largest choke size in their IDA 48

[priobe]

I am curious as to if anyone ever tried large bore chokes on their BB. There has been many threads stating that the BB ford should be using the Gene Burg IDA systems, or the TWM system because of the larger bores in their bodies.

According to some readings to size the choke, one should use a choke that is 20 % less the intake valve. So in the FE case I believe the largest intake valve is about 2.19. So converted to mm this gives you 55.6 mm.

Now minus 20% = 54.513.

So the correct choke size should be 54.5.

I was thinking of ordering 46 mm choke to try in my car (when it comes back from painting).

However, they say it will be difficult to tune with such a large choke. But if this is still on the low side of the choke why would be difficult to tune. I understand the vacuum signal will be weaker but if I were to use the Gene Burg units it will be even harder to tune.

Your thoughts

[carmine]

Priobe you have an error
55.6 minus 20 percent = 44.8
Also it's the angle created after the small or choked diameter
that plays such a large roll in creating a signal at the nozzel
As you bore your choke larger and the main bore stays the same
in the case of the 48ida it's 48mm, the angle gets reduced.

This is why the 58 bergs were made, to keep that angle near it optimum
thus giving a good signal at nozzel and more air flow to satisfy a large bore big block.

Rule of thumb you don't want to have less than a 6mm
smaller choke than main bore diameter
eg; 48ida - 6mm = 42mm choke dia
any larger than this and angle on choke is reduced and signal
on main nozzel is reduced which will make it hard to reduce the big flat hole created, unless your running WOT all the time.

[priobe]

Thank you for the correction and the great explaination.

Has anyone tried these bigger chokes on our motors or is this all off of theory?

[Gaz64]

A book of mine states the following for individual runner intakes:

Trumpet/carb bore equal to inlet valve size.

Intake runner to match carb base and taper down to 85% of the inlet valve size in the valve pocket above the valve seat.

Venturi equals 85% of the carb bore/valve size.

[Tom Kirkham]

You might want to check out:

http://www.empius.com/2009_catalog/empi2009_pg83.html

[Stentor]

Tom,

Thanks for posting the link to the EMPI 51 mm carbs. I know that Inglese offers these as part of their induction systems. I am getting ready to switch to webers on my car and was considering these 51 mm carbs from EMPI instead of 48 mm Webers (to provide a bit more flow and top end for my bored and stroked FE).

However, I am not familiar with EMPI and was told that these carbs are made in China--which makes me a bit nervous about putting them on my car.

Is anybody familiar with or used carbs from EMPI?

Thanks,

Stentor

[dlampe]

I have 45's and 42's on the shelf in the garage. I have used them in the past and they worked great on big blocks or high rev small blocks. Let me know if you need a set.