13 replies to this topic

[Gdowle]

hello,

Im after some advise on the coolant passages on the block. Do i just tap the hole and stick a grub screw or bolt in it or do i need to re drill the hole to line up with the 12g940 head?

Anyone had any overheating problems if not drilled? Drilling seems to be a problem as it needs to be flush to seal?

thanks

[bmcecosse]

Don't drill anything! Just use a 1275 head gasket. DO make sure you have clearance for the exhaust valves- do you know about that?

[Gdowle]

yes the machine shop has cut valve reliefs for exhaust side. 2 coolant passages dont line up with the gasket and ive heard it will shorten the life of the gasket or leak straight away? ive got a BK450 gasket to go on it.

[PhilipGCaldwell]

I have it on good authority you have to block up 1 water passageway, this is to stop pressurisation of the head causing failure, you can get away with not doing it though, personal preferance, I chose to do it in the end

This one

[l_jonez]

I have it on good authority you have to block up 1 water passageway, this is to stop pressurisation of the head causing failure, you can get away with not doing it though, personal preferance, I chose to do it in the end

This one

Yep you have to block off that hole, I tapped it a plunged it. I still had trouble with it blowing from the cylinder, in the end I welded it up and had the block skimmed

[Gdowle]

so no need to re align the holes just block that one up and jobs a gooden? ive got the block all stripped down ready to rebuild now, so if extra work is required to make it last i dont mind.

[l_jonez]

Yep just block the one, the others are fine, if you use a copper head gasket the water way holes in it are bigger which means every thing lines up ok

[full metal mini]

im ready to fit a cooper head (12g295) on my pre A+ block
as you can see the gasket leaves shadows of water passages of head on block.

must i redrill the holes to allign the heads holes or will it be ok?

the head comes from a cooper engine, i dont know if the cooper block has bigger water passages to fit with the head

water passages look like with those of the 12g940, if i redrill the passages on the block ill need to put a water pump from 1275 (bigger holes, needs bigger flow?)?

sorry if i posted in a wrong thread but on searching i find this to be more related to my issue

Attached Files

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Edited by full metal mini, 23 March 2011 - 09:06 PM.

[Dan]

The 12G295 is a small bore head, it fits the small bore block perfectly. All you need to do is correct the chamber volume for your CR.

[full metal mini]

im trying to get a 9:1
do you think its ok for a cruising set up?

[huw_jenks]

im trying to get a 9:1
do you think its ok for a cruising set up?

9:1 sounds okay, I don't think you'd want more than 10:1 for a daily driver. Have you worked out the ratio exactly though? I'm no expert on this subject, but it is good to know what compression you are running.

[bmcecosse]

Later 998s were 10:1 Cr as standard - so aim for at least that! How thick is your 295 head - and are you using flat top pistons?

And - i've never blocked off any waterways when doing the 940 head on a small bore block.........

Edited by bmcecosse, 24 March 2011 - 10:00 AM.

[timmo]

To be honest, i haven't heard of having to do this either. I have put a 940 on my 1098, must admit first time i took it out for a test drive (today) the head gasket blew .....But it blew outwards the water pump end, which i believe it was because the head must have been resting on the pump and not sealed...have now taken a bit more off the top of the pump.
The question now is....Do i block this waterway up or not?

[timmo]

As the head was off today, i decided to block the hole...Just glad i read this now and not after i had the head bolted back on and running around ..... would have been worring about it all the time