Cylinder Head Compatability

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P34Fan
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Cylinder Head Compatability

Post by P34Fan »

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
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Post by chris knowles »

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!

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mds666
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Post by mds666 »

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...

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And I think compression is pretty much the same

Post by AndyC »

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

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P34Fan
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Cylinder Head Compatability

Post by P34Fan »

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.
:twisted:

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nigelrobertson
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Post by nigelrobertson »

Is that Tyrrel P34 fan? :)

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Post by Peter »

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

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mds666
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Post by mds666 »

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
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Re: Cylinder Head Compatability

Post by peppo »

Hi,

what's the difference of the valves size?

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

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MrCoolA
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Re: Cylinder Head Compatability

Post by MrCoolA »

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.......
Previously Jerry (Taylor)
Now "Black Flag"


Lotus Excel SEI1989 253.6hp 190lbft
Lotus Elise S3 1.6. Motorsport Green 2011.

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mds666
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Re: Cylinder Head Compatability

Post by mds666 »

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
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Re: Cylinder Head Compatability

Post by peppo »

they told me same valve size 8)

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