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Hi everyone.
Just been doing some research on intake runner length for my engine build.
if I make peak torque in my ls1 at 4800rpm I need a runner length of 12.39"
if I push that rpm up to 5000rpm I need 15.39" runner length.
15.39This is measured from the back of the inlet valve to the common plenum area.
So I'm curious as to what the runner length is of a factory plastic ls6 intake manifold.
from back of valve to face of the cylinder head is about 4.25" from memory. (Might be wrong)
That means I only need an intake runner length between 8.15 to 11.15 long.
This is based on if the Wallace Racing Calcs is correct too. Because I'm not sure if I'm supposed to enter the @50 lift or the total duration of the cam.
Generally a longer runner shifts peak torque downward, not upward. A stock LS1 or LS6 intake has an 11" runner, if that helps.
yes that's what I was curious about.
The factory runner is 11 inch long plus the valve to cylinder head face makes it 15.25" long.
so given i want to move the power band up in the rpm a shorter runner is what i need.
the Holley midrise 300 137 manifold has a runner length of approximately 9" plus the valve to face measurement puts me around the 13.25" runner length. Spot on for my application i believe.
Thank you.
My fast 102 and Trickflow 235’s measured 16.5 intake runner inlet to Valve. I cut it down to 14.75 and reshaped the runner bellmouth.
it felt like it was starving for air at around 6500 rpm’s now it seems to be good up to the 6800 I run it to. Low end isn’t much different from what I can tell. Seems like it was a good trade off.
Last edited by jasons69chevelle; May 4, 2024 at 01:18 PM.
what do you mean by tank?
If you mean drop off I have already thought of that and have bumped the static compression ratio up from 10 to 1 to 11.3 to 1.
That should cover any loss in the lower rpm range from a shorter intake runner.
I have also increased overlap to add more exhaust scavenging and have built a DV inspired exhaust system that actually sucks like no tomorrow. This will also increase cylinder fill with fresh air fuel mixture to make more hp and torque.
Hi, I need to know your Exhaust Runner length?
Lance
I have a custom built 4 into 1. The exhaust primary pipes are 1.62" inside diameter and 2" outside diameter steam pipe to retain heat to increase exhaust gass flow volisity further into the exhaust system.
they average 32/33" long. To a tapered collector 3.5" down to 3" that is 10" long. They go to 100cel cats and twin 3" true dual exhaust system with a expansion chamber that is 355 cubic inch in size. Mufflers are straight through race style glass packed Mufflers. This is when I was building the exhaust system
Are you sure you're not just a spammer trying to gain post count?
Yet another bot waiting for updates. They usually have a common user name in one word, and their birth dates are 1991-1993. Weird.
I’ve banned more than I can count in the last 6 months…prolly 25-30 no kidding, just here in Internal Engine alone.
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Intake runner length 
