5.7GLI non-vortec repower to a Vortec 5.7L and possibly a 383 stroker.

[Bigdave196]

So if you build a 383 and keep it in the 5000 to 5100 range, you don't need the higher cfm carb. My guess would be a good 600 cfm carb would work.

Got it, thank you.

 

[Bigdave196]

Just picked up a 98 5.7L block with the 062 heads. It looks like these were the upgrades to the 217 heads that came on my boat originally. Intake runners are both 170cc and they both have 1.94/1.50 valves in them as well. The block is a 080 casting. I am thinking that i will get a carb and an intake that will replace the TBI. The vortec heads have cam limitations, does anyone have a recommendation on what cam to run?

 

[Scott Danforth]

Below is the link to my cam and performance changes I went thru

http://forums.iboats.com/forum/engin...q271c?t=503800


Since my motor wasnt a roller, I went with the CL12-236-3 - Comp Cams 'Xtreme Marine' Hydraulic Flat Tappet

Operating Range: 1300-5500 RPM
Duration Advertised: 262? Intake / 268? Exhaust
Duration @ .050'' Lift: 218? Intake / 224? Exhaust
Valve Lift w/1.5 Rockers: .462'' Intake / .477'' Exhaust
Lobe Separation Angle: 112?

since your motor is a roller, I would suggest one of the following:

http://www.compperformancegroupstore...Category_Code=

or

http://www.compperformancegroupstore...Category_Code=

my vortec heads were machined for hi-lift cams, however there are bee-hive valve springs that you can purchase without machining.

 

[Tail_Gunner]

Lots of info there and some crazy pricing,,
http://www.hotrod.com/how-to/engine/ccrp-0808-383-stroker-small-block-chevy/

 

[Scott Danforth]

Mild build isnt too crazy

 

[Tail_Gunner]

By crazy I mean.......Scat 9000 Series rotator1-92000-1{{{Summit}}} Racing$489.95..

Agreed on that mild build it would make a healthy boat engine.

 

[Scott Danforth]

Agreed on the mild build being a healthy boat engine. Im trying to figure out how to convince the admiral that I need to spend 2 boat units on a 383 stroker short block.. I think I need to introduce a power issue by backing off the timing and mis-adjusting the throttle Then again, I really want to do something stooooopid like forged internals and slap on a Magnuson SC-120 supercharger

 

[Tail_Gunner]

Agreed on the mild build being a healthy boat engine. Im trying to figure out how to convince the admiral that I need to spend 2 boat units on a 383 stroker short block.. I think I need to introduce a power issue by backing off the timing and mis-adjusting the throttle Then again, I really want to do something stooooopid like forged internals and slap on a Magnuson SC-120 supercharger

On a similar note i beleive i forgot to winterize my little 4.3 it would be a dam shame if that 14yr old engine cracked and a new one had to be replaced...However when all the part's for a new engine came she would smell a rat and simply ask why didnt you just get one already to go and the jig would be up...:moony:

 

[Bigdave196]

Is there any certain camshaft that is recommended for a little more grunt/power for this build that I am doing? The XM270HR camshaft sounds amazing, but I am running my exhaust through the prop. You wouldn't be able to hear that sweet lumpity lumpity noise that we have grown to love. Is there a similar performance producing camshaft to help bring me over the 300 hp mark. The Vortec heads are supposed to give me somewhere around 30-40 HP over the factory 250/260 HP.
Thank you.

 

[Bondo]

Ayuh,..... Lumpity, lumpity in a boat motor ain't so good,.... Reversion,.....

Look for something like 214/ 218?, just under 1/2" lift,....

The next step above an RV cam, or the RV cam cut,...

 

[Bigdave196]

Thank you Bondo

 

[Scott Danforth]

the XM270 is the biggest cam you can put in the boat with thru-leg wet exhaust without reversion. any more durration and you need to adress the exhaust. it will sound lumpy when you back the idle off and run on muffs in the driveway.

keep in mind, your 260hp is currently at the prop. thats just about 290 at the flywheel.