That one sounds good. Any reason you don't like the 925 spring though?

 

I will look at the 925 and the others. The 930 was the recommended "premium" spring.....

I wrote an email to Comp Cams through their "cam help" section to see if what they will/will not do for me.....


Is it a difficult process to set the VS height??? That's my concern. I am confident on the removal process but I will need assistance on the VS height....

Thanks.

Bob

 

I talked to the guy at a place called Corvette Corral. The used to advertise a 500hp BB for dirt cheap, he also said he has done so many corvette engine swaps that he can get it done in a day really cheap.

I think he's out of business now...I guess he didn't charge enough

But I had heard at the time he was a brillant Chevy engine builder. He told me that springs are a VERY important thing to consider.

He said that their rating is only valid when they are new, and that after a short time they lose a lot of strength. Therefor he uses much stronger springs than you would think are required.

The guys name is Steve.. and Corvettecorral.com has be gone for at least a couple years now.

~Jay

 

I never saw the 925 or 930 on the CC spring chart list. So I can't determine if it's good or bad without information.

Bob - Setting the spring height is easy. I just recently changed springs on my car using a air compressor and spark plug hole adapter. I used the type of lever that screws down on the rocker studs.

But anyway buy a digital or dial caliper. When you open up the jaws of the caliper the center guid rod comes out. You use it as a depth gauge. while your spring is installed on the car measure from the bottom of the retainer to the top of the spring pocket shim.

My AFR heads had H-roller springs with @1.850 installed height. Every valve had 3 steel shims below the spring. They were two .065's and one .020 So anyway it had been shimmed up from the valve pocket bottom .150 So I bought some springs and .010 shims. The springs were rated on the chart for 1.950 and I actually installed them at 1.990 with one .010 shim under each spring. It made my .700 max lift springs now .740 max lift. I only lift them .620 so I'm not even stressing them

 

I have a set of CC 929 springs which are NASCAR type restrictor plate springs and they work well. I have an "extra" set of these springs Summit wants $131 dollars, I'll sell my set for $115 shipped to anyone in the 48 staes that wants them. These springs will work with a "street roller" or high RPM falt tappet race application (you need to know what you are doing to run them in a flat tappet engine.) Email me if these will work for you. Thanks.

 

Ok i'm dyno expert but have seen vlv float before. And it usualy buys the farm once u get it there. I mean once the springs are over stressed they float and fail to seat the vlvs at much lower rpm. Also the lifters start to hammer the cam lobes (because the springs can't control the lifters on the lobe ramp) and cam life is now short(er).
But on the coin's other side Bob the lighter the spring u can run without reaching vlv float the longer ur cam/vlv train (seats) will live. But u can run any engine to vlv float when unloaded - that's y off roaders normaly have rev limiters.
Since changing vlv springs is easier than anything else y not start with those. But don't be surprised if no improvement is seen. And in that case i would try retarding the cam for more rpm though ur low torque seems to be suffuring already. Hmm.

Since u mentioned the HEI did u have the ignition curve set for best mechanical adv? And correct vac can? Sorry i don't know what BB needs but the fastest way is to find someone/shop with a dist machine. BTW my brand new MSD dist was way slow with full mechanical at 'bout 3200 rpm.
Yea now my Ouigy board points at that dist curve. So spend $150 on that dist or even set it yourself with a dial back timing light, bag of springs and a long slow uphill grade for test runs. Next measure idle vac to set/choose the vac adv can and back to that road for more uphill runs in hi-gear.
Really Bob now that i think of it just pull a couple of those suspect springs and measure seat press/coil bind - should be way bad if had run to float.
Well u got my 2 pennys here but maybe i save u some $$$ too.
Good luck and post what u find. cardo0

 

gkull- thanks for the infor here. Based on the 930 spring, it looks like it is installed at 1.90" but the free length is 2.32". So, the idea is to "install them" and after continually using the dial caliper to measure and add shims until I get it to 1.90".

I suppose that once I know the "formula" (# of shims and correct thicknesses), I can do the other 15 valve springs quicker than the first one?


I think what irritates me the most about this whole thing is that the Comp catalog I have here states that the RECOMMENDED maximum lift for the 924 spring (the one I have installed now) is .525" lift. This cam's lift is .552" and .555"......... yet they have the 924 spring listed at their "standard" choice in the catalog listed along with this XE274H camshaft....

They will be hearing from me.

