I'm on a project for an iron vortec head, but since those vortec heads were borne out of the LT-1 head, I figure this topic will also apply to our aluminum LT-1 heads.

I cut the seats and some had to be cut deeper than others and will of course require shimming of the springs. The cam I'm using is a mild one, .425 lift or so as my goal is low end torque only, on a truck. So, I just got stock vortec springs, b/c they're only $40 a set. Almost identical to what came on the LT-1, single-wire. The LT1 springs have about a 1/32 larger ID.

So, I tried finding shims for stock vortec head and had no luck. Their installed height is supposed to be 1.70" and give about 80 pounds at that height. I look at the LS1 yellow springs I just happen to have laying around, and they're to be installed at 1.80" and give about 80 pounds at that height.

So, I just use the yellow LS1 beehive springs that are to be installed at a height that is .100" taller than the stock springs, and don't worry about shimming, because my cam is relatively mild. Retainers are comp's 787-16 which are made for these springs on non-LS heads with 11/32" valve stems, so I use stock keepers.

I'll have more spring pressure on the valve seats that I didn't cut so deep, I figure about 110 pounds.

Am I asking for trouble by being lazy ? I just can't find shims for the huge-a$$ valve guide bosses on the vortec heads and the beehive LS1 springs fit right on perfectly.

 

Whats the difference in setup heights?

If the difference is greater than .015, why not just go back, re-do the valve job and cut all the seats the same depth?

110lbs seat pressure is fine for a hyd roller.... with valve lift only .425 lift - Those LSX springs are only going to be like 280LBS over the nose, which is again fine and no where near being a problem.

Will

 

Oh gawd, I think I'd probably shoot myself if I had to cut those seats anymore, I used neway cutter and did it by hand, 60 then 31 then 46 and then blend the chamber. Getting the seat widths and their location on the valve face exactly correct was a very time-intensive matter. Next time I'll just buy heads, it'll be cheaper. Luckily the LS1 springs are spec'd to put out about the same force at 1.8" installed height as the stock springs put out at 1.7". I didn't cut more than .100" , and folks have successfully used the LS1 springs (roughly eqiv. to Comp's 918's) as direct drop-ins installed at 1.7". I won't have the same force on all the seats, but I think that the force on all the seats will be within operable range. The seats on the vortec heads looked like crap as they came off the truck motor, waaayyyy too wide, like .100 on the exhaust and intakes were at least about 0.080.

Some of the guide bosses, which dual function as spring locators, are of different o.d.'s. Many of the LS1 springs just fit nice over them, while springs when put over others have a little interference, but they do go down all the way. If there was a spec where the seat (bottom) of the valve spring was required to have some amount of lateral play, I'd be concerned, for as it is, some of them are quite snug up against the valve guide bosses.

 

IF you did the cuts in that order thats why your having such a hard time.

1st cut should always be the seat angle 45* (in your case)

2nd cut should be your top cut... 31* is a bit steep for Vortec's... I use a 21* on my limited class oval track motors with Vortec's....

3rd cut should be your bottom 60* to narrow up the seat.

With stock casting that like the top angle to blend to the chamber - I make the 45* about .040-.060 bigger than the valve size so when I make the top angle, it cuts it to size and leaves a nice chatter free angle that blends to the chamber .060-.100 wide.... The I use the bottom cut to narrow up the seat to whatever I need... on a street car .080 width on the 45* is good... then use a bowl cutter or whatever to make the bowl the correct size.... Vortecs like about 88-90% of the valve size.

Same process on the exhaust. I use a 45* seat, 30* top and 65* bottom.

Be careful as the 30* top cut, as it cuts away the excess 45* very quickly and you'll end up making the 45* seat angle cut too small.... leaving a big margin between the valve size and the seat, which will screw up the curtain area and hurt low lift flow on the intake.

Will

 

On a used head like that, I do a little 60 just to clean it up and see where things are, then I slop it with dye and do a 31 until the cut I make is just concentric, i.e., the cutter is just taking enough away to make a uniformly wide circle of a cut. Then I cut a 46, dye up the valve, stick it in the guide and rock it 1/8" back and forth and remove it and observe where the seat is on the valve. If too close to the margin, I cut the 31 more, if off the other way, I do the 60 more. On an intake I shoot for .040 wide seat and have the outer portion of the seat about .015 of the valve face up off the margin. Exhausts are wider for heat transfer. I blend the outer of the 31 deg cut with a dremel ever so carefully and inspect everything with a friggin magnifying glass. Its time intensive but I don't think I can get the quality anywhere else.

 

edit: I wrote "rock" but I should have written "rotate"

 

Your making too many cuts.... and all that re-cutting is why your sinking the valve job on some seats and not others.

If you do things in the order I told you, once you make that 45* on the seat - You'll immediately be able to see where everything else is... easy as pie to judge your initial cut with a dial caliper set to the valve size.

Considering the tooling your using a .040 wide intake seat is not going seal on the street with that low valve spring pressure.... I wouldn't cut them less that .060 for a regular street car and we have a Serdi.
Will

 

It was only on a couple that it went too deep, and only because I tried a "radius blade" from neway and didn't fully appreciate all of what it would wipe with a couple turns.

Valve springs do not provide pressure, springs provide force by the equation F=kx, k being the spring constant and x being the displancement. Pressure is force over area. Accordingly, the pressure of the valve face on the seat depends on the seat area. Physically, the same spring FORCE on a smaller seat AREA, such as my 0.040" seats will translate into a greater PRESSURE of the valve on the seat than would a wider seat which would see less pressure from the same spring force. "Valve spring pressure" is a misnomer. I've done heads previously cutting the angles in the order I did, which is recommended by Neway for over half a century and they all came out fine. I'll never use that radius blade again, but please don't misunderstand me, it wasn't Neway's fault, it was mine for proceeding too quickly.