Actual performance data for exh upgrades

[northern baja]

I've got a 350 that will grow when its overhaul time and would like to upgrade my exhaust.
My starting point is 1995(pre-Vortec) 350 MAG mpi with quick-n-quiet exhaust in a 21' Baja.
Do I need to upgrade? Dennis Morre sells some good looking mild performance replacements from GLM for around $500. I see alots of ads, but few offer performance numbers or data. Many outfits offer aluminum manifolds in the $800-1100 range. whose best? Is it worth it? I wouldn't be happy if I spent the money and time to install and ended up with no real gain.
Anybody seem a tech article or comparison of sb exhaust?
:confused:

[HP350SC]

You will see little or no improvement doing exhaust manifolds only on a stock 350. If you're dead set on changing, Stainless Marine is the best value IMO. Check [URL=cpperformance.com]. If you want to go faster, one word...SUPERCHARGER!!!

[powerplay230]

OK how about if going from base 454/330 to 502/415 using same thru-hull's from Merc. Wish there were more tests on such...I only picked up 300 Rpm with same prop with Bravo I?
Rick

[HP350SC]

Originally posted by powerplay230
OK how about if going from base 454/330 to 502/415 using same thru-hull's from Merc. Wish there were more tests on such...I only picked up 300 Rpm with same prop with Bravo I?
Rick If I'm reading this right, you replaced the 454 with a 502 and are running 300 rpm more. What was before and after rpm? If it's accelerating faster you need to go up on prop pitch. I would also say you would benefit from better manifolds.

[powerplay230]

With new motor about 4400rpm verifed by teck with dwell tack, before hand 4200rpm. Out of hole slightly better, cruising at 32-3500 Much better. Onlly thing I am worried about is using same spark box (?) which with the additional initial timing seems just fine. run 92 Gas...
thks,
Rick
:confused:

[HP350SC]

Should be around 5000rpm. I suggest you put all information about boat on here and see what we can suggest. 23 v-hull?cabin? Need to know drive ratio, prop style, pitch, total timing, carb. size etc.

[gnarley]

Originally posted by HP350SC
Should be around 5000rpm. I suggest you put all information about boat on here and see what we can suggest. 23 v-hull?cabin? Need to know drive ratio, prop style, pitch, total timing, carb. size etc.
And don't forget to say what the MPH is at what RPM's

[powerplay230]

Reccomended- 52-5400? I need to do some homework-
driive ratio.... Here's what I know= 23 foot boat with cuddy 23 degree deadrise, Bravo 1 drive with Bravo )21 prop).. Engine is a Mark IV rated at 450 Hs at 6 or so. And I may have left off-
Using a stock Mark IV ignition from the "Mark IV enginees.. whhich I think is liimiited at 45 or 4500?

[canuck1]

Originally posted by northern baja
I've got a 350 that will grow when its overhaul time and would like to upgrade my exhaust.
My starting point is 1995(pre-Vortec) 350 MAG mpi with quick-n-quiet exhaust in a 21' Baja.
Do I need to upgrade? Dennis Morre sells some good looking mild performance replacements from GLM for around $500. I see alots of ads, but few offer performance numbers or data. Many outfits offer aluminum manifolds in the $800-1100 range. whose best? Is it worth it? I wouldn't be happy if I spent the money and time to install and ended up with no real gain.
Anybody seem a tech article or comparison of sb exhaust?
:confused:
I'm not familiar with what exhuast you have now,Are they logs or center risers? I have tried several different types on my last 2 boats, both small blocks.

[powerplay230]

Sorry left off speed- low 60's depending on upwind or downwind, also Edel' carb -#1410? 750 with 1" spacer and I think without looking a world products manifold which was highly recommended by local engine guru (Hencke at Force 10).. I know engine is rated by Merc at 5-5200 @ 415 Hsp..left weight off at 4200..