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Intake to exhaust valve ratio

Started by BONERACIN, April 10, 2012, 05:54:37 AM

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BONERACIN

April 10, 2012, 05:54:37 AM
Is there a rule of thumb for this?
Boneracin
"Uncle Sam made me cut off my mullet"

Admiral Akbar

#1
April 10, 2012, 06:17:25 AM
Nope..

Max

BONERACIN

#2
April 10, 2012, 07:01:54 AM
Is it just based off experience?
Boneracin
"Uncle Sam made me cut off my mullet"

TorQuePimp

#3
April 10, 2012, 07:35:23 AM
Partially what will fit in the stock seats,there are other reasons to put a larger exhaust valve in and I am sure it would start some sort of arguement.

Admiral Akbar

#4
April 10, 2012, 07:51:01 AM
Quote from: BONERACIN on April 10, 2012, 07:01:54 AM
Is it just based off experience?

Its based one what you are starting with.. Ground up 70-80% is the best, but it can change if you are starting with something that is already built.

Max

PanHeadRed

#5
April 10, 2012, 07:57:21 AM
>Intake to exhaust valve ratio.....Is there a rule of thumb for this?<

Yep. Don't let them touch.

xzo124

#6
April 10, 2012, 08:01:36 AM
Quote from: PanHeadRed on April 10, 2012, 07:57:21 AM
>Intake to exhaust valve ratio.....Is there a rule of thumb for this?<

Yep. Don't let them touch.
:up: :up:....xzo

Rusty Steel

#7
April 11, 2012, 08:47:39 PM
Quote from: PanHeadRed on April 10, 2012, 07:57:21 AM
>Intake to exhaust valve ratio.....Is there a rule of thumb for this?<

Yep. Don't let them touch.
LMAO.. :hyst:
If it ain't broke... Fix it until it is.

prodrag1320

#8
April 12, 2012, 04:36:23 AM
it can be down to 65% and still be OK,alot of factors such as int valve size & TDC lift will can restrict the ex valve size & flow (we like 70-85% here)

PanHeadRed

#9
April 12, 2012, 04:43:17 AM
Bone, like Kirby said pay attention to the flow rates not the diameters. Parts crashing together has a large influence, and puts limits on their size.

TXChop

#10
April 12, 2012, 05:50:04 AM
Coming from a total head flow newb...

Are these head flow % the same for an 88ci build with a 203 cam.
or a max effort street motor looking for 180hp?

dirty jim

#11
April 12, 2012, 06:29:08 AM
THERE WAS A HEAD PORTER FROM CALIFORNIA BACK IN THE '70'S WHO FOUND THAT AN EXHAUST VALVE DIAMETER OF 82 PERCENT OF THE INTAKE WAS IDEAL. SHORTLY AFTER MASS PRODUCED "CRATE" HEADS BECAME POPULAR IN THE CAR INDUSTRY. SORRY I CAN'T REMEMBER HIS NAME,....OLD AGE IS A BITCH.

clawdog60

#12
April 12, 2012, 10:27:03 AM
smokey yunick :up:

aharp

#13
April 12, 2012, 10:14:34 PM
Quote from: PanHeadRed on April 10, 2012, 07:57:21 AM
>Intake to exhaust valve ratio.....Is there a rule of thumb for this?<

Yep. Don't let them touch.
;D ;D ;D
Speed costs money. How fast do you want to spend?

RevFastEddy

#14
April 14, 2012, 08:18:58 AM
Flow figures 1.2 to 1.6 is a typical good flow ratio.. That said that is your port size, shape, valve size, chamber shape, exhaust system and so on.. so which is better a 1.85" valve or a 2" valve... answer, one that matches the criteria above and final use.
SAEPE EXPERTUS, SEMPER FIDELIS, FRATRES AETERNI
Vietnam 67-68, Red Beach

Don D

#15
April 22, 2012, 06:20:36 AM
How large valves, the relationship?
How long is a rubber band?
The ideal will change according to the CR. The idea is to clear the cylinder of pressure before heading uphill. The CR will change what is needed and the space available, plus which head casting, will change what can be used practically
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