1984 and 1986 Carburetors for Z24 Engine

[Sephakrid]

I've been spending a bit of time learning about the Hitachi DFP384 carburetors so that I can swap in a replacement if my current one starts to have issues. It turns out there's quite a few varieties out there! Here are the pages from my 1984 service manual and a screenshot of a 1986 manual that someone scanned.

 

1984

 

1986

 

Unfortunately the ID is just an ink-stamped thing on the fuel bowl.

 

Anyway, I'll probably make some more posts as I start taking this thing apart. Grad school apps are finally finished so I have some time to work on 720 stuff!

[datzenmike]

I notice the California has the smallest primary jet sizes at 94 while Canadian and heavy duty are 110 and 111. This would run much leaner and lack power... good for economy and emissions though.

 

My car is or was from Nevada which has an average altitude of 5,000 feet. The jet in it was in the high 90s to match the thinness of the air but I'm literally at sea level. It ran good but I got a local carburetor and was surprised to find it had a 112 jet!!! I swapped it just to see and the results were noticeable on the ass dyno. Thicker air needs more gas. It made more power (when needed) but also got better mileage.

[DwayneOxford]

Life's always better when properly fed.

My son took off for CA in his S-15. He'd installed a performance chip. Bypassed altitude compensation, had trouble getting over Rockies. 

[DwayneOxford]

 

"Unfortunately the ID is just an ink-stamped thing on the fuel bowl."

Soak in carb clean obliterates that.

Edited December 2, 2023 by DwayneOxford

[None_zero]

On 11/30/2023 at 11:26 PM, datzenmike said:

I notice the California has the smallest primary jet sizes at 94 while Canadian and heavy duty are 110 and 111. This would run much leaner and lack power... good for economy and emissions though.

 

My car is or was from Nevada which has an average altitude of 5,000 feet. The jet in it was in the high 90s to match the thinness of the air but I'm literally at sea level. It ran good but I got a local carburetor and was surprised to find it had a 112 jet!!! I swapped it just to see and the results were noticeable on the ass dyno. Thicker air needs more gas. It made more power (when needed) but also got better mileage.

I never considered this. As you know I took a shot in the dark and ordered the carb off Amazon. Though it seems to be working pretty well. Gas mileage doubled from 9mpg to 18-20mpg but I have no idea what the jet size is 

[Sephakrid]

I finally had some time to start taking the spare carburetor apart. I was mostly interested in seeing the inside of the B.C.D.D. Here's a gallery that shows the inner and outer diaphragms as well as the bypass air control valve and vacuum control valves:

 

https://imgur.com/gallery/TLYRhJg

 

The outer diaphragm was in surprisingly good condition, and seems to be made out of soft fabric-reinforced vinyl (wild guess). The inner diaphragm looks to be made out of some kind of rubber.

 

 

[datzenmike]

Often the idle hangs up and won't return and among several causes is the sensitivity setting on the BCDD. Turn the screw counter clockwise to dial it back.