Hey, I know its not third gen, but I wanna get some more power out of my 1997 Chevy pickup with a 350 Vortec. What is the biggest cam I could use without having to replace valvesprings and having to burn a new prom? ( I assume a LT4 Hotcam would be too much)..

Thanks!!

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BigBlockJason
85 Z28 T-Tops
http://communities.msn.com/JasonsStuff/homepage

 

Stock vortec heads can not take over.480" of lift. The springs are weak. I tested them against stock corvette springs and they opened at 30 lb less then the corvette's. In my '69 Camaro I used compcams extrem energy 270 and replaced the springs with crane H-11 tool steel springs. If you are going to put in a new cam I would really consider replacing the valve springs. The hot cam is too much for stock heads. When I decided to replace the stock cam I call comp cams tect line and with there advice pick a good cam for what I wanted.

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1987 Camaro IROC-Z w/ 305 tpi/5-speed/9 bolt 3.45 gear/L98 Corvette heads/ T.E.S. headers/ LT4 production cam/ 1.6 rockers/ Flowmaster exhaust.
1969 Camaro with '96 350 vortec truck engine w/ mods

[This message has been edited by Todds1987iroc (edited April 12, 2001).]

[This message has been edited by Todds1987iroc (edited April 12, 2001).]

 

going with the LT4 hot cam and keeping the stock rocker ratio would probably put you in a good range. you can't burn a prom since your truck don't have one. the stock programming would work, but buying a power programmer would make some aspects of it easier to compensate along with raising the shift points. since your truck stock can't be manually shifted out of first, programming changes would pretty much be well worth it along with the speed limiter change.

 

I'm guessing that the biggest cam you could install would be about 22 3/16" long...

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Later,
Vader
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"What a Day..."
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BBJ,

The other problem with Vortec heads is that the limit of lift is reportedly about 0.480" before the retainers crash into the upper ends of the valve guides. If you want to use any lift close to that, you should machine the guides down to provide clearance, or install longer valves (like Pontiac valves from '68-'71 or early-style BBC valves).

Using Poncho valves from a Ram Air IV or older 11/32" BBC valves gives several advantages:

The stems are longer, allowing the use of screwed studs and guide plates with minimal depth machining (or no real machining at all);

Spring installed height can be optimal with minimal depth machining on the heads;

The extra space for very tall, stiff springs is useful;

The valve faces are larger than the commonly available "2.02/1.60" sizes, allowing up to 2.19" intakes and 1.94" exhaust to be fit into the SBC heads (with some chamber massaging);

On the other side of the coin:

The taller valves require longer push rods, which requires the elongation of the push rod holes in the heads in most engines;

The valve train is heavier, but that can be offset by the correct, larger springs;

You might not be able to effectively use all that flow on an EFI fuel system.

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Later,
Vader
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"What a Day..."
Adobe Acrobat Reader

 

in the january 2000 chevy high performance, they ran .510 lift on stock vortec heads and had no clearance problems. it was later stated that the valve springs would not likely survive as long under that much stress, but they did fine under dyno testing.