I think I found a unicorn 2.0

DiDueColpi · December 02, 2021, 09:52:12 PM

Been cleaning up after the floods and found a crank that I had squirrelled away and forgot about.
It's an NOS 2.2 litre Lotus crank.
It just happens to fit into a RV8 block like it was made for it. Sort of.
There's enough material and strength to machine it for narrowed v8 rods.
So the RV8, Lotus 16V, flat plane, Lover engine just got a major injection of renewed interest. (and Art thought it was dead

)

Live like you mean it.
Fred

joe_padavano · December 04, 2021, 10:39:33 AM

Good discussion of why this might not be the best idea.

https://www.enginelabs.com/tech-stories/the-earth-isnt-flat-the-reality-regarding-flat-plane-crankshafts/?utm_source=rss&utm_medium=rss&utm_campaign=the-earth-isnt-flat-the-reality-regarding-flat-plane-crankshafts

BlownMGB-V8 · December 04, 2021, 11:06:27 AM

So it needs to be a long rod engine with at least a 2:1 rod ratio. What is the stroke of that crank?

Jim

88v8 · December 05, 2021, 05:10:56 AM

Good discussion of why this might not be the best idea

It could be a good idea if you want to incorporate a massage seat.

Ivor

DiDueColpi · December 06, 2021, 02:42:35 PM

I have 2 cranks to choose from Jim. The short one (2L) is 2.726" stroke and the 2.2L is 3.000" stroke.
I own a 1979 308 GTS and a customer has a SCG 335 LS flat plane v8. Neither one has an objectionable vibration.
I agree that a long rod engine would be best so the 2L crank would be used if this proceeds.
This all started because I didn't want to spend the money on 4 custom cams. That rational has become silly.
Now its all about the sound.....and someone said it couldn't be done.

Cheers
Fred

minorv8 · December 07, 2021, 01:15:28 AM

What is the width of the rod journal i.e. how much you need to narrow the rods ?

turbodave · December 07, 2021, 07:37:59 AM

Interestingly TVR built a supercharged 2.0 V8 for the Italian market (to get around the engine capacity compliance of the time). Was de-stroked to 2 litres. Not much info about it, and they didn't sell many - not surprisingly.

BlownMGB-V8 · December 07, 2021, 11:53:52 AM

The 3" stroke would only require a 6" rod and that would certainly be possible. I have 7" rods in my 340 with it's 3.8" stroke so you have plenty of room and could even go longer. Custom pistons of course, move the pin closer to the ring package but a smaller, lighter wrist pin becomes an option, as do nascar take out rods. If you can score a set of Pankle rods those are SWEET! Must be something like 2 grand a set new but I found a set on ebay for right around $100 very lightly used. I highly recommend them. They are going in John's stroker 300. Bearing inserts might be a little hard to find though. Advantage of the lightest rod/piston package you can manage is that it may be possible to internally balance it. Which then gives you a wide selection of flywheels and dampers. Do you have the 2" rod journals or are they smaller?

Jim

DiDueColpi · December 07, 2021, 04:34:44 PM

The rod journal is 2.000 inches Jim.
I have enough room to safely widen the journals to 1.500 inches Jukka,
That means that a SBC rod could be used with a little bit of its sideburns shaved off.
The engine will end up at either 4.0L or 4.4L with the current bore.
The Pankle rods are a very interesting option Jim. They look really nice, very light and would certainly be strong enough. It looks like the most common are the 6.2 inch with what looks like a Honda bearing size. Not sure that I want to grind the crank down 0.150 to make them fit though.

minorv8 · December 08, 2021, 07:08:38 AM

IIRC my stroker TVR crank had something like 1.5xx wide rod journals. I narrowed a set (actually 2 sets) of SBC rods to fit that crank. I believe the final rod big end width was 19.40 mm (0.763 mm) and I had to machine some 0.090" from BOTH sides of the rod. And yes, finding suitable rod bearings was a bit hard.

