barron

Whats it going to cost to up grade merc 420's to 600hp? And can it be done w/o blowers?

DMOORE

1.stroke it to 496
2. good heads
3. intake
4. carb
5. have RMbuilder do a cam



Not cheap but very doable.


Darrell.

Griff

It would probably cost less to add blowers and would be just as reliable.

Rookie

iTrader: (4)

I turned my Merc 425's into 590HP.

1. Fully ported and wedged steel heads flow 380in 270ex cfm(done by JimV)
2. 9.6:1 SRP forged pistons 0.070" over
3. Wieand Stealth dual plane intake with the floors welded up to match the heads.
4. Solid roller cam 252 264 @.050 0.630" in 0.630" ex on a 108
5. Barry Grant 750's (carbs are a little on the small side, should use 850's for more power)
6. 6000-6500rpm was 585-590HP
Edit:
7. Dry exhaust to the tips

KAAMA

iTrader: (1)

Don't know how reliable the dyno was, but I had a pair of 468cid Naturally Aspirated engines make 620hp with Merlin OVAL port heads with 2.30" intake valves and well done bowl/pocket port work done to them, Dart single plane intake manifold, SOLID roller cam, tubular dyno headers, 9.5 comp ratio........they supposedly made 620hp @5700rpm. This was back in 1994. Have fun.