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Shortening barrels
http://international2cvfriends.com/forum/viewtopic.php?f=7&t=1703		 Page 1 of 1
Author:  Rhythm Thief [ May 18th, 2010, 1:26 am ]
Post subject:  Shortening barrels
How much can you shorten them by before getting into bother? I'd like to raise the compression of my 8.5:1 pistons to around 10:1. Presumably I'll need to have the carb rejetted as well, and advance the ignition. All advice welcomed!
Author:  ken [ May 18th, 2010, 2:19 am ]
Post subject:  Re: Shortening barrels
Why 10:1, as that would probably mean using octane booster as well as 97 or 98 grade fuel? :(
Also, raising the compression usually requires that the ignition advance is reduced, not advanced, because the rate of flame spread will be faster.

ken
p.s. I doubt that 10.0:1 is possible with 8.5:1 pistons + shortened barrels, unless you choose to ignore the sound of pistons hitting the heads... :roll:

Rhythm Thief wrote:
How much can you shorten them by before getting into bother? I'd like to raise the compression of my 8.5:1 pistons to around 10:1. Presumably I'll need to have the carb rejetted as well, and advance the ignition. All advice welcomed!
Author:  Rhythm Thief [ May 18th, 2010, 12:17 pm ]
Post subject:  Re: Shortening barrels
ken wrote:
Why 10:1, as that would probably mean using octane booster as well as 97 or 98 grade fuel? :(
Also, raising the compression usually requires that the ignition advance is reduced, not advanced, because the rate of flame spread will be faster.

ken
p.s. I doubt that 10.0:1 is possible with 8.5:1 pistons + shortened barrels, unless you choose to ignore the sound of pistons hitting the heads... :roll:


Fair enough. I don't know why I've got 10:1 in my head, I'm sure I read it somewhere. But let's say I had my barrels shortened by 0.5mm each. Is that feasible? Would it give a useful increase in power? Or is none of it worth the bother and should I just build myself a good spare engine with no mods?
Author:  Sean [ May 18th, 2010, 7:44 pm ]
Post subject:  Re: Shortening barrels
just build a good engine

decent barrels new rings, if you need to buy a replacement set get the 9:1s

dress the oil pump cover if its not too badly scored, get a new one if it is

get everything set up well sort the mating faces of the manifold make sure its got a good insulater under the carb,
do the valves and guide oil seals

take the primary jet out to 107

set the timing to 32* max advance and it will be tipitytopity

Sean
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