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Old 01-06-2013, 10:26 PM
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vortec heads on older gm

I have a 1995 TBI 5.7 truck engine vin K will1996 vortec heads work on this engine ?

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Old 01-07-2013, 12:01 AM
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Quote:
Originally Posted by lowhirod View Post
I have a 1995 TBI 5.7 truck engine vin K will1996 vortec heads work on this engine ?
They'll fit if your motor is a Gen I motor with conventional cooling system and not an LT1 Gen II motor. I have no idea how much you would gain from this head swap though, because I know little or nothing about EFI systems.
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Old 01-07-2013, 02:07 AM
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Quote:
Originally Posted by lowhirod View Post
I have a 1995 TBI 5.7 truck engine vin K will1996 vortec heads work on this engine ?
To keep the TBI EFI system, you will need to use a Vortec-specific TBI intake (shown below); earlier intakes have a different bolt patterns and will not bolt up to the Vortec heads and the ports don't match even if they did.

One other way around the TBI problem is to use a Vortec carburetor intake w/a TBI adapter (also shown below) to mount the TBI throttle body to the Vortec intake manifold.

Click on images for link to Summit:




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Old 01-07-2013, 05:56 AM
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.. Your '95 prolly has rather poor flowing swirl port TBI heads, the swirl thing kinda blocks the ports, so the superior flowing Vortec heads should give a noticable boost in performance. Especially with headers and free flowing exhaust... may also be going from 76cc chambers to 64cc chambers for a good boost in compression ratio...
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Old 01-07-2013, 07:28 AM
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yes but intake manifold has different bolt pattern.

Some ppl have drilled the intake holes out and made them work but not pretty. Best to buy heads made for your engine. Many companies make cheap heads for gen I v8s. Vortec have nothing on good after market heads. Some of which only cost 600 to 1000 per set.
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Old 01-07-2013, 01:45 PM
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Originally Posted by lowhirod View Post
I have a 1995 TBI 5.7 truck engine vin K will1996 vortec heads work on this engine ?
They will bolt on but require a Vortec to TBI intake. This will not have EGR ported from an exhaust crossover as it is not cast into the Vortec head. EGR requires external plumbing as was done on the 1996 up Vortec truck engines.

The TBI EFI will be OK with the original cam and rockers for the RPM range of the original engine. Given the computer limits top RPM and road speed you can't really get into problems unless you change the cam, rockers or terminate the EGR. If you do any of those changes you will need a new chip see these people if you do >>> TBI CHIPS <<<. If you want to rev higher and or increase top speed you will also need a new chip.

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Old 01-07-2013, 04:29 PM
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.. A big advantage is Vortec heads can be scored used for about $100... grab the Vortec intake manifold with them...!
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Old 01-07-2013, 06:54 PM
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I,m after low in torque. I tow a 30 hp tractor with a half ton truck
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Old 01-07-2013, 10:04 PM
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.. Well, then, your current throttle body should be big enough/fine...
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Old 01-08-2013, 02:16 PM
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Originally Posted by lowhirod View Post
I,m after low in torque. I tow a 30 hp tractor with a half ton truck
In that case you're better off leaving it as original. Unless you increase the displacement anything you do to the heads or cam will reduce bottom end torque, push the torque peak an horsepower to higher numbers but also they will be at higher RPMs than what the current LO5 peaks at. This will drive you to stiffer final gearing to restore power at cruise back to where it was with the swirl port heads.

If you really need more bottom end the best way to attack the problem is with more displacement, and the best way to do that is with a 383 stroker kit. The other ways of getting there with the engine you have is with a stiffer rear axle ratio. This will give the engine more mechanical advantage in all gears and will cause it to operate closer to its torque and power peaks in normal use.

You have to keep in mind that new trucks since the mid 1980's are very much an exercise in systems integration design. The Swirl Port head is made to work with TBI and actually does very well with a carb. The Vortec was made to work with port injection and with that set up doesn't surender much if any bottom end torque. But when that head is mated to TBI or a carb a very noticable drop in bottom end torque is seen. The overall performance gain in this situation for the Vortec happens above 2500 RPM which is significant, but unless you rev the engine up you can't get that advantage with TBI or a carb and these heads.

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Old 01-08-2013, 05:01 PM
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.. The Vortec heads will help low end torque (1500-3500 RPMs) some if they offer a change from 76cc chambers to 64cc chambers... but I don't recall if the swirl port heads are 76cc or not... just remember the swirl ramps blocking the intake port flow...
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Old 01-08-2013, 05:36 PM
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5.7L SP = 64 cc
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Old 01-08-2013, 06:01 PM
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Originally Posted by BuzzLOL View Post
.. The Vortec heads will help low end torque (1500-3500 RPMs) some if they offer a change from 76cc chambers to 64cc chambers... but I don't recall if the swirl port heads are 76cc or not... just remember the swirl ramps blocking the intake port flow...
There are 2 Swirl Port heads on the 350 engines the casting ending in 191 is 76 ish ccs the one ending in 193 is 64 ccs.

I have yet to do or to see a dyno run where the Vortec head picked up torque on the bottom end without also changing pistons from dish to flat top.

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Old 01-08-2013, 06:06 PM
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.. That may be because they always increase the cam size as well...
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Old 01-08-2013, 07:00 PM
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.. That may be because they always increase the cam size as well...
No I talking head to head comparison on an otherwise idential engine or as much as it can be given the intake also needs to change in-so-far as bolt pattern is concerned so while it's the same intake model i.e. Edlebrock Performer RPM for example it still is not the same piece of equipment from one test head type to the other.

Bogie
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