Bottom end strengthening on 2-bolt block
12-14-2003, 10:33 AM
#1
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Join Date: Nov 2003
Posts: 1,211
Bottom end strengthening on 2-bolt block
I have a 2-bolt LT-1 in my car.
When I rebuild it I plan to re-use the block because it's well seasoned.
My plan is to zero-deck it, line bore it and hone it with torque plates.
I don't plan to convert to 4-bolt because I don't want to remove meat from the webs to drill the holes.
Instead, I want to stud the bottom end, and I plan to lighten the entire reciprocating assy as much as feasible.
My question is this; I have concernes about using main caps that are of a substantially different metallic composition than the block because I am concerned about metals expanding at different rates when the engine heats up.
I suppose this would mean that using billet steel caps would worry me because of it's expansion characteristics.
I'm wondering if Nodular iron main caps would be close enough to the metallic composition of the block to alleviate that concern.
I also wonder if there are other strengthening techniques that I am not aware of. (I don't want to fill the block, because this is a street car)
The plan is to build a 383, because it's more cost effective than a 396. I intend to use 6" rods and forged pistons.
The rev limit on this motor would likely be about 6500rpm and I MAY decide to use a power adder.
If I use a blower or turbo it would be running under 15lbs of boost, probably under 10, and if I used nitrous, I would use a progressive controller and most likely limit myself to a 200 shot, maybe 250, but that's unlikely.
I'd like some input on my thoughts so that I can address all my concerns BEFORE I begin spending money.
Thank you.
When I rebuild it I plan to re-use the block because it's well seasoned.
My plan is to zero-deck it, line bore it and hone it with torque plates.
I don't plan to convert to 4-bolt because I don't want to remove meat from the webs to drill the holes.
Instead, I want to stud the bottom end, and I plan to lighten the entire reciprocating assy as much as feasible.
My question is this; I have concernes about using main caps that are of a substantially different metallic composition than the block because I am concerned about metals expanding at different rates when the engine heats up.
I suppose this would mean that using billet steel caps would worry me because of it's expansion characteristics.
I'm wondering if Nodular iron main caps would be close enough to the metallic composition of the block to alleviate that concern.
I also wonder if there are other strengthening techniques that I am not aware of. (I don't want to fill the block, because this is a street car)
The plan is to build a 383, because it's more cost effective than a 396. I intend to use 6" rods and forged pistons.
The rev limit on this motor would likely be about 6500rpm and I MAY decide to use a power adder.
If I use a blower or turbo it would be running under 15lbs of boost, probably under 10, and if I used nitrous, I would use a progressive controller and most likely limit myself to a 200 shot, maybe 250, but that's unlikely.
I'd like some input on my thoughts so that I can address all my concerns BEFORE I begin spending money.
Thank you.
12-14-2003, 07:23 PM
#2
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Join Date: Oct 1998
Location: Southern CA
Posts: 705
I never thought that the different expansion rates were an issue when installing 4 bolt steel caps. I know milodon makes ductile iron ones. Either way, it's not going to be cheap. The block has to be machined and align honed for those caps to work. 
12-15-2003, 02:11 AM
#3
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Join Date: Feb 2001
Location: Bay Area, CA, USA
Posts: 1,967
Many have done 4 bolt conversions on stock 2 bolt LT1 blocks with much success using different metals than the block. You should have nothing to fear, I would also splay the 2 outer caps to have even more strength in the setup.
12-15-2003, 07:25 AM
#4
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Join Date: Nov 2003
Posts: 1,211
Maybe I wasn't very clear...
I do NOT want to install 4-bolt caps.
I'm planning to run 2 bolt caps with studs.
What I'm wondering is whether or not Nodular Iron caps have basically the same expansion characteristics as the block and whether there are additional strengthening things I can do, other than filling the block or converting to 4-bolts.
For instance, does someone make a girdle and if so, does anyone have experience with them?
I do NOT want to install 4-bolt caps.
I'm planning to run 2 bolt caps with studs.
What I'm wondering is whether or not Nodular Iron caps have basically the same expansion characteristics as the block and whether there are additional strengthening things I can do, other than filling the block or converting to 4-bolts.
For instance, does someone make a girdle and if so, does anyone have experience with them?
12-15-2003, 08:44 AM
#5
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Join Date: Nov 2003
Posts: 40
Originally posted by LameRandomName
Maybe I wasn't very clear...
I do NOT want to install 4-bolt caps.
Maybe I wasn't very clear...
I do NOT want to install 4-bolt caps.
