Dart 308's out of the box no portwork

Yes that is on the dyno.

hmmm wonder what the flow test comparison is between those and magnum rectangle ports is? I can say that these cams adleast sound fkn kick ass at idle ; ) I think that I will port the heads, manifold, and a set of 496 manifolds and call it done. That is more work that I was thinking of doing but valve guides could use replacing and rest is just port work. I would think that would kick me into 70mph level but if not maybe just be happy and put the money into gas; )

keep in mind the Darts have the raised exhaust ports and are
2.25 intake valves compared to the 2.19

stock rectagle ports will make good power ported though!!!

Rec Heads
 

Al ittle off subject but...I found two mag motors with both motors having bad rods...
Its a gen IV with rectaglar heads. intake shot as with eshaust.
I have a pair of stock non mag motors which I would like to beef up upper end. The long block has 50 hours on it, but I beleive remains non forged internals. My mechanic thinks the cam is beefer but cant confirm. Its a 292 1988. I plan to purchase aftermarket Exhaust. My intakes are new and carbs just rebuilt. My heads are mismatched. One is small oval peanut, the other is lage oval. the boat still runs in its specs range. Will porting Rec heads make nay differnce? Will it need a new carb/intake to get the max out of the hp? Will the internals really brak down. I run it hard 20-30% of the day.

That bottom end is good under 5krpms but cast pistons can't take detonation. IMO the juice ain't worth the squeeze. adding the top end will put your rpm range higher and you will probably only gain couple mph. I think the exhaust is a good investment because they add power and save weight, plus cast are gonna rust out eventually and possibly damage your motor. Just my 2 cents. You would also need the intake and carb setup to match for that rpm range.


It seems to me that the dart heads aren't that much better than the stock rectangle ports. Looking at my cam specs vs. merc 420 specs it just seems to be a tad to big if I upgraded my motor to 420 specs , which I believe is gil exhaust and 1.7 roller rockers.... the gears are turning hard now; )

Thanks JG...what exhuat people recommenad keeping in mind the space is tight...and why 496 Mercs? They special/made well compared to GIl/Stainless Marine/ImCO, etc?

i disagree on the heads they lend themselves for more power to be made.

my motors make more power than a 420 and with WAY less cam and dual plane intakes!

the power is in the heads

no gil , or some stainless system would be better than 496 exhaust is just a cheap option to upgrade to. If i were to personally use it, I would port them as much as possible to flow as much as possible.

I don't doubt that they are better but I personally don't want to spend the extra money over just porting mine.

i agree