JPrevost

So is it possible to just install -0.050 valve locks and gain the 50 thou clearance between the locks and valve seals? If so, do I need new retainers? Shim the valve springs up off the head by 50 thou? Longer valves?
The cam I'm looking at is the xe274h (not roller) and it has .490 lift on the exhaust. Currently the 330hp gmpp crate motor has .460 lift on the exhaust and I expect there is still acceptable clearance between the locks and seals. I'm trying to avoid getting the machine work done
Last question, is there any proof anywhere that shows fulcrum roller lifters make any more horsepower? I'm thinking the friction is so low that going from 1.5 stamped to 1.5 roller is just a waste of money at this point. Maybe if going to 1.6 but I can't see spending the $$$ for like 2 or 3 hp if that's all it's good for.
Thanks in advance.

Lo-tec

I guess it would depend on the installed height of the springs for the xe274. I recently built a vortec small block using new heads and a xe262 (.462/.469) lift and my machinist had to machine the heads for the clearance necessary for this little cam. You might get into trouble with rocker arm/retainer clearance if you raise it too much. I've never tried it, but if it were that easy I think my machine guy would have done it. Supposed to be .475" lift max. out of the box per GM.

As far as the stamped versus roller debate, I think some of the power gain from aftermarket rockers is that they are made better and give you the correct ratio. I've never measured one myself, but have read where some stamped ones are closer to 1.4 ratio instead of 1.5. Comp has them in a 1.52 that would give you a little extra lift.

NastyL98_T/A

shimming the springs will do nothing more than increase your seat pressure and decrease net lift before coil bind. If you're trying to assemble a set of performance heads PROPERLY, you'll want to measure your installed heights and shim the springs accordingly to get consistent spring pressures on each valve. Depending on the casting, some of the Vortec heads are good to .495" without machining the guides. Measure from the top of the guide to the bottom of the lock and subtract .060" for clearance and there's your max net lift number. As for the rockers, the benefit comes from less friction which frees up HP but more power will come from aluminum bodied rockers that will lighten up the valvetrain.

JPrevost

That's what I'm thinking... that the lighter valvetrain is just inertial savings as apposed to friction. There is hardly any friction developed so it would make sense that the gains have all been seen at rather high RPM where inertial forces start to really add up.
As for the spring shimming, I know I have to shim them properly and I was just confused about the locks. I wasn't sure what dimension they were. I figured correctly that it moves the locks and retainers UP meaning you would need to shim the springs to get the installed height and seat pressure correct.

Lo-tec, are you sure you needed the heads machined? I only say this because sometimes a shop is a little slow and if they see the opertunity to do some more work they're going to do it. It's not a bad thing but sometimes un-necessary where the machinist makes judgement calls. If I had a machine shop that was cheap and local I'd definatly just machine them but I don't so I'm going for mail-order parts to see if it'll help. I think I might be onto something if the self-aligning rockers don't touch the retainers! That's my only worry. Thanks Damon for confirming my thoughts.

84z28350

The roller rockers wont give much of a gain but you can get up to 50HP switching to roller lifters.

JPrevost

Yeah, I've got a few quotes for custom roller cams. I know what I want and am just looking for somebody to make it. If it's too expensive I'll just stick with the flat tap until the rest of the parts on the motor start to wear (40k miles on the engine).

Lo-tec

I've been using the same shop for 15 years, and I do trust my guy. He's fixed stuff for free on a new rebuild that I f'd up. I asked the same question when I dropped off the heads.

As far as running the -.050 locks, you would have to put one in to see if it sits higher. Might be worth a call to the manufacturer. They get pretty thin at the bottom (which is where the locking ridge?? would be moved to), and might not give you the .050" clearance you're looking for. Summit and scoggin dickey sell modified heads with upgraded springs that should work with this cam.

Another downside with the stamped rocker debate is with bigger cams and stiffer valvesprings they will deflect more and cost a little power.

BMmonteSS

I mocked up my heads with the offset locks, and they do just what they are supposed to, they move the retainer up .050, if you throw a .050 shim under them there really isn't any difference from machining your guides. I actually used them only on the intake side of the heads I had, because I did away with the valve rotators on the exhaust side, so the exhaust side had about .050 thou taller installed height. With the offset locks on the intake side and proper shimming I was able to get the installed pressure I needed and I'm good to go all the way to .530 lift on unmodified stock heads. I had to go with a funky spring to get everything to work out, but you shouldn't have this problem with the vortecs.

What springs are you going with?

JPrevost

Which ever you are using... care to share that bit of info?
That was my other concern BUT if you have to run a shim you can run a wide shim which means you can run a wider OD spring yes/no? Obviously with the ID the spring would just be a single, no double or damper but I think it would be more practical than having the heads machined.

What are the valve rotators and what part numbers if any do you have?
Now I wonder why all of those budget vortec builds didn't think of this before? Is there a downside or did they just want to use double springs so machining was the only viable option? I think that's what they did since most of them are lemmings and just go by the cam manufacturers spring recommendations. Your thoughts...

BMmonteSS

I think alot has to do with people getting confused quick when they start measureing installed heights and rather have a machine shop take care of it.

Valve rotators, are these big bulky things that were supposed to rotate the exhaust valve in order to promote even wear on the valve tip, but they rarely worked and weighed alot. GM quite using them, and your vortecs didn't come with them.

