.5 over bore on 2.25?

[bmohan55]

Is this possible...or what I mean to ask "is this wise?" I went with a .03 over bore and read that .04 is the max one should do? I assumed that was due to cooling issues...educate me please.


http://cgi.ebay.com/ebaymotors/1970-LAND-ROVER-SERIES-2A-SWB-TRUCK-CAB-FULLY-RESTORED-CONCOURSE-CONDITION-/330658043773?pt=US_Cars_Trucks&hash=item4cfcc1577d

[rwollschlager]

this may be a moot point but what units of measurement are you using? he's using millimeters and I'm assuming you're using inches?

[SafeAirOne]

this may be a moot point but what units of measurement are you using? he's using millimeters and I'm assuming you're using inches?

...which is +.020" so it's just fine.

I believe that a half an inch (.5") is slightly more than the factory recommends a cylinder be overbored. ;)

[bmohan55]

thanks, although I'm still far from "educated"!

[westcoastkevin]

Sometimes, it comes down to what size pistons you can get. Sometimes, some piston sizes are way more expensive than others too.

[mongoswede]

a friend had a custom set of pistons made up for a project...they cost $600 for the pistons and I think they came with some related parts too.

[gambrinus]

You can usually get standard, .020 , .030 and .040 pistons...

[mearstrae]

I think the issue is, "Why the .040 inch max overbore." Usually the engines water jacket sets the max overbore as well as clearance issues within the engine block and on the cylinder head. Also, as mentioned if you did decide to go over to say, .050 inches, pistons would be very costly and run a risk of ruining the engine. You may read of racing engines with wild overbores, but they are specially constucted to allow, in some cases,.100 overbores.

'95 R.R. Classic Lwb
'76 Series III hybrid 109
'70 Rover 3500S

[Regan]

I just had my 2.25 rebuilt and had to go 0.60 over. parts are rare and had to come from England. I was tol this is the max and certainly it can be done, as I am driving it, no problems. Part are hard to get, but still avaiable or was 6 months ago. We had to go this large when we found out that the engine was rebuilt once before and bored out to 0.30 or 0.40. I can put you in touch with person should you need this larger size.

[mongoswede]

I just had my 2.25 rebuilt and had to go 0.60 over. parts are rare and had to come from England. I was tol this is the max and certainly it can be done, as I am driving it, no problems. Part are hard to get, but still avaiable or was 6 months ago. We had to go this large when we found out that the engine was rebuilt once before and bored out to 0.30 or 0.40. I can put you in touch with person should you need this larger size.


You are close but your actual numbers are .060", .030", and .040". 0.60" over is more than half an inch diameter increase on every cylinder. If you went this much you would cut right through the cylinder walls into the water jackets and you would likely be into the adjacent combustion chamber.

I suspect that your engine rebuilder did not go an additional .060 (sixty thousandths) over the first .030 (thirty thousandths) but was a total of 060" over stock.

[bmohan55]

I just had my 2.25 rebuilt and had to go 0.60 over. parts are rare and had to come from England. I was tol this is the max and certainly it can be done, as I am driving it, no problems. Part are hard to get, but still avaiable or was 6 months ago. We had to go this large when we found out that the engine was rebuilt once before and bored out to 0.30 or 0.40. I can put you in touch with person should you need this larger size.

I was told that if you need to go further than .04 it's better to re-sleeve the cylinders. Not wishing any bad karma on you but it seemed to make sense to me. MY .03's are in already and I'm in the final stages of buttoning it up.

[mongoswede]

major overboring reduces the thickness of the cylinder walls which in turn changes the way that heat is transfered around the engine. There is also less wall there to deal with combustion. If the walls are too thin you could actually crack the block or experience increased blowbye due to changes in bore expansion etc. Hence the resleave suggestion.

[Regan]

In regards to my orginal post and 0.60 over, what I meant to say is that it was boared to .60 total over stock. This is the max you can go, I am told from over the pond and geting parts was hard. Right now, I have 600 miles on the rebuild and the 2.25L, with HO head and other goodies, it running as good as it gets. It was running a little hot, but I did add an A/C and evaporator/condensor, restricting air into radiator. We fixed than with a larger aux. fan and everything thing is going well now. Rear axle failed and front wheel drive does not work, but that's another story.

