Intake runner query

Octobox

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Land rover series
Hi all I’m new to this forum, so hello to everyone. I am trying to get more torque from my land rover 2.25 5 bearing engine. So far i have skimmed 6mm of the head taking it to around 11:1cr -200psi across the board, ported intake and exhaust from graham bell tuning manual, 3 angle valve job all round with bulleted guides, made a full stainless exhaust and manifold 3-2-1. I intend to run a set of bike carbs 35mm- the ports are also 35mm ID. The exhaust was built for peak torque at 3000rpm but online calculators suggest 31mm intake track, so what should i do? Go 35mm all the way or go 31mm increase velocity and have a hideous miss match into the port mouth?
 

obi_waynne

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The very general rule of thumb is going with a short, wider inlet runner moves the torque curve up the rev range whereas long, narrow runners move the curve down the rev range.

The mismatch at the port can be minimized with a tapered end rather than sudden shelf. Your Valve job will also help mitigate any additional turbulance created in the flow.
 

Octobox

New member
Points
11
Location
Uk
Car
Land rover series
The very general rule of thumb is going with a short, wider inlet runner moves the torque curve up the rev range whereas long, narrow runners move the curve down the rev range.

The mismatch at the port can be minimized with a tapered end rather than sudden shelf. Your Valve job will also help mitigate any additional turbulance created in the flow.
Thanks for taking the time to reply waynne. I had tried to flair the end with a pipe expander but it just cracks, even with heat. I like the idea of the smaller, longer runner for better torque low down. Looks like I’m turning some tapers up on the lathe.
I’d post some pics to further explain, but I’m a newbee ☹️.
 

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