408 lt1
Last year someone was trying to sell a few of what he claimed were the like 1o LT1 "bowtie" blocks made as prototypes. I know someone else who converted two Donovan aluminum blocks to use everything LT1 including the mechanical waterpump and opti. He later sold one of the blocks.
Its all in the tune.
My shortblock is also built for ~12.5:1 CR with close to stock CC heads and my cam is 108LSA...and it will be ran on pump gas.
These are not gen1's, they love high compression even on a street car. Its the dynamic CR that you need to worry about anyways.
These are not gen1's, they love high compression even on a street car. Its the dynamic CR that you need to worry about anyways.
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From: Kinston North Carolina
Haha ok.. your running a solid cam. My question to you is what kinda duration at .050 are u running. With 224 degrees duration at .050 and a 107.5 LSA in a 383 is gonna make a ton of cyl pressure. I mean he said it wouldnt run, probably b/c whoever tuned it put to much timing in it and it caused detonation. With that kind of cyl pressure on pump gas u would have to pull so much timing out of it to keep it alive. Say what u want to but that cam is just too small for the combination.
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Yea man i realize u can get away with alot of STATIC compression on a computer controlled motor. Thanks to good working knock sensors you can run them on the ragged edge. But that dont exactly mean u can dive off the deep end and throw just any camshaft in it. Hell you can run 14:1 compression in it if u put a big enough cam in it to blead off the pressure. Thats why u cant just pick any cam for just any combination. Camshaft selection is crucial. And man the two words CYLINDER PRESSURE defines dynamic compression.
There are guys running 12:1 with 22x intake duration hydraulic cams.
Hell my stock shortblock setup with .052 quench is running 11.2-3 cam is 226/234 110 makes about 230psi cranking compression, doesn't detonate on 36degrees of timing, though from what I have learned more recently I might back that off. Think it is not necessary and just not detonating because the chamber is good.
Hell my stock shortblock setup with .052 quench is running 11.2-3 cam is 226/234 110 makes about 230psi cranking compression, doesn't detonate on 36degrees of timing, though from what I have learned more recently I might back that off. Think it is not necessary and just not detonating because the chamber is good.
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There are guys running 12:1 with 22x intake duration hydraulic cams.
Hell my stock shortblock setup with .052 quench is running 11.2-3 cam is 226/234 110 makes about 230psi cranking compression, doesn't detonate on 36degrees of timing, though from what I have learned more recently I might back that off. Think it is not necessary and just not detonating because the chamber is good.
Hell my stock shortblock setup with .052 quench is running 11.2-3 cam is 226/234 110 makes about 230psi cranking compression, doesn't detonate on 36degrees of timing, though from what I have learned more recently I might back that off. Think it is not necessary and just not detonating because the chamber is good.
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From: Kinston North Carolina
Im starting to wonder why myself. I just like to see what others are running and how they liked it. But it looks like all people wanna do up here is tell you your absurd for wanting bigger cubes and more power. And from what ive seen nobody is taking advantage of the extra cubes when it comes to selecting a cam.
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Improper tuning which leads to detonation is probably the #1 killer of engines. Im not knocking anyones engine combination up here. What people dont realize when you are running that tight of cyl pressure on even race fuel the tune has to be spot on. If the motor were to go lean even the slightest bit or the timing jump or go eratic at all then you can just about bet your life on it that its gonna detonate some especially on pump juice. You pretty much eliminate all margin for error. Anybody can engineer a combo that will run decent but you gotta make it live to.
Another thing to consider is with port injection port to port variance and intake flow varaiance will have a greater impact on individual cylinder AFR than it would with a carb or TBI. Seen a few examples I suspect a single higher flowing port combined with aggressive tuning destroyed. The overwhelming majority of us only look at bank to bank AFR, the intake is not perfect balance wise and when the heads are inconsistent it magnefies the problem, might have one cylinder a point high and one a point low on AFR, the lean one will detonate.
Far as displacement with the usual heads and intakes I don't feel much over a 383 ends up well matched. Don't get me wrong, I know a few guys who have done 408 and they are happy, at the same time they both express shock at my car because it runs better than most of the strokers guys put together.
There are a number of ways to go about any goal.
Far as displacement with the usual heads and intakes I don't feel much over a 383 ends up well matched. Don't get me wrong, I know a few guys who have done 408 and they are happy, at the same time they both express shock at my car because it runs better than most of the strokers guys put together.
There are a number of ways to go about any goal.
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From: Kinston North Carolina
Another thing to consider is with port injection port to port variance and intake flow varaiance will have a greater impact on individual cylinder AFR than it would with a carb or TBI. Seen a few examples I suspect a single higher flowing port combined with aggressive tuning destroyed. The overwhelming majority of us only look at bank to bank AFR, the intake is not perfect balance wise and when the heads are inconsistent it magnefies the problem, might have one cylinder a point high and one a point low on AFR, the lean one will detonate.
