LT1 Rotating Assembly Questions
LT1 Rotating Assembly Questions Hey everyone. Going to a swap meet this weekend and was looking for a sweet deal on a rotating assembly. I know I need a 1pc. rear main but still had questions. My plan is a N/A 383 with AI/LE heads. Cam is undetermined, however I don't have to pass emissions:
1. Are there any setups I should avoid?
2. Will most if not all 1 pc. rear main setups work for SBC in an LT1?
3. Not looking for ridiculous power so I am open as to cast versus forged on the crank. Obviously would like forged, but if I am only making 400 - 450HP after the setup, I think, from my readings on here, a cast crank would be OK, yes?
4.Regardless of cast/forged crank, a good set of forged rods and pistons might be best. Should I be concerned with H-beam versus I-beam rods?
Please ask any questions so I can get the best answer possible. Thanks again, everyone!
1. Are there any setups I should avoid?
2. Will most if not all 1 pc. rear main setups work for SBC in an LT1?
3. Not looking for ridiculous power so I am open as to cast versus forged on the crank. Obviously would like forged, but if I am only making 400 - 450HP after the setup, I think, from my readings on here, a cast crank would be OK, yes?
4.Regardless of cast/forged crank, a good set of forged rods and pistons might be best. Should I be concerned with H-beam versus I-beam rods?
Please ask any questions so I can get the best answer possible. Thanks again, everyone!
Hey everyone. Going to a swap meet this weekend and was looking for a sweet deal on a rotating assembly. I know I need a 1pc. rear main but still had questions. My plan is a N/A 383 with AI/LE heads. Cam is undetermined, however I don't have to pass emissions:
1. Are there any setups I should avoid?
2. Will most if not all 1 pc. rear main setups work for SBC in an LT1?
3. Not looking for ridiculous power so I am open as to cast versus forged on the crank. Obviously would like forged, but if I am only making 400 - 450HP after the setup, I think, from my readings on here, a cast crank would be OK, yes?
4.Regardless of cast/forged crank, a good set of forged rods and pistons might be best. Should I be concerned with H-beam versus I-beam rods?
Please ask any questions so I can get the best answer possible. Thanks again, everyone!
1. Are there any setups I should avoid?
2. Will most if not all 1 pc. rear main setups work for SBC in an LT1?
3. Not looking for ridiculous power so I am open as to cast versus forged on the crank. Obviously would like forged, but if I am only making 400 - 450HP after the setup, I think, from my readings on here, a cast crank would be OK, yes?
4.Regardless of cast/forged crank, a good set of forged rods and pistons might be best. Should I be concerned with H-beam versus I-beam rods?
Please ask any questions so I can get the best answer possible. Thanks again, everyone!
2.) Any 1 pc. rear main SBC crankshaft/piston/CR will work.
3.) IMO, if you're using anything other than the stock crankshaft, go with a forged piece. The rotating assembly should be able to handle 150% as much as you plan to throw at it for reliability's sake.
4.) H-beams are always nice, but not a necessity at your desired power level. I'm using Scat forged I-beams. Definitely go with a forged piston mated to a 6" rod.
Trending Topics
I can recommend Ohio for forged crank and rods, Keith Black Forged aluminum pistons. I'd stick with 5.7 rods because of how far the wrist pin moves up and starts encroaching on the oil ring land. I set up my 383 all forged bottom end with balancing, billet splayed caps, rings and clevite 77 bearings for $1562.00.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo I guess I am feeling a little overwhelmed with information in trying to research this setup. I guess I would love to have a NA 383 with a set of TFS heads from AI and a cam with a rough idle and keep the compression to where I can still run pump gas (93 octane). Whatever the car makes in HP it makes, however, it needs to be more streetable than track only. I do not need to pass emissions where I am.
I would like to keep the build under $7K. I guess my questions now would be:
1. Can I buy a rotating assembly without knowing the full specs of the heads I am using? In other words, can I get the heads milled appropriately to achieve the compression ratio I want based on the piston specs?
2. I saw someone posted on here they had a 383 with 5.7" rods. I thought 383's were a 400 crank with 6" rods?
3. Is 12:1 compression reasonable on pump gas given a good dynotune? If I wanted more umph afterwards, could I give it a small shot of N2O or a small supercharger < 6lbs? (I know the SC would blow the 7K buildout of the water)
Sorry I seem a little lost in all this now.
I would like to keep the build under $7K. I guess my questions now would be:
1. Can I buy a rotating assembly without knowing the full specs of the heads I am using? In other words, can I get the heads milled appropriately to achieve the compression ratio I want based on the piston specs?
2. I saw someone posted on here they had a 383 with 5.7" rods. I thought 383's were a 400 crank with 6" rods?
3. Is 12:1 compression reasonable on pump gas given a good dynotune? If I wanted more umph afterwards, could I give it a small shot of N2O or a small supercharger < 6lbs? (I know the SC would blow the 7K buildout of the water)
Sorry I seem a little lost in all this now.
