Rover 2200TC compression increase

Cam2002

Cam2002

New Member
After considerable searching for a piston to suit I have had no success so far so the other idea I have had was to have the crank offset ground you can go to +.040" big end bearings so I was thinking I could get it offset ground plus if needed for the sake of the crankshaft strength make up the rest of the .060" needed to increase comp say .020" off the block that would create about .040" slack in the upper chain which the tensioner should be able to take up okay.

Anyone done any offset grinding of cranks b4 and can tell me their experience it's not a racing car that's being built just street car
 
The actual offset grinding isn’t a big deal, same setup as an undersized bearing grind. You’ll have a slightly longer stroke (increasing capacity as well as compression ratio). Reversal loads (the load of the reciprocating assemble changing direction at tdc and bdc) will be very slightly higher. But marginal I think.

One thought to avoid you decking the block and slackening the chain: with the higher point of TDC you could take off some of the piston crowns, that will increase CR pretty heavily while also lightening the pistons. Might want to check the crown thickness first though, as that’s a critical area of piston strength.

Sorry for the long reply, but I think it’ll work.
 
sdibbers said:
The actual offset grinding isn’t a big deal, same setup as an undersized bearing grind. You’ll have a slightly longer stroke (increasing capacity as well as compression ratio). Reversal loads (the load of the reciprocating assemble changing direction at tdc and bdc) will be very slightly higher. But marginal I think.

One thought to avoid you decking the block and slackening the chain: with the higher point of TDC you could take off some of the piston crowns, that will increase CR pretty heavily while also lightening the pistons. Might want to check the crown thickness first though, as that’s a critical area of piston strength.

Sorry for the long reply, but I think it’ll work.
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My thinking with the offset grinding is the critical factor in weakness isn't so much grinding undersize as the amount of journal overlap between the big end and mains as I belive that is the biggest stress point. I was thinking but I've had a massive brain fart for like 3 days now is if they were offset ground .030" that would give me .060" of extra height which is roughly what I need for the compression ratio increase. Plus the bonus I was thinking with increasing the stroke was it should in theory increase lowdown torque over not just a standard 2.2 but a 2
2 with custom made pistons. Wether its by much or not I have no idea. I had a look last night and the only thing with it is the con rods bolts get quite close to the bore if the stroke was increased I'd have to be careful of that I don't think it would be an issue but I'll have to get my engineers op on it.

George's idea was if I found a piston that was near it could be turned down a little bit however I haven't even been successful in that lol
 
+ 0.030” will give you an extra 0.060” stroke but only another 0.030” at tdc (unless, as you say, you go for custom pistons and or conrods).

The crank is pretty sturdy on the four pots, there’s some talk of the block flexing, I’m not sure I’ve seen that on my bored out 2000 block.
 
sdibbers said:
+ 0.030” will give you an extra 0.060” stroke but only another 0.030” at tdc (unless, as you say, you go for custom pistons and or conrods).

The crank is pretty sturdy on the four pots, there’s some talk of the block flexing, I’m not sure I’ve seen that on my bored out 2000 block.
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I can go to .040" with the crank grind as that's the biggest shells I can get undersize. So I'd still have to make up .020" to make the full .060" for the full ratio maybe I would need to have summit skimmed off the block after all which again leaves the timing thing. See I think custom rods and pistons would be way way out of my budget
 
On the custom piston front, JP make new 2200 pistons, I would imagine it’s not too big an ask to have a set of those made to spec? IMG_2048.jpeg
 
sdibbers said:
+ 0.030” will give you an extra 0.060” stroke but only another 0.030” at tdc (unless, as you say, you go for custom pistons and or conrods).

The crank is pretty sturdy on the four pots, there’s some talk of the block flexing, I’m not sure I’ve seen that on my bored out 2000 block.
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incorrect, if you offset grind you only gain the amount your reduce the crank pin by, its all to do with the centre of the crank pin, trust me ive had shed loads of cranks offset ground over the years
 
Penguin said:
incorrect, if you offset grind you only gain the amount your reduce the crank pin by, its all to do with the centre of the crank pin, trust me ive had shed loads of cranks offset ground over the years
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I trust you! II know of your work.
 
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