I also stopped to pick up stock TB from a friend, he has the restricrive kn adapter, he had no tools at all to get tb off boat so im going back over later but will be paying gimmefuel a visit too!!

Here's my two cents on the K&N filters that dbkski posted pictures of. Back when I was playing around with my 502 MPI's trying to make cheap horsepower I used one of these filters. It took 3 mph out of my 32 Sunsation. Took awhile to figure it out. The stock tb on a 502mpi has the bores spaced 5+ inches apart out to out. When you put a filter adapter on with a 4inch round opening, and yes that's the one you get from K&N you are restricting the air coming in from the two outside edges of the tb. Making things worse is that at wide open throttle the throttle plates are actually protruding into the filter adapter by 1/2 the width of the diameter of the plates, further restricting the air when you most want it. Pull the filter off, leave the adapter on, and look into the intake with the throttle wide open and you'll see what I mean. Oh, and do this with the engine off. he he. Moral here is, don't use a round adapter on an oval shaped intake.

I completely agree, i have the good non restrictive one iny possession and am picking up thr restricted looking one in morn so i will test both and post this week

X3

Here is a pic of the "good" kn air filter flame arrestor that obviously tyler crockett designed I picked up from gimme fuel today. I'm hoping to see a near zero hp drop with it with the biggest 58 mm TB

It has over 100 sq inches of area not including the folds and entry piece is a nice oval. I also tried this entry piece designed by SB friday on the 566 mm tb it matches and it seemed to lean motor out, hp did NOT change. I added fuel and hp decayed slightly, I leaned it out further and hp decayed also, I was surprised I couldnt find a gain anywhere. I will be testing stock TB with restrictive flame arrestor, good flame arrestor , no flame arrestor then switching back to 58 mm with good one too.

That brings back memories.

When your done, you can make like DM and DV and write a book on these motors. LOL.

Funny thing Scott is once this 502 is dynoed, installed in my old boat and gone I will probabaly never have anybody ask me to build a MPI motor or dyno/test or suggest any of these parts combinations again LOL since its been 15 or 16 years since one was sold! I'm doing all these test because these questions come up time and time again. Back when I made 12 more hp on my 540 on Crocketts dyno with my modded 56mm TB I spent the money and had 2 spare throttle bodys bored out to sell on a exchange basis. Guys talked about buying them, called me, pm'd me but here 10 or 12 years later they are still sitting on my shelf. Its on dyno though and I'm always in the quest for info. I will guess right now that w stock throttle body and ****ty gen 6 style flame arrestor motor wont break 500 hp as its down to 510 with the biggest TB and gen 6 flame arrestor, I also bet the round one sold by azsm that is on many boats will dyno pretty low too, especially once big TB goes back on, the dyno doesn't lie, I will post my findings sometime this week, hope to be dynoing tomm afternoon but I have to go climb in a boat full of black mold, raccoon shiit etc to rob the stock TB tomm when I get up, THATS going to be FUN!!

these flame arresters can be a joke, years ago did a 489 w/ 177 blower, had this nice looking eddie marine arrester, 1st time out made 0 boost, was checking everything, talked to Tom @ wieand, told me to take arrester off and run it...made 6 psi, had fairly tall 9" K&N's on my gibson, tried one of those made 5.5, unreal what a difference they make, I am sure the blower deal made much worse.

You don't plan on doing anything with a 100% stock intake, do you? That is what I would really like to see the difference, is it worth it for me to pull my intake and mill the runners? All the information thus far is great!