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48 MM WEBER VERSES 51 MM

Any type of technical questions or info

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rotor_speed
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48 MM WEBER VERSES 51 MM

#1 Post by rotor_speed » Tue Mar 13, 2018 5:56 pm

HIya all,
atm on my fresh 13b n.a weber 4 port Bridgeport balanced and clearanced high comp motor I am running a 51 mm weber which has been port matched to manifold.
I have changed the low down jet from 70 down to a 65 jet
just wandering if it would make low down drivabilty better by going back to a 48 mm weber instead ?
would I loose any hp by doing so ?,as I have heard that the 51 mm weber can make up 10 hp more on the dyno run tune ?
your thoughts pls ?
also r.e pre mix can you loose power by making the mix with too much oil ?
atm I'm running 250 ml per 20 lt of 98 bp fuel with motul 800 full synthetic oil while its still running in.
thanks in advance guys
cheers
Last edited by rotor_speed on Tue Mar 13, 2018 6:11 pm, edited 1 time in total.



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KYPREO
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Re: 48 MM WEBER VERSES 51 MM

#2 Post by KYPREO » Tue Mar 13, 2018 6:10 pm

I reckon you should have a read of this as it has a HEAP of invaluable info on setting up webers: viewtopic.php?f=16&t=75611

And these on 48 vs 51:

viewtopic.php?t=167260

And especially this: viewtopic.php?f=4&t=247704

Read Dazz's advice.

It's not just about the throttle plate size (ie 48 vs 51) it's also about the choke/venturi diameter. What chokes are you using?

In future please google your tech questions first and if necessary post further questions in an existing topic. This not only helps keep info in one spot making it easier to find, but also improves google search rankings for ausrotary also making it easier for others to find answers in future. This is for all tech topics and is one of the number one ways you can help this site continue.

Also follow the suggested topics in the "Similar Topics" section below.

I just googled "48 vs 51 weber 13b bridgeport" and the above posts were in the top 3 results!

Start reading and enjoy!


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rotor_speed
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Re: 48 MM WEBER VERSES 51 MM

#3 Post by rotor_speed » Tue Mar 13, 2018 6:11 pm

yeah ok then!



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Re: 48 MM WEBER VERSES 51 MM

#4 Post by green200b » Wed Mar 14, 2018 11:35 pm

Rotrvw,

You have been advised previously by several members to run with the 48mm Weber, mostly when you were still called rotrvw. But if that isn't enough, try following KYPREO's links until you get the answer you want.


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Re: 48 MM WEBER VERSES 51 MM

#5 Post by green200b » Thu Mar 15, 2018 8:12 am



green200b, aka Alistair

1981 RX-7 Sport, 12A turbo - daily
1974 Capella RX-2, 13B - cruiser
1982 Hilux, 350 Chev - tow vehicle and 4WD
1980 Datsun 200B - sleeping

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Re: 48 MM WEBER VERSES 51 MM

#6 Post by KYPREO » Thu Mar 15, 2018 8:39 am

There you go, i indeed gave good advice! The thing about advice is you can only give it. It's up to receipient of the advice to follow it.

Glen. To be honest i wouldn't change out your carb now. With a blank canvas a 48 is the way to go. Now you have invested, it's probably not worth changing out. You should look at your choke size though and see if they are too large.

If you want down low driveability a bridgeport is never going to be great.


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WTB series 3 RX-7 shifter boot in off black/grey

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