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Discussion Starter · #1 ·
I have a stock Vortec motor I am putting Summit Vortec heads on. What will happen if I install 1.6 rockers? Will it increase my midrange torque? Need a little boost around 3500 rpms going up hills on the highway in my k2500 truck.
 

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Probably not much but a little, this change on a mild cam only nets a hand full of ft lbs and horses.

Pretty much the same with the head swap assuming your Summit heads are some version of their idea of the Vortec head there isn’t much to be had if anything than a more crack resistant casting if iron and a 40 pound weight loss if aluminum. The Vortec head is pretty optimized you got to play with the expensive spread for any torque or power gains and those mostly take place above where the stock Vortec cam and valve train, EFI and exhaust system will go.

Unless there is something else going on here like replacing cracked heads or worn out rockers or these parts are leading into bigger changes I have to say that this is wasted money.

Unfortunately the degree of changes needed to I’m assuming a 350 in a K2500 truck are very extensive and quickly clash with the computer program which drives not inexpensive computer changes.

The shortest direction in these trucks is a 383 or find an install a big block with its injection and computer which gets into reprogramming the security since that is tied to inside the computer to a key ID, not that it can’t be worked.

I highly recommend that if you buy trucks thinking of them as life time investments that you don’t buy anything newer than the 1995 model year. The 1987 through 95 puts the computer between you and the engine and in cases of the 4L80E and 4L60E transmission are pretty easy to back date to a carburetor and conventional ignition which opens the possibilities of changing between displacements or adding hot rod parts pretty easy. 1986 and earlier either have a computer that is a carburetor management toy that is easily sidelined or never had any computing electronics at all so making changes is simple. My guideline to customers that asked first was simply buy something 1986 or older and put the money you’d drop on a new model truck into a refurbishment of an old one, that builds a life time investment.

Like I told my wife when I put the SBC in my old S15, somebody, somewhere will be making old SBC parts long after I’m dead and gone from this world.

Bogie
 

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Discussion Starter · #4 ·
Sorry I didn't mention my truck is a '90 with TBI. It's my daily driver work truck (handyman). My odometer broke at 300,000 aprox 600,000 miles ago. Yes I have about 1,000,000 miles on it.
 

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Discussion Starter · #5 ·
So in other words I need mileage or I would have installed a 383 or 400. I'm rebuilding it now. 30 over Vortec with factory roller cam. Hope my Obd 1 and TBI accept the slight change.
 

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Discussion Starter · #6 ·
I do have a nice exhaust system with shorty headers. Wish someone made a tunable aftermarket computer for this.
 

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In 1990 you should have the 700R4 which is the 4L60 without an E.
If that's the case, you should be able to run a good ole fashioned HEI with your choice if carburetor.
The major stumbling block with this conversion would be an electronic controlled transmission, which you don't have.
But don't get excited yet, because im not 100% sure what you have.
 

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Discussion Starter · #8 ·
Yes 700r4 but I think the converter lock-up is computer controlled. I want to keep the TBI as it has been trouble free for 600,000 miles, never floods, needs no choke, cold starts everytime, never fluctuates at high or low altitudes, etc, etc
 

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I’ve done several stock L31 Vortec engines into the 87-95 trucks converting them to the TBI of those years and several L31 Vortec cam changes into TBI engines. For the most part the TBI computer pick up this type change without a hiccup. GM’s use of high LSA values on the their cams (RamJet excluded) keeps manifold vacuum to RPM to throttle position close enough that the O2 sensor can trim into any needed changes. It will handle 1.6 rockers, headers and dual exhaust with this cam as well,but that is the high side limit that it will do without reprogramming the chip.

This is more successful with a fresh engine as the computer only has so much learn authority so when some to all of this has been used to keep a worn engine adjusted so it runs, making hotrod changes to a tired engine will usually find the computer is out of space to make any more adjustments.

Bogie
 
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