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| | |-+  48mm inlet valves on CE heads, 94mm bore?
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Author Topic: 48mm inlet valves on CE heads, 94mm bore?  (Read 4748 times)
Jonny Grigg
Full Member
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Posts: 232



« on: January 25, 2014, 15:08:18 pm »

There is no doubt that the heads on my engine are ultimately going to hold it back. At the moment I am not brave enough to suggest to my wife that it would be a good idea to switch out my Comp Elim heads to Component Development/ Strip Dominator type castings, so for now I am looking at how I get the most out of what in have- unless I break it of course!

So, at the moment my motor is 2442, using a Webcam 251, 14:1 compression and a pair of comp elims. These have 46*40 valves, but I am using a pair of Terminator carbs, which we had to vent down to 44s to get the thing jetted sensibly. Clearly we are not getting the best out of the carbs right now.....

So, whilst sat on my sofa I have been thinking about a number of potential changes.... I originally chose 46mm valves as i had read that 48s on a 94 bore put the valve too close to the chamber wall, detrimentally affecting flow and swirl into the chamber. In effect, the 46mm  valve was better than the 48. Did I get this wrong? Would a 48 valve flow better than the 46?

The motor is nitroused, but at the moment I would like to run near to or into the 10s normally aspirated if possible.....

I would appreciate any comments to my ramble.

Thanks,

Jonny.
« Last Edit: January 25, 2014, 15:10:02 pm by Jonny Grigg » Logged

No Compromise. O/FF111
K-Roc
Full Member
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Posts: 194


« Reply #1 on: January 25, 2014, 17:48:28 pm »

A motor of your size should definitely benefit from the larger intake valve,  HOWEVER just increasing the valve size without also modifying the port and chamber probably will not make any difference, or you may even loose power. ( most likely the latter)
Your discharge Co-efficient will most likely nose dive... ( flow CFM per sq. inch of valve size)

Think of it this way....The valve head is the biggest restriction in the port... So if you go from a 46 to a 48 valve with no other changes, you have put a larger blockage in the port  the air has to get around a bigger valve head as it enters the chamber...... Now you have increased the seat throat size as you increase the valve size when you do your valve job,... This is why you need to perform extra port work  above and below the valve seat to get your co-efficient back to where it was, or better. You may even need to lift the 48mm valve higher... It all depends on the port,seat, chamber...

Cheers. K-Roc,

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Mike Lawless
Sr. Member
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Posts: 386



WWW
« Reply #2 on: January 27, 2014, 19:26:59 pm »

Bigger is better.

Way too big is just about right
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Winner, 2009 Bakersfield March Meet
2006 PRA Super Gas Champion
2002-2003 DRKC Champion
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Udo
Hero Member
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Posts: 2077



« Reply #3 on: January 28, 2014, 20:31:30 pm »

I have used 50's in a 94 bore . If you ask Pat Downs he will get some for you ..

Udo
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K-Roc
Full Member
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Posts: 194


« Reply #4 on: January 28, 2014, 22:24:35 pm »

I have used 50's in a 94 bore . If you ask Pat Downs he will get some for you ..

Udo

With a 40mm Exhaust ?   Wink
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BeetleBug
Hero Member
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Posts: 2836


Snabba grabben...


« Reply #5 on: January 28, 2014, 22:27:30 pm »

I have used 50's in a 94 bore . If you ask Pat Downs he will get some for you ..

Udo

With a 40mm Exhaust ?   Wink

51 x 40 valves - 94 bore - 286hp - 2386ccm
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10.41 - 100ci - 1641ccm - 400hp
Taylor
Hero Member
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Posts: 577



« Reply #6 on: January 29, 2014, 01:35:08 am »

I have used 50's in a 94 bore . If you ask Pat Downs he will get some for you ..

Udo

With a 40mm Exhaust ?   Wink

51 x 40 valves - 94 bore - 286hp - 2386ccm

Did you move the valves over towards the exhaust or just notch the cylinders?
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goose
Jr. Member
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Posts: 58



« Reply #7 on: January 29, 2014, 04:53:02 am »

just curious
what kind of horsepower are you getting n/a ie without the nitrous?
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2015 the year finally racing
BeetleBug
Hero Member
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Posts: 2836


Snabba grabben...


« Reply #8 on: January 29, 2014, 07:23:22 am »

Did you move the valves over towards the exhaust or just notch the cylinders?

Angle flow heads and it was (is) tight. No nitrous, NA. High compression and not for the street.
« Last Edit: January 29, 2014, 13:38:36 pm by BeetleBug » Logged

10.41 - 100ci - 1641ccm - 400hp
Udo
Hero Member
*****
Posts: 2077



« Reply #9 on: January 29, 2014, 13:29:04 pm »

I have used 50's in a 94 bore . If you ask Pat Downs he will get some for you ..

Udo

With a 40mm Exhaust ?   Wink

No 39

But more important is the port work


Udo
« Last Edit: January 29, 2014, 18:22:33 pm by Udo » Logged

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