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| Joined: | 05-01-2005 |
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(Snip)... I have the possibility to get a 912 hybrid engine. It has iron liners and is believed to have a HC head. Is there any way to check by numbers if the information is correct?Check the engine number stamped into the top side of the block's rear flange... near/ above the starter. The number will start with the engine's model code... 907, 910, 911, 912 or 920. That will quickly tell you if the hybrid is based upon a 912 or 910 block & main bearing panel assembly.
Engine Number format examples:
LC 910 8210 20520
DC 907 7606 12844
1st letter = basic engine build spec (early engines used a 1-leter prefix).
2nd letter (if used) = engine equipment variation.
907 = Model (also 910, 911, 912 & 920).
7606 = Year & Month of manufacture (1976, June).
12844 = Serial Number.
Note that Lotus part numbers, like the block/ MBP assemblies and cylinder head numbers given below, begin with the model number in which the part was first used. But a block assembly that starts with B912 doesn't mean it was exclusively a 912 block. Once introduced, it was used across the range. For instance, the bucket tappet used in the 9XX from the 907 through the early Turbo 910s is the same as that used in the vintage Lotus-Ford Twin Cam, and carries a Lotus Elan part number, A026E0024Z... ie, where it was first used.
If 'part' numbers appear on the parts, they will be 'stamped' into the parts. Numbers 'cast' into the parts are the raw, un-machined casting numbers... same with forged parts.
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Block & Main Bearing Panel Assembly (match-machined sets):
The 912LC used the iron liner block ass'y, B912E0750J. Note that the 912LC and Pre-1986 910 Turbo shared the Iron Liner block. A Turbo 910 with a 912LC block has the correct block.
The 912HC used the Nikasil liner block ass'y, A910E9195J. Note that the 912HC and 1986-onward 910 Turbo shared the "Nikasil" Liner block. A 912HC with a "Turbo" block has the correct block.
The block/ MBP were re-tooled late in the game, and the Esprit S4s used block ass'y A910E2604J.
*~*~*~*
Cylinder Head Assy:
The 912LC used cylinder head ass'y, C907E0703J.
The 912HC used cylinder head ass'y, A912E9056J.
The Esprit S4s & Sport 300 Zeus head is P691.4005.800BJ.
(Zeus is the name of the foundry that produced the new head).
Other 907 heads (Federal Elite, Eclat, Esprit S1-S2):
A907E0703SH 1974 Federal WITHOUT air injection ports.
C907E0703S as above, but without heater water take-off port in right-rear corner.
B907E0703S WITH Federal air injection ports near exhaust ports.
D907E0703S as above, but without heater water take-off port in right-rear corner.
Federal 910LC heads (Iron liner engines):
A910E0703J Federal Carbureted 910 Turbo WITH air injection ports.
Federal 910HC heads (Nikasil liner engines):
A910E9057J Federal Fuel Inj'n 910, both Bosch & GM, thru Esprit S4, WITHOUT air injection ports.
P691.4005.800BJ big valve Zeus head, Federal GM fuel inj'n, 300Hp Esprit S4s & Sport 300.
Combustion Chamber Depth = 12.32-12.57mm (0.485-0.500 in)
Inlet valves ... = 35.47-35.65 mm (1.396-1.404 in) all thru Esprit S4.
Inlet valves ... = 36.37-36.63 mm (1.432-1.442 in) big valve (+1mm), S4s & S300 .
Exhaust valves = 30.70-30.91 mm (1.209-1.217 in).
All heads will fit all blocks without the need to fettle. Turbo 910 heads up through the 1993-94 Esprit S4 have the same size valves as the 907, and are a direct fit. However, the Turbo exhaust valves are an upgrade material to take the greater heat, and hence, a different part number. A 907 head will interchange onto one of those Turbo engines, but the exhaust valves won't be up to the task, long term. The late Zeus 910 head used on the Esprit S4s and Sport 300 had 1mm larger diameter intake valves, and will also bolt onto a 907.
Compression ratio is controlled by the pistons, not the cylinder head's combustion chamber. An "HC" head is a head from a HC engine, but there's no such thing as a "high compression head". And all 9XX cylinder heads will result in the same compression ratio when retro-fitted onto different vintage short-block assemblies.
