Changing cylinder heads on 'A' series engines is by no means a new idea, since the maximum BHP available using a traditional 5-port is between 100-140bhp specialists have come to realise the cast iron siamese cylinder head is just not up to producing any more power regardless of how far 5-port cylinder head modification has come since the days of the famous David Vizard books. The first big change has to be the Arden 8-port cylinder head which is now available from minispares. At first stages the 8-port was used with Ammel carbs which were difficult to set up, then fuel injection was introduced and good power figures were starting to show, next was the first twincam 16v conversion, this was based around a ford BDA design but manufactured by KAD to solely fit the 'A' series. The latest head to hit the market is the AKM 7-port which has now been re-introduced by Minisport allowing the use of a pair of DCOE webers or fuel injection. All but the 7-port after market heads mentioned are based on a crossflow port design, crossflow means each valve has its own port of entry or exit allowing for massive power increases over the dated siamese design.
below we have some examples of various different cylinder heads all using the same spec bottom end, these tests were carried out on our dyno and are guidance only.
- 1380cc using a standard bottom end. 310 scatter camshaft, 5-port 38 x 31 off-set full race head, 1.5 roller rockers & 45DCOE weber carb 142bhp
- 1380cc using a standard bottom end. 310 scatter camshaft, 7-port 37 x 31 full race head, 1.5 roller rockers & 2 x 45DCOE weber carbs 158bhp
- 1380cc using a standard bottom end. 310 scatter camshaft, 8-port 37 x 31 full race head, 1.5 roller rockers & Jenvey fuel injection throttle body's 167bhp
- 1380cc using a standard bottom end. 300 camshafts, BMW 'K' Twincam 8v full race head, 2 x 40DCOE weber carbs 158bhp
- 1380cc using a standard bottom end. 300 camshafts, BMW 'K' Twincam 16v full race head, BMW 'K' 34mm fuel injection throttle body's 178bhp
- 1380cc using a standard bottom end. L1/BD3 camshafts, KAD Twincam 16v big valve race head, Jenvey fuel injection throttle bodys 188bhp
All the above cylinder head conversions require extensive modifications to the engine and are NOT a direct replacement for the 5-port BL cylinder head. In our experience building many of the above they all have there own pro's and con's, the BMW 'K' twincam conversion is no more difficult or easier. but is certainly an option to consider.
Now take a look at the Morspeed build guide and decide for yourself.
Morspeeds build guide has been designed around a using a standard engine changing only limited parts for what we feel are a must for ANY modified 'A' series unit regardless of its cylinder head. there will be options within the guide pointing out various modifications which will enhance the performance even further, these extra modifications will have a separete link showing cost and how the modification affects the performance of the engine.
Unit D, Scotlands ind est, Coalville, Leicestershire, LE67 3JJ TEL:+ 44 (0) 1530 830369 FAX:+ 44 (0) 1530 833171
16v Conversion guide:
FULL RACE 1380cc 'K' TWINCAM 16v @ 178BHP
So whats new??
Welcome to Morspeed performance tuning
The thought of grafting a BMW motorbike cylinder head on to a 'A' series block can to some seem confusing or so difficult its not worth the bother, well here at Morspeed we have decided to provide you with a run down of what is required and needed to build yourself a twincam engine capable of between 140-180bhp!! there has been other build guides available which sell for around £20, but these guides are VERY basic and we feel does not show the full extent of the conversion. As Morspeed were the FIRST company to pioneer a successful twincam conversion in 8v & 16v we hope our guide will enable you to decide for yourself if the 'K' conversion is for you.
FULL RACE 1380cc KAD TWINCAM 16v @ 188BHP