^^^^^ And engine builders using them thats even worse.

Any thoughts on the M1-601? It's a crate 502 and I put the Hardin bulkhead on it with the HP6 threads but all of the HP6 filters I've found are 4-5/8" which leaves half the seal unsealed as the bulkhead base is only 4" across. The M1-601 is thinner and should fit nicely.

It does have the internal bypass and I can't figure if that's a good thing or not. The relief valve on the block pad is the heavier mercruiser unit but not blocked off.

Never mind. The M1 filter has the wrong thread pitch.

If you have the room Wix/Napa offer an extra large oil filter for SBC./ BBC engines. It is known as a truck filter, a hair over 8 inches long, more flow and filtering ability. Wix # 51794, Napa Gold 1794, and a racing version is also available from Wix under part # 51794R, but be warned the racing version has a much higher micron rating. While that does allow a slight increase in flow, it also allows slightly larger particles to pass through the filter media. Recommended for racing only with frequent oil and filter changes.

I put System 1 filters on EVERYTHING I build! Last filter you will have to buy!

WIX 51060 or WIX 51060R???? The R filter flows 28 GPM but only filters down to 61 micron whereas the OEM Mercury filter would appear to be 8 GPM flow and 10 micron filtering. Based on this, it seems to me the 28 GPM flow is way overkill and you're trading off tighter filtering for it. The specs of the WIX 51060 are in line with the Mercury filter. Would that be a good choice? Any insights appreciated!

100% would recommend the Wix filter. Have used them on everything from combines, semis, and boats. Very quality product.