1971 Donzi Classic 18 power....

**Greg G** · 01-17-2017, 01:40 PM

About the fastest 18 Classic in the country is running a 383 with Whipple. He has done many radar runs at 90mph but has extensive set up time including a -2" to be able to achieve this somewhat safely. Just as a data point, the next 18's run in the mid to high 70's with standard Bravo drives. As has been said, the 24 degree deadrise round bottom takes a lot of seat time to get used to. Good Luck. I suspect if you converted and hung a 300X off the back of an 18 you would do a true 80.

**XstreamVking** · 01-17-2017, 02:03 PM

Originally Posted by FUJIMO

You think an old school high horsepower 2-bolt main small block will take jumping in & out of the water, the way those old Donzi 18's do? I don't know. Agree with the heads/compression thought. But he will have to spend some money. No matter how you choose to attain a "dependable" 450 h.p., you will be spending some money.

For a boat that is dependable, will run longer, and will be fun to own, fugi you are correct. A merc pkg will be hard to beat. In the end it may not cost a lot more than the "car motor" with many mods.....I would lean to the merc pkg myself for a lil Donzi...

**FUJIMO** · 01-17-2017, 02:35 PM

...You would have one of the fastest classic Donzi 18's out there. This is the way to fly. Closed cooling standard. Bolts right in.

**FMP** · 01-17-2017, 02:41 PM

These will give you what you want but you'll need to match it to one of his Vortec style intakes.
http://www.edelbrock.com/automotive/...c-200-sb.shtml
http://www.edelbrock.com/automotive/...r-gap-sb.shtml
and the cam etc.

**FMP** · 01-17-2017, 02:45 PM

Or one off his Vortec crate
http://www.edelbrock.com/automotive/mc/crate-engines/chevy-442.shtml

Add the above 200 runner heads and make even more

**FMP** · 01-17-2017, 02:58 PM

http://www.edelbrock.com/automotive/mc/crate-engines/chevy-519.shtml

should wake it up

**XstreamVking** · 01-17-2017, 03:00 PM

Vic makes some nice stuff, but be prepared to cut off your left arm to pay for it.

**FMP** · 01-17-2017, 03:03 PM

Worth it, I run the 170 Vortec heads.

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**Capt.Insane-o** · 01-17-2017, 05:31 PM

Originally Posted by Classic18

Thank you for the feedback....it is all very helpful. I'm feeling some "closing in", but more to go. I like the idea of the fast-burn heads. As I understand this SP383 has them......maybe a better option for me (if I can afford it)! Here's a link.

http://www.chevrolet.com/performance...p383.html#dyno

I currently don't have a raw water pickup in the hull, it was tied to the Volvo outdrive. I'll look for the transom-mounted style....

*not intended for marine applications.*

You have to change the cam to a different lobe center line and upgrade valve springs, and running a set of cmi bypass headers is almost a must.
It's easy to tell who has built marine engines on here and who looks in the catalog

Call Tyler and chat with him sometime, he'll get ya going in the right direction.

**Classic18** · 01-17-2017, 06:50 PM

Originally Posted by Capt.Insane-o

*not intended for marine applications.*

You have to change the cam to a different lobe center line and upgrade valve springs, and running a set of cmi bypass headers is almost a must.
It's easy to tell who has built marine engines on here and who looks in the catalog

Call Tyler and chat with him sometime, he'll get ya going in the right direction.

I tried to call him, no response. Left a message. I did find a marinized SP383 with 435 hp that might work...it.ts a new engine so not able to find any experiences. The engines above are great, but they are very expensive....I really do appreciate the feedback! I also heard the Holley fuel injection system is not coast guard approved.

**Classic18** · 01-17-2017, 08:49 PM

Originally Posted by Capt.Insane-o

*not intended for marine applications.*

You have to change the cam to a different lobe center line and upgrade valve springs, and running a set of cmi bypass headers is almost a must.
It's easy to tell who has built marine engines on here and who looks in the catalog

Call Tyler and chat with him sometime, he'll get ya going in the right direction.

Understand. I am told they can marinize it for me.....

**FUJIMO** · 01-17-2017, 09:07 PM

Most all of the small-block horsepower building parts you buy, will not be Coast Guard Approved. Only marinized engine assemblies, and marine engine packages, will be Coast Guard approved.

**XstreamVking** · 01-17-2017, 09:22 PM

Lot of airboat guys run the ZZ383 and now the newer upgraded SP383. They are new block, 4 bolt roller motors with good internals. Not the same as marine I know, but they seem to run out fine and last. I have a ZZ383 in my old Camaro and while it gives 450 hp, it is not very wildly cammed or have hi compression. The fast burn heads are the key, and it still uses pump gas.

**Capt.Insane-o** · 01-18-2017, 12:39 AM

It's the camshaft and to some more extent not having forged pistons or being clearenced properly along with the oil bypass needing to be modified. The hyperutectic cast pistons wear heavily in the wrist pins when run over 5k for extended time.

There was or still is a 385 hp "fast burn" 383 that made a decent boat motor with few needed changes.I've put many of those in smaller bajas and checkmates. Prop them @ 5200 and they've pretty happy.