One Carb Or Two?
Posted 11 November 2013 - 07:19 PM
Hi,
I've done a quick search, it might be a stupid question but, will the valve clearances have to be different because the 295 is on an A+ 998??
Or is it just the same clearance as my CAM4810 head??
Spec: A+ 998, Standard camshaft, stage 1 w/12g295 head
Thanks,
Iain.
Crazy About Mini's
Posted 11 November 2013 - 07:52 PM
12 thou both inlets and exhausts.
Keep an eye at clearances if the 295 has not been converted to unleaded
One Carb Or Two?
Posted 11 November 2013 - 08:01 PM
Cheers bud, my 295 has had the unleaded inserts put in
TMF fantasy F1 winner 2012
Posted 11 November 2013 - 08:45 PM
Have you had your 295 head skimmed? The combustion chambers on a 295 are around 4cc larger than a standard 998 head. If you have not had the head skimmed your compression will be low.
Speeding Along Now
Posted 11 November 2013 - 09:28 PM
I have just bought a 295 head and was wandering what thickness it should be to get the compression ratio correct on an A+ engine with dished pistons, at the moment it is 70mm ish thick. Did you have the unleaded valve seats fitted? if so how much did it cost?
Uncle Cooperman, Voted Mr TMF 2011
Posted 11 November 2013 - 11:18 PM
You need to do the measurements and calculations to ensure that the comp ratio is correct.
This includes measuring the volume of the piston dish, the volume above the piston crown level to block deck level, the gasket volume (nominally 2.7 cc for a 998) and the existing combustion chamber volume.
Some 998's have dished pistons whilst some are flat top.
Once you know the existing C.R. you can work out what combustion chamber volume you need for your desired C.R. and have the head skimmed to give exactly that volume.
Then the new head will work properly.
TMF fantasy F1 winner 2012
Posted 12 November 2013 - 12:25 AM
I have just bought a 295 head and was wandering what thickness it should be to get the compression ratio correct on an A+ engine with dished pistons, at the moment it is 70mm ish thick. Did you have the unleaded valve seats fitted? if so how much did it cost?
When I had a 295 head redone with hardened seats by Southams it cost around £300. That included hardened seat, new valves, guides and springs.
One Carb Or Two?
Posted 13 November 2013 - 08:37 PM
Cheers for the replies!
Regards to CooperMan, i have done that lengthy process already (by reading another one of your posts). Got all the numbers i needed and measured my chambers. Turned out i had a 'non molested' 295! I work it out to a 10.1:1 CR (seemed a popular CR for a grunty 998). Ended up getting it skimmed by 0.08858. This calculation was VERY precise and took a lot of time!
Regarding andyt, i bought a whole engine that had this head on. Turned out that it had never been skimmed (standard thickness being 69.85mm). But it has had 2 new inlet valves put in and the unleaded inserts already, so i am unable to give a price. But i have read that it isn't cheap!
Cheers,
Iain.
P.S... For anyone who is wondering, the head is now on the car. Done a compression test and i have 174psi (give or take a couple of psi) on all four cylinders. My only problem with installing the head was not researching that the head would foul my water pump pulley! Ooops... Bit on luck the engine came with the smaller one!! 
One Carb Or Two?
Posted 13 November 2013 - 08:41 PM
Pictures on the head after being skimmed and having the valves lapped back in:
Iain.
Stage One Kit Fitted
Posted 13 November 2013 - 09:23 PM
Speeding Along Now
Posted 13 November 2013 - 10:08 PM
Hi Iain nice looking head, mine is very rusty at the moment where it has been left in a shed for the last 10 years but like yours measures 2.75 inches thick which is completely the standard measurement.
I might have to steal your measurement for skimming it too!
Regards
Andy.
Uncle Cooperman, Voted Mr TMF 2011
Posted 13 November 2013 - 10:16 PM
Hi Iain nice looking head, mine is very rusty at the moment where it has been left in a shed for the last 10 years but like yours measures 2.75 inches thick which is completely the standard measurement.
I might have to steal your measurement for skimming it too!
Regards
Andy.
You cannot use someone else's measurements as you may have different piston dish volume, the pistons may sit further down the bores at TDC or the chambers may be slightly different in size if they have been opened out at all.
The only way to be sure your engine will be right is to measure and calculate it yourself.
One Carb Or Two?
Posted 14 November 2013 - 12:35 AM
As CooperMan said, it's different with every engine/head to determine how much you need to skim. I done a rough calculation that for every 1mm you take off you can loose around 1.9cc.
It is a lengthy process, a few calculations, but as soon as you have the correct measurement of your 295's chambers, then that will give you good ground. But by what you're saying about your 295, it seems the likely hood of them being the standard 28.3cc is pretty high. But in no way take my word for it! Do the measurements!
Regarding bmt216a, the 295 will give you a good gain in power (once again, that's if the time is put in to correctly work out what needs machining). Also, i am running a standard cam, yes. I have only put this head on my engine because i needed a head gasket change anyway and the head was just sitting there... I'm currently building up another A+ 998, same condition as mine, but it's going to have a 266 cam for more lift and the duplex timing gears for a bit of extra strength.
Hope this helped! But do ask more questions if you have them, hopefully i will be able to help you out!
Iain.
One Carb Or Two?
Posted 14 November 2013 - 12:43 AM
Looks good! There's a 295 on ebay at the moment I was interested in but measures 69.6mm, was worried the valves would foul on my 998.
It shouldn't foul on the block, i have taken a good 2.25mm off mine now and it's fine.
Super Mini Mad
Posted 14 November 2013 - 06:11 PM
Looks good! There's a 295 on ebay at the moment I was interested in but measures 69.6mm, was worried the valves would foul on my 998. was originally saving for a Keith Calver stage 3 but this being the fraction of the price would be better. Are you running a standard cam?
Why dont you just use a 12G940 head and recess the exhaust valves into the head? It flows better than a 12g295 as standard.
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