20 replies to this topic

[robminibcy]

hi, what's going to be better value interms of potential power gains and cost out of a 12g295 head or a modified 998 head? Can a standard head be machined to 295 spec? I already have a standard head in need of refurb whereas I'd expect to be paying £50+ for a 295 that would still need a refurb and skimming for a 998.

Edited by robminibcy, 13 February 2014 - 07:19 PM.

[miniman24]

I think a 295 would be better (large valves and chamber work) than a modded standard head but expensive to do - but so is modding a standard head. I bought this from ebay with brand new Rim Flo valves for £150 and just had it skimmed (only a few thou) to obtain a 10:1 compression ratio on my engine and it should be a good power increase over a standard head for comparatively little cost :)

 

[ACDodd]

Ports are too big on a 295 head. For a 998 engine best to mod a 998 casting. However in terms of cost a 295 might be a better choice if have one which is actually serviceable. Not many in the uk who will actually do a proper small bore head with actually small ports.

 

AC

Edited by ACDodd, 13 February 2014 - 09:31 PM.

[miniboy94]

if you want a 295 head on a 998 block you have to pocket the block allowing vavles to clear iv had it done to mine and was ace like i noticed a big difference but not many places do it that the think ?

[robminibcy]

if you want a 295 head on a 998 block you have to pocket the block allowing vavles to clear iv had it done to mine and was ace like i noticed a big difference but not many places do it that the think ?

sure that's not a 12g940 head your on about. That. 12g295 is a 998 cooper head.

[Gremlin]

if you want a 295 head on a 998 block you have to pocket the block allowing vavles to clear iv had it done to mine and was ace like i noticed a big difference but not many places do it that the think ?

You don't on a 295, thinking about it, surely it would be if the valves were further apart

Edited by Gremlin, 13 February 2014 - 09:53 PM.

[robminibcy]

cheers for the advice. Does anyone have an idea of a rough cost of what i would pay to have a standard head modified to 295 ish spec?

[ACDodd]

No, its not 295 spec you want thats the point.

 

AC

[AFMike85]

Wo Wo Wo!!! ACDodd how are you a "Mini Doc" handing out info like that? Cooperman would be all over you for how wrong that answer was.

Rob, If you're building a fast road 998 or other small bore you WANT a 12G295 the original Cooper 998 head used with D-top pistons. They don't make either anymore but good un-touched heads are a bit hard to find now. It's cheaper to get a 295 and have it done up then mess with the standard 998 head hands down. The 1275's 12G940 head is the one you need to pocket the block or sink the valves for, if you have any other questions use the search function and search for 12G295 or fast road 998, I use google, gets better results for the site.

[ACDodd]

Oh dear. It shows how stuck in the past views like the 295 is the best thing since sliced bread is! The intake port runners are too large for a 998 based engine.

Best choice does not mean cheapest. Cheapest and best would be the 940 head, next would be a 295 head. The best would be an extensively modded stock 998 head, simply because it would have the smallest intake runners thereby maintains maximum average torque across the useable rev range.

Old school thinking has moved with the times. My job as a mini doc is to let people know that.

Ac

Edited by ACDodd, 14 February 2014 - 06:16 AM.

[madaboutcherry]

I,ve modified a few 998 heads in the last 40 years, and I always start with 12g202. they're usually quite cheap and unmolested.

[jaydee]

I was debating this port size matter for ages.

I'm glad that finally some reputable engine builder are starting to share this information to the public.

Kudos to AC, we all know about this issue, but nobody provides this info on the net.

[jaydee]

I,ve modified a few 998 heads in the last 40 years, and I always start with 12g202. they're usually quite cheap and unmolested.

 

 

Vortz was only one of those who were builing hot small bore engines back in the days (especially during the 80ies) and all of them used modified 202 casting, due to the port size. 

Apart form some 1060 spec, the 998 and 1040 engines all used 202 castings.

Edited by jaydee, 14 February 2014 - 02:04 PM.

[087dave]

What about a worked standard head
Like cam4810?

[miniman24]

Mine has had minimal porting work done, concentrating mostly on the chamber shape, correct skim and smoothing of the chamber. Hopefully it should be about the best head I can get for my 998 in my budget! However I didnt know that porting to 295 spec affected the torque as much as it supposedly does so thanks for the info AC!