Last edited by afterburner82; Sep 11, 2009 at 08:19 PM. Reason: One additonal comment.
I guess I am feeling a little overwhelmed with information in trying to research this setup. I guess I would love to have a NA 383 with a set of TFS heads from AI and a cam with a rough idle and keep the compression to where I can still run pump gas (93 octane). Whatever the car makes in HP it makes, however, it needs to be more streetable than track only. I do not need to pass emissions where I am.
I would like to keep the build under $7K. I guess my questions now would be:
1. Can I buy a rotating assembly without knowing the full specs of the heads I am using? In other words, can I get the heads milled appropriately to achieve the compression ratio I want based on the piston specs?
2. I saw someone posted on here they had a 383 with 5.7" rods. I thought 383's were a 400 crank with 6" rods?
3. Is 12:1 compression reasonable on pump gas given a good dynotune? If I wanted more umph afterwards, could I give it a small shot of N2O or a small supercharger < 6lbs? (I know the SC would blow the 7K buildout of the water)
Sorry I seem a little lost in all this now.
I would like to keep the build under $7K. I guess my questions now would be:
1. Can I buy a rotating assembly without knowing the full specs of the heads I am using? In other words, can I get the heads milled appropriately to achieve the compression ratio I want based on the piston specs?
2. I saw someone posted on here they had a 383 with 5.7" rods. I thought 383's were a 400 crank with 6" rods?
3. Is 12:1 compression reasonable on pump gas given a good dynotune? If I wanted more umph afterwards, could I give it a small shot of N2O or a small supercharger < 6lbs? (I know the SC would blow the 7K buildout of the water)
Sorry I seem a little lost in all this now.
Forged Ohio crankshaft
Forged Scat I-beam 6" rods
Forged SRP -5cc pistons
Decked block, zero deck height
4-bolt main (2-bolt would be fine as well)
AI 200cc heads/cam package (52cc chambers)
.026" head gaskets
This results in a SCR of 12.4:1 (DCR of 9.1:1). I run a mail-order tune from PCMforless (no dyno-tuning yet). Haven't been to the dyno just yet, but it runs what it does with no KR.
If you have all forged components, spray away! Remember, nitrous loves compression. I plan on a 200+ shot in the near future.
My engine ended up being around $8500, somewhere around there.
You sound like you're looking for a setup very similar to mine.
Forged Ohio crankshaft
Forged Scat I-beam 6" rods
Forged SRP -5cc pistons
Decked block, zero deck height
4-bolt main (2-bolt would be fine as well)
AI 200cc heads/cam package (52cc chambers)
.026" head gaskets
This results in a SCR of 12.4:1 (DCR of 9.1:1). I run a mail-order tune from PCMforless (no dyno-tuning yet). Haven't been to the dyno just yet, but it runs what it does with no KR.
If you have all forged components, spray away! Remember, nitrous loves compression. I plan on a 200+ shot in the near future.
My engine ended up being around $8500, somewhere around there.
Forged Ohio crankshaft
Forged Scat I-beam 6" rods
Forged SRP -5cc pistons
Decked block, zero deck height
4-bolt main (2-bolt would be fine as well)
AI 200cc heads/cam package (52cc chambers)
.026" head gaskets
This results in a SCR of 12.4:1 (DCR of 9.1:1). I run a mail-order tune from PCMforless (no dyno-tuning yet). Haven't been to the dyno just yet, but it runs what it does with no KR.
If you have all forged components, spray away! Remember, nitrous loves compression. I plan on a 200+ shot in the near future.
My engine ended up being around $8500, somewhere around there.
Did you have to do any clearancing for valves?
FormerVendor
Joined: Apr 2006
Posts: 154
Likes: 0
From: Bartlett
I would run a 6" or 6.125" rod. Scat Procomp I beam with the 7/16 arp hardware would work, but a good h beam isn't that much more.
Last edited by Corey @ Clayton Racing; Sep 12, 2009 at 12:47 PM.
The reason some choose 5.7in rods over 6 is because they want a little more stability. I was going to go with a 6 but I did a little bit of homework and decided I didn't want to chance comprimising the rod with flexing. Too short is just as dangerous as too long though. When you make the rod longer you give a more desirable angle for the rod to go up the bore and not as much thrust on the side of the piston. However that means you have to move the wristpin closer to the oil ring and you start to encroach on the cam. 5.56 rods like in the 400 didn't favor high revs at all and are a grenade waiting to happen. I chose 5.7 because it was the in between for 5.56 and 6.0 and I think GM got it right with that length, it also still give's me plenty of room to run my forged h-beams and have plenty clearance for any cam I choose. As for building the motor and then thinking of the heads later, you should have it planned out first and piece everything together as time/money permits. I've watched plenty of people throw the best components at stuff blindly without thinking of combination and end up with a really poor running motor. I shot for a 11:1 cr with a 62cc chamber (TFS 195 GenX) and with the 5.7 rod 3.75 stroke and +6.40cc piston (Flat top) I got an 11.07:1 CR. I planned for a lower compression ratio than most people are running because I'm planning on this car being a driver without 104+ octane, and I'm also going to shoot it with 2 stages of 150+. But 90% of LT1 heads save for the TFS' wont work with my setup because of the smaller chamber sizes that are typically around 54-52cc and would blow my CR through the roof, I know this but I planned it specifically for the TFS GenX Heads only.
