Cylinder Head Compatability

P34Fan · Post by **P34Fan** » Fri May 02, 2008 09:05

Hi All,
New to the forum, will post pictures of the car once its going again.
Will the cylinder head and cams off the 912 high compression engine fit the 912 low compression engine.
If it does, what improvements do you get apart from reduced oil leaks etc.
Regards
Ken

chris knowles · Post by **chris knowles** » Fri May 02, 2008 13:00

From memory putting the red top SE HC head/cams on the black top LC block is a big no no, as the differences between the LC and HC are quite elaborate and stretch beyond those improvements like "nicosil liners" and "extra jet on the carbs" differences that are often discussed.

No doubt someone who knows these engines far far better then I will be along shortly to explain!

mds666 · Post by **mds666** » Fri May 02, 2008 21:56

the port sizes are bigger on the hc head... apart from that theres a moderate improvement on the water ways and thats it... you can put the cam carriers on to an lc head by the way... save you rebuilding the engine...

AndyC · Post by **AndyC** » Sat May 03, 2008 14:18

AFAIK the capacity of the combustion chamber in the heads is roughly the same and the way the HC gives a higher compression ratio is by having pistons that are slightly taller from the gudgeon pin to the top.

Also consider that the HC gives 20 BHP more than the LC, but also has an improved exhaust manifold, so swapping heads may give very little difference.

Andy

P34Fan · Post by **P34Fan** » Mon May 05, 2008 07:38

Thanks for the info gents.
So has anyone port and polished the head on their LC engines + match ported manifolds etc.
Different cams ?
Has anyone fuel injected their cars?
What systme did they use?
What sort of power gains did they get?
Sorry to be full of questions but love the motor just trying to bring it along a little.

nigelrobertson · Post by **nigelrobertson** » Mon May 05, 2008 08:58

Is that Tyrrel P34 fan?

Peter · Post by **Peter** » Mon May 05, 2008 09:23

I'm pretty sure i remember a LC owner posted he got somthing like 190hp and 180lbft torque from a head port an tubular 421 manifold. standard 107 cams, i can imagine that must have made a very nice tractable engine for a road car

mds666 · Post by **mds666** » Mon May 05, 2008 10:31

i would sugest thoes figures are very optomistic...

my engine:

ported head + matched manifold (CNC'd 174cfm)
special inlet cam
104/L14 exaust cam
HC pistons (ballanced)
ballanced bottomend (crank rods and steel flywheel)
Fuel injected (DTA E48, distributorless, 45 ITB's)
Proper 4-2-1 manifold

gave 198.6 (from memory) at northampton motorsport so thats a real figure... and 170lbft ish

now there is more to come from it by playing with the induction leinghts and better trumpets (im using std ones at the min...) but the standard airbox is not a limiting factor even with a £7 airfilter in it... i spent time dooing power runs with airbox closed with filter in it, closed with no filter in it and open with no filter in it... not a blind bit of diffrence... to put some miths to rest...

peppo · Post by **peppo** » Fri Aug 19, 2011 15:05

Hi,

what's the difference of the valves size?

I'm considering to port my head (lc) or buy an hc one...

MrCoolA · Post by **MrCoolA** » Sat Aug 20, 2011 08:42

peppo wrote:Hi,

what's the difference of the valves size?

I'm considering to port my head (lc) or buy an hc one...

If Mark (MDS666) isn't back on then try a call/email to Mike at Lotusbits, he if you don't know runs/builds 912 race engines and if a font of knowledge, as is Mark.......

mds666 · Post by **mds666** » Tue Aug 23, 2011 23:10

hi jerry i am still about... just...

looked at my old girl today... i really should get her finnished... now the astra is done i shouldnt have much excuse...

peppo · Post by **peppo** » Fri Sep 02, 2011 14:22

they told me same valve size

The Lotus Grand Tourers