Thread: 5.7 5700 vortec power plant

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Originally Posted by McQueenRacing

I have a bone stock 5700 sb motor. I have my vortec intake and carb ready to swap on. I know about the lift issue with the vortec heads and was wondering if somebody could direct me to a camshaft with the proper lift that will give me the kick I need in the rpm range for a half mile asphalt track

Make an appointment or drop in to the track and have a talk with the senior technical inspector. He will be the final word on whether or not you can do something to the motor or the car.
The problem with L-31 heads is the valve guide. It is too fat to run anything but a single spring without damper and too tall to allow any meaningful cam lift. The guide must be cut for smaller diameter all the way down to the spring seat to make room for a good spring with damper and it must be shortened to provide clearance between the bottom of the retainer and the valve guide seal. Most fellows will cut the top of the guide for a 0.530" I.D. seal like this one..... http://www.summitracing.com/parts/cca-503-16/overview/

The question is: Do the rules allow head work or not? If not, you are forced to use the heads as is, with the single spring with no damper spring and a camshaft that limits valve lift to around 0.420". (Remember, you must leave a safety margin of roughly 0.060", so you cannot use up all the space on a stock L31 head. You must leave a safety margin and that dictates 0.420 lift at the valve to prevent the bottom of the retainer from crashing into the stock guide seal if the motor is accidentally over-revved).

All cam grinders make 0.420" lift rule, hydraulic flat tappet cams for circle track racing. Here's a listing from Howards as an example.....
http://www.competitionproducts.com/H.../products/312/

When choosing a camshaft for any motor, the static compression ratio must be taken into consideration. Here's a list that I compiled suggesting the SCR to be used with any particular cam.....
http://www.crankshaftcoalition.com/w..._compatibility
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