Just thought I should let ya'll know what I learned from the dyno. Just had my new 509ci HP500 carb built and dynoed by Bruce.

The only real standout was flame arrestors. My eyes are now opened!

results: only changes here were what's on top the carb

Velocity stack(hat) 565hp@5400

stock(8"x3") HP500 flame arrestor 544hp@5300 -21hp

Gaffrig (8"x5") SS screen arrestor 557hp@5400 -8hp

K&N (9"x5") K&N element 565hp@5350 -0 hp

I will be using the large K&N filter arrestor!!

I don't have dyno sheets in front of me yet. As soon as I do I'll post more results.

Thanks, Eric

One thing I should add....the Gaffrig and the K&N both had a slightly raised base plate that had a "bell" style flange. I think that is one of the contributing factors here.

The stock HP500 arrestor didn't have any type of "bell". It just sits flat on the carb flange. I think that really disturbs the incoming air. The other factor is size. The stock one is just too small.

Eric

Pretty interesting numbers there Eric. Cool.
Looks like the K&N gave you the same HP as the open stack, but at 50 rpm less. Hows that? Be curious to see what the torque numbers were with those changes.

Wonder what my Gaffrig 10x3 arrestor is doing? We only ran the stack when we did mine.

Jerry

Thanks for posting the numbers. I hope to have Bruce build some motors for me next season. I'd be curious if there is a difference between a round K&N and an oval one. Some of these oval billet air cleaners are sweet looking.

Dan

K&N also makes a an air horn for the 4150/4160 style Holley. I have one mounted under my K&N flame arrester. I wondered if it is actually doing any good or harm. Any have dyno info on them?

Tom Earhart has done simular tests and only saw a 3hp differance' that was between a large K&N(with a stack) and no cleaner at all. We pulled SuperV's with the real ****ty looking plate type flame arrester like comes on a 7.4 and it made as much HP as nothing but a large velocity stack, we did'nt have a K&N along for comparison but it would have been interesting....
Don

i wonder how the stock flame arrestor with only the last screen mesh in works?

Dredge, We did remove all but the last layer of mesh from the stock HP500 arrestor. It still had the 21hp loss. Anybody want to buy it??

I think the difference between a round and an oval would be not much. I think Im going to order a K&N custom 66 oval. The one with the flames. With 5" element hieght.

The #'s on the big Gaffrig and K&N were given to me by Bruce over the phone. I'll get more details when I get the dyno sheets.

Jerry, Id say that your 10" x 3" is costing you some hp. If you have room maybe get a taller one. As for the 50 rpm, I don't know.

talk more soon! ERic

One of the automotive mags recently did a comparison between the different sized K&N filters. They were all identical in HP-virtually no loss. I think that K&N's size recomondations are bases off of a dirty filter. Because marine motors don't really suck dirty air, you can get by with the smallest of air filters.

Are those numbers back to back dyno pulls...same day, weather, etc. ?