9 replies to this topic

[me madjoe 90]

I have lots of time on my hands at collage between lessons and i have been told im alowed to bring bits in to do from my project. As long as there not to big they said if i need help they can help me out as well. Since i dont have all the equiptment to do stuff at home i though this is good idea.

So getting to the point i have a 1988 mini city and am doing an auto to manual convertion.
The engine i picked up is a standerd 998 out of a syimler aged car. I have been told that its done around 50000 mile and seems to look that way(most likely done more).

Now while i have the engine out i was trying to think of bits i can take off and do at collage and first thing tought was the head. As well as replacing the usual bit like valve stem seals and all the other bits, giving it a general clean up and so on i wanted to have a go a porting. I have read David Visards books on it and a few others and want to give it ago, but im just wondering wether its worth the efffort as i want to keep the car standerd for insurance resons but id like it to run nice.

Dose any one know what the gains will be and wether its worth it. Also if you have any ideas of other bits i could do at collage that arnt to expencive that would be great thanks. Even if its just things like cleaning parts and replacing seals/ gaskets it would give me something to do, and as i say they have the stuff to do it all there.


thank all posts are apriciated

[Cooperman]

There is no doubt that an improved cylinder head is the key to improved performance with the A-series engine. The standard head is just so poorly designed unless you have an 'open-chamber' head such as a 12G295 (Cooper 998 head) or the 12G940 whih is fitted to all the 1275 engines.
It is easy to get a good improvement by de-shrouding around the valves and opening up the port throats by removing most of he valve-guide bosses. As you say you have Vizard's book it's all in there.
Don't forget that if you take material out of the combustion chamber this will lower the compression ratio and you need to not lower it, but raise it to, ideally, about 10.2:1.
Good luck with the job.

[me madjoe 90]

There is no doubt that an improved cylinder head is the key to improved performance with the A-series engine. The standard head is just so poorly designed unless you have an 'open-chamber' head such as a 12G295 (Cooper 998 head) or the 12G940 whih is fitted to all the 1275 engines.
It is easy to get a good improvement by de-shrouding around the valves and opening up the port throats by removing most of he valve-guide bosses. As you say you have Vizard's book it's all in there.
Don't forget that if you take material out of the combustion chamber this will lower the compression ratio and you need to not lower it, but raise it to, ideally, about 10.2:1.
Good luck with the job.

How could i raise the CR afterwards if i do

[benb12]

I've been reading David Vizard's Tuning BL's A Series Engine, I would say it'sworth doing if you have access to the tools. There's one graph which shows power improvements by basic flow improvement modifications, presumably that includes everything in that chapter such as modifying the valves etc. BHP went from 60 to 66, torque went from about 71 to 73 lbs/ft. I would say do it, doesn't cost anything and should make a noticeable difference.

[benb12]

There is no doubt that an improved cylinder head is the key to improved performance with the A-series engine. The standard head is just so poorly designed unless you have an 'open-chamber' head such as a 12G295 (Cooper 998 head) or the 12G940 whih is fitted to all the 1275 engines.
It is easy to get a good improvement by de-shrouding around the valves and opening up the port throats by removing most of he valve-guide bosses. As you say you have Vizard's book it's all in there.
Don't forget that if you take material out of the combustion chamber this will lower the compression ratio and you need to not lower it, but raise it to, ideally, about 10.2:1.
Good luck with the job.

How could i raise the CR afterwards if i do

Skimming the head.

[me madjoe 90]

I've been reading David Vizard's Tuning BL's A Series Engine, I would say it'sworth doing if you have access to the tools. There's one graph which shows power improvements by basic flow improvement modifications, presumably that includes everything in that chapter such as modifying the valves etc. BHP went from 60 to 66, torque went from about 71 to 73 lbs/ft. I would say do it, doesn't cost anything and should make a noticeable difference.

ok thank you for your input seems worth it to me

I shall remove my head at some point and set about grinding bits off it then

[me madjoe 90]

There is no doubt that an improved cylinder head is the key to improved performance with the A-series engine. The standard head is just so poorly designed unless you have an 'open-chamber' head such as a 12G295 (Cooper 998 head) or the 12G940 whih is fitted to all the 1275 engines.
It is easy to get a good improvement by de-shrouding around the valves and opening up the port throats by removing most of he valve-guide bosses. As you say you have Vizard's book it's all in there.
Don't forget that if you take material out of the combustion chamber this will lower the compression ratio and you need to not lower it, but raise it to, ideally, about 10.2:1.
Good luck with the job.

How could i raise the CR afterwards if i do

Skimming the head.

ok i think i know someone who can do that for me

[Cooperman]

There is no doubt that an improved cylinder head is the key to improved performance with the A-series engine. The standard head is just so poorly designed unless you have an 'open-chamber' head such as a 12G295 (Cooper 998 head) or the 12G940 whih is fitted to all the 1275 engines.
It is easy to get a good improvement by de-shrouding around the valves and opening up the port throats by removing most of he valve-guide bosses. As you say you have Vizard's book it's all in there.
Don't forget that if you take material out of the combustion chamber this will lower the compression ratio and you need to not lower it, but raise it to, ideally, about 10.2:1.
Good luck with the job.

How could i raise the CR afterwards if i do

Skimming the head.

ok i think i know someone who can do that for me

You complete the head mods, grind in all the valves and fit a set of plugs. Then you make sure each chamber is the same size to within +/- 0.25cc by filling each chamber in turn with paraffin using a burette or shrynge. This also gives you the chamber volume.
From this, and after measuring everything else, like how far the piustons sit down from the block deck at TDC, you can calculate what the ideal chamber size is for the compression ratio you want. Then you put that amount of paraffin into a chamber, with the head absolutely level and measure how much needs to be skimmed from the head fact to reach that fluid level.
Just do the measurements and calculations accurately and you'll have a good engine.

Edited by Cooperman, 08 January 2010 - 02:02 PM.

[bmcecosse]

It's really really NOT worth doing this with a standard 998 head. Try to find at least a 12G202 head and work on that. As above - a 12G295 is much better - and a 12G940 head will be VERY much better. All these other heads will also benefit from your 'porting' efforts - but a standard 998 head is just not worth spending the time and effort!

[jaydee]

Agree with the above..you need bigger valves..
I run a 1456, which is basically a CAM4180 with higher compression, and it has only been ported because i havent access to a machine shop to fit bigger valves and i'm currently waiting for my new cylinder head which will be done to my spec.
All i can say is Yes it runs better than a standard head, but will give you only a couple more bhp (plus i find it very restrictive when used with the kent 256..)