Engine
before

509
stock 088s
cam Cam, gen6 roller , 570/580 with 1.7rr [email protected] 230int 236exh 114lsa
springs 1.540 dia 140lbs at 1.940 and 425lbs at 1.250
Weiand 256 , twin 750s, stock pulleys , showing 5psi at 5000rpm
stock thunderbolt ignition with V6 module
Drake aluminum headers, dry to the transom " 4" tips
AEM wideband with O2 sensor 3" from collector
12.5 A/F at 5psi 5200rpm WOT
picked up ten mph from HP500 so I am guessing 600hp?


now
540"
Merlin cast iron Grumpy Jenkins , 345cc
everything else same..

Dropped a valve seat which took out heads and pistons, so i am not doing this
to make more hp just to get it back on the water but would still want to know what to expect.
I know my boost reading will probably drop to 3-3.5 psi but that doesnt bother me too much,
I wont be stepping up boost because of lack of intercooler (wont fit under hatch) and fact this blower would not be reliable at higher levels.
I am thinking torque will go up by 50lbs due to extra cubes but hp will stay same.
Yes?No? What the hell?

You should see a nice gain, how much, hard to say. Of course the blower is pretty small.

Is there any specific reason you tuned to 12.5 with the wideband with a blower? Most marine blower guys tune to low 11's. I wonder if that contributed to valve seat failure. Or maybe not enough timing?

The added cubes will net you more than the heads and as its already been said your boost level will probably drop slightly and you may have to speed the Wieand up a bit to get back to that boost point and it's a small displacement unit for that. Modify the hatch and make room for an intercooler, make sure an intercooler is sized for the added heat of a harder working blower as air temps on inlet mixtures will be a real critical item to making more power. In any event it will make more power. Best of luck with it!

Best Regards,
Ray @ Raylar

I didn't see if these heads are ported or not. I have a set that are ported and for a design that's 15 years old...I feel they flow fairly well at 363 / 282 @ .700 lift. I have read that these heads respond quite well to porting. The guy that flowed my heads was a little concerned with the intake to exhaust flow % being at 74.3% (stock % is mid to low 65%) but I've been told that with a blower app. it's not as critical as it is with a n/a app. Hope some of this info may help in some way. Mark

thanks everyone,honestly wasnt looking for a big gain right now,
I was happy with power it already had, just figured if I had to redo it might as well step
up the parts for the future.

I did not think I needed an A/F of 11 for such low boost levels?

Heads have blended bowls, polishing, and port matched,nothing fancy.

I will be leaving the blower alone as far as pulleys,if I lose boost that is fine,
I know that the 575 uses same blower and there guys pulling 650-700hp out of those,
More than I need at this point, I need to start saving for drive upgrade before I make too much more power!

You really need more cam to make that engine come alive.

I think you will only see about a 5% gain in power. The heads will flow more, but the blower was already compensating for for the 088's by forcing air through. Boost pressure will probably drop with the increased flow, so you could go with a smaller pulley and make some more power that way.

not really looking for more power, Bravo is at limit as is. Thats why I am not pullying up blower.
5% would be fine by me with my current setup.
considering I gained 10mph from a HP500 im guessing I was around 600hp already.
Im thinking 635-630hp now but at a lower rpm?

Yes, peak torque and hp should drop a couple hundred rpms.

Did you already purchase the heads and hardware? I have 2 sets of Grumpys I'm taking off my engines in the next couple of weeks. Set up complete with 2.30/1.88 valves, spirngs, 10* locks/retainers. About 20 hrs on both sets. $1200 OBO each pair.

yup, bought them off swap shop here, $950 complete including shipping.