12-15-2003, 09:36 AM
#6
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Join Date: Apr 2001
Location: Tampa, FL USA
Posts: 284
Making a 2 bolt block a splayed 4 bolt cost me 400 bucks caps included (billet). the webs on a 2 bolt are stronger than the webs of a 4 bolt. If your gonna have a power adder you better have a 4 bolt bottom end. I have not heard of a girdle for the LT1 as of yet
12-15-2003, 11:23 AM
#7
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Join Date: Oct 2002
Location: Upstate NY
Posts: 2,931
Re: Bottom end strengthening on 2-bolt block
Originally posted by LameRandomName
I have a 2-bolt LT-1 in my car.
When I rebuild it I plan to re-use the block because it's well seasoned.
My plan is to zero-deck it, line bore it and hone it with torque plates.
I don't plan to convert to 4-bolt because I don't want to remove meat from the webs to drill the holes.
Instead, I want to stud the bottom end, and I plan to lighten the entire reciprocating assy as much as feasible.
My question is this; I have concernes about using main caps that are of a substantially different metallic composition than the block because I am concerned about metals expanding at different rates when the engine heats up.
I suppose this would mean that using billet steel caps would worry me because of it's expansion characteristics.
I'm wondering if Nodular iron main caps would be close enough to the metallic composition of the block to alleviate that concern.
I also wonder if there are other strengthening techniques that I am not aware of. (I don't want to fill the block, because this is a street car)
Heating the main bearing journals from 70 degree room temp to 270 degrees (F) would enlarge them about .003. If you used steel caps, it would be about 10% less, or .0003 difference. That's if the caps get that hot. If you use a power adder, .0003 is going to be the least distortion problem you have, especially with 2-bolt caps.
Nodular iron and cast iron have expansion characteristics so close that you'd need to know the grades of cast iron and nodular iron to be able to quantify the difference in main bearing bore expansion.
You have made up your mind on the 4-bolt thing. Anyway, IMO you'll gain way more strength from the 4-bolt caps than you will lose by drilling and tapping the extra holes, and then filling them with steel studs.
If you stay with 2-bolt caps, use steel rather than nodular. The cost to 4-bolt vs. steel 2-bolt isn't much, and you have a better chance of using the power adder successfully with the 4-bolts.
Lightweight reciprocating bits are a good idea.
The plan is to build a 383, because it's more cost effective than a 396. I intend to use 6" rods and forged pistons.
The rev limit on this motor would likely be about 6500rpm and I MAY decide to use a power adder.
If I use a blower or turbo it would be running under 15lbs of boost, probably under 10, and if I used nitrous, I would use a progressive controller and most likely limit myself to a 200 shot, maybe 250, but that's unlikely.
I'd like some input on my thoughts so that I can address all my concerns BEFORE I begin spending money.
Thank you.
Bottom line, IMO, is don't use the power adders if you insist on staying with the 2-bolt block, no matter what caps you choose. Using methods which have proven to work is often a better choice than trying new things.
I have a 2-bolt LT-1 in my car.
When I rebuild it I plan to re-use the block because it's well seasoned.
My plan is to zero-deck it, line bore it and hone it with torque plates.
I don't plan to convert to 4-bolt because I don't want to remove meat from the webs to drill the holes.
Instead, I want to stud the bottom end, and I plan to lighten the entire reciprocating assy as much as feasible.
My question is this; I have concernes about using main caps that are of a substantially different metallic composition than the block because I am concerned about metals expanding at different rates when the engine heats up.
I suppose this would mean that using billet steel caps would worry me because of it's expansion characteristics.
I'm wondering if Nodular iron main caps would be close enough to the metallic composition of the block to alleviate that concern.
I also wonder if there are other strengthening techniques that I am not aware of. (I don't want to fill the block, because this is a street car)
Heating the main bearing journals from 70 degree room temp to 270 degrees (F) would enlarge them about .003. If you used steel caps, it would be about 10% less, or .0003 difference. That's if the caps get that hot. If you use a power adder, .0003 is going to be the least distortion problem you have, especially with 2-bolt caps.
Nodular iron and cast iron have expansion characteristics so close that you'd need to know the grades of cast iron and nodular iron to be able to quantify the difference in main bearing bore expansion.
You have made up your mind on the 4-bolt thing. Anyway, IMO you'll gain way more strength from the 4-bolt caps than you will lose by drilling and tapping the extra holes, and then filling them with steel studs.
If you stay with 2-bolt caps, use steel rather than nodular. The cost to 4-bolt vs. steel 2-bolt isn't much, and you have a better chance of using the power adder successfully with the 4-bolts.
Lightweight reciprocating bits are a good idea.
The plan is to build a 383, because it's more cost effective than a 396. I intend to use 6" rods and forged pistons.
The rev limit on this motor would likely be about 6500rpm and I MAY decide to use a power adder.
