383 build for 20 ft 1984 grew bowrider

**guimond47** · 05-28-2017, 01:01 PM

hello all, new here, new to boat builds, there for I have quite a few questions.

Last year I bought a 1984 grew boat. the previous owner had the engine "built" here locally, typicly when I was buying it I was only going by what he was telling me it had... heres what it had after I took the motor apart

-Through haul exhaust (under water level, meaning not plained out its quiet, plained out its stupid loud)
-Stainless marine headers( I looked into theses and their like 4000$US price- wow lol)
-He said it had crane roller rockers, they look like crane billet rocker arms but they don't have a name on them or ratio, so idk what they are... that's an issue for me
-I pulled the cam and it had a flat tappet cam, nothing special, no numbers on it.. I measured the lift and it seemed to have and even .250 lift.
- it had 4 valve cut relief pistons
- the heads were 884 gm heads(if I remember correctly) 76 cc heads. just truck heads, nothing fancy..
- edelbrock performer intake, edelbrock marine 750cfm(too big for the cam he had. wouldn't run with it)
I may be missing a few things but the block is cracked due to previous owner.. soo I bought a 383 stroker short block.

heres my plan

-the short block has a gm 400 crank
- looks like keith black pistons with two valve relief
- arp main studs and connecting rod studs

now ill be wanting to use my stainless marine headers, through haul, intake, edelbrock carb, these rocker arms I know nothing about, im stuck on choosing the right cam and heads... I would be happy with 400hp/400tq numbers.. I don't mind spending some cash. the block is a common gm number 0010(not roller rocker) . and I would like 10.5 compression ratio. I don't mind running 91octane.
I would like the biggest bestest perfroming cam.

im unsure if my shortblock is balanced though. the 400 crank has drill marks in the counter weights...

if some experts can chim in and help me with a decent set up that would be great. I was gonna buy aluminum heads that flow 210cc and 64cc chambers but im not entirely sure that that's what I need. unsure about a cam. if the current truck heads I have can get me 400 hp then ill stick with it. also might want to stay with a flat tappet cam... let me know your opinions. thanks

**vnemous** · 05-28-2017, 03:05 PM

Pretty much a high performance outboard site here. Some one might chime in but you might get more help on a site called offshoreonly.com

**FMP** · 05-28-2017, 03:28 PM

No expert but I can't say enough about Edelbrock ETEC 170 heads, great. Match it to a Edelbrock Vortec RPM 7116 intake and a mild Comp marine cam hydraulic is fine just use good lifters, about 450/470 lift. Extreme Marine 262H is a good start.You'll make your numbers no problem and it will run great low end torque. Just make sure your drive will take it and welcome aboard.

**flabum1017** · 05-29-2017, 05:54 PM

Stick with marine cut cams to minimise overlap.... overlap will cause water ingestion with the exhaust under water.

**FMP** · 05-29-2017, 06:03 PM

Those Extreme Marine Comp cams are great street cams for heavy 4x4s or street car. As the old guru said at Comp, your K20 will have a tendency to water, lol.

**Scottko** · 05-29-2017, 11:43 PM

Don't inboards run counter clockwise (as viewed from the belt drive pulley) and car/truck engines run clockwise?

The car/truck engine can be built to run either direction, but you need a special cam and oil pump for sure. Probably other stuff too.

**flabum1017** · 05-30-2017, 06:06 AM

Originally Posted by Scottko

Don't inboards run counter clockwise (as viewed from the belt drive pulley) and car/truck engines run clockwise?

The car/truck engine can be built to run either direction, but you need a special cam and oil pump for sure. Probably other stuff too.

They run standard rotation unless you have twins with 71 series transmissions where one will run counter.