[KingLT1]

Correct. I would look at conical springs but they may not have much advantage over beehive at those rpm peaks. I like your thinking...a mild cam with a single spring should work well with a VVT limited setup.

I like the specs on this cam. https://www.speedinc.com/speed-inc-l...-camshaft.html

[6spdhyperblue]

That cam is actually pretty much what I was wanting Conical sounds like a good idea for the speedinc one.

I haven’t seen that one before.

At first I was thinking if cam motion lobes would be mild enough to run oe lt1 springs if I picked the .576 or maybe even down to the .567 lift lobes? the hotcam is .570 but likely slower ramps than even cam motion? Maybe I’ll call them.

My thought is, I would like to keep the pressures down and not beat up the seats, on top of that, keep the load off the phaser.

Edit: found it on Katechs 0* lockout kit
“ These Chevrolet Gen V mechanical lock outs are used to prevent the VVT mechanism from retarding in high horsepower applications with high cylinder pressures. As cylinder pressures increase the amount of force needed to open the exhaust valves increases which can force the VVT mechanism to retard excessively. ”

Is that plausible? If that’s the case, how would the lt4 or a whipple lt1 handle it? Isn’t the cyl pressure much higher in that application? Or is the cyl pressure only an issue when the high rate springs and plus size fuel lobe are loading it

[KingLT1]

Originally Posted by 6spdhyperblue

That cam is actually pretty much what I was wanting Conical sounds like a good idea for the speedinc one.

I haven’t seen that one before.

At first I was thinking if cam motion lobes would be mild enough to run oe lt1 springs if I picked the .576 or maybe even down to the .567 lift lobes? the hotcam is .570 but likely slower ramps than even cam motion? Maybe I’ll call them.

My thought is, I would like to keep the pressures down and not beat up the seats, on top of that, keep the load off the phaser.

Edit: found it on Katechs 0* lockout kit
“ These Chevrolet Gen V mechanical lock outs are used to prevent the VVT mechanism from retarding in high horsepower applications with high cylinder pressures. As cylinder pressures increase the amount of force needed to open the exhaust valves increases which can force the VVT mechanism to retard excessively. ”

Is that plausible? If that’s the case, how would the lt4 or a whipple lt1 handle it? Isn’t the cyl pressure much higher in that application? Or is the cyl pressure only an issue when the high rate springs and plus size fuel lobe are loading it

You know that is a good question I honestly don't have a answer for but from what I have found it only appears to be a issue with high rpm and larger cams. So I am going to say you might be on the right track with high rate springs and the larger fuel lobe theory.

[oldman]

The conical look good but they do have a LOT of pressure. It was interesting to know that when superchevy did a VVT cam install on the Vette, they went with conical springs on the VVT lifter?!? what???? I honestly think conical would be complete overkill on a mild lobe. GM use OEM springs on the hot cam with a max rec rev of 6600 RPM. I do think a beehive would work for mild lobe cams. I did not do any further research as I already had TSP twin springs and these do seem to work well enough on my low lift gentle ramp cam motion cam.

https://www.texas-speed.com/p-6431-p...-pac-1219.aspx


The srpring rate of the conical is 519 lbs / inch with a 145 # seat. That is heck of stiff... just off the cuff it looks to be TWICE as stiff.
https://www.compcams.com/675-lift-co...m-lt1-ls7.html

Here is the TSP twin spring and and it looks to be 246 lbs over .650" that would mean a .575 cam would see 218 lbs + 145 seat = 363 open. So with a low lift cam the TSP twin spring becomes pretty reasonable to my mind in terms of open pressure. Which makes sense as it is designed for .650 lift aggressive ramp cams.
https://www.texas-speed.com/p-5440-t...-seatseal.aspx

So to address boost, we know GM went to a titanium valve to make the intake that much lighter for a boosted application, slightly small cam too. All it all it must mean the LT1 under boost must be marginal at best with the stock cam lobe, diffidently would NOT meet OEM longevity / reliability spec.

[cmitchell17]

Originally Posted by oldman

The conical look good but they do have a LOT of pressure. It was interesting to know that when superchevy did a VVT cam install on the Vette, they went with conical springs on the VVT lifter?!? what???? I honestly think conical would be complete overkill on a mild lobe. GM use OEM springs on the hot cam with a max rec rev of 6600 RPM. I do think a beehive would work for mild lobe cams. I did not do any further research as I already had TSP twin springs and these do seem to work well enough on my low lift gentle ramp cam motion cam.

https://www.texas-speed.com/p-6431-p...-pac-1219.aspx


The srpring rate of the conical is 519 with a 145 # seat. That is heck of stiff.
https://www.compcams.com/675-lift-co...m-lt1-ls7.html

The GMPP calibration file for the LT535 has a 7100 rpm extreme fuel cut rev limit, and a 7000 rpm in gear rev limit. I think its really surprising they used stock springs.

I think I remember from the LS1/LS6 the main RPM limiting factor was that the natural frequency of the valvetrain was in the high 6000 rpm range. I wonder what it is for the LT1. I would assume they would never allow operating at or close to the natural frequency or any multiples of it.

