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Does anyone have the flow rates (Cfm) at lifts .2 to as high as .7 for the stock LT1 cylinder heads. I assume they are the same for both aluminum and cast-iron versions?
Does anyone have the flow rates (Cfm) at lifts .2 to as high as .7 for the stock LT1 cylinder heads. I assume they are the same for both aluminum and cast-iron versions?
You assume wrong. The Cast Iron heads had a couple of years longer develpment and the intake ports are better. I would not build a LT1 without porting the heads. Airflow is power.
Don't crap up another thread of mine, guys. Help me or be a smelly orifice about what I want to do. I will be asking around to cam makers about my desired custom cam specs for this proposed build. I am eager to learn about it.
Don't crap up another thread of mine, guys. Help me or be a smelly orifice about what I want to do. I will be asking around to cam makers about my desired custom cam specs for this proposed build. I am eager to learn about it.
We have attempted to help you.
What we cannot seem to get across to you is that a person can build more torque across the whole RPM band with a proper cam than you will get with what you have dreamed up.
When I get a spare moment I will fire up DD2000 and put you down something on paper and graph your proposed cam compared to what I have in-mind.
I will even go so far as to leave one at stock displacement and stroke one to 383 using the TPI.
Then I will model what I have in mind with both stock displacement and 383. Using higher compession with stock aluminum heads and ported aluminum heads.
Phoenix, everyone here has the best intentions. You can't fault the responses from people when they have repeatedly given you good (and factual) information, and you've completely ignored it because it doesn't fit the narrative you are after.
Anyway, here are the numbers I have. I can't remember where I found them nor how accurate they are so maybe someone else can verify.
If those numbers are completely wrong, someone feel free to correct me. Those are supposedly for stock 1993 Camaro / Trans Am aluminum heads. My understanding of the cast iron heads is they actually flow slightly less than the aluminum heads and have larger chambers. (I could be wrong about that also)
Another point to note is how the flow drops on the intake side above .500" lift. This indicates the port is becoming turbulent. The short turn is typically the culprit for this, but it can be a variety of things. Something else to consider with this is flow numbers are obtained at just 1 psi depression (28" of water) where as the pressure drop in the cylinder near peak piston speed can be 3+ psi at 5000+ rpm, forcing higher port velocity at a lower lift, and thus hitting this wall at a lower lift. This is where cam design becomes important.
I can be a child about this "vision" I have for my LT1 that excites me. However, the build must constrict itself to the realm of dedicated daily driver. I may be horribly wrong about the camshaft idea for the stroker in tandem with the intake I wish to use. The only thing I can use to help you see what I am seeing, as "a child" is through this...
This build WILL be done right but I need to know for certain that what I am looking for will be met with performance I can accept from torque levels to projected fuel economy.
There's no harmonic tuning to speak of below about 3500 rpm. This is especially true at part throttle and high manifold vacuum. You are bound by the laws of physics and thermodynamics where you can only pull so much power and efficiency out of given parameters. BSFC, VE, and CE are the main driving forces here and all are more greatly influenced by chamber shape, bore and stroke, compression, fuel atomization, and turbulence, none of which you can easily change (if at all) with a given engine. You can attempt to pull fractional percentage gains here and there, usually at a huge expense and no guarantee of results, along with major trade-offs in the mid-range and top end. At the end, you'd still be miles ahead to just go with a different engine that's better designed around what you're after.
There's no harmonic tuning to speak of below about 3500 rpm. This is especially true at part throttle and high manifold vacuum. You are bound by the laws of physics and thermodynamics where you can only pull so much power and efficiency out of given parameters. BSFC, VE, and CE are the main driving forces here and all are more greatly influenced by chamber shape, bore and stroke, compression, fuel atomization, and turbulence, none of which you can easily change (if at all) with a given engine. You can attempt to pull fractional percentage gains here and there, usually at a huge expense and no guarantee of results, along with major trade-offs in the mid-range and top end. At the end, you'd still be miles ahead to just go with a different engine that's better designed around what you're after.
If TPI has the stock runners on a 350 it actually starts working around 2,800 rpm and roughly 70 KPA and above. When I had my TPI setup I only saw marginal gains in torque between 2,800 rpm and 4,200 rpm. Compared to the dual plane high rise intake and a 454 TBI I had before I saw losses at every point both below and above that narrow RPM band. The TPI did give slightly better fuel economy than the TBI because I was able to run it leaner. It had slightly better throttle response as well. Beyond that its a waste of time IMO to try to convert a LT1 to TPI. I used the TPI setup because I bought the parts dirt cheap and it was one of the only cheaper MPFI intakes at the time for a small block chevy. My current 383 with a dual plane port injected intake and 1200 cfm 4bbl dry throttle body would run off and leave the Vortec head TPI 383 with siamese ported SLP runners I built at every point in its powerband. Would not even be a comparison.
