looking for vortec head rocker arm advice

[othtim]

Hi. I'm looking for some advice regarding my current build. Here are the specs:

83' Monte carlo, 3300lbs w/o driver or fuel. TH350, 1800 RPM stall. 2.23 rear end. Will be running 255/60/r15s (or maybe 265, whatever is cheaper at the moment 😀). Stock rear diff right now. Will beef up later.

355 SBC - 2 bolt, 1 peice rear main. Stock crank and rods, flat top Speed pro pistons. rotating assembly has 90,000 kms on it. Melling HV oil pump, double roller timing chain.

Vortec heads (906 casting), rebuilt to stock specs 90,000 kms ago. Edelbrock Performer dual-plane manifold. Q-jet carb will stay for now. Exhaust is Hooker Comps out a summit dual 2-1/2 kit w/ balance pipe.

Hydraulic flat tappet cam. Unsure of the cam specs. Previous owner said it was a moderate performance cam, but I cannot confirm this. I measured piston to valve clearance using the clay method. I'm going to assemble the (stock) valvetrain and measure the lift and specs with a dial gauge. That's about all I can do for now.

My main question is this. I've heard Vortec heads need help on the exhaust. I have a huge amount of piston-to-valve clearance on the exhaust side. I was considering running 1.6 ratio rockers on the exhaust side. Is this neccessary or a good idea considering the heads are basically stock? What cam lift can the stock springs support? How can I find out the max lift my springs can support? Should I upgrade the valve springs? Will I see any gains if I go to a needle bearing type full-roller rocker arm? Right now it is the stock stamped steel.

Any advice would be appreciated.

 

[stomis]

Hi. I'm looking for some advice regarding my current build. Here are the specs:

83' Monte carlo, 3300lbs w/o driver or fuel. TH350, 1800 RPM stall. 2.23 rear end. Will be running 255/60/r15s (or maybe 265, whatever is cheaper at the moment 😀). Stock rear diff right now. Will beef up later.

355 SBC - 2 bolt, 1 peice rear main. Stock crank and rods, flat top Speed pro pistons. rotating assembly has 90,000 kms on it. Melling HV oil pump, double roller timing chain.

Vortec heads (906 casting), rebuilt to stock specs 90,000 kms ago. Edelbrock Performer dual-plane manifold. Q-jet carb will stay for now. Exhaust is Hooker Comps out a summit dual 2-1/2 kit w/ balance pipe.

Hydraulic flat tappet cam. Unsure of the cam specs. Previous owner said it was a moderate performance cam, but I cannot confirm this. I measured piston to valve clearance using the clay method. I'm going to assemble the (stock) valvetrain and measure the lift and specs with a dial gauge. That's about all I can do for now.

My main question is this. I've heard Vortec heads need help on the exhaust. I have a huge amount of piston-to-valve clearance on the exhaust side. I was considering running 1.6 ratio rockers on the exhaust side. Is this neccessary or a good idea considering the heads are basically stock? What cam lift can the stock springs support? How can I find out the max lift my springs can support? Should I upgrade the valve springs? Will I see any gains if I go to a needle bearing type full-roller rocker arm? Right now it is the stock stamped steel.

Any advice would be appreciated.

The only way to check your max lift on the springs is to bring them to a machine shop and let them compress them and check it.

Your idea would be replicating what a dual pattern cam achieves and is a very common choice for vortec heads cam wise.

Now as far as lift amounts go you need to check the retainer to seat clearance with a caliper to get the max lift your heads will allow.

Theres really no reason not to upgrade the springs theyre quite cheap if you get the seats cut to a more common size.

As far as roller vs stamped its a matter of friction. Yes you might see a small gain with roller rockers. I've seen some say its a gain of 5-10hp and some say its 20-30hp. They do make the motors job easier which is always worth something if its lower heat and wear at the least.

 

[othtim]

Thanks. I'm planning to take the heads to a machine shop to get the valve guides cut down. I am still not 100% sure if I am going to keep the existing cam or not. I want to make 13.5s with this car, but the lift I can use is limited unfortunately. There is not a lot of piston to valve clearance since I added 64cc vortec heads and flat-top pistons to an engine originally designed for dish pistons and 76cc swirl-ports. So it seems I am mechanically limited as far as lift goes - so I want to pull power out of the engine via efficiency - hence the idea for good full-roller rockers.

Do you have any suggestions for getting more flow out of the Vortecs in the 1500-6000 range while retaining the dual-plane manifold, and keeping lift low (like around .45, or whatever this step up cam is)? I'm considering stepping up the stall converter. But my manifold is a single-plane edelbrock performer, and the cam delivers power off-idle. So unless I stepped up the cam and manifold, is there any point in upping the converter lockup? Right now it is the 1800rpm stock stall converter.

 

[stomis]

Thanks. I'm planning to take the heads to a machine shop to get the valve guides cut down. I am still not 100% sure if I am going to keep the existing cam or not. I want to make 13.5s with this car, but the lift I can use is limited unfortunately. There is not a lot of piston to valve clearance since I added 64cc vortec heads and flat-top pistons to an engine originally designed for dish pistons and 76cc swirl-ports. So it seems I am mechanically limited as far as lift goes - so I want to pull power out of the engine via efficiency - hence the idea for good full-roller rockers.

Do you have any suggestions for getting more flow out of the Vortecs in the 1500-6000 range while retaining the dual-plane manifold, and keeping lift low (like around .45, or whatever this step up cam is)? I'm considering stepping up the stall converter. But my manifold is a single-plane edelbrock performer, and the cam delivers power off-idle. So unless I stepped up the cam and manifold, is there any point in upping the converter lockup? Right now it is the 1800rpm stock stall converter.

You should have no problem hitting 13.5 in a vortec headed 350.

Yes a stall converter will get you down the track faster. I'd say given your motor specs and depending on rear end gears I'd try a 2500-3000 stall converter. That should work nicely.

I would switch out to a dual plane. The edelbrock airgap is said to pretty much be the best dual plane on the market right now.

 

[othtim]

Hi. I already have a performer dual-plane manifold. I can't justify swapping out to a air-gap performer, first, cause I still have the stock hood, and second, cause I just bought this one on sale 🙂 I'm gonna get the head work done at the end of the month, and then buy a camshaft and converter to match. Thanks for your help.