Skimming the head of a late style 56cu in ?

LittleCharger · **Joined:** April 1st, 2012, 12:29 am **Posts:** 1445

phillnjack wrote:

the oval port 70hp carbs are the way to go on the oval 56, they let through more juice than the Bridgeport carbs.
I spoke to a few people who had tried the Bridgeport large bore and they were better than the 60hp oval port, but NOT as
good as the 70hp plastic top carbs from the proper 70 oval port.

i hope to have a good run with mine in the next few weeks and will report my findings with these bigger carbs.
what i am hoping for is about an extra 400to 500 rpm top end with more punch in the lower and mid-range using the same prop
that i was running with the 60hp carbs for testing.

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What size Venturi are the 70hp carbs?

phillnjack · **Posted:** February 8th, 2016, 8:12 am

1 1/2 for the big bore 70hp carbs.
exactly 1/3 larger than the 60hp versions.

make sure you measure at the back , as the fronts are both the same size.

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LittleCharger · **Joined:** April 1st, 2012, 12:29 am **Posts:** 1445

phillnjack wrote:

1 1/2 for the big bore 70hp carbs.
exactly 1/3 larger than the 60hp versions.

make sure you measure at the back , as the fronts are both the same size.

.

The 1 1/2 is that not the throat of the carb? and not the venturi?

phillnjack · **Posted:** February 8th, 2016, 8:29 am

yes that would be the actual bore at the back of the carb not the bit in the centre.
But you will see a massive difference in sizes of the venturi in the middle of the cars, its a huge difference of atleast 1/4 inch.

I did have everything wrote down , will try and find this for you.

phillnjack · **Posted:** February 8th, 2016, 8:43 am

this is a picture showing the 60hp carbs on the engine with front of airbox removed .

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this pic shows both the 70hp on left and 60hp on the right. both front on pics to show venturi differences

.

LittleCharger · **Joined:** April 1st, 2012, 12:29 am **Posts:** 1445

Curious on the Venturi size of the 70hp carbs, I suspect the Venturi is the same as the bridge port 70 carbs which is your limiting factor on what's gonna go through them

phillnjack · **Posted:** February 8th, 2016, 8:36 pm

from what I have noticed the venturi is a touch bigger than the bridgeport carbs.
you get more fuel /air flow than Bridgeport carbs.

maybe they can be found easy in Canada and usa, but here they are like gold dust to find.

LittleCharger · **Joined:** April 1st, 2012, 12:29 am **Posts:** 1445

phillnjack wrote:

from what I have noticed the venturi is a touch bigger than the bridgeport carbs.
you get more fuel /air flow than Bridgeport carbs.

maybe they can be found easy in Canada and usa, but here they are like gold dust to find.

Do you not own them???

phillnjack · **Posted:** February 9th, 2016, 8:53 am

yes I have the oval port carbs now fitted on my engine.

it took me over a year to get a set, then I found this site.
I managed to buy them off a very helpful member of this forum.

all the pics of carbs ive put on are my own carbs both 60 and 70 versions.

LittleCharger · **Joined:** April 1st, 2012, 12:29 am **Posts:** 1445

Well when you get a chance perhaps you can measure the venturi on the 70hp ones, most racers say they don't see any difference between the various versions of the 70hp carbs, a part number of those ones would be handy for guys as well.

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Skimming the head of a late style 56cu in ?

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