Thread: need advice on my sbc 350

Tweet

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

put a roller cam in it----------the vortec should already be set up for rollers-make sure you have the correct manifold for the head angle and gaskets

+1 on the roller cam. Also, with .490 lift and 1.6 rockers, you're probably going to have retainer to valve guide clearance problems. Stock Vortecs usually won't go much over .480 without cutting the guides or changing springs and retainers. Your combo will put you around .522 lift.

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


.

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

also can someone estimate what my idle is going to be like with these cam spces, and what my timing should be

The suffix number is stamped on the block deck, passenger side, just in front of the end of the cylinder head and very close to the passenger side water pump boss.....sometimes there is an alternator hiding the alpha-numeric stamping.
http://www.chevyasylum.com/tech/V8Stamp2r4t.jpg

10243880 is the casting number for the Vortec 5700 RPO L31 350 motor that was used in pickups and vans. It is much sought-after because it came from the factory with a roller cam and one-piece rear main seal.

10239906 is the casting number for the L31 heads, the heavy duty ones with exhaust seat inserts. The other head that Chevy used on these L31 motors is casting number 12558062, the lighter-duty version without the heavy duty exhaust valve seats. Seats in the 062 heads were induction hardened.

Here's a tutorial on the heads....
http://www.crankshaftcoalition.com/w..._cylinder_head

Chances are pretty good that the flat tappet camshaft will not last. Here is another tutorial telling you why......
http://www.crankshaftcoalition.com/w...ips_and_tricks

It seems a shame to begin a build with the most sought after roller cam block and best production heads that Chevy ever cast up and then screw it up with a flat tappet cam and some fosdick 1.6 rockers.

.

The suffix number is stamped on the block deck, passenger side, just in front of the end of the cylinder head and very close to the passenger side water pump boss.....sometimes there is an alternator hiding the alpha-numeric stamping.
http://www.chevyasylum.com/tech/V8Stamp2r4t.jpg

10243880 is the casting number for the Vortec 5700 RPO L31 350 motor that was used in pickups and vans. It is much sought-after because it came from the factory with a roller cam and one-piece rear main seal.

10239906 is the casting number for the L31 heads, the heavy duty ones with exhaust seat inserts. The other head that Chevy used on these L31 motors is casting number 12558062, the lighter-duty version without the heavy duty exhaust valve seats. Seats in the 062 heads were induction hardened.

Here's a tutorial on the heads....
http://www.crankshaftcoalition.com/w..._cylinder_head

Chances are pretty good that the flat tappet camshaft will not last. Here is another tutorial telling you why......
http://www.crankshaftcoalition.com/w...ips_and_tricks

It seems a shame to begin a build with the most sought after roller cam block and best production iron heads that Chevy ever cast up and then screw it up with a flat tappet cam and some fosdick 1.6 rockers.

Edelbrock 7116 or equivalent is the intake manifold you need to use with the L31 heads.

.

Strongly suggest that you listen to Tech and see if you can return that cam & lifter set. If you choose to use it and it loses one or more lobes you will have circulated microscopic, highly abrasive particles throughout your engine, and you'll likely be looking at a total teardown to hot tank the block, then starting over with new bearings, rings, roller cam, etc, etc. Some of the most experienced engine guys out there say that with a flat tappet cam and today's over the counter oils it's not a question of IF the cam will fail, it's a question of WHEN.

Originally Posted by rspears

Some of the most experienced engine guys out there say that with a flat tappet cam and today's over the counter oils it's not a question of IF the cam will fail, it's a question of WHEN.

The 383 in my 46 was built about 15 years ago with a Comp flat tappet cam. It was broken in right and the oil was changed regularly. I had to tear it down last year and found 2 cam lobes beginning to go bad. That wasn't even the reason for the tear down, but it would have been eventually. It's going back together with a retro fit roller cam. I don't build many engines, but I won't build one without a roller cam from now on. Too much time and money invested to roll the dice on if the cam will hold up.

Mike