Stroke engine 3L - 4L. Is it possible w/o sandwich plates?
Discussion
Would it be possible to increase the capacity of a 3 litre 12 cylinder engine with a bore and stroke of 77mm x 53.5mm to 4 litres by increasing the stroke from 53.5mm to 71mm without using some form of spacer/sandwich plates and still using the same block? The compression ratio is 11.8/1. I read that somebody has done this but without some kind of spacer between the head and block wouldn't the piston hit the valves? If a sandwich plate is needed would it go in between the cylinder head and block or the sump and block? Actually would a sandwich plate work? How would you increase the length of the bore with a sandwich plate? Thanks very much in advance for any replies.
miurasv said:
Would it be possible to increase the capacity of a 3 litre 12 cylinder engine with a bore and stroke of 77mm x 53.5mm to 4 litres by increasing the stroke from 53.5mm to 71mm without using some form of spacer/sandwich plates and still using the same block? The compression ratio is 11.8/1. I read that somebody has done this but without some kind of spacer between the head and block wouldn't the piston hit the valves? If a sandwich plate is needed would it go in between the cylinder head and block or the sump and block? Actually would a sandwich plate work? How would you increase the length of the bore with a sandwich plate? Thanks very much in advance for any replies.
The stroke of an engine is down to the crankshaft and nothing else.By 'sandwich plate' I take it you mean some sort of spacer to lift the block and not convey an afternoon snack from the kitchen to the place of consumption? I've used one to lift wet liners from a short stroke engine up enough for use in a long stroke set of cases but it made zero difference to the swept volume of the engine.
This isn't going to work unless you do a lot of calculations and a lot of modifications. A sandwich plate would go between the block and head if the pistons were having to travel above the block. All of what you suggest sounds hugely expensive but it's doable.
A more viable option would be to lower the compression (lower compression pistons) and use a couple of turbo's. This route would definetely work.
A more viable option would be to lower the compression (lower compression pistons) and use a couple of turbo's. This route would definetely work.
miurasv said:
Would it be possible to increase the capacity of a 3 litre 12 cylinder engine with a bore and stroke of 77mm x 53.5mm to 4 litres by increasing the stroke from 53.5mm to 71mm without using some form of spacer/sandwich plates and still using the same block? The compression ratio is 11.8/1. I read that somebody has done this but without some kind of spacer between the head and block wouldn't the piston hit the valves? If a sandwich plate is needed would it go in between the cylinder head and block or the sump and block? Actually would a sandwich plate work? How would you increase the length of the bore with a sandwich plate? Thanks very much in advance for any replies.
Wayyy too vague. Some engines it may be possible..others it will not. Presumably you have the parts in front of you...start measuring.Thinking about this some more...
Can you fit a stroker crank and shorter con-rods? This would be the easy option with regards the bottom end.
I doubt there's enough metal on the big end journals to grind them smaller but further offset for more stroke, you'd have to remove about 9mm off the diameter which would seriously compromise the strength of any crank, let alone something as long as a V12.
Of course you now have cam profiles that are designed for a short stroke engine which is a whole new can of worms...
Can you fit a stroker crank and shorter con-rods? This would be the easy option with regards the bottom end.
I doubt there's enough metal on the big end journals to grind them smaller but further offset for more stroke, you'd have to remove about 9mm off the diameter which would seriously compromise the strength of any crank, let alone something as long as a V12.
Of course you now have cam profiles that are designed for a short stroke engine which is a whole new can of worms...
you need some numbers.
what the deck height of block? existing rod length? etc so you can work out the compression height of the pistons? what the Counterweight radius etc
then you can work out if you can get a custom piston to fit, shorter rod or whatever. then you need to see if there is anything inside the block the crank or rod will hit for example the inside of block etc
ive seen people increase capacity by that amount as a percentage with an overbore and longer stroke without a deck plate. you need some specifics though.
that stroke change 53.5 to 71mm results in a longer throw of 8.5mm and some OEM pistons can be reduced by that amount without compromising things much but others cant. so then you might need to look at the rod length, the longer stroke and shorter rod puts the piston close to crank at BDC. the rods alos get close to the bottom of bore so you need a slim shoulder profile etc
what the deck height of block? existing rod length? etc so you can work out the compression height of the pistons? what the Counterweight radius etc
then you can work out if you can get a custom piston to fit, shorter rod or whatever. then you need to see if there is anything inside the block the crank or rod will hit for example the inside of block etc
ive seen people increase capacity by that amount as a percentage with an overbore and longer stroke without a deck plate. you need some specifics though.
that stroke change 53.5 to 71mm results in a longer throw of 8.5mm and some OEM pistons can be reduced by that amount without compromising things much but others cant. so then you might need to look at the rod length, the longer stroke and shorter rod puts the piston close to crank at BDC. the rods alos get close to the bottom of bore so you need a slim shoulder profile etc
Edited by Inline__engine on Wednesday 3rd August 23:52
Edited by Inline__engine on Wednesday 3rd August 23:56
There are a number of issues to deal with when increasing the stroke, simply using a sandwich plate or shortenkng the rod rarely solves them all, protrusion of the piston skirt from the bottom of the bore can cause some issues, the least of which is increased NVH, collision between the piston skirt and the crank counterweight could also be a major problem, contact between the rod flank and the bore wall could also occur due to increased rod angle. You may well have a problem controlling compression.
Generally increasing the bore size is a more effective way of gaining capacity.
Dzve
Generally increasing the bore size is a more effective way of gaining capacity.
Dzve
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