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| 12g295 head, work required for fitment. https://www.ausmini.com/forums/viewtopic.php?f=2&t=41352 |
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| Author: | clubmn [ Wed Apr 23, 2008 11:08 am ] |
| Post subject: | 12g295 head, work required for fitment. |
Do you have to skim the head to bring the comp up if fitting this head for another application, ie 998moke donk. I did once fit one to my 850 and it went allot better but i didn't do any work to it, wiped it of the sprite and put it on the mini. So what advice do u have for me, skim it how much? or should i not skim it for the sake of keeping it original. |
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| Author: | matt850 [ Wed Apr 23, 2008 11:18 am ] |
| Post subject: | |
i put one on my 998 recently and i think we took 30 thou off. Leaves enough for another skim later if it becomes necessary. Could possibly do with a little more than that though. Cheers |
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| Author: | Mike_Byron [ Wed Apr 23, 2008 11:19 am ] |
| Post subject: | |
The good DrMini has on several occasions given details on how to measure how much "meat" is on a 295 head. I don't have the information at hand but you can search for it. How much meat is on it determines how much you can skim it to bring it up to a reasonable compression. Yes it will run better because of the better gas flow and bigger valves. But the compression will be fairly low and you will suffer on hills etc. Now, just about all S/H heads will have a warp in them and you can almost count on the valve guides being worn and the valve seats will need refacing. Since your going that far - you might as well get hardened exhaust valve seats fitted so you can run unleaded fuel. Its not a big expense - I have had several heads done in the not so recent past and it comes to about $300, if you shop aroound the various machine shops. Its the old "do the job properly and do it once" theory and you will be very very pleased with the results. Mike |
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| Author: | matt850 [ Wed Apr 23, 2008 11:27 am ] |
| Post subject: | |
Sound advice Mike, Grieg (Mini Classic) checked it all out for me. All of the above was done and it goes a treat. I feel a little more off the head wouldn't hurt on the hills though but I still have plenty of "meat" to do that at a later date |
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| Author: | 1018cc [ Wed Apr 23, 2008 11:49 am ] |
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Mike_Byron wrote: The good DrMini has on several occasions given details on how to measure how much "meat" is on a 295 head. I don't have the information at hand but you can search for it.
I know the post you are talking about but am buggered if I can find it 
I know that the head starts off at 2.75". I'm pretty sure Drmini put up a post that said so many thou off is 1cc (or similar). |
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| Author: | Wombat [ Wed Apr 23, 2008 12:50 pm ] |
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Other option is to put in flat top pistons (major engine out job) GR has a range of flat tops and the 1100 ones should be here any day now |
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| Author: | Mike_Byron [ Wed Apr 23, 2008 3:29 pm ] |
| Post subject: | |
A couple of more notes on a mini with a 295 head. It will make the mini quite a nice car to drive and enjoy and basically the A series engine is a pretty good and strong engine. However, adding bolt on performance will not substitute for reconditioning the engine. If its driven spiritedly and revved harder (because it will) it will quickly show wear in other places. The taboos on a mini engine are wheelspins, flat changing and dropping the clutch on change downs with a bag full of revs. Apart from putting serious loads on the gearbox the downchanging causes the crankshaft to whip and this can lead to snapped centre main bearing caps. If you watch racing drivers who know what they are doing in a mini, they always use the formula of slow into a corner and fast out. The revs are kept constant. They dont rev it to a maximum in the lower gears and the use the engine torque rather than revs to accelerate. A higher performance mini uses quite a bit more engineering than just a head, cam, carbies and extractors to make it a good quick reliable motor. The other point is that if the head gives you 15% more performance then you are going 15% more quickly. You still need to pull it up quickly and safely so the brakes need to be in tip top condition to match the performance - more so than in a standard mini. Having delivered the Ausmini Occupational Health and Safety Officer's sermon - enjoy. Mike |
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| Author: | albino235 [ Wed Apr 23, 2008 3:38 pm ] |
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I agree with what Mike just said and another few things, if you have drum brakes just adding a better head might not justify spending the $'s upgrading to disks and there are things that you can do with drums. This has been discussed in other threads. For calculating the head skim, I think GR told me that 80 thou is the maximum skim you should do on a 295, don't quote me on that though, but it surprised me at how little it was. To find out how much meat you have on the head now it is best to get out the calipers and measure the thickness from the face to the inside of the water passages. Put a margin for error on this though. You can also measure the total head thickness but I don't know the figures for this... I am sure the doc will fill us in. And while were on this topic can anyone tell me what the maximum safe skim for a 202 head would be? Cheers, Alex |
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| Author: | drmini in aust [ Wed Apr 23, 2008 7:29 pm ] |
| Post subject: | |
Graham likes to skim 295 heads no more than .060", .080" would be his maximum and not for a turbo motor. The problem with skimming smallbore heads is the deck face is thin to start with. The more you remove, the more likely you are to blow gaskets. A 202 head is in the same boat- it's the same basic casting but with better port shapes and bigger inlet valves. Standard original thickness was 2.750" as said. Speaking of gaskets, the best one about for a smallbore now is the ACL Monotorque, available from Karcraft for $19.00. |
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