Jensen-Healey & early Lotus 907 heads had 24mm intake ports.
Later 907 / 912LC heads had larger, 25.5mm intake ports.
912HC/ Esprit S4s & Sport 300 Zeus heads had even larger, re-contoured intake ports with special intake valves with the backside of their heads contoured to complement the port's tulip shape.
If you're porting the ultimate race or track day head, the Zeus head is the best starting point. Second best is the late 907/ 912LC head with 25.5mm ports.
The intake manifold to head gaskets all have the same size port openings, so laying one on different vintage heads quickly highlights differences in port sizes.
*~*~*~*
Cylinder head gaskets have changed over time, and new gaskets came with new torque specs for installing the head. Lotus hasn't sold the original steel-asbestos-steel gasket for decades, but if J-H sources still sell it, then you can use the torque spec in the manual. The current Lotus composite gasket uses a torque-angle spec in degrees, and the similar aftermarket composite gasket from JAE requires a torque wrench, but to a higher torque than original. When you buy a new head gasket, 'ASK' for the current torque spec to use with it.
Schorse wrote:
(Snip)... More importantly will the block fit the Getrag box directly or is some adaption needed?The short answer is that it will fit directly.
The bell housing mounting flange at the back of the block is the same pattern for all 9XX 4-cylinder engines. The J-H Getrag/ bellhousing that bolts to a 907 will also bolt to a Turbo 910S... I just don't advise the combination, unless you wish to see the Getrag grenade.
Early J-H 907s had a rear main rope seal, and later engines were configured for a rear lip seal. From that change point onward, there's very little difference in Lotus 9XX four cylinder blocks, in terms of fundamental dimensions. As some accessories were added, like A/C, complex brackets were used at first to adapt the new bits. Whenever the block was re-tooled, the opportunity would be taken to add new bosses or flanges as required to eliminate or simplify the bracketry, but the block's "engine function" dimensions remained fundamentally unchanged.
All the width difference between the 907 and the 910, 911, 912 & 920 is in the Main Bearing Panel (MBP). The joint with the block has the same footprint, then the MBP flares outward as it goes down, like a skirt. It's double walled. The original narrow wall is still there, then a gap, then the outward-flared wall. Of course, the sump is also wider to mate with the wider MBP.
Two exceptions. 1) Aluminum is not as strong as cast iron, so the necked down spigot diameter at the bottom of the cylinder liner (the part that pilots into the cylinder block) had to have a thicker wall in aluminum... which meant a larger OD. That, in turn, required a larger spigot bore diameter in the later "Nikasil" blocks. Externally, all major block dimensions were the same. An iron liner block can be re-bored to take the larger OEM Nikasil liners (ie, they're metal safe), but you can't cut a Nikasil block smaller to take iron liners. Aftermarket suppliers provide custom iron liners in aluminum dimensions as an inexpensive alternative for replacing Nikasil liners.
2) The 920 2.0 liter Turbo used the same basic cylinder block casting, but the deck height was slightly reduced (same casting, different machining). That change forced a ripple effect cascade of small parts changes that makes the 920 block a poor choice for a 907 owner looking for a replacement block. The 920 engine saw limited use in the Esprit GT3 which was originally developed for the Italian market (big tax on engines over 2.0 liters), and was later sold in the UK and Euro markets. The 920 and GT3 were never sold in North America, never sold in high volume, and are the rarest of 9XX street engine parts. If you don't own an Esprit GT3, then IMHO, the 920 parts hunt just isn't worth it.
Schorse wrote:
btw the guy said it would be a turbo block but as it has iron liners this seems improbable correct?Scroll back up to the Engine Number format, above, and notice that it provides the engine's build date. Lotus used iron liners on all it's engines, 907, 910, 911 & 912, up through 1985. The Nikasil coated aluminum liners were introduced across the board in the 1986 model year. So it's very possible that a turbo block assembly could have iron liners, depending upon it's vintage.
In each case, the cylinder block has spigot bores (liner sockets) machined to ID's appropriate for the liners being used. Other functional dimensions in the block are unchanged.
Last edited on 04-13-2014 03:54 pm by Esprit2