The springs I'm using won't work on the vortecs because of large OD of the guide, which requires a spring without an inner spring or even a damper (flat looking spring). Come to think of it, thats why my brother ended up getting the guides cut down, and the seats enlarged. The LT4 springs were too large to fit in the seat, and none of the run of the mill chevy springs would fit because of the large guide. You can't run a larger OD shim, there's metal that needs to be removed to make room. This was 2 years ago, so some things are just coming back to me. We were going to run the old school valve springs with the damper removed, but he decided to get the guides cut down since the heads were off the car and the machine shop only wanted 20 bucks to cut them down (they like me )

I think your only option is to do the offset lock shim shuffle and use a heavier spring and remove the damper. What exactly the damper does is beyond me, when I checked the spring pressures of my springs I removed them just to see how much force they exerted and it was only about 10 lb's at installed height. I can't remember the part number but I remember having 120 lb on the seat and just short of 300 open, which is pretty stout for hydraulic lifters. They were friggen expensive too, at 120$ but they were the only spring I could find that would give me the right spring pressure at my higher than normal installed height without going over 300 lb of open pressure. You might give comp cams a call and ask them what will happen if you run a spring without the damper installed and see what they say. If it'll work, any run of the mill HP chevy spring will work.

JPrevost

Oh, here I was thinking you had vortec heads .
As for the shim, it looks like there is only a little big of grinding required to use larger shims. Unlike the older heads, the spring seats are on a loft. There is a little material on the back but it looks like just a soft grinding would take it right off.
I think I'm going to have to end up either forking up the money for machine work (for valve springs) or beehive springs. The beehives would be nice but they're REALLY expensive.

chevymec

iTrader: (5)

I running a set of GMPP Vortec heads with stock springs and a Lunati 292 duration 480 lift cam. I have had no issues with clearance or withthe springs. Although if I go any bigger cam it will require the spring seats to be machined for a bigger spring. I wish now that I had spent that little bit more and got a set from SDPC with the springs already fixed.

BMmonteSS

No, I have bastardized setup of a valvetrain thats a compromise of what I had and how much money I had at the time.

My brother on the other hand does have them, and thats what I'm baseing my observations off of.

Chevymc: Did you measure how much room you actually had? I was so suprised by my measurements that I checked them twice and sure enough they were kissing the seal at .460 lift and were compressing it pretty good by .490 The seals we were using might have been thicker than stock, since they came out of a generic rebuild kit. We contiplated useing the cheapy rubber umbrella seals since they gave us more room, but went with the positive seal intake syle seals. (metal locking spring around the base) The stock springs are super soft, they were around 75 lb's @ their installed height, you may be getting into valve float because of these springs.

JP: I would look into the beehive springs, they may cost more, but are designed to run without the inner damper. I didn't notice how the seat was formed on the vortecs, if it is like you said, then grind away and get a "cup" shim and go with the LT4 springs, they are dirt cheap and work with the hot cam with 1.6 rockers which is .525 lift. Finding a cup shim with the large ID might be difficult though.

chevymec

iTrader: (5)

^^^ Didnt measure anything. No problem with valve float either. Took the heads out of the box, installed the cam and I was on my happy way. They helped carry the car to a 12.56@110.5 also.

BMmonteSS

I slapped together some old stock heads and promptly rounded off a half a dozen cam lobes with only .460 lift. I think I took a dump in Mr. Murphy's coffee in another life or somthin

AJ_92RS

I had planned on trying just what you're talking about JP. Using .050" higher locks then shim the heads .050" - .060" (.060" is an easier shim to find).

The problem is the valve guide boss becomes HUGE down by the spring seat. I measured mine and IIRC, they're .860" diameter. The 981 springs (which is what Comp recommends for the cam you and I both have) are .880" WITHOUT the damper.

Anyway, the problem is finding shims with that ID. I haven't found any yet.

DM91RS

I found this thread doing a search for something else but maybe I can help.

JP.........I'm running a .480 lift cam and would not hesitate to go to .490. I used offset locks and shims to keep the spring pressure the same as if there were no offset. If you want I can look up the lock and shim numbers that I used. I'm running full roller 1.6 rockers also. I don't have them installed now but I also purchased and would run with the cam you mentioned Manley springs pn......22410-16. They will fit the stock Vortec valve pockets. Just remove the dampers. I have this done with the Comp cams springs that I am running now. I also used the stock Vortec retainers. I would measure it all though to be safe no matter if myself or whoever is running certain parts as with(most) parts variences are commonplace. PM me if you want more details. After all you do for others I hope I can be of some help!

DM91RS

I just remembered reading what AJ_92RS wrote. I had the shims ID bored out to fit the outside of the guide which is rather large.

DM91RS

Sorry to not finish but my memory sux........DynoDon posted the Manley springs as the one to use back years ago. IIRC Kevin was running them with a HOT cam or something similar and Don was running a ZZ4 cam with them.

You going to try this?

JPrevost

Interesting. I don't know what I'm going to do yet until I figure out what I'm doing with this motor. I might just get the pockets machined I was hoping not to have too but having priced out the beehives I think machining might be easiest... especially if I run into any problems with the springs. They're charging $$$ for those beehives. I wonder if stock LS1 springs and retainers would work
Running no damper... I don't know if I like that idea.

DM91RS

That's cool.........myself I will be running the ZZ4 with the 1.6's unless I change my mind which is entirely possible. With the 1.6's the exh would be around .544. I've purchased a set of Comp 987's for that set up and will have to up the seats to 1.44 when I change it over to the 350 again.