SB

iTrader: (1)

Since your 89 has quadrajet carb:
if you want aluminum:
Edelbrock 2116

aluminum with brass lined water jackets:
Edelbrock 2516

If want cast iron:
engine quest IN350MA – Intake bolt hole pattern for use with 1996 – 2002 cylinder heads – VORTEC <<

kornegle

I had a 1990 Wellcraft 216 Eclipse many years ago with a 260 Mercruiser and it did about 52 mph with a 21P Mirage prop. I pulled the engine and installed a set of new Vortec heads from Jegs. I installed a Comp Cams flat tappet 212* / 218* @ .050, .447 / .462. I removed the Vortec springs it came with, and installed 1970 Z28 outer valve springs only without the inners and they were around 115 - 120 lbs. on the seat. The inners would have required machine work to the heads. This cleared everything without using the expensive beehive springs and the retainers did not touch the guides. I used an Edelbrock Performer Vortec manifold with anodized water passages, because I kept the Quadrajunk carb. If you use a Holley you should get the Edelbrock RPM Air Gap Vortec manifold and that would be close to 20HP more than the manifold I used. I also installed 1.52 aluminum roller rockers, and a roller timing chain. Those heads will raise the compression close to 9.5:1 depending on which heads you had but I did not run more than 30* timing and used mid grade fuel. I also had a K&N velocity stack, and exhaust tube instead of the exhaust bellows, and perhaps a few other minor things I forgot. Anyway, I was very pleased. I had to use a stock 23P Mirage prop and it ran 61 mph @ 5000 rpm trouble free for at least 8 years before I sold it and it is still running trouble free according to the new owner. So go ahead and do it, I think you will be happy.