lt1-xjs

Ported heads with bigger valves has nothing to do with the valve seals. The type of spring and retainer used dictate the type. Some require the seat and guide to be machined to be installed, changing the type and or size of seal. used.

Ed Wright

iTrader: (1)

>Ed, What can say regarding what you know about
>the Comp 918 beehive failures back around 2008?


Never used them, so can't really say. I have been told this by reps from two cam companies, and one spring company. Problem spring run in heat treat batches. So, stay away from a given heat treat batch if you break springs. Normally one heat treat batch will go to one customer, since they order them in "batches". I was told by my guy at PAC that the heat treat batch number can be found on the end of the box, but I have to admit to never looking for it. Comp used to use PAC for their race springs (Remember Pacaloy 9000 springs?) No longer using PAC. I use PAC for my race car. 8500 in the lights, .850" lift, been getting a full season from them. Have three sets with a full season on them, and still check OK. 360 on the seat new, 1015 lbs open, still ~320lbs on the seat, over 800 open. I carry them for spares. Really happy with PAC.

joelster

To the OP:

How high do you expect the engine to spin? The cam is pretty small for trying to feed 383 cubes. Any idea on the headwork other than stage 2? If the heads are mediocre and the cam is small, it's not going to feed the motor, no matter how perfect you set up the springs. I used comp 918's on my TFS heads, and they had Si/Manley 2.02/1.60 valves. The spring pressures were nothing huge (130/323 off of the top of my head). My little 350 would pull clean right up to 7k. Your springs would have to be whooped for them to poop out at 6k. When my car developed issues over 6k (back in 2007), the culprit turned out to be the opti. We took it apart and the bearings were all corroded allowing the rotor to wobble. Under 6k it was just fine.

Ed Wright

iTrader: (1)

And, a properly ported factory manifold is not (regardless what you read on message boards) so restrictive as to cause a 383" to pull 3" of vacuum above 6000. My 383", with an LT4 manifold, didn't do that at 8000.

quik95lt1

iTrader: (7)

very true what ed and joel said.......the stock intake is MUCH better than most make it out to be.......and as for springs PAC is a good spring as ed said as is PSI I swear by the PSI springs I ran a set for 3 years on my car 8000+rpm traps with .715 lift they never moved in pressure I just replaced them for the sake of age......don't skimp on springs it can destroy your motor

ahritchie

iTrader: (1)

Peaking at 6200 RPM....6400-6500 RPM shifting point is just fine with me, it's primarily a street car. Those heads are CNC ported, not sure how good their CNC program was, but they came with a flow sheet that said they flowed 280ish CFM intake/200 exhaust. Apparenlty, the old heads were on somebody's bracket racer Camaro, so I guess they lived a hard life one 1/4 mile at a time who I asssume had a much bigger cam than me considering the triple valve springs, the heads had very little carbon buildup when I got them although they were 10 years old. I don't think it's the opti, it's got a relatively new MSD one and the car is garage kept and not driven in the rain at all. The dyno shop insisted it was a valvetrain issue of some sort, more than likely springs due to the normal torque and hp #'s until the valve float starts a at upper RPMs.

ahritchie

iTrader: (1)

Thanks for the info, I'll find out later today what the machine shop guy says I need after taking a look.

ahritchie

iTrader: (1)

Yea, it can't be my intake, it is ported and has a stock ported 52mm TB. I'm thinking it must be my old school G2 intake cold air intake elbow..it's not much bigger than the stock one, and it's hooked up to a 4" specter intake tube with a 12" high flow cone filter which can't be that restrictive.

I've got to remember to test this theory when I dyno it just to see the #'s and run it with an open MAF.

ahritchie

iTrader: (1)

It turns out after further investigation that LS1 valve seals fit my heads due to the machine work...wierd, who knew?! Now the shop has to hunt down some tiny exhaust leak I can smell but not hear...and she's back on the road with over 400 RWHP! (hopefully)

BALLSS

"My" new MSD Opti proved to be the source of my high RPM stumble, car would just nose over around 5200-5500 RPM. Chased springs, injectors, plugs/wires, tune (and Ed was gracious enough to look at data even though my issue was not tune related). Put back on my used AC Delco Opti and it has been on years now.

On the valve seals for the CM heads. You say the LSx ones fit fine, but any machinest would mic the stand and order the size. Summit, JEGS, etc all have them from various (Trick Flo) brands. I get the full jacket Viton seals. Can't remember size but just mic your heads to find out if the LSx ones are not spot on.

springs, I have the Comp 918's on ported AL heads w 2.02/1.60 Ferra valves in a small XFI cam 383.

ahritchie

iTrader: (1)

Well the shop finally finished up my car due to some delays since the shop was closed most last week due to the 4th, turns out I had a leaky valve cover, leaky tail shaft seal on the trans, and they replaced a leaky header collector, not to mention the valve spring replacement. I'm pretty excited not to be smelling like gas and exhaust after a drive Who know's, maybe I'll be getting over 12-13 MPG now

If it ever stops raining around here, I'll take it out for a shakedown run with the new springs and see if it's making some real top end power very soon

ahritchie

iTrader: (1)

One question about the "bad opti" theory...IF it was my opti (which I doubt, but anything is possible if an opti is involved), would the engine still rev over 6K with a bad opti? Because I have revved it out to 6500 RPM before, it just stopped pulling hard at 6k, no stumbling or missing or anthing of that nature. Was it like you hit a wall and it won't rev any higher or just a nosedive in power which was my issue

KW Baraka

iTrader: (7)

Absolutely.

With a bad opti, you'll primarily have mis-fires (mostly at higher RPMs) or the car flat won't run. But a bad opti won't act as a rev 'limiter'.


