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Heads for an 1100.
https://www.ausmini.com/forums/viewtopic.php?f=2&t=80386		 Page 1 of 2
Author:  Speedwell Racer [ Sat Feb 16, 2013 8:29 pm ]
Post subject:  Heads for an 1100.
Hey guys,
Slowly putting a list together of parts for my 1100 build.
I've been offered a 12g295 head for $200 Ono
Would it be worth getting and doing some port work etc and bolt on top of my 60thou over 1100 block?
I've heard abit about 295 heads and want some more info performance wise versus other heads etc!!

Cheers, Rhys
Author:  drmini in aust [ Sat Feb 16, 2013 9:35 pm ]
Post subject: 
295 head is good, it takes way more than $200 spent porting say a 202 head to make it as good as a 295.
Of course you can improve a 295 further, all it takes is even bigger valves, some more porting, and $$$.
Author:  XC9000 [ Sun Feb 17, 2013 2:15 pm ]
Post subject:  Heads
Go with the 295 at that price its worth every penny.

The Mk1's were factory fitted with larger valves and very crack prone. When i discovered my Mk2 was cracked we consulted with the local mini expert and he would happily show numerous cracked 295s on his shelves.

My recommendation for durability is to port / polish and shave but leave the valves unless you are looking for the very high level of performance with as with roller rockers big cam carby and exhaust improvements. Do those in favour of bigger valves. Don't forget to burette the chambers so that you have identical volumes. Check your valve guides and of course replace the inlet valve seals.

And weren't you saying this in an 1100cc...hmmm

My two penneth worth... :?
Author:  Speedwell Racer [ Sun Feb 17, 2013 10:45 pm ]
Post subject: 
Thanks guys..
Yes it's an 1100 currently has a 202 head and 40thou over pistons.
Just gonna clean it up and bore it to 60thou, a nice cam Kent 266 or Re13, hif44 or 40mm weber!
Author:  raisto2 [ Mon Feb 18, 2013 6:04 am ]
Post subject: 
I think XC9000 is asking if it's actually still 1100cc..

drmini in aust wrote:
an 1100 bored to +.040" is an 1132. +.060" gives 1152.
Author:  sam_1100 [ Mon Feb 18, 2013 7:25 am ]
Post subject: 
Is the 295 complete? Standard/Any work already?
If my memory serves my correct, the 295 is better to start with and requires less work to get flowing really well, but a 202 has alot more potential and if worked properly can go further than a 295 could?

If you are going to do the head properly with big valves, double springs, porting, etc, just take your current 202 head off and drop it off somewhere to get done! Put the $200 you save into a better porting job.

My 202 is a screamer! Cost an arm and a leg though.
Author:  XC9000 [ Mon Feb 18, 2013 12:40 pm ]
Post subject:  Double Valve Springs
Before you go down the direction of doulble valve springs I recommend you PM / Talk with TheMiniMan (Matt) who has put a lot of development into the different strength of springs; what to use and specifically what not to use. :wink:

I was not aware that you could get a 202 head better performing that the 295. I'd research the advice first to obtain a level of consistency. And if the 202 developed head cost a shipload then I dont understand why you wouldnt start with a $200 295 and leave the valve diameters (and stainless inserts) alone. They are big enough. What may be more important is fine seating and the shape from port to the valve.

BTW stainless inserts for ULP have been known to dislodge in race heads. ouch :!:

Oh and, I stated isnt it an 1100cc implying that you are going to a lot of trouble for an 1100cc engine bored or not. My viewpoint is that in historic racing its either 1000cc or 1300cc limit and the 1100cc is not a competitive start. Hillclimb small engine category is 0-1600cc. Therefore the good old 1098 isn't a good competition fit, save for rallies, motorkhana etc. for what it may be worth.

