4.3 Non Vortec to Vortec head upgrade questions

[bryank75]

I have a 18' Celebrity with the Mercruiser 4.3LX 4bbl sterndrive package. Its a 1992 so its a non balanceshaft but it does have roller valve lifters. Was wondering if it would be worthwhile to buy the 4bbl Vortec manifold and a set of Vortec heads off a 1996 up S-10/Blazer. I run a 21 pitch prop.

Bryan

 

[Bondo]

Re: 4.3 Non Vortec to Vortec head upgrade questions

Ayuh,... You'll see a fairly honest 20hp increase in power...

If yer motor has flat-top pistons, rather than dished, you might have to allow/ adjust the compression ratio with yer choice of headgaskets,...
So long as you keep it under the hi-9s:1, it'll run just fine...
The vortecs, by design, allow higher comp ratios, without the threat of detonation..

 

[bryank75]

Re: 4.3 Non Vortec to Vortec head upgrade questions

So Bond-O it would hang with a 5.0 mercruiser in a similar boat? Bear in mind I hold a 90lb weight advantage : )

 

[bryank75]

Re: 4.3 Non Vortec to Vortec head upgrade questions

Would the Mercruiser/Weber Carb have to be recalibrated or would it be ok as is? Also do you know what CFM the V6 Carb is rated at? Is it a 500 cfm or a 600 cfm?

 

[Bondo]

Re: 4.3 Non Vortec to Vortec head upgrade questions

Would the Mercruiser/Weber Carb have to be recalibrated or would it be ok as is? Also do you know what CFM the V6 Carb is rated at? Is it a 500 cfm or a 600 cfm?

Ayuh,... The carb is a 600/ 650 cfm, 'n shouldn't need any changes...
But,...
Sparkplug color inspections will tell ya for Sure...

 

[RogersJetboat454]

Re: 4.3 Non Vortec to Vortec head upgrade questions

I have a 18' Celebrity with the Mercruiser 4.3LX 4bbl sterndrive package. Its a 1992 so its a non balanceshaft but it does have roller valve lifters. Was wondering if it would be worthwhile to buy the 4bbl Vortec manifold and a set of Vortec heads off a 1996 up S-10/Blazer. I run a 21 pitch prop.

Bryan

Just be sure the heads on that 1996 Blazer were from a Blazer with the plastic upper intake and separate upward facing throttle body (if it was a 95 production date, it may have a left over engine). The 1995 Blazer had a 4.3L labeled Vortec, but the heads truthfully weren't real vortec style combustion chambers. You can tell those engines apart from a real vortec by looking at the intake manifold. The false vortec's have an all aluminum intake manifold with an integral throttle body (cast into the upper plenum) that faces frontwards.