Building 2 Holley 660's

Lyonsperf

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I'm in th process of building two 4224's for a tnnel ram set up.
Got new billet baseplates and some 1850 metering blocks so I can add a power valve.
Any one got any advice on mods to do?
Been working on Holleys my whole life but these are abit different.
 

itey

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Why change base plates?

Do the 1850 blocks have flat or cupped plugs in the top of the main wells?
 

Lyonsperf

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The two carbs I bought off a guy on Facebook were in bad shape.
Both baseplates were beat up, with one converted to the gear drive on the shafts and the cam linkage cut away.
Allstate carb makes new billet bases for them, so I ordered a pair.
The new metering blocks I got have extra reinforcing on the jet side and have cup plugs in the top.
 

itey

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Do you intend to use the original 660 primary blocks on the secondary? If they are original 660 block they have flat plugs in the main wells with the E-tubes. The flat plug is a holder for an emulsion tube in the main well. It would be nice if you had old 1850 blocks which have the flat plugs with the tubes, so both ends of the carb have similar metering calibration.

The billet bases ..... many Chinese CNC beauties have too-wide and too-long T-slots. Original Holley slots are .026" width, some billet bases have slots .031" or more so they tend to over-fuel in the slot range of low power throttle position and this creates a problem with richness at small throttle opening where the largest percentage of engine run time occurs, so plug fouling is the result. BLP bases are the most true to the old-school OEM Holley bases which usually run the best.

The disclaimer "usually" is because some engines are outliers and whatever runs good is OK, but 99% of the time the too-wide and too-long slots are a problem for an engine that needs to run good in cruising such as on the street.

If you want adjustable curb idle on the secondary you see you will need to drill the intersecting passages in the body to connect the metering block face to the base gasket face. To use secondary curb idle the secondary idle air bleeds will need to be enlarged so it won't be so rich. It would actually be very acceptable to use the original metering plates. Just use the power valve blocks to replace the original primary blocks and leave the secondary be.

Don't forget to drill the vacuum passage in the body from the base into the PV chamber. Old 660s from the '60s and early '70s don't have that hole drilled but don't ask me how I know.
 
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Lyonsperf

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Thanks for the reply. I was planning on using the 660 primary blocks in the secondary, but one of them is not drilled for mixture screws!
I have a ton of old holley parts to dig through. I know I have the old 1850 blocks. I just thought I would start with a clean new set of blocks but they are different then what i'm used to.
This is gonna be a slow project as I already have a setup on my tunnel ram that will hold me over until I get these the way I want them.
 

itey

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Mounted straight ahead they don't need 4-corner idle. Sideways, it is best to have curb idle on both sides so both sides of the manifold are wet. If idle fuel is only on one side it has to be richer than necessary on the wet side so it is rich enough on the dry side and the over-rich wet side will foul plugs.

Root your bone pile for another pair of the 1850 blocks to match the pair you already have.

The new bases should have provision for near 1-to-1 linkage. If so, use power valves in both ends.

You will need to drill the passages in the secondary side of the body to connect the idle circuit through the body, from the metering block to the base
 

Lyonsperf

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Thanks, I plan to do exactly that. I milled the choke towers off the other day on the mill and plan to tap the bleeds so I can change air and idle bleeds.
I have a booster install tool, so i'm gonna change to annular boosters. One of the original ones is crooked.
I'll post updates on my build thread when I have some pics.
 

itey

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I would just straighten and tighten the original boosters. Not too sure annular boosters are a good idea in such small venturis if a factor in your purpose is best power because they will choke off a lot of air flow. They could be good for a street driving cruising deal where maximum power is not a primary goal.
 
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