LS1- Going Back Together Q&A
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Teching In
Joined: Dec 2012
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From: Lewisville, TX
LS1- Going Back Together Q&A Here she is, back from Kim Barr's after getting machining, and after alittle painting, grinding, and polishing in the garage, I need to decide on head gaskets. .040 or .050, then the heads go on. I'm trying to figure what the compression ratio change is. It's bored to 3.905 with 241 66cc heads. He did a cleanup on the heads, but I don't think much was taking off, but the heads and block both got milled down some. I was told it'd be around 10.8 with a .040 thick gasket by Kim. Is 10.8:1 area good for the street as a DD? What size gasket do I need to be looking for as far as the bore goes? It's bored out to 3.905, but I noticed when I made those plexi glass covers, that the old gasket bore is actually bigger than 3.905. Do I need to use gaskets for a 6.0 with a 4.000 bore, stock size, or what? I may be looking too much into this, but everything so far has been built off numbers, so I wanna stick to that. Diamond says if at .000 deckheight @ 9.240 the comp. is at 10.3, so decked block and heads he took off .003-.004 he said total. What would be the best gasket to go with?
Build Thread: https://ls1tech.com/forums/conversio...03-s-10-a.html
Also- Would you replace these? I was told by Kim that they were fine. Opinions? They all look the same.
TECH Fanatic
Joined: Jun 2011
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From: Katy, TX
what rotating assembly are you using? I would run higher compression if you can, just be aware of possible PTV issues if you are using flat top pistons and a big cam.
Be sure to measure your deck height after assembly - on all 8 pistons.
For my build, I targeted 11.4 SCR with a quench of 0.036". To hit those numbers I optimized my piston selection, piston deck height, head milling, and head gasket thickness. I'm using Wiseco -3cc pistons with big valve reliefs, and a "mild" 224 cam, so my PTV is 0.250" minimum.
Be sure to measure your deck height after assembly - on all 8 pistons.
For my build, I targeted 11.4 SCR with a quench of 0.036". To hit those numbers I optimized my piston selection, piston deck height, head milling, and head gasket thickness. I'm using Wiseco -3cc pistons with big valve reliefs, and a "mild" 224 cam, so my PTV is 0.250" minimum.
Looks good. If you want to be cheap use stock gm mls gaskets you can get them for $35 a pair at the dealer. At this point since its a pretty mild build I would do it, you won't miss 4-5 hp and will be less sensitive to fuel octane
Don't mess with the cam bearings they look ok
Don't mess with the cam bearings they look ok
Thread Starter
Teching In
Joined: Dec 2012
Posts: 40
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From: Lewisville, TX
Stock crank, stock conn. rods, 3.905 Diamond flat-top pistons, LS1 Hot Cam, stock rockers, haven't measured push rods yet. Heads and block are milled down. How do I know if the PTV clearence is ok? I was going to use the .040 gasket, but what I need to know is, do I get a gasket that is closest to 3.905, or just go with a bigger bore gasket like ones for a 6.0/4.00 bore? I don't want to lose compression, and I'm not worried about the cost.
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That's what I used for calculations. I am of the opinion that building a rotating assembly that if my cam bearing look like that, $30 is worth replacing them. I am doing that on my build. About the same coloring on my bearings as yours shows.
That's what I used for calculations. I am of the opinion that building a rotating assembly that if my cam bearing look like that, $30 is worth replacing them. I am doing that on my build. About the same coloring on my bearings as yours shows.
Thread Starter
Teching In
Joined: Dec 2012
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From: Lewisville, TX
I've just heard bad things about changing the bearings. It's already back together, and i decided to roll with them. They make a 3.910 MLS .040 thick that I think I'm going to go with. They also have one that's .027 that would put it right at 11:1, but I've got to call Kim first and make sure I'm got the clearance.
TECH Fanatic
Joined: Jun 2011
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From: Katy, TX
As long as you get a gasket that is larger diameter than your bore and the combustion chamber you will be fine. I'm running a 4.135" bore gasket on my 3.903" bore engine (which is way over sized), but I considered that extra volume in my compression ratio calculations.
