Vortec heads on a '90 K5?

[MaxCrack]

I have an opportunity to buy 1990 K5 for cheap but it has some burnt valves and a blown head gasket.

I installed a set of Vortec heads on my '75 and I am very happy with them. But I don't know what differences there are between the '75 and the '90 intake manifold other than carb vs. TBI of course.

Is this a bolt on part for a '90 or do I need to change the manifold to match?

Thanks

 

[4X4HIGH]

It will require a special TBI manifold and also a relocate kit for the EGR system.

 

[dyeager535]

Also need a custom PROM.

 

[4X4HIGH]

Also need a custom PROM.

Why would he need a prom if all he is doing is swapping on vortec heads onto the 90 short block?

 

[dyeager535]

Because Vortec chambers are different, and the fast burn chambers require totally different fueling and timing to keep from detonating since non-fast burn chambers require more timing than the Vortecs do.

 

[4X4HIGH]

Because Vortec chambers are different, and the fast burn chambers require totally different fueling and timing to keep from detonating since non-fast burn chambers require more timing than the Vortecs do.

Hmm, never heard that before.

 

[dyeager535]

Plenty of info about that on the tuning forums. Vortecs typically want 2* less than all previous GM iron heads. Pretty easy to see why, change combustion chamber efficiency, ignition timing is going to need to be different.

Had to take timing out of my setup, pinging during transition from light throttle cruise to light acceleration, and climbing hills. Sounds like I've still got a bit climbing logging roads @4000 ft, but I haven't spent any real time tuning this thing, just enough to keep it from pinging on the freeway.

 

[Thunder]

Besides better air flow above 3800 RPM I dont see where Vortec head chambers are much diferent than 193 TBI truck heads. The 193s on 1/2 ton trucks have fast burn chambers and a 9.2 CR same as vortecs. They just dont flow as well as vortecs. If all you did was replace a set of 193s with a set of vortecs and kept everything else stock they should run fine. Of course if you mod the engine to match the air flow that Vortecs are capable of then you need a chip.

 

[35dp]

Gm has a kit in the GMPP catalog that included 'everything' to swap the older tbi trucks to vortec heads and their kits mention nothing about proms or having to modify them.

 

[dyeager535]

Look nothing like:

GM has done a few things with "after production" parts that baffle me, sending out a TBI Vortec replacement kit without a correct PROM doesn't surprise me.

 

[Thunder]

I realise that Vortecs and 193 are not the same. Vortecs are far more fefined. 193s were GMs first attempt with fast burn and has swirl ports. But they have the same CR and they are both fast burn chambers.
The truck TBI 747 ECM and light duty truck PROM will run fine on vortecs as long as everthing else is stock.

 

[dyeager535]

They can call them fast burn chambers, but the design is obviously different as shown by the pics. Different chamber designs require different timing, bar none.

If you think you'll get the same performance/results without tuning, go right ahead, I'm not going to argue it.

As an edit, here is an L98 chamber. This is what my setup was designed for. Installing Vortec heads resulted in pinging. Dunno what more I can tell anyone.

 

[Thunder]

I never said you would get the same performance as a later model truck. All I said was that Vortec heads will run on a stock TRUCK TBI ECM. They have a lot diferent timing and fuel curve than your stock TPI PROM. L98s are a far cry from TBI swirl port heads too. IMO L98s not as good for a truck.