help with heads

[dieselman123]

hey everyone, I need some advice from the experts. I currently have a 350 bored .30 over and planning on rebuilding it with flattop pistons. the question I have is that im not for sure about the heads that came with it. the casting number of the heads is 993. can anyone tell me about the heads and are they any good because I really don't know what size cam to use not knowing about the heads. I want a nice lopy idle but not to the point to where I loose vacuum.  not looking to build a race motor but just something that can get up and go if I need it to. I was thinking maybe a 272 with a lobe separation of 110. any advice would be greatly appreciated. thanks in advance!!! its going in a 1983 Silverado swb also

[rich weyand]

A "nice lopy idle" means the engine is cammed for horsepower at high rpm, but bottom-end torque will suffer.  An engine with a lot of torque in the bottom runs real sweet at idle.  So ask yourself this question: "Do I want good 0-50 times (getting off the line), or do I want good 50-90 times (two-lane passing)?"

A nice lopy idle means it will be a brick getting off the line unless you put a high-stall-speed torque converter in it, which is really rough on transmissions, u-joints, diffs, and transfer cases.  Been there, done that.

Now, if you want torque down low and good performance up top, you have some choices.  Look at Comp 12-235-2 and 12-238-2, for example.

You probably want to read through this thread:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=26206.0

And read this article:
http://www.crankshaftcoalition.com/wiki/How_to_choose_a_camshaft

[dieselman123]

yea you are right don't really want to replace a brand new torque convertor. just want some get up and go off the line. will the heads I have now be any good because ive been reading a lot of bad reviews on the 993 heads

[rich weyand]

The 882 and 993 heads are smog-era heads.  Low compression ratio and not very good swirl and flow characteristics.  The hot setup is to go with Vortec heads.  That being said, that's all I know about them, other than the fact that heads -- replacing them, machining them -- are expensive.

The cheap way to get the most out of the setup you have is to cam the engine properly and make sure the rest of the induction system doesn't get in the way.  The way to do that is to put a Comp 12-235-2 or 12-238-2 cam in the engine, use a good dual-plane manifold, and use long-tube headers with duals, good-flowing mufflers (Flowmaster 40 (louder) or 50 (softer) for example), and an H-pipe (4x4) or X-pipe (2WD).

You'll be looking at 300 hp and 400 lbft of torque, at low enough rpms to be useful and fun in daily driving.  To go much higher than that, you need to lose the heads.  Go too much higher than that, and you will start dynamiting driveline components if they aren't all upgraded for the extra horsepower and torque.

[dieselman123]

will anyone of these cams require me to do anything special to the heads besides getting them cleaned and making them true again

[rich weyand]

You'll need new lifters for a new cam.  I would also recommend new springs.  These cams have more lift than stock, and lifter springs get tired with age and mileage.

[square81]

Im running vortec heads on my 355. I like them. Not sure on my cam shaft it works good for me. I did some scrounging around and found a used set. Got them checked over and slapped them on. I know you can buy new ones for under 400 or 500 complete ready to go. Do some research there are diffent casting numbers on them.  Both are good but one flows better then the other.

[dieselman123]

Hey square81 just wondering what kind of compression you have out of your combo, what kind of piston and head gasket did you use

[square81]

I belive the compression ratio is around 9:1. I run flat top pistons but im not sure what head gaskets. The machine shop put the heads on for me. I know there felpro.

[Dan75k20]

As rich said 12-235-2 i have that cam,in my 010 block bored 30 flat tops  882 heads 600 edelbrock 1405 dual plane performer intake throttle response is awesome

[BADAZ chevy guy]

 Just curious. Would the same cam, carb and manifold you described for  dieselman123 work with Vortec heads? What do you think the throttle response would be?