Looks good. If you want to be cheap use stock gm mls gaskets you can get them for $35 a pair at the dealer. At this point since its a pretty mild build I would do it, you won't miss 4-5 hp and will be less sensitive to fuel octane
Don't mess with the cam bearings they look ok
Don't mess with the cam bearings they look ok
TECH Fanatic
Joined: Jun 2011
Posts: 1,343
Likes: 8
From: Katy, TX
Martin@Tick Performance had a great analogy for quench...
Copy/Paste from his post....
https://ls1tech.com/forums/17289289-post33.html
Copy/Paste from his post....
Here is a good visual about how quench effects the burn rate and efficiency of the combustion chamber:
You have a roaring bonfire going. In each hand you have a coffee can full of gasoline. To demonstrate how quench effects combustion we take one can full of gas and slowly pour it on the fire. The fire flares up slowly, and only flares up as you pour gas on the fire. This demonstrates a loose quench figure. Too loose and/or in this visuals case, pour too slowly and it never really even flares up, just fizzles.
Now, in the other hand you take that can full of gasoline and you baseball pitch it with all your might at that bonfire. The bonfire explodes with combustion as soon as the can full of gasoline hits it. This is from the gasoline being tossed and tumbled around with oxygen right before combusting which in turn is exposing more surface area and making for more "droplets" of fuel to be burned which causes the fire to flame up very quickly. This demonstrates tight quench where the air/fuel mixture is "squished" together by the quench pad/surface of the piston and cylinder head causing the air/fuel mixture to be tumbled and tossed around exposing more surface area and "droplets" of fuel before the spark plug fires causing the air/fuel mixture to be ignited.
Now that we have this visual, too tight of a quench figure can cause the combustion event to go out of control just like a wildfire when too much wind is present and cause detonation and or total meltdown of your engine internals to happen. Too loose of a quench figure and the fire never even flames up at all. You need to find a balance point for your application whether it be N/A, Nitrous or boost. N/A engines can tolerate more quench because there is no oxidizer present in the combustion chamber/cylinder like there is in a nitrous engine. Heavy nitrous engines need a looser quench figure to become tunable on large volumes of N20. Boost likes to be treated like a N/A motor when it comes to quench as there is no oxidizer chemically and physically speeding up combustion and the flame front, just immense cylinder pressure.
I always urge my N/A customers to run a .040" gasket for added quench in lieu of milling their heads or in conjunction with milling their heads. What's done is done since you already ordered them Nate, but I would of opted for the 63cc chamber and a .040" gasket.
Either way it should run great!
You have a roaring bonfire going. In each hand you have a coffee can full of gasoline. To demonstrate how quench effects combustion we take one can full of gas and slowly pour it on the fire. The fire flares up slowly, and only flares up as you pour gas on the fire. This demonstrates a loose quench figure. Too loose and/or in this visuals case, pour too slowly and it never really even flares up, just fizzles.
Now, in the other hand you take that can full of gasoline and you baseball pitch it with all your might at that bonfire. The bonfire explodes with combustion as soon as the can full of gasoline hits it. This is from the gasoline being tossed and tumbled around with oxygen right before combusting which in turn is exposing more surface area and making for more "droplets" of fuel to be burned which causes the fire to flame up very quickly. This demonstrates tight quench where the air/fuel mixture is "squished" together by the quench pad/surface of the piston and cylinder head causing the air/fuel mixture to be tumbled and tossed around exposing more surface area and "droplets" of fuel before the spark plug fires causing the air/fuel mixture to be ignited.
Now that we have this visual, too tight of a quench figure can cause the combustion event to go out of control just like a wildfire when too much wind is present and cause detonation and or total meltdown of your engine internals to happen. Too loose of a quench figure and the fire never even flames up at all. You need to find a balance point for your application whether it be N/A, Nitrous or boost. N/A engines can tolerate more quench because there is no oxidizer present in the combustion chamber/cylinder like there is in a nitrous engine. Heavy nitrous engines need a looser quench figure to become tunable on large volumes of N20. Boost likes to be treated like a N/A motor when it comes to quench as there is no oxidizer chemically and physically speeding up combustion and the flame front, just immense cylinder pressure.
I always urge my N/A customers to run a .040" gasket for added quench in lieu of milling their heads or in conjunction with milling their heads. What's done is done since you already ordered them Nate, but I would of opted for the 63cc chamber and a .040" gasket.
Either way it should run great!
