Thread: need advice on my sbc 350

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Originally Posted by sbcpower

Hey guys so I have a stock vortec 350, that I would like some input on. I'm using stock internals, i bought a rpm air gap intake, a comp cams hydraulic flat tappet cam set with .490 valve lift on intake an exhaust, duration is 274 intake an 286 exhaust, and 230 intake an 236 exhaust at .050, with lobe separation at 110. I bought 1.6 ratio roller rockers, .800 pushrods, 2300 stall converter, an a holley 750 vacuum secondary. Any input Wether this is going to work well or if there is something I should change would be very appreciated

1. I do not recommend an Air Gap intake on a street motor if you have any kind of cold weather. The cold intake could present driveability problems. Street motors need heat in them to assist in the vaporization of the fuel/air mixture.

2. Chevrolet used the Vortec handle on many, many of its motors. To identify your motor, see the links below.....

BLOCK CASTING NUMBER......
https://www.google.com/search?hl=en&...2F%3B400%3B338

SUFFIX NUMBER.....
https://www.google.com/search?hl=en&...ml%3B400%3B319

CYLINDER HEAD CASTING NUMBER.....
https://www.google.com/search?hl=en&...tm%3B300%3B210

Find these numbers and post them for us please.

3. The days of flat tappet camshafts are gone. They are technology left over from the last century and cannot be trusted because of unknown metallurgy. Read through this tutorial to learn the problems with them.
http://www.crankshaftcoalition.com/w...ips_and_tricks

If your block is a Gen I block that did not have rollers in it, you should install a retro roller cam and kit from Howards Cams. 600 bucks will buy the cam and lifters, another 10 bucks will buy the thrust button. Tack weld a piece of 1/8" thickness steel onto the back of the sheet metal timing cover for the thrust button to run on, so the button does not "oilcan" the cover. Set thrust button clearance at 0.007" to 0.010" using additional gaskets if you need to. If the cover then interferes with the water pump, either grind on the back side of the water pump a little or use additional water pump gaskets to space it out from the front cover for clearance.

4. If the motor is an L31 Gen I and is stock (maybe 9.4:1 static compression ratio), it needs a camshaft NOT to exceed 210 degrees intake duration. The 230 intake on the cam you have chosen out of thin air will not match up with the static compression ratio and the motor will be a pig on the bottom end.

5. No street motor needs 1.6 rocker arms. They lend additional stress onto the valvetrain and if there is one thing the motor does not need, it is more stress on the valvetrain. Racing is a different story. If you need an additional 10-12 hp to drive around your competitor, go with the higher ratio rockers.

6. No such thing as .800 pushrods. Did you mean 7.800"? If so, how did you determine that the motor needs that length pushrod without checking the geometry????
https://www.youtube.com/watch?v=o5is9BsH5OU


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Hey guys thanks for the responses, I am a first time engine builder, and a lot of the parts listed are what ive read from other engine builds I have read online, I understand the difference between flat tappet an roller camshafts, and honestly the only reason I went with flat tappet was the cost, and the kit came with cam an lifters, springs, retainers, and keepers, I just need new valve guides. the pushrod length was 8.00, I put the decimal in the wrong place, and I got that number from the engine build I saw with a similar cam, but I appreciate the post of the video on rocker geometry, and im definitely going to remeasure so I can get it perfect, how do you remeasure the lift with the 1.6 ratio rockers, an the engine casting number is 10243880 I believe, an the head casting number is 10239906, I don't know where to find the suffix number