Esprit HC Block with non HC internals and head - Advice
Discussion
Hi All,
Cutting a long story short, I have a Esprit 1984 2.2 Turbo.I have put a piston through the side of the block and unfortunately the block isn`t repairable.
I have been offered a bare block (no crank, pistons, rods etc...) The block I believe is a HC block and has Aluminium liners and not the cast liners I have in my current block.
From research I know the pistons were different on the HC engines, but will a non-HC piston work fine ? also will a non HC head also work fine.
Are there any other pitfalls I should watch out for or know about ?
Can anyone list the differences between a HC engine and non HC ?
Also I am looking at swapping the pistons and make them drop forged. Is there a known off the shelf piston I can use ? or am I going to have to get them specially made ?
Thanks in Advance for all advice
Rob
Cutting a long story short, I have a Esprit 1984 2.2 Turbo.I have put a piston through the side of the block and unfortunately the block isn`t repairable.
I have been offered a bare block (no crank, pistons, rods etc...) The block I believe is a HC block and has Aluminium liners and not the cast liners I have in my current block.
From research I know the pistons were different on the HC engines, but will a non-HC piston work fine ? also will a non HC head also work fine.
Are there any other pitfalls I should watch out for or know about ?
Can anyone list the differences between a HC engine and non HC ?
Also I am looking at swapping the pistons and make them drop forged. Is there a known off the shelf piston I can use ? or am I going to have to get them specially made ?
Thanks in Advance for all advice
Rob
> The block I believe is a HC block and has Aluminium liners
> and not the cast liners I have in my current block.
Rob,
The Nikasil liner block would be a nice upgrade for your engine.
> but will a non-HC piston work fine ? also will a non HC head also work fine.
The non-HC head will work fine, but the non-HC pistons won't. Aluminum expands more with temperature than iron does. So the clearance between the piston & iron liner starts out bigger than required when cold, then the aluminum pistons expand more than the liners as the engine gets hot, closing up the clearance. The final hot clearances end up much tighter than when cold, right where they need to be for normal running.
In a Nikasil HC-engine, both the pistons and liners are aluminum, so both expand at about the same rate. Therefore, the cold clearances are much tighter, more like the final, snug running clearances. If you put your loose-fitting LC pistons into the HC Nikasil liners, the hot clearances will end up too big. That's not good.
Also, you 'don't want' the original LC pistons anyway. They were cast, and marginal for the task. Over time they fatigue, and ultimately fail. They all fail, it's just a matter of when. Usually the ring lands collapse first, or you can just punch a hole through the crown. If you're going to invest in an engine rebuild, then buy a set of forged pistons. SJ Sportscars has original Malhe forged pistons for a reasonable price. And 'JE Pistons' make a nice forged aluminum piston for the 9XX engines. Contact your favorite Lotus parts specialist.
The head gasket was changed to a composite material in 1993. It's crushed thickness is about 0.5mm (0.020") thicker than the original gasket. As a result, the head is raised by a similar amount, lowering the compression ratio by about half a point. 7.5:1 becomes 7.0:1. When the new gasket entered production, Lotus started machining the block decks lower by that same amount, so 1993-onward engines have the correct spec compression ratio. But older engines (your engine) rebuilt with the new gasket lose compression. If you elect to buy new forged pistons, then order a compression ratio that is half a point higher than you would have otherwise wanted... like 8.5:1 instead of 8.0:1.
The new head gasket was a package-deal... gasket, upgraded head studs, and a higher torque spec. The higher torque will over-stress/ yield the old studs. Your best move is to replace all the head studs with the later OEM upgrade studs (identifiable by a dimple milled into the top end), or the even better ARP head studs. The ARP studs require an even higher torque, so the torque you use will depend upon the studs you install. But if you retain the old low-spec studs, then you also have to use the old lower torque spec. It will work, but not as well, and you lose the major sealing benefits of the new Goetze composite head gasket. I strongly recommend that you buy upgrade studs, and the ARP studs are the best. The ARP studs have fine threads, you you'll also need matching nuts. ARP requires that you use their propriatary thread lubricant, and their torque spec... make certain your parts supplier includes them.
Everything else fits the HC-block as before... bearings, head, sump, bell housing, water pump, front & rear main seals, engine mounts... all that stuff. Only the liners and pistons are different. Aluminum is not as strong as iron, so the liner's wall thickness has to be greater in the bottom, reduced- diameter spigot that slips into the block. Since the aluminum liner has a larger spigot diameter, the HC-block also has to be bored larger to receive it. With the exception of the spigot bore diameters, the iron-liner and Nikasil-liner blocks are fit-interchangeable with all the other parts.
