lsj build questions
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Joined: 05-21-08
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From: central arkansas
lsj build questions
ok so i'm currently rebuilding my engine for the second time. First time the engine blew a hole in the stock no1 piston at 13,000 miles. After chevy cancelled my warranty only for having a cold air intake i decided to rebuild myself. being young and on a budget, this is how the build went the first time. obviously i needed pistons so i purchased the diamond pistons from intense-racing.com along with new bearings, a cometic gasket, 2.8" pulley, 60# injectors, full 3" exhaust from zzp and that was it. remember i was on a budget. after honing and getting off a little slag that the bad piston left behind my cylinder wall was just a hair past the tolerence for the ring gap but **** i couldnt afford another set of pistons so i went with it. after the build my engine always burnt oil but my compression was good until i put 10,000 or so miles and then the compression started dropping slowly. what had me confused is that even with my good compression when i dyno tuned i was only producing 217whp when i was expecting more and should have had more. here recently i started spitting oil out my exhaust and my compression had started getting worse so now being a little older, make more money, and learned a little about building on a budget, i decided to tear the engine down again and start over. now, here comes my questions. I'm ordering the ported head with 78# valve springs, stage 1 cams, cooling mods, and pistons all from zzp. obviously my cylinder walls are worn past stock bore. i can get new pistons cheaper than buying and having new sleeves installed. what should i do? 88mm pistons will not work without machining the stock sleeves. i've read that you do not want to do that, but i was told that i could use an LE5 block. will all my other components match up with the LE5 block? or could i get by with something on the block that i have now? Still with buying a LE5 block and new pistons, it comes out cheaper than sleeving my lsj block. I need help.
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Joined: 11-15-06
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From: Jackson, NJ
LE5 is gen II block, so it'll be a bit stronger.
LE5 bottom end (all stock) will bump up your compression.
if you install lower compression pistons and be ready to go.
the real question is: where do you want your powerband?
the short-stroke of the LSJ gives you a higher rod ratio. a higher rod ratio breathes better in the top end, so it'll pull longer. piston dwell at TDC is a bit longer, so you can run less ignition advance. higher rod ratio means less side-loading, so in theory, it will last longer as well.
the LE5 has a lower rod ratio. which means, it'll give a lot more torque and give it a lot earlier in the power band. however, top end breathing will always suffer, so power will taper off after the crossover point (5252rpm). headwork, cams, etc won't ever truly defeat this. an engine's ability to breathe is usually controlled by the rod ratio.
also, you have to use a clutch/flywheel combination for the LE5. the LSJ clutch/fly will not bolt up. (LE5 has 6 bolt fly, the LSJ/LNF has 8)
also, some LE5s don't have the external oil cooler like the LSJ does... but the LE5 does have the squirters inside.
please refer to post #8 in this thread:
https://www.cobaltss.net/forums/2-0l...builds-292623/
LE5 bottom end (all stock) will bump up your compression.
if you install lower compression pistons and be ready to go.
the real question is: where do you want your powerband?
the short-stroke of the LSJ gives you a higher rod ratio. a higher rod ratio breathes better in the top end, so it'll pull longer. piston dwell at TDC is a bit longer, so you can run less ignition advance. higher rod ratio means less side-loading, so in theory, it will last longer as well.
the LE5 has a lower rod ratio. which means, it'll give a lot more torque and give it a lot earlier in the power band. however, top end breathing will always suffer, so power will taper off after the crossover point (5252rpm). headwork, cams, etc won't ever truly defeat this. an engine's ability to breathe is usually controlled by the rod ratio.
also, you have to use a clutch/flywheel combination for the LE5. the LSJ clutch/fly will not bolt up. (LE5 has 6 bolt fly, the LSJ/LNF has 8)
also, some LE5s don't have the external oil cooler like the LSJ does... but the LE5 does have the squirters inside.
please refer to post #8 in this thread:
https://www.cobaltss.net/forums/2-0l...builds-292623/
Last edited by DaFlyinSkwirl; Feb 8, 2013 at 06:04 AM. Reason: added link
Thread Starter
New Member
Joined: 05-21-08
Posts: 73
Likes: 0
From: central arkansas
this is great info. i really like my longer pull, so could i not just get a set of lsj pistons anywhere that are just a little oversized to keep from re-sleeving or finding an le5 block? the le5 block swap just has me a little nervous and afraid ill bite off more than i can chew. im still new to this.
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Joined: 02-01-11
Posts: 2,799
Likes: 2
From: modesto
LE5 is gen II block, so it'll be a bit stronger.
LE5 bottom end (all stock) will bump up your compression.
if you install lower compression pistons and be ready to go.
let me add to this
u have to clock the reluctor wheel on the crank. And the le5 flywheel will not fit inside the f35 trans.
the real question is: where do you want your powerband?
the short-stroke of the LSJ gives you a higher rod ratio. a higher rod ratio breathes better in the top end, so it'll pull longer. piston dwell at TDC is a bit longer, so you can run less ignition advance. higher rod ratio means less side-loading, so in theory, it will last longer as well.
the LE5 has a lower rod ratio. which means, it'll give a lot more torque and give it a lot earlier in the power band. however, top end breathing will always suffer, so power will taper off after the crossover point (5252rpm). headwork, cams, etc won't ever truly defeat this. an engine's ability to breathe is usually controlled by the rod ratio.
also, you have to use a clutch/flywheel combination for the LE5. the LSJ clutch/fly will not bolt up. (LE5 has 6 bolt fly, the LSJ/LNF has 8)
also, some LE5s don't have the external oil cooler like the LSJ does... but the LE5 does have the squirters inside.
some le5s did have oil coolers.
please refer to post #8 in this thread:
https://www.cobaltss.net/forums/2-0l...builds-292623/
LE5 bottom end (all stock) will bump up your compression.
if you install lower compression pistons and be ready to go.
let me add to this
u have to clock the reluctor wheel on the crank. And the le5 flywheel will not fit inside the f35 trans.
the real question is: where do you want your powerband?
the short-stroke of the LSJ gives you a higher rod ratio. a higher rod ratio breathes better in the top end, so it'll pull longer. piston dwell at TDC is a bit longer, so you can run less ignition advance. higher rod ratio means less side-loading, so in theory, it will last longer as well.
the LE5 has a lower rod ratio. which means, it'll give a lot more torque and give it a lot earlier in the power band. however, top end breathing will always suffer, so power will taper off after the crossover point (5252rpm). headwork, cams, etc won't ever truly defeat this. an engine's ability to breathe is usually controlled by the rod ratio.
also, you have to use a clutch/flywheel combination for the LE5. the LSJ clutch/fly will not bolt up. (LE5 has 6 bolt fly, the LSJ/LNF has 8)
also, some LE5s don't have the external oil cooler like the LSJ does... but the LE5 does have the squirters inside.
some le5s did have oil coolers.
please refer to post #8 in this thread:
https://www.cobaltss.net/forums/2-0l...builds-292623/
your cylinder pressure was dropping from excessive wear and being out of round and from more then likely using the grit on the hone my question Is what do the pistons look like post up some pics
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