Also.....for those who don't know.....Combination Motorsports Stage 2 heads were.....in no uncertain terms.....top notch pieces of work. They flowed very well, all the way up to .700" lift and made excellent power. Also, being CNC ported, they were very consistent from port to port and from one head to the next.


Finally, CompCams 918 behive springs......I'm pretty sure that the bad batch that came out about 6 years back are off the market; there shouldn't be any real issues running those springs, now. I had a set in my old police package Caprice from 2003 until the car got hit/wrecked in 2010....close to 120K miles. Springs were great, IMO.


OP.....congrats on finally gettin' things sorted out! I know the feeling of relief that comes with that !

KW

ahritchie

iTrader: (1)

Good to know, I'm pretty sure it's the springs in this case, it just runs too smooth for it to be the opti. Good to hear some postive feedback of the heads too....they were once among the best CNC ported LT1 heads you could buy, and everybody had good things to say about them, but that was a long time ago before the company went under (10+ years)...anyways, the flow sheet that came with them looks very comparable to the modern Ai 200cc heads, and the CNC ports look awesome. Next step is to get it on the dyno for a final run just to see what HP # it makes for ***** and giggles.

96capricemgr

iTrader: (1)

The CM stuff was good FOR IT'S DAY, I can't think of any CM equipped cars that actually ran all that great.

Puck

iTrader: (17)

My CM spec'd cam ran 11.7s in a stock shortblock with 140k on it when it was a daily driver. Owner was great to deal with too. Nothing special about the combo, heads were just some crappy local shop ported heads that I picked up dirt cheap used.

Not the fastest around, but salad shooters on all corners and drove it an hour to the track and back the same way I drove it to work every day, just let a few PSI out the rear tires when I got there.

Compared to a lot of results I see on here, I'd say that wasn't too bad for what it was.

ahritchie

iTrader: (1)

It was finally dry enough this AM for a shakedown run with the new springs, I did a couple pulls in 4th gear to 6500 RPM and it's pulling very strong now, no hiccups or dead spots, so I think it's safe to say the opti was not the issue. I can even drive it with the windows up without stinking up the car or getting carbon monoxide poisioning

I can't say enough about the shop that did the work...he only charged me for 4 hrs labor for the valvespring job and just charged me parts for all the other crap he fixed with the oil leak, exhaust leak, trans leak; just because they like my car so much and like working on fast cars Check out Hughes Automotive if your LT1 needs some love in the Charlotte area

They even have a sweet LT1 on their website! Check it out in the 55' Chevy:

http://www.hughesautomotivecenter.com/

ahritchie

iTrader: (1)

Well, I finally took the car back up to PCM for less for some dyno pulls after fixing (most) of the issues, no oil leaks, exhaust leaks, better CAI, HOWEVER there's still a high rpm ignition/valvetrain issue, even with the new Lunati beehives the tech there recommended:

Type: .600" Lift Ovate Beehive Valve Spring
Seat Load: 130@1.800"
Open Load: 318@1.200"
Rate (lbs/in): 313

The HP curve falls off a cliff (-100hp) at 6K....this cam should peak at 6200, also you could hear it breaking up (raspy sound) at high RPM, Alvin the tuner/dyno operator says it's probably still valve float and suggested my MSD opti could be to blame for the breaking up (as others mentioned here too); He also suggested springs with a seat load of 135lb-155lb at installed height (more than my current ones). They noted every MSD opti they ever came across is pure Lol...at least I didn't pay full price for it, I got slightly used for $150 with the shortblock I bought.

So I guess, the next plan of action is double checking installed valve spring height via one of those custom measuring tools (I paid a shop to install them ), double checking pushrod length, and probably the oh so lovely and familiar opti replacement

I also called Lunati again to see what they have to say (wanted to make sure last guy I spoke to wasn't high or something ) They assured me those beehives SHOULD be up these aggressive lobes I hear so much about, however, he also suggested, "If you got valve float, then you got valve float" lol, and said a lot of guys with this cam were running the part #73925K2 LS style valve springs with good results (with factory seals).

Type: Lift LS Dual Valve Spring
Coil Bind: 1.100"
Seat Load: 153@1.810"
Open Load: 400@1.150"
Rate (lbs/in): 379

I'm assuming my opti is partly to blame, however, what is everyone's thoughts on upgrading springs to the LS dual ones? I'm not sure if I should trust the Lunati techs anymore, not to mention Alvin at PCM for less is suggesting I need more seat load on the springs (135-155lb)...I do intend to check the existing springs are installed at correct 1.8" height though very soon. Who's a valve spring expert around here?

bowtienut

iTrader: (1)

I don't know how demanding those Voodoo cam lobes are on valve springs, but those 918 springs sound marginal to me for those cam specs. I wouldn't use those springs for much more than a CC503-ish cam.
I'm running about 160 on the seat with beehives. On paper, my cam doesn't look much different from yours .. 228/234 .617 lift w/1.6's. It peaks at 6400 (in a 350) but pulls cleanly past 7000.
BUT..... with that said, I see in your post just above from last July that the car pulled cleanly to 6500. So......if you trust your tach, I'd say it's more likely that something went south in the ignition rather than in the valvetrain.

Are you running stiffer pushrods and NSA rockers?

Catmaigne

iTrader: (6)

Definitely get a stiffer spring and lighten up the valvetrain if you can. Titanium retainers are always good.

I have the Crane 10308-1 kit with 130 seat @ 1.850 and 400 open @ 1.150 and have read that they're on the edge with something like a cc306. Granted, the steel retainers are dual springs are heavier but I think those beehives you're using aren't enough.