Far as displacement with the usual heads and intakes I don't feel much over a 383 ends up well matched. Don't get me wrong, I know a few guys who have done 408 and they are happy, at the same time they both express shock at my car because it runs better than most of the strokers guys put together.
There are a number of ways to go about any goal.
Far as displacement with the usual heads and intakes I don't feel much over a 383 ends up well matched. Don't get me wrong, I know a few guys who have done 408 and they are happy, at the same time they both express shock at my car because it runs better than most of the strokers guys put together.
There are a number of ways to go about any goal.
Those are good points, you also have to look at cylinder hotspots, low or slow coolant flow around a certain part of the cylinder.
Most high compression, big headered, solid cammed cars have the knock sensors turned off. Mine are. They have to be.
Mine is on the ragged edge I know, It takes alot more than just slapping it together. Cooling system has to be over built. You have to get the coolest aircharge you can(hence the hood I have, its functional) Be careful where you get fuel, I use a very busy Shell station, and only use busy stations so the fuel stays fresh. Quench has to be TIGHT(mine is .039) no sharp edges in the cylinder. Also the head has to have a good quench pad and new style chambers.
My cam is 254@.050.
If ya want a 408 and make it worthwhile you need a LARGE set of heads , single plane, 1 7/8 headers.
I almost bought a 410 inch LT1 out of La, it made 500 to the tires with a turbo 400, AFR heads, sold roller and a 12 bolt. It is in a twin turbo T/A now. Runs in the 8's.
I considered a 396 HARD, but got a good deal on the 383 I have now.
Most high compression, big headered, solid cammed cars have the knock sensors turned off. Mine are. They have to be.
Mine is on the ragged edge I know, It takes alot more than just slapping it together. Cooling system has to be over built. You have to get the coolest aircharge you can(hence the hood I have, its functional) Be careful where you get fuel, I use a very busy Shell station, and only use busy stations so the fuel stays fresh. Quench has to be TIGHT(mine is .039) no sharp edges in the cylinder. Also the head has to have a good quench pad and new style chambers.
My cam is 254@.050.
If ya want a 408 and make it worthwhile you need a LARGE set of heads , single plane, 1 7/8 headers.
I almost bought a 410 inch LT1 out of La, it made 500 to the tires with a turbo 400, AFR heads, sold roller and a 12 bolt. It is in a twin turbo T/A now. Runs in the 8's.
I considered a 396 HARD, but got a good deal on the 383 I have now.
Last edited by FASTFATBOY; Jan 3, 2009 at 12:44 PM.
Thread Starter
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From: Kinston North Carolina
Those are good points, you also have to look at cylinder hotspots, low or slow coolant flow around a certain part of the cylinder.
Most high compression, big headered, solid cammed cars have the knock sensors turned off. Mine are. They have to be.
Mine is on the ragged edge I know, It takes alot more than just slapping it together. Cooling system has to be over built. You have to get the coolest aircharge you can(hence the hood I have, its functional) Be careful where you get fuel, I use a very busy Shell station, and only use busy stations so the fuel stays fresh. Quench has to be TIGHT(mine is .039) no sharp edges in the cylinder. Also the head has to have a good quench pad and new style chambers.
My cam is 254@.050.
If ya want a 408 and make it worthwhile you need a LARGE set of heads , single plane, 1 7/8 headers.
I almost bought a 410 inch LT1 out of La, it made 500 to the tires with a turbo 400, AFR heads, sold roller and a 12 bolt. It is in a twin turbo T/A now. Runs in the 8's.
I considered a 396 HARD, but got a good deal on the 383 I have now.
Most high compression, big headered, solid cammed cars have the knock sensors turned off. Mine are. They have to be.
Mine is on the ragged edge I know, It takes alot more than just slapping it together. Cooling system has to be over built. You have to get the coolest aircharge you can(hence the hood I have, its functional) Be careful where you get fuel, I use a very busy Shell station, and only use busy stations so the fuel stays fresh. Quench has to be TIGHT(mine is .039) no sharp edges in the cylinder. Also the head has to have a good quench pad and new style chambers.
My cam is 254@.050.
If ya want a 408 and make it worthwhile you need a LARGE set of heads , single plane, 1 7/8 headers.
I almost bought a 410 inch LT1 out of La, it made 500 to the tires with a turbo 400, AFR heads, sold roller and a 12 bolt. It is in a twin turbo T/A now. Runs in the 8's.
I considered a 396 HARD, but got a good deal on the 383 I have now.