If I use a blower or turbo it would be running under 15lbs of boost, probably under 10, and if I used nitrous, I would use a progressive controller and most likely limit myself to a 200 shot, maybe 250, but that's unlikely.
I'd like some input on my thoughts so that I can address all my concerns BEFORE I begin spending money.
Thank you.
Bottom line, IMO, is don't use the power adders if you insist on staying with the 2-bolt block, no matter what caps you choose. Using methods which have proven to work is often a better choice than trying new things.
12-15-2003, 11:51 AM
#8
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Join Date: Feb 2001
Location: Bay Area, CA, USA
Posts: 1,967
Originally posted by LameRandomName
Maybe I wasn't very clear...
I do NOT want to install 4-bolt caps.
I'm planning to run 2 bolt caps with studs.
What I'm wondering is whether or not Nodular Iron caps have basically the same expansion characteristics as the block and whether there are additional strengthening things I can do, other than filling the block or converting to 4-bolts.
For instance, does someone make a girdle and if so, does anyone have experience with them?
Maybe I wasn't very clear...
I do NOT want to install 4-bolt caps.
I'm planning to run 2 bolt caps with studs.
What I'm wondering is whether or not Nodular Iron caps have basically the same expansion characteristics as the block and whether there are additional strengthening things I can do, other than filling the block or converting to 4-bolts.
For instance, does someone make a girdle and if so, does anyone have experience with them?
12-15-2003, 12:04 PM
#9
Registered User
Join Date: Dec 2000
Location: Chattanooga, Tennessee
Posts: 487
I saw a lower end girdle at the website below, but I don't know if he does them for LT1's:
http://www.badasscars.com
Dave
http://www.badasscars.com
Dave
12-15-2003, 12:24 PM
#10
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Join Date: Dec 2003
Location: New Orleans, LA
Posts: 56
I would recommend the 4 bolt but whether you need it or not depends on how much boost and how high you rev it. I personally built and race a 400 smallblock with a 177ci Weiand Pro Street Roots blower and I used 2 bolt block BUT on 400 smallblocks, 2 bolt blocks have larger main caps than the 4 bolt ones(I own 2- two bolt blocks, one 4 bolt that is all stock). BUT running a two bolt blower motor. I run 190,000psi ARP studs on the mains, Eagle ESP H-beam 4340 forged steel rods with 190,000 psi rod bolts, and Keith Black hypereutic 30cc dishtop blower pistons. It works for me and I was pushing 12psi at 6700-7000rpms(tach was slower than realized and didn't know it until put a rev limiter) but now with the MSD BTM box it's bumping the rev limiter at 6000 and has 9psi at that rpm.
SO, my point is a two bolt CAN endure a lot but on a 350 the two bolt main caps are the same size as the four bolt caps so I'd opt to drill it for the splayed caps or even normal 4 bolt if you aren't going crazy on boost or rpms.
ALSO, I run a STANDARD grind crank(stock cast at that!)- key is clearances, I would never run an undersized crank on a blower motor.
Just my two cents from running blowers and having great sucess. If you are curious, check out my webpage and see for yourself.
SO, my point is a two bolt CAN endure a lot but on a 350 the two bolt main caps are the same size as the four bolt caps so I'd opt to drill it for the splayed caps or even normal 4 bolt if you aren't going crazy on boost or rpms.
ALSO, I run a STANDARD grind crank(stock cast at that!)- key is clearances, I would never run an undersized crank on a blower motor.
Just my two cents from running blowers and having great sucess. If you are curious, check out my webpage and see for yourself.
12-15-2003, 12:29 PM
#11
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Join Date: Oct 2002
Location: Toledo, OH
Posts: 1,639
If you listen to many people on this board listen to oldsstroker since you are new i thought that would be good info. And that makes not much sence staying away from 4bolt because you have to drill metal out, you are gainign 100 times more strength by adding the two extra bolts than you are losing in material, also the center two bolts are still studs.
If you are set on 2bolts though, stay away from power adders above 150hp like everyone said.
If you are set on 2bolts though, stay away from power adders above 150hp like everyone said.
12-15-2003, 06:31 PM
#12
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Join Date: Nov 2003
Posts: 1,211
Well, you know....
Maybe I should reconsider.
The main reason that I wanted to stay away from 4 bols was that I was worried about weakening the webs. I figured I'd be better off to stud the two bolt and balance well.
So you folks figure that my fear is unfounded? That I wouldn't strengthen the main caps at the expense of weakening the webs?
Maybe I should reconsider.
The main reason that I wanted to stay away from 4 bols was that I was worried about weakening the webs. I figured I'd be better off to stud the two bolt and balance well.
So you folks figure that my fear is unfounded? That I wouldn't strengthen the main caps at the expense of weakening the webs?
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