The reason some choose 5.7in rods over 6 is because they want a little more stability. I was going to go with a 6 but I did a little bit of homework and decided I didn't want to chance comprimising the rod with flexing. Too short is just as dangerous as too long though. When you make the rod longer you give a more desirable angle for the rod to go up the bore and not as much thrust on the side of the piston. However that means you have to move the wristpin closer to the oil ring and you start to encroach on the cam. 5.56 rods like in the 400 didn't favor high revs at all and are a grenade waiting to happen. I chose 5.7 because it was the in between for 5.56 and 6.0 and I think GM got it right with that length, it also still give's me plenty of room to run my forged h-beams and have plenty clearance for any cam I choose. As for building the motor and then thinking of the heads later, you should have it planned out first and piece everything together as time/money permits. I've watched plenty of people throw the best components at stuff blindly without thinking of combination and end up with a really poor running motor. I shot for a 11:1 cr with a 62cc chamber (TFS 195 GenX) and with the 5.7 rod 3.75 stroke and +6.40cc piston (Flat top) I got an 11.07:1 CR. I planned for a lower compression ratio than most people are running because I'm planning on this car being a driver without 104+ octane, and I'm also going to shoot it with 2 stages of 150+. But 90% of LT1 heads save for the TFS' wont work with my setup because of the smaller chamber sizes that are typically around 54-52cc and would blow my CR through the roof, I know this but I planned it specifically for the TFS GenX Heads only.
Static compression is just that, a static figure, and has no bearing on engine performance (dynamic compression is the more important figure). On a good tune, running 9.1:1 DCR on 93 octane is easily doable.
6" rods offer too many advantages over their 5.7" counterparts when set up and clearanced correctly, IMO.
You sound like you're looking for a setup very similar to mine.
Forged Ohio crankshaft
Forged Scat I-beam 6" rods
Forged SRP -5cc pistons
Decked block, zero deck height
4-bolt main (2-bolt would be fine as well)
AI 200cc heads/cam package (52cc chambers)
.026" head gaskets
This results in a SCR of 12.4:1 (DCR of 9.1:1). I run a mail-order tune from PCMforless (no dyno-tuning yet). Haven't been to the dyno just yet, but it runs what it does with no KR.
If you have all forged components, spray away! Remember, nitrous loves compression. I plan on a 200+ shot in the near future.
My engine ended up being around $8500, somewhere around there.
Forged Ohio crankshaft
Forged Scat I-beam 6" rods
Forged SRP -5cc pistons
Decked block, zero deck height
4-bolt main (2-bolt would be fine as well)
AI 200cc heads/cam package (52cc chambers)
.026" head gaskets
This results in a SCR of 12.4:1 (DCR of 9.1:1). I run a mail-order tune from PCMforless (no dyno-tuning yet). Haven't been to the dyno just yet, but it runs what it does with no KR.
If you have all forged components, spray away! Remember, nitrous loves compression. I plan on a 200+ shot in the near future.
My engine ended up being around $8500, somewhere around there.
here's what I'm running
http://www.eaglerod.com/index.php?op...d=34&Itemid=41
I make a little under 400rwhp through an auto with no problems. not exactly a RA I'd trust to high rpm or nitrous though especially with the eagle balance in it. my setup stops making power around 6k rpm so this isn't an issue for me.
I kinda wish I would've went forged with a good balance so I could bottle it and rev it higher without worry, but this was my first motor build that I'd ever put together and I wasn't about to put a $2k+ rotating assembly in a motor I wasn't even sure would last. so oh well live and learn but I had no idea I'd do everything right
http://www.eaglerod.com/index.php?op...d=34&Itemid=41
I make a little under 400rwhp through an auto with no problems. not exactly a RA I'd trust to high rpm or nitrous though especially with the eagle balance in it. my setup stops making power around 6k rpm so this isn't an issue for me.
I kinda wish I would've went forged with a good balance so I could bottle it and rev it higher without worry, but this was my first motor build that I'd ever put together and I wasn't about to put a $2k+ rotating assembly in a motor I wasn't even sure would last. so oh well live and learn but I had no idea I'd do everything right
With the cam I'm running and my rod length my dynamic was 10.173 according to keith black (United Engine and Machine) calculator (I did the calculation with what I remember off the top of my head, when I did it the last time with all my specs sitting in front of me I got 9.9:1DCR). And I'm not running gapless rings. Don't get me wrong, the 6in is a great rod length. I just prefer the 5.7 rod being that the chance for rod flex is smaller (not that I'm too worried about it), clearance for larger cams, and I don't have to push the wrist pin higher. Once again it's a preference.
Last edited by 93Z2871805; Sep 16, 2009 at 07:36 PM.
