Rock10 Posted May 1, 2022 Share Posted May 1, 2022 In the ongoing journey to get the car back on the road, we decided to replace the fuel pump with the correct AC421 model. I was hoping someone could identify the one that was on the car. The only number I can see is 529. 1 Link to comment Share on other sites More sharing options...
Jolly_John Posted May 1, 2022 Share Posted May 1, 2022 The "529" is the AC fuel pump number. The 529 fits 1940, 1941, and 1942 BUICK series 40 and 50. ALSO, it likely fits up into the early 1950's same models, but my parts book doesn't go that new. John 2 Link to comment Share on other sites More sharing options...
32buick67 Posted May 1, 2022 Share Posted May 1, 2022 The 529 pump was used on these Buicks: 1934 Series 40 specs: 2 Link to comment Share on other sites More sharing options...
32buick67 Posted May 1, 2022 Share Posted May 1, 2022 2 Link to comment Share on other sites More sharing options...
Rock10 Posted May 1, 2022 Author Share Posted May 1, 2022 Thanks 🙂 Link to comment Share on other sites More sharing options...
Dave39MD Posted May 2, 2022 Share Posted May 2, 2022 That pump looks a lot different than the 421, are you sure on the year of your engine? Dave Link to comment Share on other sites More sharing options...
Rock10 Posted May 3, 2022 Author Share Posted May 3, 2022 Misunderstanding. We bought a rebuilt 421 for our car. The pump pictured is the one that was on the car when we got it. I was trying to get some info on it. Link to comment Share on other sites More sharing options...
Dave39MD Posted May 3, 2022 Share Posted May 3, 2022 No misunderstanding, just hard to see how the 529 would work with that arm where a 421 should be. It may be the angle of the photos. Dave Link to comment Share on other sites More sharing options...
Rock10 Posted May 3, 2022 Author Share Posted May 3, 2022 Can't explain that. One runs on the bottom of the cam lobe, the other on the side. It did work. We just wanted to proper piece for our car. Don't know if the vacuum part works because we didn't use it. Link to comment Share on other sites More sharing options...
Bloo Posted May 3, 2022 Share Posted May 3, 2022 (edited) There was a long thread about something similar a while back but it was involving 1938 Buicks, not 1936. Apparently Buick changed the pump as well as the flange it bolts to. The car presented with the wrong version of the pump, mounted upside down because apparently that was how it could engage the cam, leaking oil because the flange was backwards. Edited May 3, 2022 by Bloo (see edit history) Link to comment Share on other sites More sharing options...
Rock10 Posted May 3, 2022 Author Share Posted May 3, 2022 Wow. Ours was mounted with the vacuum side up. Seemed to work OK. We do wonder if it was the source of our knocking noise. Link to comment Share on other sites More sharing options...
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