Swapped out 5.7 for vette 327

[boatdog327]

I bought a aftcabin 260 cracked 350 5.7. Yanked it out put a small journal 327 in wondering if 76cc heads with 1.94 intake and 1.50 exhaust valves be ok.

 

[alldodge]

Going with less cubes isn't the way to go IMO, and you don't want a cam made for a car in a boat
Suggest go to a junk yard and get a truck 350

 

[boatdog327]

Wondering about the cc size of heads do they need to be 76cc or 64cc and wich one for 5,000 rpm and 6,500 rpm

 

[boatdog327]

I also have the cam out of the mercruiser in it.

 

[GA_Boater]

What are you doing for exhaust?

 

[boatdog327]

Had to swap out the mercruiser to omc

 

[boatdog327]

Just found me a set of 333882 heads. Anyone think these be great in my boat

 

[Scott Danforth]

Wondering about the cc size of heads do they need to be 76cc or 64cc and wich one for 5,000 rpm and 6,500 rpm

unless you build a racing drive with pressurized oiling, 6500 RPM will eat the drive. stay below 5500 RPM, preferably closer to 5000-5200 RPM max

putting the boat cam in your 327 compared to the 350 that was in there will drop your power down more in the 200-230hp range max. remember, there is near zero overlap in a marine cam and they top out at a max of 270 degrees of duration for a radical boat cam with wet exhaust. the stock mercruiser cam is closer to about 234 degrees of duration compared the the 295 degrees of duration in the 327 vett spec'd GM3849346 cam which only made power from 3000-6500 RPM.

the base 327 engine in the vette had 250hp at the crank at 4400RPM. the 350 that was in the boat to begin with had about 285hp at the crank

the 327 came with 10.5:1 in the base and L75 and 11.25:1 in the L76. both of which will be too high in a boat with pump gas

either get a proper boat motor, build a proper boat motor, or start with a truck motor as indicated above.

think less high RPM sports car motor, think more low RPM High torque tow truck motor. the loading on a boat is basically similar to a dump truck stuck in 4th gear going up a 4% grade while driving in sand and pulling a trailer.

that small journal 327 may work well in a 16 foot wooden boat (nearly no load), however anything bigger will kill the motor.

 

[Bondo]

Ayuh,..... The 327 is a De-stroked 350,..... Just the opposite of the 383 mod,......

1/4" shorter stroke, Kills the torque output,......

 

[boatdog327]

Bought the 333882 heads with 1.94 valves. I have a 350 coming. But for now this 327 is gonna have to do for this season. But wondering how a 383 will do when I do my swap again.

 

[alldodge]

Not sure the accessories will bolt to a 327, but do use only marine parts (carb, distributor, alternator) because we don't want to read about ya in the news

 

[Scott Danforth]

the 882 are 76cc smog motor heads. what pistons are in the motor (final static CR)?

Agree with AD, not sure if any of the MC accessory drive brackets will bolt up without the extra mounting holes on the cylinder heads that were not on the early auto heads.

 

[boatdog327]

Staying with the marine carb + intake, fuel pump, alternator, starter etc. Had to pull those service type heads cause no accessory bolts let alone the water jackets are blocked with rust and gunk. Besides the head gaskets are 20 some years. These 882 have the 1.94 intake valves but 76cc. The original on the 5.7 was 64cc with 1.94 valves. Those 4580624 heads look like great flowing heads. But was told those heads are the junkiest and belong nowhere but the scrapyard.

 

[Scott Danforth]

are you sure about the 4580624 head casting. they dont show up on any SBC casting info sites.

and static compression ratio is more than just the heads, need to know gasket, deck height and piston specs along with the cylinder head combustion chamber.

 

[Scott Danforth]

do you mean 458642's? same combustion chamber as the 882's. a 76cc smog motor head

 

[boatdog327]

Yep

 

[boatdog327]

Turns out even those 462624 heads are 76 cc as well why are people using 76 cc heads when all they do is knock down performance. Well I done bought 882 1.94 76 cc heads. So lower the number or higher the number. I guess the only way to find out is to throw these on And hope they perform better than those 3991492

 

[Scott Danforth]

Turns out even those 462624 heads are 76 cc as well why are people using 76 cc heads when all they do is knock down performance. Well I done bought 882 1.94 76 cc heads. So lower the number or higher the number. I guess the only way to find out is to throw these on And hope they perform better than those 3991492

No one wants to use 76cc smog motor heads. 64cc heads have been used since the 80s.

Again, combustion chamber size is only part of the mix.....bore, stroke, piston design, chamber design, chamber size, runner volume, deck height, gasket thickness, and cam profile all work together.....or they dont work.