Thanks.

Bob

 

BTW David Vizard writes a stock HEI starts to drop sparks at 5200 to 5750rpm. Easier to replace than a vlv spring.
Good luck. cardo0

 

Cardo0- Thanks for this and your other posting. I am going to swap out to the Proform HEI module as well. Keith at the dynoshop had stated that he thought he had heard valve float at the 5000+ mark or so. That chart really brought all this to light.... otherwise I would have still been in the dark......

Bob

 

Bob: It's not the ignition crapping out. It would have shown on the AFR chart. If the ignition misfires you will have tons of oxygen getting out the tailpipes as the mixture does not burn. This will show as a very lean mixture. Your mixture stays rich so there's no misfire.

 

Markus!

Yeah- I know that the springs have got to go. I am going to order the 930's as recommended by my good friends at Comp and then I am going to document everything to show them that the 924's are NOT a good recommendation for this cam. What a joke that is...

I'll leave the ignition module in there for now and see how the dyno run goes after the spring swap.....

I do appreciate your help and keeping this thread going!

Do you think the cam will be "ok" as far as wear goes after swapping in the new springs?


Bob

 

As long as you didn't run it too long in valve float the cam should be fine. I'd still ask you to talk to comp about the 925's as I like their closed pressure better.

 

I will see what they say on the 925's IF I can get through to them... I have been trying today....

Thanks!

Bob

 

gkull/Zwede,

I just got off the phone with Comp Cams. Brian over there has stated that these 924's will work with the cam.

However, he is recommending that I "shim up" the springs .060 so that the installed height is 1.840 instead of the current installed height of 1.900" (I hope they were set at the 1.900" from the machine shop).

I am going to get a hold of some of these shims, and a VS install tool. I have the OK on borrowing the neighbor's air compressor.....

He stated (as Zwede did) that the 930 spring will put alot of pressure on that flat tapp cam....

I will get moving on this!!!

gkull- I appreciate your info on the installed heights- now I finally know what you are talking about!!! Thanks.

Bob

 

Bob,

I must respectfully disagree with comp cams. Yeah, I know, they built the thing and should know but the math doesn't add up.

If you shim your springs 060 to an installed height of 1.840 you will get a seat pressure of 133 lbs and open pressure (intake) of 295 lbs. Too much seat, not enough open. It will move your valve float up several hundred rpm but not enough.

I would just hate if you went through all that trouble just to still have float (although a little higher up).

 

However, he is recommending that I "shim up" the springs .060 so that the installed height is 1.840 instead of the current installed height of 1.900" (I hope they were set at the 1.900" from the machine shop).

When ever you shim up to gain pounds your loosing total max lift.

That is why I get higher pound than I need and undershim. It looses seat and open pounds, but gains in the max lift possible. Springs then run cooler and last longer.

Your right Bob, Once you understand spring installed height it's pretty easy to make informed decisions.

 

Thanks for getting back to me.

Ok, so do think the 925's will do it?

At this point, I am really at a loss... I don't know which way to go. Do you think that the 925's rate of 395 lbs. is too much compared to the 930's at 352 lbs?

Seat pressure:

925- 122 lbs.

930- 142 lbs.

I'll order springs but I need to do this in the next hour or so!!

Bob

They are

 

Bob: Both the 925 and the 930 will have almost identical open pressures. The difference is in the seat pressure like you saw in the specs. Both are fine with your lift as far as coil bind is concerned.

The rates are 395 lbs per inch for the 925 and 352 lbs per inch for the 930. The difference is 43 lbs per inch. With your lift of slightly more than 1/2" the difference is about 20 lbs which is what you see in the seat pressure.

If you manage to get through again to comp it would be good to ask if they see any problems running the 925's. To me they look perfect for your application.

 

The 925's list the open load at 399 lbs at 1.2" from their website. Isn't that a bit too much?

You had mentioned earlier in this post that they were at 339 lbs, so I don't know if that was an error or not. I don't know what to believe as there are different rating depending on whether you are looking at a Comp catalog, the Summit, or Jeg's website....

Thanks for sticking with me on this.....

 

Yes, but the open load at 1.2" is a useless spec. With an installed height of 1.900", 1.2" is 0.700 lift. So sure they have 399 lbs, but only if you have a 0.700" lift cam. With your 0.555 lift it will be 339 lbs which is a great open pressure for a hydraulic you intend to take to 6000 rpm.