Hot Rod Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter #1
I pulled a set of vortec heads off of my 1996 k1500 vortec 350. I plan to use them in a moderate build of a different 350 that will be getting edelbrock performer rpm intake and carb. I'd like to throw a cam in it too, and I heard that vortec heads have some restrictions as to the lift they can handle. I don't want to machine the heads, or buy new ones, simply because I don't have the money to. So, with that being said, what kind of lift/duration should be safe to run? Im hoping to at least go 1hp per ci. Thanks! :) :D
 

·
Wrench Turner
Joined
·
4,952 Posts
.470 to .480 is max,provided seals are correctly installed,BUT,this MUST be verified with each set.Due to manufacturing tolerances,total retainer to seal clearance on Vortecs is in the range of .510 to .530.This will allow for a lift of .460 to .480 & still maintain a .050 safety margin.AGAIN....after .450,you MUST verify the actual clearance of your set of heads.You can also use a set of beehive springs with appropriate retainers to gain more lift clearance w/o machine work.A low cost alternative for this is using LS valve springs with Comp 787 retainers.The springs can be purchased new for approx. $60 & the retainers run $50 to $60.this setup will give just over .500 lift.For 350 HP,something along the lines of the ZZ4 cam,4 bbl,headers w/ free flowing exhaust will put you just about there.
 

·
Registered
Joined
·
17,612 Posts
There is at least one thing I can agree with concerning Joker's post, that you should do a trial assembly without springs. Use a socket to tap the seal down firmly onto the valve guide and trial assemble without springs. Use a heavy grease like wheel bearing grease on the valve face/valve seat, on the retainer and locks to help hold the whole mess in position. Wrap your index and middle fingers around the valve under the retainer like you were pulling back the string on a bow and arrow and pull up and twist to fully seat the valve and keepers in the retainer. You can use short lengths of clothes hanger wire with the ends well-rounded and held in place with a needle nosed pliers, then measured with a micrometer or dial caliper to find the distance between the top of the seal and the bottom of the retainer that would engage with the seal. Let's say you came up with a measurement of +/- 0.480". Deduct 0.050" safety margin and you are left with 0.430" max valve lift before the bottom of the retainer comes crashing into the seal. You can't get in there with the stick of a dial indicator and be correct, because you have to angle the tool to get there and all readings are therefore false. Use little short sticks of clothes hanger wire and a needle nose pliers.

If you don't own a dial indicator, at least purchase an inexpensive Chinesium unit. Everybody who is messing with anything automotive needs a dial caliper. Don't make the mistake of purchasing an electronic unit. Been there, done that, every time I reached for it, the batteries were dead. Dial calipers are bulletproof. Here's an inexpensive unit that would serve you well. You want a 12" unit so you can measure block deck height.
http://www.ebay.com/itm/Dial-Calipers-Precision-12-Inch-White-Face-Stainless-Steel-Import-NEW-/291396545885?pt=LH_DefaultDomain_0&hash=item43d8966d5d

Ghetto grinding refers to grinding on the bottom of the stock retainers to provide more clearance between the bottom of the retainer and the top of the seal. If, for instance, you found through your mock-up that you were going to be limited to 0.430" lift, you could put the retainers on a surface grinder (any local machine shop can do this for you) and remove 0.050" from the bottom of them, making room for 0.480" valve lift or remove 0.080" to clear a 0.510" valve lift. If you want even more lift, do as Joker described with the springs and retainers. Use caution though, and make certain that the valve tip still sticks up far enough past the top of the retainer so that the edges of the rail rockers don't push down on the retainer and unload the whole mess. The rocker should contact the valve tip only and no part of the retainer. Also, run them through a cycle to check for rocker stud to rocker clearance. I normally used a length of small diameter solder stuck in there and run through a cycle. If the solder is pinched flat, you're going to have a problem if you don't clearance the rocker with a die grinder and small stone. And also, don't even think of using anything but the rail rockers if you don't go the whole way with screw-in studs and guide plates. You won't like the results of using conventional rockers without guide plates, as the rocker tip will wallow off to the side of the valve tip and the whole mess frags itself.

You may not have had an opportunity to read through this tutorial, but it has some good points in it....
http://www.crankshaftcoalition.com/wiki/Vortec_L31_cylinder_head

.
 

·
Registered
Joined
·
3,414 Posts
You will need to know the specifics of the valve spring that your desired camshaft requires to know exactly how to proceed with setting up the heads.
 

·
Registered
Joined
·
13,465 Posts
I pulled a set of vortec heads off of my 1996 k1500 vortec 350. I plan to use them in a moderate build of a different 350 that will be getting edelbrock performer rpm intake and carb. I'd like to throw a cam in it too, and I heard that vortec heads have some restrictions as to the lift they can handle. I don't want to machine the heads, or buy new ones, simply because I don't have the money to. So, with that being said, what kind of lift/duration should be safe to run? Im hoping to at least go 1hp per ci. Thanks! :) :D
Cutting the top of the guide is about a 100 to 150 dollar job, if you have it done along with a valve job the heads probably should have done any way the machinest will probably throw the guide cut in for 75 bucks. You can buy the tools to do it yourself for about a 100 including the cutter head and its guide. All you need then is an electric drill and some of Techs recommended measuring tools.

Another way to get at this is if the cam you select isn't too wild and recommends other than stock springs, you can run a set of GM beehives and their unique small retainer which will get enough clearance for about .5 inch without cutting anything.

Bogie
 

·
Registered
Joined
·
17,612 Posts
You will need to know the specifics of the valve spring that your desired camshaft requires to know exactly how to proceed with setting up the heads.
In my opinion, while this is generally true, if you use a cam that signs off by ~5500, you can use stock valve springs to help prevent cam/lifter failure with a flat tappet cam. Begin with new springs. This would be applicable, in my opinion, up to about 215 degrees @0.050" tappet lift, corresponding to somewhere around 8.75:1 to 10.0:1 static compression ratio. You don't want to run any more than about 9.5:1 with iron heads on pump gas anyway. A Crane Energizer 272-H10, for example, would be a good match for 9.5:1, resulting in a dynamic compression ratio of 8.46:1, perfect for pump gas and iron heads when used with a tight squish of 0.035" to 0.045".

A 355, using L31 heads, 12cc dished piston, zero deck and Fel-Pro 1003 head gasket will produce 9.54:1 static compression ratio.

.
 

·
Registered
Joined
·
17,612 Posts
I couldn't edit the above post any more, but that combo results in a squish of 0.041" and sets the motor up to use aluminum heads in the future. (not wise to use shim gaskets with aluminum heads due to fretting of the aluminum. Use a composition gasket such as the Fel-Pro 1003).
 

·
Registered
Joined
·
3,414 Posts
I tend to worry about valve springs. I checked some recently from a stock Vortec head and none had more than 65lbs on the seat. At least get some of the Z28 springs.
 

·
The mobile view is crap
Joined
·
1,876 Posts
There is tons of info about vortec heads on the internet. A simple Google search should answer any question you have about them.
 
1 - 9 of 9 Posts
Top