Best Headers
 

Hi there,

i know its a question that all of you hered but but i am going to ask it again!

Which are the best headers out there for 502mpi v-belt ??

just saw these : http://www.cpperformance.com/product...t-headers.htmc

The better question is...how much do you want to spend? and is it worth it to put on an MPI. You are looking at pricey stuff for a low performance motor.

i know, but thats what i have ..........wish had a 1650 :-)

so what you recomend as headers that are high perfomance ?

I would use a good aluminum exhaust, Dana marine, Stainless Marine.. Even the new exhaust that merc uses on the the 496 and 502 base engines flow pretty good..

yes i saw it there is a kit with exhaust Dana,MSD distributer and K&N liked it ..............anyone did this mod ?

My father went with the Gil headers, plus the K&N mod. He had bought the Dana exhaust which I liked but had to return the Dana headers because the bolt pattern was not accurately machined/drilled. Left and right motors below (the blocks are now Dart 540 cu.in.). You might gain a few mph then you will need to sort out prop(s) (add cup or go larger) and have your ECU reprogrammed. The motors kept the Mercury 502/415 cylinder heads, mild cam, 87 octane motors, 520 hp on Innovation Marine dyno, 90-92 mph, no reversion.

Don't waste $$ on MSD. There are plenty of engines up to 800 hp running GM HEI ignition.

JRider is correct; your best bet is to look for a better ready-to-go engine and sell yours as an unmolested take-out...

so if i do the Dana headers and K&N maybe i go 5000rpm because rite now i am doing 4200rpm and speed of 60mph with my Scarab 26 (prop 25)

I do not think your optimistic performance gain is realistic, maybe 200-300 rpms, maybe....someone on this board has made a similar mod to what you want to do, and will be able to give a more accurate answer. My reply is only a guestimate....

i see that you put a mild cam on in it ..........can you tell what cam it is ?

look at imco call Dave talk to him

Something you should consider is, if you are only spinning 4200 rpm at full throttle, you are over-propped by quite a bit. Getting to the right prop will help your performance aspirations in and of itself.

I have been looking for the cam specs, when I find them (if I find them I will message you)....

x2

So true! The boat should be running at 5 grand now before any mods!

I installed cmi's 454/502 etops on my fountain. They are advertised as a direct replacement for bravo equipped boats.They are a nice piece, and reasonably priced around 3,000/per set. I had a few issues getting them to work with my merc silent choice and some plumbing/fitment issues but the support I got from CMI was well worth it.

Loved my IMCO Powerflow's on my M3 502! They sounded great too.

KE wil out perform a header,,also eddie marine makes a good set..they are anodised so they will last a long time..

4200 ..... yup something deffinately out of whack .

If your motor is stock, do a bigger cam also. Full length headers work better with cams that have some overlap which allows scavenging.

i agree with you all, i just bought this boat from miami and i live in Malta Europe!!
the mechanic here told me that it has volvo penta headers on it and these are differnet from the merc they are restricted when compared.

that is why i am not changing the prop for now. i will do the headers and K&N filter (maybe a good cam)

also i have the fuel regulator disconected and the pipe that goes in it is blocked . any one know why they block this ?

i agree with you all, i just bought this boat from miami and i live in Malta Europe!!
the mechanic here told me that it has volvo penta headers on it and these are differnet from the merc they are restricted when compared.

that is why i am not changing the prop for now. i will do the headers and K&N filter (maybe a good cam)

also i have the fuel regulator disconected and the pipe that goes in it is blocked . any one know why they block this ?

Bingo, they are the best, but not cheap. I have (2) new sets that I saving for my monster motors build......

K&E's do make POWER!
http://www.diamondperformanceparts.com/home.php?cat=282

And sound absolutely amazing!!!!

Diamond P is making them now, not KE.

Don't waste your money anywhere else...this is it, hands down.

Don't think my neighbors on the canal would agree about the amazing sound part :), They are a bit loader than most headers also, but that is part of how they make so much power! I put Shotgun mufflers on my last set and didn't lose any speed....

If they used 454/502 Volvo exhaust manifolds I can't see them being too restrictive.

Now, the unhooked regulator on the other hand could be causing the engine to run too rich. In turn losing power and rpms. Hopefully someone that knows more will chime in.