BlownMGB-V8 · December 08, 2021, 10:54:33 AM

I had the same thought but in the end I just went ahead with it. If it's a forged crank I shouldn't think there would be a worry. You will have to run your numbers to see if it all fits with the 6.2" rods. I think it should. I think that's the length I'm using in the 300 strokers and so far no issues. The heads of the capscrews are small enough to clear the inside of the block with no problem. Using a slipper style piston that is quite light. Zero deck and a 30 or 35cc dish.

Those rod caps are pinned and have that wavy mating surface and they go together like the finely crafted pieces they are. No oil squirt hole and no internal pin oiling though. Not a problem with a roller cam or ohc setup.

Jim

DiDueColpi · December 08, 2021, 02:24:26 PM

The 4.0L rv8 rod is 6.110 inches with a 2.80 inch stroke. So I'll have room for the 6.20 rod on a 2.726 stroke.
The comp height on the rover pistons is very generous so the 3 inch crank and 6.2 rods should have enough room to work as well.

roverman · December 09, 2021, 06:53:49 PM

Fred, I like like you thinking. Aren't both Lotus cranks, cast ? Going to ad custom additional counter weights ? Cheap HP is using the exhaust cams on the intake. If/when I can get hold of a new GT 500, flat plane, as a raw forging..... The sbf raw forgings
CAN be machined to fit RV8. Onward, Art.

minorv8 · December 10, 2021, 12:45:16 AM

Here are a couple of photos of the TVR 2,0 litre V8.

My friend has a new flat plane crank for this engine, I had a photo of it but it´s too well archived. Could not find it...

tvr%20s-supercharged%20v8s%20moteur1.jpg

tvr%20s-supercharged%20v8s%20moteur1.jpg

tvr%20s-supercharged%20v8s%20moteur2.jpg

minorv8 · December 10, 2021, 01:05:55 AM

My latest engine has a 91,5 mm stroke i.e. around 3.60" number. The block is a later P38 type cross bolted block. The plan was to use Crower 6 inch rods with Icon stroker pistons. That did not work because the pistons were 60 thou above the deck at TDC and Icon did not recommend machining the pistons down. Top ring land was pretty shallow to begin with. OK, having seen Nascar pistons at Charlotte Nascar musem I realized that you can live with way shallower ring land, at least for couple hundred miles.

I found a set of 5.95 SBC H-beam rods that almost fixed that problem. I only had to machine 10 thou off the pistons, in reality it was closer to 15 thou. Anyway, these rods did not clear the block completely. Maybe because they were later SBC rods for 2.100" pin whereas the Crowers were for earlier 2.000" pin.

Fitting a set of 2.100" rods to a crank with a 2.000" rod journal is another story...

roverman · December 10, 2021, 01:59:16 PM

Gen III Hemi's make pretty good power and material above ring is quite thin, 3-4mm. ? This is why they anodized the crowns.
Art.

MGBV8 · December 14, 2021, 03:53:44 PM

Don't forget to use a larger ring end gap when the ring is closer to the piston top, Jukka.

phongshader · February 15, 2022, 01:06:03 PM

I know this is an old post...looking at forged Lotus 2-2.2 liter cranks, they are around $2k. You can get cast cranks for a bit cheaper but the oil galleys are going to be in the wrong part of the journal for the connecting rods. I like that no custom cams need to be made, which I'm sure is a big cost/time saving. Art is looking at getting raw ford cranks to machine, would it make sense to try and get raw Lotus 2-2.2l cranks to machine? They must exist as there are forged cranks on the market...or maybe get those manufacturers to finish a crank to your specs?

roverman · February 16, 2022, 01:43:14 PM

Fred and all, thin part-line on these 2.0 and 2.2L Lotus cranks ? I've looked at a few 2.L cranks, all cast ! Un-boosted V8,with short
stroke, will tend to be low on torque. If you find OEM, 180 deg. V8 cranks to look at, you can measure/duplicate their counterweight
design. Good Luck, Art.