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Old 03-23-2008, 07:28 PM
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L31 vortec 350 ?

Does anyone know what kind of cam came in a 98 model 350 vortec engine out of a truck? The cam is a roller, need to know the lift.

Thanks in advance.
T.

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Old 03-23-2008, 07:39 PM
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Do you have the cam out of the motor?
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Old 03-23-2008, 07:50 PM
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Yes, but it is at the shop, guess I'll get the numbers an check with GM or put it back in an see if can take a measurement. Also will the vortec heads except 2.02 an 1.60? The heads are 98 062 castings numbers vortec heads with 64 cc chambers.
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Old 03-23-2008, 07:56 PM
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Using your dial caliper, measure across the nose and heel of any intake lobe. Now measure across the lobe side to side and deduct from the larger nose/heel measurement. Now multiply the answer by the rocker arm ratio and you have the theoretical valve lift. Now do any exhaust lobe the same way.
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Old 03-23-2008, 08:02 PM
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Quote:
Originally Posted by Bowtie man
Also will the vortec heads except 2.02 an 1.60? The heads are 98 062 castings numbers vortec heads with 64 cc chambers.
Do you know if the heads will except 2.02 an 1.60's.
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Old 03-23-2008, 08:28 PM
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Others on this board like F-BIRD'88 may be better equipped to answer this question.

I'll give you my opinion though. I'd rather do some bowl blending and shaping than I would changing to larger valves. I'd be more interested in the shape of the mixture kernel as it passes the intake valve and would be afraid that shrouding the kernel with the larger valve would negate any benefits that the larger valve may provide.
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Old 03-23-2008, 08:47 PM
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Yeah, I'm thinking about just cleaning runners up some an matching the gaskets. I have not worked with the vortec heads much, don't think the bigger valves will fit an may not benefit from the cost much.
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Old 03-24-2008, 03:20 AM
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The larger valves will fit, but without some deshrouding they won't do much good. Usually vortecs respond to pocket porting pretty well, but increasing valve size (depending on the porting) doesn't really do too much until the "mild" porting stage where the whole port is treated to mild work.

Lift should be in the .455-.465 range at the valve. Divide by 1.5 to get the lobe lift. I know that's not specific, but its a ballpark anyway.
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Old 03-24-2008, 11:02 AM
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That cam is tiny and probably for low rpm use. Look up the stock horsepower and torque numbers for that motor you'll see the rpm it peaks at.
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Old 03-24-2008, 05:38 PM
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Checked it with calipers today mearsured at 412 lift.
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Old 03-25-2008, 01:13 AM
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If you are after 430hp or less, stay with the stock sized valves.
The intake port will not gain flow by typical "pocket porting" it.
The stock intake port will not gain flow by just cutting in a 2.02 valve. it will actually loose flow.
The stock intake port form is highly advanced. It flows 228cfm and works very well. Has very good critical low/ mid lift flow. It will respond to specific complete porting work, but not by much. Don't screw it up. Takes a full port+chamber effort and 2.02-2.05 valves to really make a difference. Then the airflow gets up there for racing purposes. But might as well start with a race head if that is what you want.
The intake side can be tweeked up to the 240+cfm range, but you have to know exactly what you are doing or you will effect the overall balance.
When it comes to working with this head, as far as porting goes, its is best to try and just make it into a little better "Vortec head", than trying to make a full on ultimate race head out of it. (Just go buy a race head)
If you do not know exactly what you are doing, leave the intake side alone and just do the exhaust side, (full port) possibly with new 1.60" valves.
And just 30 deg back cut the valves. you'll make very,very good power.

A pro head porter can get well in excess of 260cfm out of these heads,
but they don't work cheap. You won't get this kind of flow doing your own heads without a flow bench and head porting experience.
If you want 500hp, start with a 500hp head. It will be cheaper.
This is a "torque head". Best for under 450 hp build ups. $$$Hard to beat$$$ and near goof proof in the 400+/- hp build up range.

Last edited by F-BIRD'88; 03-25-2008 at 01:25 AM.
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Old 03-25-2008, 07:37 AM
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From what we have seen the 906 and the 062 non Mexican heads work the best with 2.000 valves and no gain with a 2.020 valves and on the Vortec heads going to 2.020 and 1.600 valves is not the hot set up as on the Vortec heads its very thin between the two valves and we have seen them crack accross the deck of the head when guys have tried this.

We are restricted to 1.94 and 1.500 valves in these engines and with Ford flat tappet cams, 11:01, HP600 Carb we have seen 515 horse and 485 torque with just a good valve job, bowl hawg work and deshrouding on the intake side and no hand porting.

On the 383's we have built with this head we have seen 455 horse and the 355's we have seen 432 horse.

We have seen that the Vortec heads react to duration more then lift.

Now the RHS heads with no hand prting but some good seat geometry and bowl hawg work flow 253.
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Old 06-23-2008, 11:29 PM
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Interesting statement in regard to the duration on the L31 perf

What would you say the best cam would be to optimize a stock set of 060 gmpp heads? I am building a 355 w/ flat top pistons. I have a gmpp high rise aluminum intake and plan on headers. I am looking for a good combo for my 77 z28
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Old 06-24-2008, 02:48 AM
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Quote:
Originally Posted by sting_ray08884
What would you say the best cam would be to optimize a stock set of 060 gmpp heads? I am building a 355 w/ flat top pistons. I have a gmpp high rise aluminum intake and plan on headers. I am looking for a good combo for my 77 z28
Will need more specific info on the details of your motor and car to recomend something.
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Old 06-24-2008, 12:09 PM
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http://www.fullsizechevy.com/forums/.../t-226749.html Stock L31 cam specs
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