 1 & it's in the motor!

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

hi, i think they need to be opened up 2-3mm depending on the manifold & expected power, this is only on some of the port not allover. Std ports are only 25mm sq approx. Check your exh manifold it will be bigger than the std exh ports

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1275

My gasket is not modified...

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Lillee - 1969 Morris Mini K