Vortec upgrade 4.3

[wileecoyote]

My 87 4.3 OMC has cracked the block, has anyone retrofitted an 87 OMC Cobra setup to the new Vortek motor? I've heard the mounting points and ignition is going to be different. Anyone who's done it or tried it let me know! Or anyone with a good 4.3 87 shortblock, give me a shout

 

[wileecoyote]

Re: Vortec upgrade 4.3

anyone?

 

[180shabah]

Re: Vortec upgrade 4.3

The mounting points for the engine are all the same(the intake manifold will be different, you will need a vortec specific IM). What makes a vortec a vortec, are the cylinder heads(extra 25-30 hp on this engine), that's it. There are some small differences due to changes over the years. Newer engines DO NOT have provisions for a mechanical fuel pump, so you must use an electric one(with appropriate shut-off). There was also the addition of a balance shaft in the early nineties, it eats up a little hp but makes a HUGE difference in vibration.

 

[180shabah]

Re: Vortec upgrade 4.3

I just looked at your original post date. WOW! This is usually the kind of thing people jump on around here, Don't know how you got lost for 3 days.

 

[wileecoyote]

Re: Vortec upgrade 4.3

Thanks for the input! I was looking an as far as I could tell it was the same things you had mentioned. You know after you get into it though there is always something. I was curious if the Ignition system would work the same, and I could keep the factory OMC shift interupter, or if mods had to be made there. I was hoping others had done this and had some insight. My clearance on the shift lever is tight too, I don't want the lever hitting the cover.

 

[fourwinnsdook]

Re: Vortec upgrade 4.3

Bump for you, i think you should go ahead and try it soo all of us (incl. me) who are intrested in this swap can see how hard it is... How does it feel to be the guinny pig? Just do it. Good luck with it, i'm sure between all of us here we could help you enough to get it going!

 

[tommays]

Re: Vortec upgrade 4.3

The issue will be 12" and 14" flywheels and two piece VS one piece rear main ,which makes a lot of small PITA problems



I dont no the way around it BUT it causes porblems with droping in and bolting up


Tommays

 

[fourwinnsdook]

Re: Vortec upgrade 4.3

What about rebuilt old style block with new vortec heads?

 

[180shabah]

Re: Vortec upgrade 4.3

One more thing to look at(I forgot that you had an OMC) will be your exhaust manifolds, If they wrap slightly over the top of the head(when viewed from the front) then they will need to be replaced with Merc style manifolds. The vortec heads are slightly taller.

 

[wileecoyote]

Re: Vortec upgrade 4.3

I just installed OSCO replacment exhaust manifolds(which is killing me that the boat won't run after $1000) and I'm almost sure they are Merc manifolds with new funky risers to fit the OMC. The difference in the flywheel shouldn't matter if a new coupler is used(as long as the Cobra shaft fits in the coupler) The Vortec was used with the Cobra was it not? I can't imagine they had to change too much. If only someone had already done it already!!!

 

[180shabah]

Re: Vortec upgrade 4.3

The vortecs didn't enter the scene until '96, so it was never used on a cobra. All of your bottom end concerns (coupler, flywheel, starter etc.) can be addressed by using a block of the same vintage as your current one, just substitute the vortec cylinder heads.