Wayne
Author:  raisto2 [ Mon Feb 18, 2013 12:57 pm ]
Post subject: 
from what I've heard, it doesn't take all that much to revert the 1098 back to a 998 as they're essentially the same block?
I think it's only the crank and pistons? possibly the con rods too?
which then could go in the under 1000cc events, and you're still able to push respectable power out of the 998's.. although a 1275 is the better starting block if top figures is what you're after..
*please correct me if I'm wrong.
Author:  Timbo [ Mon Feb 18, 2013 1:16 pm ]
Post subject: 
Yes the 998 and 1100 block are the same, as are the conrods. The crank and pistons differ. If you're fitting a 295 head to a standard 1100 (or a 998) with flat or dished pistons you need to plane a substantial amount off it to get the compression ratio right. The problem is that you need to do the calculations for the engine you're fitting it to and modify the head to suit. If you later decided to convert your 1100 to a 998, you might find that the compression ratio is no longer correct.

Tim
Author:  drmini in aust [ Mon Feb 18, 2013 1:27 pm ]
Post subject: 
Timbo wrote:
Yes the 998 and 1100 block are the same, as are the conrods. The crank and pistons differ. If you're fitting a 295 head to a standard 1100 (or a 998) with flat or dished pistons you need to plane a substantial amount off it to get the compression ratio right. The problem is that you need to do the calculations for the engine you're fitting it to and modify the head to suit. If you later decided to convert your 1100 to a 998, you might find that the compression ratio is no longer correct.

Tim

If it's a 1098 with flat tops + 295 head, the C/R will be about 8.9:1 (same as Mk2A Sprite was). Of course if overbored +.080 or more, the C/R will be higher.
If it's a 998 with flat tops it'll be less, if a 998 still with dished pistons it'll be a LOT less (under 8.0:1).

Most Mini engine tuners in Sydney (well, the 3 I talk to) say don't shave a smallbore head more than about .070" tops. The deck gets too thin, which can give gasket sealing problems.

As you say, some calcs need doing.

@XC9000,
a 202 can be made to outperform a 295 but it takes lots of time and $$$. I have done a few roady ones in the past. GR still does them for race heads, but take your $,$$$ with you. :wink:

[edit] here's a couple of shots of the last 202 head I did, before chambers got polished.
Chambers are pretty big in 2nd pic because it was going on a Sprite 1098 bored to 1220 with Imp flat top pistons.
Image
Image
Author:  XC9000 [ Mon Feb 18, 2013 7:02 pm ]
Post subject: 
drmini in aust wrote:

@XC9000,
a 202 can be made to outperform a 295 but it takes lots of time and $$$. I have done a few roady ones in the past. GR still does them for race heads, but take your $,$$$ with you. :wink:


Live and learn - thanks Kev.:o

And don't I recall somewhere that the 295 chamber is a greater 'diameter' (for want of better explanation) than the smaller bore heads, and then there is the risk of the inlet valves colliding with the 998 / 1098 piston tops? In the past i recall seeing pistons with 'inlet valve dishes'. I think this explains it??? Help Doctor or someone :?:
Author:  sam_1100 [ Mon Feb 18, 2013 7:42 pm ]
Post subject: 
If he has an 1100 why would he want to go back to a 998.......
Enlighten me my friends
Author:  mattsmadmini [ Mon Feb 18, 2013 7:46 pm ]
Post subject: 
sam_1100 wrote:
If he has an 1100 why would he want to go back to a 998.......
Enlighten me my friends


120+ flat tops, worked 295, wedged and worked crank, race cam.... good for 9000rpm.... yummy... nothing like a screaming 998... :twisted:
Author:  sam_1100 [ Mon Feb 18, 2013 7:58 pm ]
Post subject: 
But if you already have a good 1100... Why would you want to lose the easy power gain from the extra cc's :roll:
Despite the higher revving capabilities
Author:  XC9000 [ Mon Feb 18, 2013 8:04 pm ]
Post subject: 
sam_1100 wrote:
If he has an 1100 why would he want to go back to a 998.......
Enlighten me my friends


Only to compete in <1000cc class. If the engine is that yummy :D :D
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