Achieving desired compression ratio
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From: Oskaloosa, Iowa
Achieving desired compression ratio When building a motor is it more desirable to use more dish on the pistons or larger combustion chambers on the heads? It will be a boosted build so maybe not as critical as an NA build but if I have the options I’d like to use the most ideal method of achieving my desired compression ratio. Also considering ls9 head gaskets. How much will the larger bore of the gaskets effect compression ratio? Assuming it would lower it a bit more.
Thread Starter
Joined: Jun 2005
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From: Oskaloosa, Iowa
Are pistons with more dish actually thinner? For example if I could choose between 2 cc dish pistons with 66cc chamber heads or 8cc dish pistons with 59cc chamber heads would one be preferred over the other assuming aftermarket casting heads so deck thickness wasn’t a factor with excessive milling to achieve the combustion chamber size?
This would be a fully forged stock stroke motor.
This would be a fully forged stock stroke motor.
I thought this was a decent read. http://blog.jepistons.com/dish-dome-...the-difference
I believe the top piston ring location is determined by the depth of the dish. I'd rather run less dish/flat top with a larger chamber head to have more meat in the piston than running a giant dished piston and tiny cc heads.
I believe the top piston ring location is determined by the depth of the dish. I'd rather run less dish/flat top with a larger chamber head to have more meat in the piston than running a giant dished piston and tiny cc heads.
Thread Starter
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From: Oskaloosa, Iowa
Ok after changing my mind nearly every day I think I’m finally getting close to a decision. I’m leaning towards a TSP aluminum 347 with trick flow as cast heads with a jamcam and giving it nearly everything my D1x can dish out on E85. -2 cc Diamond pistons, Callies compstar rods, k1 crank, main studs, trick flows with 62 cc chamber, ls9 gaskets, head studs, ls7 lifters, stock rockers.
Thread Starter
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From: Oskaloosa, Iowa
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Personally I wouldn't do the LS9 headgaskets on a 3.9 bore motor. They do work and lots of people have done them, but I personally would prefer a gasket that is sized for the bore you're running.
And if you can, if you can swing it, I would go larger displacement. Would it be much more to do a stroker since you're already looking at doing a forged crank, rods, and pistons?
And if you can, if you can swing it, I would go larger displacement. Would it be much more to do a stroker since you're already looking at doing a forged crank, rods, and pistons?
Thread Starter
Joined: Jun 2005
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From: Oskaloosa, Iowa
Personally I wouldn't do the LS9 headgaskets on a 3.9 bore motor. They do work and lots of people have done them, but I personally would prefer a gasket that is sized for the bore you're running.
And if you can, if you can swing it, I would go larger displacement. Would it be much more to do a stroker since you're already looking at doing a forged crank, rods, and pistons?
And if you can, if you can swing it, I would go larger displacement. Would it be much more to do a stroker since you're already looking at doing a forged crank, rods, and pistons?
Considering reasonable lead times I need to get this ordered within the next couple weeks so I need to make up my mind.
Thread Starter
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From: Oskaloosa, Iowa
I wouldn't, but that's just me. You're a stalled auto, leave the heads stock and put a cam in it for the intended rpm range with a good split since A) centrifugal and B)ls3 heads need the split..... and let the ls3 eat.
Thread Starter
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From: Oskaloosa, Iowa
If I stay cathedral and reuse my intake/throttle body, fuel rails and injectors, rockers arms...then all I need to buy is better cathedral port heads to have a reasonable top end in which an better intake/throttle body could be swapped out later easily.
I also don't like buying used parts so picking up a used ls3 top end may seem economical for the performance I don't want to chance used parts.
Why not buy an entire stock LS3 and add cam, springs, pushrods, a timing chain and oil pump and done? Detoxx did almost 1000whp on a SBE ls3. It would be a known used running motor instead of buying piece meal.
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From: Oskaloosa, Iowa
I'm not saying you or anyone else is wrong. I read about the stock bottom end life every day here so I get it for the value. There is also nothing wrong with my current ls1 I'd just like more power and feel like 650 rwhp is already further than I like pushing this thing. I'd rather pull it then push it to the point of knowing it's a ticking time bomb. I want a forged motor and basically was set on an all forged 347 like I mentioned earlier until the email I received today recommending either the iron 6.0 or ls3. That got me thinking how can I do a forged rods/pistons ls3 and still keep it under budget. I'd be happy with the forged 347 which is actually cheaper even with a forged crank and arp main studs. I can never make up my mind, but I need to decide if I want to get this short block by the end of March. I have a bunch of time off in March burning up last years vacation before busy season. From there on it's over time all summer so I will not have much time.
I was simply pointing out how much stronger the stock ls3 is than a stock ls1 or a 6.0 liter. I get the peace of mind from a forged motor. I would either just go forged 5.3/5.7 or stock ls3, just my 0.02.
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Joined: Jun 2005
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From: Oskaloosa, Iowa
Hopefully I’ll get some questions answered from Tsp today and make my decision. Still seems like my original plan is best fully forged and main studded 5.3 aluminum block bored to 3.905 for a 347. At that point the block becomes the weak link, but talking to people that have done it the sleeves are still thicker than an ls1 block so 900 shouldn’t be a problem which was the number tsp gave me for the block limit. The only thing to decide then is stick with the stock stroke or go ahead and go with a 4” crank for the 383. Common thinking is stock stroke on a boosted motor, but 20 extra ft lbs or so down low would be nice in a street strip toy.
You're gonna see a lot more than 20 foot pounds from a stroker.
I recommended going bigger cubes so you have more power right out of the box. A stock LS3 should hold what you want no problem. But if you can sell your current engine you can offset the cost of the LS3 DRAMATICALLY and if you build your current motor you actually are going to spend a lot more.
I would do the build LS3, since that's what you want and have budgeted. I would upgrade to the LS3 top end later when you have the money. GMPP ported LS3 heads are under $1500 new if I remember right and brand new they only around 1200. The intake is about 300 new. I just sold a used LS3 intake for 160. You should be able to put together a LS3 topend buying things for good deals here and there for as much or less than buying cathedral heads, if you are doing ported or aftermarket. And again you can sell your current top end to offset the cost of the LS3 top end.
Just trying to add to the confusion here lol.
I recommended going bigger cubes so you have more power right out of the box. A stock LS3 should hold what you want no problem. But if you can sell your current engine you can offset the cost of the LS3 DRAMATICALLY and if you build your current motor you actually are going to spend a lot more.
I would do the build LS3, since that's what you want and have budgeted. I would upgrade to the LS3 top end later when you have the money. GMPP ported LS3 heads are under $1500 new if I remember right and brand new they only around 1200. The intake is about 300 new. I just sold a used LS3 intake for 160. You should be able to put together a LS3 topend buying things for good deals here and there for as much or less than buying cathedral heads, if you are doing ported or aftermarket. And again you can sell your current top end to offset the cost of the LS3 top end.
Just trying to add to the confusion here lol.
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Joined: Jun 2005
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From: Oskaloosa, Iowa
Well after talking to them and thinking some more I placed my order for the LS3 with wiseco pistons and K1 rods with stock crank. I'll make up my mind on the top end and then choose a cam after that.