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I think the main thought wht97ws6ta is getting at is that asking any engine to run mid 12's in compression (not in a boost situation where pressure fluctuates) is playing with fire. Reminds me of some of the guys i know from back home with their mud trucks running 13 and 14:1 compression on iron cranks and hyper pistons standing around scratching their heads when they blow sky high in a mud pit. Well how's that happen? Could be the huge compression ratio, the insane cam, the antique camel hump heads with dome pistons, the lack of any upgrades to the fuel system (aside from a holley fuel pump). The answer isn't in the parts, it's in the combination...and if you mismatch one major thing, everyone else gets a smokeshow. I know from experience on an old ford fairmont wagon with a 5.0 swap. I skimped on the fuel system due to lack of money and a friend had a nitrous kit laying around...and a good idea turns into parts everywhere.
wht97ws6ta, the car had a good tune up. It was not lean, there was no detonation, and there were no signs of detonation. Nothing on the plugs, no knock retard, no signs on the pistons, etc. It was just failure.
As for the spiral lock causing all that mayhem, you have got to be kidding me. The reason the spiral lock was out in the loose is because the piston broke into so many pieces that there was nothing to hold it.
There is nothing in that motor that is going to break the crankshaft. The crankshaft is broken because it broke. It was a weak one for whatever reason.
Working at a machine shop I would expect you to have a little more sense with figuring out what went wrong in a motor.
As for the spiral lock causing all that mayhem, you have got to be kidding me. The reason the spiral lock was out in the loose is because the piston broke into so many pieces that there was nothing to hold it.
There is nothing in that motor that is going to break the crankshaft. The crankshaft is broken because it broke. It was a weak one for whatever reason.
Working at a machine shop I would expect you to have a little more sense with figuring out what went wrong in a motor.
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wht97ws6ta, the car had a good tune up. It was not lean, there was no detonation, and there were no signs of detonation. Nothing on the plugs, no knock retard, no signs on the pistons, etc. It was just failure.
As for the spiral lock causing all that mayhem, you have got to be kidding me. The reason the spiral lock was out in the loose is because the piston broke into so many pieces that there was nothing to hold it.
There is nothing in that motor that is going to break the crankshaft. The crankshaft is broken because it broke. It was a weak one for whatever reason.
Working at a machine shop I would expect you to have a little more sense with figuring out what went wrong in a motor.
As for the spiral lock causing all that mayhem, you have got to be kidding me. The reason the spiral lock was out in the loose is because the piston broke into so many pieces that there was nothing to hold it.
There is nothing in that motor that is going to break the crankshaft. The crankshaft is broken because it broke. It was a weak one for whatever reason.
Working at a machine shop I would expect you to have a little more sense with figuring out what went wrong in a motor.
Either that crank was cracked when you put it in, or something else was wrong. Steel cranks just dont break with no more power than you were making. And who knows exactly what happened. Whenever the crank broke the piston might and probly did make some pretty good contact with the valves causing them to bust. Ive seen alot of busted keith blacks. The spiral lock deal was an assumption. And Im making these assumptions with 4 or 5 pics here. Its not like im holding this thing in my hands. Before you start pointing fingers why dont you sit down and figure out exactly what happened yourself. When you do, tell me about it. Im always up for learning new things. Ok what puzzles me is you said the thing popped the first time you hit it, free reved a little then ran fine. If the crank sheared off the first time you hit it, i find it quite hard to believe that the thing ran just fine with no knocks or loss of oil pressure. You said the car was only running a 12 flat at 110MPH. If thats all the power the thing was making then it surely wasnt enough to just break a eagle cast steel crank. Hell man im running 12.30s @ 115MPH on my stock LT1 with a stock crank. Is my crank about to break the next time i take it out? Gee mabey i shouldnt spray it no more, i might break my crank Either that crank was cracked when you put it in, or something else was wrong. Steel cranks just dont break with no more power than you were making. And who knows exactly what happened. Whenever the crank broke the piston might and probly did make some pretty good contact with the valves causing them to bust. Ive seen alot of busted keith blacks. The spiral lock deal was an assumption. And Im making these assumptions with 4 or 5 pics here. Its not like im holding this thing in my hands. Before you start pointing fingers why dont you sit down and figure out exactly what happened yourself. When you do, tell me about it. Im always up for learning new things.
Either that crank was cracked when you put it in, or something else was wrong. Steel cranks just dont break with no more power than you were making. And who knows exactly what happened. Whenever the crank broke the piston might and probly did make some pretty good contact with the valves causing them to bust. Ive seen alot of busted keith blacks. The spiral lock deal was an assumption. And Im making these assumptions with 4 or 5 pics here. Its not like im holding this thing in my hands. Before you start pointing fingers why dont you sit down and figure out exactly what happened yourself. When you do, tell me about it. Im always up for learning new things.Personally I wouldn't run a cast crank in any lt1 but a grocery getter...the stock one is plenty strong, and if you are rebuilding for high performance then just go forged.
Based on those pics I would blame the crank, the balance job, or both. I doubt detonation or installation error was a cause.