The Stovebolt Site Forums The Shop Area Engine Shop Allow me to eat some crow

Sometime back I converted my '38 from oil bath to dry paper air filter. My belief was, and still is, the paper filter does a better job of filtering. What I ran into yesterday evening led me to the conclusion that there's more to that equation than just better air filtration. Three times now (twice last night) the '38 succumbed to the proverbial hot hard start problem while lining up for a local parade. Once while lining up then again a bit later when I had to move to a different staging area. Considerable cranking led to a complete no fire situation. I know the points are set right, the timing is good and I had a half tank of gas. Running out of ideas I pulled the top of off the air filter to allow better air flow. Bingo, she started right up. After the second time I left the top off for the parade. I just came in from putting the oil bath insert back in the housing and oiling everything up. I've been a staunch supporter of running a paper filter because of the better filtration. However it appears another part of the equation is air flow. The paper filter doesn't have many miles on it and it's not dirty enough to change BUT it seems the restriction caused by the better filtration plays a hand in not allowing enough air flow to compensate for the rich hot start environment. If you're considering converting to a paper filter you probably need to consider air flow as well.

Know what you mean.
Too much air is possible as well.
I accidentally "solved" a lean tip-in problem on my Buick 455 with Quadrajet (which the PO had equipped with a 14" Moroso open filter). I put an original Buick filter can in place with the same filter, and the restrictive "snout" air entry increased the tip-in vacuum just enough to fix it (the primary throttle is larger than the snout ID).
The original Buick (and everyone else) cold air door selector prevents WOT from going rich, opens only at hard throttle or high underhood temperature.

I like to post this link for air filters by size, http://www.wixfilters.com/lookup/FilterBySize.aspx , not all, but most list the CFM of each filter. Air flow or lack of, is very important as you have found out.

I have a paper filter. The truck seems to run lean at high RPMs (smooths out if i pull the choke out slightly). I'm waiting for the filter to get a bit dirty to see if it runs better.

.How does it run without a filter? That should be the baseline for which to compare filter type performance

Good idea to test without filter; I expect that it would run leaner. Maybe I should try throwing a rag over it!