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Old 06-16-2010, 10:31 AM
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sbc build with vortec heads

I've got a crate 350, the low base hp version, non-vortec. I have a set of vortec heads that I want to swap on it. Should I do anything to the heads before I put them on, other then the basic check and inspection? I'm not planning on doing anything other then a cam swap, but I'm open to anything. (Talked myself out of making a 383.) This is going into a jeep rock crawler, so think low rpm torque.

Also, do I need to swap out the pistons? Or will the stock ones work?

Its at the machine shop now, so now is the time to offer up any advise before it gets all put together.

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Last edited by Dogsofwar; 06-16-2010 at 11:08 AM. Reason: adding a question
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Old 06-16-2010, 12:24 PM
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only thing i would do, is machine them for more lift and a new set of springs.
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Old 06-16-2010, 02:59 PM
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Quote:
Originally Posted by Dogsofwar
I've got a crate 350, the low base hp version, non-vortec. I have a set of vortec heads that I want to swap on it. Should I do anything to the heads before I put them on, other then the basic check and inspection? I'm not planning on doing anything other then a cam swap, but I'm open to anything. (Talked myself out of making a 383.) This is going into a jeep rock crawler, so think low rpm torque.

Also, do I need to swap out the pistons? Or will the stock ones work?

Its at the machine shop now, so now is the time to offer up any advise before it gets all put together.
What you need to do to the Vortec heads depends on what cam you want to use, or another way of looking at it is if you do nothing to the Vortec heads, that will limit what cam you use. The limit being about .45 to .47 inch lift at the valve and for all practical purposes the stock 1.25 inch spring diameter and original oil seals.

The upper guide needs to be machined down to fit lifts beyond .45-.47 inch. Getting bigger springs can be an issue as enlarging the spring pocket often leads to durability problems as the casting gets thin under the spring seat and tends to crack in use. Multiple springs require the guide diameter be reduced which limits seal choices. If you must up grade the springs with bigger cam, going to bee-hive designs is the best technical solution, but is a pricey one.

The Vortec head needs a Vortec specific intake because the bolt pattern is different though solvable by redrilling the heads to match earlier intake bolt patterns. This, however, does not address the taller Vortec port which makes a tenuous seal to a conventional intake's port at best, often requiring the port flange of the intake be padded up with weld and the mating face remachined.

The aftermarket and GMPP also sell other Vortec type heads that will bolt to conventional intakes and don't require additional work to make a seal with the ports. These are a bit more expensive than the original Vortec head, but give that back by accepting hot rod valve train parts without rework and manifolds other than the rather pricey Vortec specific intakes.

Bogie
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Old 06-17-2010, 08:58 PM
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Cam and lift

I've been reading about how the vortec won't allow much valve lift.

Will this cam work with the way it is set up stock?

Basic Operating RPM Range 1,000-5,500
Intake Duration at 050 inch Lift 213
Exhaust Duration at 050 inch Lift 219
Duration at 050 inch Lift 213 int./219 exh.
Advertised Intake Duration 256
Advertised Exhaust Duration 262
Advertised Duration 256 int./262 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.454 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.468 in.
Valve Lift with Factory Rocker Arm Ratio 0.454 int./0.468 exh. lift
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Old 06-17-2010, 09:50 PM
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Quote:
Originally Posted by Dogsofwar
I've been reading about how the vortec won't allow much valve lift.

Will this cam work with the way it is set up stock?

Basic Operating RPM Range 1,000-5,500
Intake Duration at 050 inch Lift 213
Exhaust Duration at 050 inch Lift 219
Duration at 050 inch Lift 213 int./219 exh.
Advertised Intake Duration 256
Advertised Exhaust Duration 262
Advertised Duration 256 int./262 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.454 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.468 in.
Valve Lift with Factory Rocker Arm Ratio 0.454 int./0.468 exh. lift
The intake side won't be a problem but yu should check the exhaust side for full lift clearance. If its too close you can ghetto grind the vortec retainers bottom for more lift clearance. Other wise find a cam with .454 lift on both.
eg Isky #201264
If you want more compression on your crate motor, install the vortec heads with a shin .015" shim gasket Felpro #1094. use felpro #1255 intake gaskets.
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