Bore and stroke, chamber design, compression ratio are all things that are actually pretty easy to change. Idk why you would say they aren't easily changed. As far as a more modern engine I feel like you must be someone on the LS train... Truthfully when it comes to spending real money for engine modifications you won't find that the LS family is at that great of an advantage over the typical old-school nearly 65 year old SBC.
Just for giggles I attempted to spec a cam per David Vizard's 128 formula for this combo.
Assuming a 10.5:1 static 383, 1.94 intake valve
Specs calc'd out to 105.5 lsa, and roughly 250 duration (@ .006) - depending on how much overlap you want.
Picked out some CompXE lobes that looked close and ran them a few different ways. Lobes were 5440 for the intake and 5442 for the exhaust. Specs are 250/262 @ .006, 206/218 @ .050, 117/130 @ .200, .288/.308 lobe lift. All tests with 1.6 intake/1.5 exhaust rockers.
I went long on the exhaust to help offset the stock(ish) exhaust manifolds.
106 LSA on a 106 ICL (best looking graph IMO)
advanced 2 degrees (104 ICL)
Here's what happens when you widen the LSA (did not play with multiple ICLs OR wider LSAs - this is enough to make the point)
114 LSA on a 110 ICL
Last edited by dirtybob; Dec 13, 2019 at 02:57 PM.
Geez... And let's be honest, the torque numbers there for about a 2000 RPM stretch VERY early in the curve are nice but outside of that it's an incredibly **** poor, disappointing, boring engine. It's gonna strike and then fall right on its face. A factory LTX would be more exciting to drive.
Geez... And let's be honest, the torque numbers there for about a 2000 RPM stretch VERY early in the curve are nice but outside of that it's an incredibly **** poor, disappointing, boring engine. It's gonna strike and then fall right on its face. A factory LTX would be more exciting to drive.
Like I said in his previous post that he deleted. Spin the tires on a dump truck but fall on its face passing a Yugo.
When I opened up the exhaust on my 2012 Titan and had it dyno'd before and after the naysayers brought up that I lost 15 ft/lbs up through about 3,000 rpm and that the truck would slow down. They missed the fact up at 6,200 rpm where it shifted it gained 50 wheel hp on a Mustang dyno. I already had traction issues off the line as it was. I took it down the track and they all beat me up that it was a lie the truck went 4 tenths of a second quicker. I went from a 14.3 to a 13.9 and gained 6 mph trap speed. Up from 92 to 98 mph. The truck was more fun to drive on the street as well. I had the same bashing when I opened up the exhaust on my 2011 M56S. The guys that had done it wemt from 2" to 2.25" pipes. I went to 2.5 to match the manifold cats outlets. Up at 6,800 rpm the car gained about 60 hp. Talk about fun getting on the freeway.
And as stated in previous deleted thread said engine has to be able to manage driving in inclement weather. I can’t imagine 450ft-lbs of torque from 2000-3500 being greatly beneficial in that scenario.
Bore and stroke, chamber design, compression ratio are all things that are actually pretty easy to change. Idk why you would say they aren't easily changed. As far as a more modern engine I feel like you must be someone on the LS train... Truthfully when it comes to spending real money for engine modifications you won't find that the LS family is at that great of an advantage over the typical old-school nearly 65 year old SBC.
You can't so easily make an LT1 undersquare. You're stuck with the same chamber shape, spark plug position, and quench. Compression ratio can be raised for sure within octane limitations. The point is that he's trying to do something with this engine that it just isn't a good design for, and any effort in doing so is just going to kill performance elsewhere and make it boring to drive.
don't think I'd waste the money on a stroker tpi when you could hit the target with a baby cam, set of headers, and a tune on an otherwise untouched 350...
Dyno2000 makes a lot of assumptions in its calculations, but I agree with it for the most part. I use Engine Analyzer Pro.
YES it does, but it's good enough for my purposes (general trends - not accurate predictions). I mostly play with junk these days and DGAF...
I don't have EA Pro anymore but even that one could give some 'out to lunch' numbers - GIGO
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LT1 Cylinder Head Flow at Lift Information. 
