recommend a jet size Holley 1920 slant six

[MCPObr44]

Hi guys

So I have been tracing down issues with my 1971 Valiant and going through the motions to get it where it's not a complete dog. It was super boggy and slow as a school bus, but I seem to have resolved all the issues and woke the car up. It would have helped if the timing hadn't been completely as far left as it could go btdc (yikes... but engine ok).

Anyways my question is now that I have the engine running right I would like to change the jet in the holley 1920. Currently it has a number 55 which I believe is what came factory in 1971... correct me if I'm wrong. Looking at my spark plugs tells me it's running lean, with a coating of frosting on each plug. So what jet size should I jump up to? Most people seem to recommend the number 58 jet, but I want to verify. The car is used on the street only.

 

[Aaron65]

I'm running a 1945 on my 225 now, but I had a 1920 on it at one time, and it seemed to like a 58 best. It's hard to tell lean or rich by spark plugs anymore (modern gas doesn't color the plugs like it used to). Jets aren't too expensive; I'd buy a 57 and a 58 (they come in pairs, unfortunately) and give them a try.

 

[MCPObr44]

Update

So I threw a 58 in there and WOW it really likes it. Now it can actually spin tires on dirt, which was impossible before. It's still got a weird bog on acceleration when it's cold but besides that the car is running a lot better. Now I just have to figure out what's with the bog and what that 2 inch flexable pipe is coming up to the air box, and I think I will be dialed. I suspect my issue might lay in a fuel hose somewhere with a crack in it, because the fuel filter refuses to fill completely.