[mearstrae]

I think you keep meaning to state .060" total over bore. .60 is approaching 5/8 of an inch, way too much for any overbore in anything. When someone says, "It's sixty over." it means sixty thousandths.

'95 R.R. Classic LWB
'76 SeriesIII Hybrid 109
'70 Rover 3500S

[dabawei]

Hi,
As I am new in this busniess, this activity end up in bigger pistons size?

Q. Can 2.5L engine piston fit in 2.25L engine After modification?

[mearstrae]

I beleive that the 2.25 and the 2.5 have the same pistons, the change in cubic inches is achieved by the stroke. 2.25 [bore:3.562" and stroke:3.5"], 2.5 [bore:3.562" and stroke:3.82"]. If I remember right there was a change in the main bearing arrangement between the two, so some change in the rods would have been necessary. Possibly someone else has better spec's on this.

'95 R.R. Classic LWB
'76 Series III Hybrid 109
'70 Rover 3500S

[dabawei]

I beleive that the 2.25 and the 2.5 have the same pistons, the change in cubic inches is achieved by the stroke. 2.25 [bore:3.562" and stroke:3.5"], 2.5 [bore:3.562" and stroke:3.82"]. If I remember right there was a change in the main bearing arrangement between the two, so some change in the rods would have been necessary. Possibly someone else has better spec's on this.

'95 R.R. Classic LWB
'76 Series III Hybrid 109
'70 Rover 3500S

Sounds great :) if I am planning to rebuilt my 2.25L engine on S2a then I can consider following (straight forward) changes:
1) change piston rod with 2.5L
2) mill cylinder head to have 8:1 compression
3) change camshaft of 2.5L engines

Any one can advise?

[Terrys]

Sounds great :) if I am planning to rebuilt my 2.25L engine on S2a then I can consider following (straight forward) changes:
1) change piston rod with 2.5L
2) mill cylinder head to have 8:1 compression
3) change camshaft of 2.5L engines

Any one can advise?

Re:#1, The increase in stroke comes from the crank throw, not longer connecting rods. I'm not certain how the two rods differ in dimensions though.

[mearstrae]

eeek... It isn't that simple. Yes, the rods are longer to accomodate the change in the longer crank shaft throw. So, just using the longer rods would probably put the pistons through the head.

'95 R.R. Classic LWB
'76 Series III Hybrid 109
'70 Rover 3500S

[superstator]

eeek... It isn't that simple. Yes, the rods are longer to accomodate the change in the longer crank shaft throw. So, just using the longer rods would probably put the pistons through the head.


Wouldn't a longer crankshaft throw require a shorter rod? I was under the impression that was how most "stroker" kits worked - bigger crank, smaller rods, and sometimes modified pistons so the skirts don't clip the crank at the bottom of the stroke.

[mearstrae]

Shorter rods would bring stock pistons lower in the bore and may cause conflict with the crank counter throws at bottom dead center. Using shorter rods would work if the piston pin position was changed for the longer crank throw. A longer rod with stock pistons would conflict with the deck [head] at top dead center. It's just that the overall length [piston and rod combination] would have to be such that it met the demands of the cylinder and crank dimensions. You'll see some really short pistons in stoker racing engines for this reason.

'95 R.R. Classic LWB
'76 Series III Hybrid 109
'70 Rover 3500S

[mearstrae]

I think that after some research this all becomes moot points. The 2.25 is a three main bearing engine and the 2.5 has five mains. Some 2.25's had five mains as part of the Harrier Project. So, unless you can change the 2.25 to the 2.5 crank, to gain the cubic inches, this may all be for nothing. It's hard to find exact spec's for L.R.'s internal bits to draw any educated conclusion as to what refits to what. [I'm glad to stick with the V-8s, everything is so much simpler, as there is all the information and parts that anyone could want...]

'95 R.R. Classic LWB
'76 Series III Hybrid 109
'70 Rover 3500S

[mongoswede]

run the stock lump or stick to simple head swaps or cam swaps to keep things on the cheap side. If you start reengineering the stock engine you will spend a ton of money for maybe 30 hp?.....and it will still be an underpowered inefficient lump compared to todays engines. If you want to get crazy you are better off putting the energy into an engine swap of one sort or another.


keeping in mind that the stock rover is built for that engine and a more powerful engine will strain the gearbox and axles, and the things on the wheels that generate heat when you push the brake pedal. So...be forewarned it is a dangerous rabbit hole to go down.