[oldman]

Originally Posted by cmitchell17

The GMPP calibration file for the LT535 has a 7100 rpm extreme fuel cut rev limit, and a 7000 rpm in gear rev limit. I think its really surprising they used stock springs.

I think I remember from the LS1/LS6 the main RPM limiting factor was that the natural frequency of the valvetrain was in the high 6000 rpm range. I wonder what it is for the LT1. I would assume they would never allow operating at or close to the natural frequency or any multiples of it.

Pretty surprising, I assume it was 6800 RPM. I'd be more worried about the stock rod bolts to be honest.

Anyway here is the comp cam master chart:
https://www.compcams.com/valve-spring-chart
glancing through the 1.8" height 7228 part number conical would have at 1.2" (.600 lift) of 399 lbs is the lightest conical I saw.

[cmitchell17]

Originally Posted by oldman

Pretty surprising, I assume it was 6800 RPM. I'd be more worried about the stock rod bolts to be honest.

Anyway here is the comp cam master chart:
https://www.compcams.com/valve-spring-chart
glancing through the 1.8" height 7228 part number conical would have at 1.2" (.600 lift) of 399 lbs is the lightest conical I saw.

Anyone know if anyone has checked the rod bolts in a high rpm engine? After seeing the 7100 extreme limit. The GMPP LT535 tune also has a WOT PE equivalence ratio of 1.08 at peak torque and 1.05 at peak HP. That's a 13.4 AFR for E10 gas or 13.98 for E0 gas. Sometimes I think there was some kind of flash error when this GMPP tune was read, its hard to believe, but I am a big believer that people overly freak out about WOT enrichment, I bet if I did the math to find the heat capacity and absorobtion potential of 5% extra fuel I bet I would find its only worth a few HP.

It makes me feel a lot better about my Johnson 2110/Pac Dual springs/ and thicker pushrods being safe on my valvetrain knowing that GM (or at least GMPP engineers) tuned it that way.

[Nabush]

A cam which keeps VVT is the Katech Torquer cam.
They pair it with PSI 1511 ML beehive springs. They keep 22 degrees VVT they told.

I just received my Katech Stage 2 engine with this config. I makes 570HP/535FT LBS crank with Katech ported heads, stock manifold, stock TB and 93. With my MSD, ported 95mm TB and E85 I hope to get 610-620 crank (540-560Whp). Which is what they advertised here on a Camaro (560whp) with same config.

[6spdhyperblue]

That is good to know. Do they provide you with the wot cam timing. Also what fuel lobe are they using?

The cam did interest me but wonder about the high valve lift.

[Nabush]

Originally Posted by 6spdhyperblue

That is good to know. Do they provide you with the wot cam timing. Also what fuel lobe are they using?

The cam did interest me but wonder about the high valve lift.

38% fuel lobe.

No I have to figure out the cam timing myself. I'll use 11 deg first like factory at wot to see how it works.

Basically full advance (0 deg) up to 3000, then gradually up to 11 deg at 6400 from memory. I'll have to test on the dyno I'm pretty sure to really see the difference.

On oem cam the 30deg are only used at part throttle...

As far as lift goes....Katech know what they are doing IMO, if they give 3 years/36,000 miles warranty they are confident... You see more Katech engine on roadcourse than all other builders like TSP, who only do drag racing (easy)

[6spdhyperblue]

Ok sounds good. Have they given you a valve spring service interval during the 36,000 mile warranty? If not I would assume a safe 36k, which is good.

Also, how much advance is ground into the cam. That would dictate how much you can advance it. Stock cam has 8.5* apparently Ground in

[Nabush]

Originally Posted by 6spdhyperblue

Ok sounds good. Have they given you a valve spring service interval during the 36,000 mile warranty? If not I would assume a safe 36k, which is good.

Also, how much advance is ground into the cam. That would dictate how much you can advance it. Stock cam has 8.5* apparently Ground in

They told me valve springs are good for 40,000 miles per PSI but recommend a check at 30,000 miles.

I don't know of much advance is ground in this cam...I can ask...

To note they told me they recommend 6800 rpm max with the psi 1511 springs and GM LS7 lifters. Though I see their dyno go up to 7000.

[NickyRacerBoy]

I bagged the cam phaser all together...I mean it's gone!
Specs:

Cam grind number LL248/365-LL262/360-114+2.
Lift with 1.8 intake .657" / exhaust .648".
Lobe separation 114 with 112 intake centerline.
Intake duration at .050" is 248 / exhaust 262.
Spring kit VSK143309 is $689 for springs, retainers, valve locks, valve seals, and spring seats.
Spring pressure 200 lbs at 1.800" installed height, 585lbs at 1.100".
Lifters with hi pressure axle oiling $849.95.



LME billet timing cover, Cam Motion LLR, Ti intake valves ported heads etc...
Tune Time Performance did all the tuning in Lakewood NJ.

[oldman]

I looked at the axle oiling but felt that was overkill on mine plus I worried about getting the correct preload, and lastly not all race parts are durable for 100K. Really it was the lack of adjustment you can get on precut pushrods. IMO you need full rollers on adjustable studs. I'm not sure how that works as there is a "seat" in the head. At Harland Sharp (some) do have an adjustable pushrod seat. TSP dunno.