I have a new vortec crate motor that I am building and have just found out 2 things about my crate motor. #1 the holes are drilled and tapped on my motor for a normal timing cover and #2 my beehive springs nor do my LS6 springs fit. I have the 906 castings and have to have the bottom part of the guide boss machined down so my springs will fit in the seats Just to for warn any one else, there is a possibility that you may have to machine your heads to run new springs. I have seen several people run them in stock heads and comp cams told me they would fit for sure so maybe its a problem with only the 906 castings?

 

O well time to have my screw in studs installed and a little machine work to make them better. Thinking of keeping the 1.94 valves and having 1.6 exhaust installed and maybe port matching my intake and heads. Any one have good results with having there heads ported? I use to hear not to port them.

 

What springs and retainers are you using?
I've installed the Comp 26918 springs and 761 retainers with no interference.
The Vortecs use a valve spring with a 1.7" installed height. The Comps require a 1.8" height. An offset keeper is required to get the installed height within reason.
Unless your shop is VERY familiar with these heads, installing larger valves may ruin an otherwise good thing. The factory valve job is one of the attributes that make these heads perform as well as they do. Unless you're into something beyond a well built street engine, I'd suggest you use them in stock trim. If you bought them used, it'd be interesting to know if they've already been worked over. Stock guides in the Vortecs are cast iron. Any head that's had a valve job done should have new guides and those will be a bronze liner or similar. That'll be obvious.
Port matching is over-rated. I wouldn't pay to have someone do it and I wouldn't take the time to do it myself. It's a lot of work for a small percentage gain. A little bowl blending will pay for more dividends. You'll have to pay though.
Screw-in studs, definitely. Possibly guide plates too unless you're going to stick with self guiding rockers.

 

It was the 981 springs with the 787 retainers. I talked to comp cams before ordering it and they recommended them. I have seen others use them too.


They are new heads on a factory L31 crate motor for a 3/4 ton truck from GM. I unwrapped in swapped out the cam, double roller timing chain, a moroso 7qt oil pan with matching oil pump and when I got to the springs it was a big NOPE.

 

Just going to sell the heads and get a set of E-Tech 170 heads from Edelbrock next week.

 

The weird thing was the LS6 springs did not fit either. They were a little thinner wire but still did not fit.

 

Remove the flat inner damper springs and any 1.25" / 1.26" od spring should fit.

The damper springs do not add to the spring tension/rate, no harm to run w/o them. I almost never use them on any head.

I'm running howards 98212 1.26" od single with damper spring, with damper removed on my stock vortec heads.. No mods to spring pockets, or guides.
I did the "ghetto grind" on the stock vortec head retainers and used +.050" locks to get the needed clearance for my lift

 

I'm guessing the problem is the ID of the 981. The Vortec stock guide has a nearly .900" outside diameter. The 981 ID is .825". The 918 spring is .885" ID and just fits. (It's a drop in upgrade).
Yes, the 981 has a damper spring which reduces it's ID. I can't comment on removing it as I've never done it.

 

Beehive springs don't have an inner damper spring...

 

26981-16 is the part # there 1.24" springs there 110# seat pressure at 1.7" install high and 292 # at .525" I can see the problem looking at there page though the inside diameter is only .825" I guess I will be using these on my 305 motor. Going to use this as an excuse to buy some aluminum heads anyways as that's what I really want. I did not see the inside diameter was .825" I just asked comp cams what springs would fit and new there was no damper spring on these and new they were the correct install high and the outside diameter was going to fit. Figured they would fit if there was no inner spring or damper The LS6 springs don't fit either as I had these as a back up if I wanted to use theme too.

 

The inner damper is to keep your springs form fatiguing pre maturely due to harmonics and I would rather not use springs with out them if there recommended. Now I am torn on if I should go with the E-Tech 200 or 170 I am running a mild cam and performer EPS and know the 170 would perform better with my set up but the 200 would allow for a much larger cam and single plane later on in the future if I ever wanted to build a 400+ HP motor.

 

According to Comps catalogue the 981 does have a damper spring. It's classed as a conical or "Beehive" spring.
The 918, also conical, has no damper.
IIRC, the 918 and it's smaller version, the 915 were among the first of the Beehives that were directed at the aftermarket. Built similarly to GM LS series of springs.

 

The regular 981 springs are not beehive but the 26981 are. There different springs. I am using the 787 retainers with them. There the same ones you use on the LS6 springs. The 787 retainer will not fit the 981 but will fit the 26981. 981 has damper 26981 no damper.

 

918 springs are for LS motor and are suppose to have a 1.8" install high and will give a high seat pressure if installed in a normal SBC with a 1.7" install high. I would have to use off set locks to use them and it would probably interfere with my self align rockers.

 

[QUOTE=2005Impalla;5863337]The regular 981 springs are not beehive but the 26981 are. There different springs.QUOTE]

I see that now. I was under the impression that the 981s you were referring were the 26981s.

 

I did this on my Vortecs and my new RHS heads both with offset locks. The RHS heads have a .100" taller valve so the installed height wasn't an issue so much as getting the exact installed height was.
No interference with my rockers but then again I'm running guide plates instead of the self aligning rockers. The small retainer offers up some additional clearence.

 

Strange. I just got a second l31r for the Camaro. 906 heads and ls6 valve springs went on without drama. A couple were slightly tight on the guide until heated slightly then they went on. They were tight because the bottom of the spring was slightly wider from the grinding process.

26981 (.825) have different dimensions than the 26918's (.885).
http://www.crankshaftcoalition.com/w...ners_and_locks

This is the second L31 I have run with this setup.

 

Just going to sell them and get the E tec 170 heads anyways and the wife is all for it so its a win win any ways. I will loose some weight off the front of the car and I wont be limited on cam selection if I decide to swap cams later.

 

For what it's worth, as an aluminum replacement for the Vortecs, the 170 Edelbrocks were my first choice.

 

I don't know if I will gain or loose any power going to the aluminum heads as I am not raising my compression but the weight savings combined with a fiberglass hood, manual steering swap and gutting the engine compartment of stuff along with some other weight saving mods will help. Still tossing the idea of doing drag springs and 90/10 shocks and taking out my sway bar in the front too. It sucks I am not driving my car today but I am going to be way happier with the new heads.

 

Certrainly going lighter is the way to going faster. I'd love to shed 200 lbs but I'm not a drag racer 100%. Street and highway cruising play a bigger role.
That said, since you're intent on spending more money of another set of heads, have you read this magazine article?
http://www.hotrod.com/how-to/engine/...head-shootout/
Interesting comparisons although I don't put complete faith in the numbers.

 

Well the vortec's are going on the motor now. Talked to the machine shop and its only $100 to machine the valve guide boss. I just want my car on the road at this point. I have some screw in studs laying around that are new so I am going to see if I can find them and have them installed too. They have no jam nut on the bottom so I don't have to have the heads milled for them to sit flat in head just pull the studs and have them tapped. He also has an engine dyno so I want to have the motor broke in and have the distributor and carb tuned. Would be way cool to have a dyno sheet and see how much power it really makes. If I have him dyno my motor I will post before with my parts list so we can take guesses on HP and torque

 

That'll be interesting and I'm looking forward to your results.
As for a guess, post up all of the mods you have: cam specs, induction setup, ignition, water pump....we can go from there.