Now that you have nice forged pistons, have the wastegate shimmed up to just under 10 psi. The dump valve vents at 10 psi, so stay comfortably below that... ~9.5+ psi.
While the engine is out, consider upgrading the spigot needle bearing (pilot bearing) in the back end of the crankshaft to a 6202-1RS ball bearing. That requires a trip to a machine shop. The Citroen transaxle's input shaft tends to work it's way past it's retaining circlip. Then the bias spring forces it forward against the crank. The shaft's clutch spline acts like a milling cutter, and chews it's way into the back of the crankshaft. That can get very expensive. The little needle spigot bearing can't resist the input shaft's advances, but the ball bearing can. If you decide to go that way, contact me for details.
Regards,
Tim Engel
> and not the cast liners I have in my current block.
Rob,
The Nikasil liner block would be a nice upgrade for your engine.
> but will a non-HC piston work fine ? also will a non HC head also work fine.
The non-HC head will work fine, but the non-HC pistons won't. Aluminum expands more with temperature than iron does. So the clearance between the piston & iron liner starts out bigger than required when cold, then the aluminum pistons expand more than the liners as the engine gets hot, closing up the clearance. The final hot clearances end up much tighter than when cold, right where they need to be for normal running.
In a Nikasil HC-engine, both the pistons and liners are aluminum, so both expand at about the same rate. Therefore, the cold clearances are much tighter, more like the final, snug running clearances. If you put your loose-fitting LC pistons into the HC Nikasil liners, the hot clearances will end up too big. That's not good.
Also, you 'don't want' the original LC pistons anyway. They were cast, and marginal for the task. Over time they fatigue, and ultimately fail. They all fail, it's just a matter of when. Usually the ring lands collapse first, or you can just punch a hole through the crown. If you're going to invest in an engine rebuild, then buy a set of forged pistons. SJ Sportscars has original Malhe forged pistons for a reasonable price. And 'JE Pistons' make a nice forged aluminum piston for the 9XX engines. Contact your favorite Lotus parts specialist.
The head gasket was changed to a composite material in 1993. It's crushed thickness is about 0.5mm (0.020") thicker than the original gasket. As a result, the head is raised by a similar amount, lowering the compression ratio by about half a point. 7.5:1 becomes 7.0:1. When the new gasket entered production, Lotus started machining the block decks lower by that same amount, so 1993-onward engines have the correct spec compression ratio. But older engines (your engine) rebuilt with the new gasket lose compression. If you elect to buy new forged pistons, then order a compression ratio that is half a point higher than you would have otherwise wanted... like 8.5:1 instead of 8.0:1.
The new head gasket was a package-deal... gasket, upgraded head studs, and a higher torque spec. The higher torque will over-stress/ yield the old studs. Your best move is to replace all the head studs with the later OEM upgrade studs (identifiable by a dimple milled into the top end), or the even better ARP head studs. The ARP studs require an even higher torque, so the torque you use will depend upon the studs you install. But if you retain the old low-spec studs, then you also have to use the old lower torque spec. It will work, but not as well, and you lose the major sealing benefits of the new Goetze composite head gasket. I strongly recommend that you buy upgrade studs, and the ARP studs are the best. The ARP studs have fine threads, you you'll also need matching nuts. ARP requires that you use their propriatary thread lubricant, and their torque spec... make certain your parts supplier includes them.
Everything else fits the HC-block as before... bearings, head, sump, bell housing, water pump, front & rear main seals, engine mounts... all that stuff. Only the liners and pistons are different. Aluminum is not as strong as iron, so the liner's wall thickness has to be greater in the bottom, reduced- diameter spigot that slips into the block. Since the aluminum liner has a larger spigot diameter, the HC-block also has to be bored larger to receive it. With the exception of the spigot bore diameters, the iron-liner and Nikasil-liner blocks are fit-interchangeable with all the other parts.
Now that you have nice forged pistons, have the wastegate shimmed up to just under 10 psi. The dump valve vents at 10 psi, so stay comfortably below that... ~9.5+ psi.
While the engine is out, consider upgrading the spigot needle bearing (pilot bearing) in the back end of the crankshaft to a 6202-1RS ball bearing. That requires a trip to a machine shop. The Citroen transaxle's input shaft tends to work it's way past it's retaining circlip. Then the bias spring forces it forward against the crank. The shaft's clutch spline acts like a milling cutter, and chews it's way into the back of the crankshaft. That can get very expensive. The little needle spigot bearing can't resist the input shaft's advances, but the ball bearing can. If you decide to go that way, contact me for details.
Regards,
Tim Engel
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