Rochester Carb Difference?

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jimrob
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Rochester Carb Difference?

Post by jimrob »

My '64 Monza has different Rochester carbs. One is a 7024024 and the other is a 7028005. I am told that the same rebuild kit fits both. I also find that the 7024024 is called a "high performance" carb, but can find nothing about the 7028005.

:dontknow: Also, the Rochester carburetor manual shows that gas should flow from the four little arms of the venturi as well as from the center. But, on my 7024024 these little arms are not drilled all the way through, therefore fuel cannot flow through them.
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toytron
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Re: Rochester Carb Difference?

Post by toytron »

Can you give good detailed pictures of the venturi cluster (I believe that is what you are referring to)? I pretty sure they made a couple of different ones across the years of corvair configurations.

Image

Ed Stevenson

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Scott V
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Re: Rochester Carb Difference?

Post by Scott V »

jimrob wrote: Mon May 01, 2017 3:52 pmthe Rochester carburetor manual shows that gas should flow from the four little arms of the venturi as well as from the center. But, on my 7024024 these little arms are not drilled all the way through
yes......the little arms should be drilled all the way through.

maybe theres some corrosion or dirt in your cluster?

-Scott V.
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toytron
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Re: Rochester Carb Difference?

Post by toytron »

Sorry I miss read your original post. Yes there should be holes going through. You might want to soak them in some carb cleaner. I usually use the gallon of chem dip for that but you could try carb cleaner in a small container and soak it over night to soften up whatever is clogging them. Then blow them out with cleaner. Make sure you wear protection because that spray had a way of squirting back at you.

Ed Stevenson

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66vairguy
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Re: Rochester Carb Difference?

Post by 66vairguy »

Buy Bob Helts Rochester HV carburetor book. The carburetors were revised almost every year and his book shows how to spot the differences and rebuild them. Clark's Corvair sells it, as do others.
jimrob
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Re: Rochester Carb Difference?

Post by jimrob »

Reply to all, My problem was that the cluster tiny holes were plugged up with crap. I had a heck of a time cleaning them out.
66vairguy
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Re: Rochester Carb Difference?

Post by 66vairguy »

Glad you got it working. Those clusters only have a casting number on them, NO part number. There were a lot of variations!

Years ago Bob Helt with a lot of help from others tried to determine the different cluster types via the hole sizes supplied from Chevy documentation and found the holes difficult to measure or group!!

There was a person in the local club that had about four dozen carburetors THAT HE DISMANTLED and put all the common parts in boxes - so all the clusters were in one box and impossible to determine what fit what!!! A sad loss of a lot of carburetors.
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Rdhog99
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Re: Rochester Carb Difference?

Post by Rdhog99 »

My experience with carburetors on Covairs is that a matched set can make a significant difference. Both banks of three cylinders will be better balanced for the smoothest running. Engine temperature on each bank is influenced by rich or lean mixtures. Not only that the carburetor part number be matched but it is common for these 50 year old carburetors to have mismatched parts or have been modified in the past. I found Bob Helt's book on identifying HV carburetors invaluable. Information in Bob's book even shows some of the small differences in carburetors of the same part number, but were used for different engine models. Automatic vs manual can have small differences such as the idle jet. Attention to these details can make an engine run just as it did when new.
cnicol
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Re: Rochester Carb Difference?

Post by cnicol »

7024024 and the other is a 7028005

7024024 is a '64 110 carb

7028005 is a '69 carb (all primary carbs) and a '68 (partial application primary carb)

Both are based on the same basic carburetor (hence the same repair kit) but their calibrations are completely different.
'61 140 PG Rampside
'66 Rear Alum V8 4-dr
'60 Monza PG coupe (sold, sniff, sniff)
'66 Corsa Fitch Sprint Conv. (First car 1971, recently repurchased)
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