Used LT1 350 Camshaft Swap Into Truck Block w/Vortec Heads?

[L31MaxExpress]

The stock LT4 studs were 3/8 on the bottom, and had a shouldered 10mm top with a matching poly style nut and 10mm specific 1.6 rocker. They were made by Crane and in the early/mid 2000s were cheaper than just about any other narrow body self-aligning rocker arm plus you got screw in-studs. I bought multiple sets of them used from lower milage cars that had been updated to aftermarket stuff, sometimes for as little as $100 for everything. I bought the whole valvetrain a couple of times too, including cam, springs and retainers.

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[rebelyell]

Any used roller cam may have "tracking" damage on lobe(s); do inspect for it and don't dismiss it.

Lotsa ways to skin the Vortec lift issue for small money: "ghetto grind" with Z28 springs.
FWIW: summit has a house brand line of 4 step-nose all USA billet steel performance roller cams under $280.

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[Hipster]

Heads are at the machine shop now. I asked about the springs, and the machinist thinks the stock springs *should* be able to handle a stock 1993 LT1 F-body cam. A Google search led me to a post that indicates the max lift of that camshaft should be .480. I found another thread about the max lift stock Vortec heads can handle; a few people said that .480 is the absolute maximum, but "right around .470-.480 lift the bottom of the retainer starts to hit the top of the valve stem seal". Should I be worried? I'm up for second opinions; the machine shop surely knows what they're doing far better than I do, but he also seemed to be guessing off the top of his head without looking up anything about the specs I'm working with.

You need a bit more room. Typically .030-.050 between retainer and seal. Over rev or float valves and crush/split the seals.

 

[Hipster]

Any used roller cam may have "tracking" damage on lobe(s); do inspect for it and don't dismiss it.

Lotsa ways to skin the Vortec lift issue for small money: "ghetto grind" with Z28 springs.

I didn't ghetto grind as the I have the guide tool. But have done the z28 springs with old school slower ramp up to about .450-.460 lift HFT's several times, about all they're good for. Not sure I would do it with a more aggressive roller cam. Typically z28's are 110-114 lbs. on the seat whether that's enough depends on the cam and spring specs. The heads i did needed the dampers pulled for the z28's also so it's all wrong for something you want to twist up.

 

[Majoraslayer]

I ended up abandoning the LT1 cam about a month ago, the scoring on the bearing surfaces plus a couple of odd wear spots on two lobes were too bad to reuse it. Instead I picked up a Summit 8800 cam per L31Man's suggestion, and it appears to be more in spec with what stock Vortec heads can handle. I'll be running aftermarket heads with screw-in studs, but I'm pretty sure they're still stock spec on lift anyway.

 

[Hipster]

t I'm pretty sure they're still stock spec on lift anyway.

Brother, do check. Crash, boom, bang is a bad day,

 

[rebelyell]

I didn't ghetto grind as the I have the guide tool. But have done the z28 springs with old school slower ramp up to about .450-.460 lift HFT's several times, about all they're good for. Not sure I would do it with a more aggressive roller cam. Typically z28's are 110-114 lbs. on the seat whether that's enough depends on the cam and spring specs. The heads i did needed the dampers pulled for the z28's also so it's all wrong for something you want to twist up.

FWIW
OE springs in Vortec heads (including 350/357 CPP crate) ... when new are about 80 lbs on seat aka closed. That 350/357 is a rather sporty roller-lifter piece; in spite of fact seat pressure ~ 80 psi.
350/357 valve lift is speced by GM at 0.473" both I&E. It's same spring PN that's OE in OE iron Vortec production head. Easily good to 6K in that motor with that hydraulic roller cam

Yes, like the OE Vortec springs (which have no dampers), one must delete the Z28 springs' flat dampers in order for spring to fit & hug Vortec guide bosses. Simply pull em out & trash em.

Also, during GM assembly, Many times those OE Vortec VS Seals are Not properly seated down onto guides; that further and unnecessarily restricts-limits valve travel before bottom of retainer smacks seal. There's an illustration and a spec for that fitment in GM Powertrain manual for L30 & L31 Vortec ... I don't have spec handy but it's NOT intended to push seal down until it can't move any farther; that'd be wrong ! ... so, please defer to GM spec.

*** Here's that spec in another man's post

Valve Stem Seals Differences

So looking at replacing my valve stem seals and notice a couple big differences between FelPro (SS72861) and GM Genuine (10212810,12564852) seals. First is that the GM Genuine exhaust and intake are separate product numbers and look different, while the FelPro set supposedly has both but they...

www.gmt400.com

Ghetto grind retainer material about 0.090" away from bottom of retainer ... No problem so long as locks aka keys are Not proud of bottom of retainer. Dry-fit valve stem, retainer & locks on bench to Confirm locks not protruding below retainer.

 

[Hipster]

FWIW
OE springs in Vortec heads (including 350/357 CPP crate) ... when new are about 80 lbs on seat aka closed. That 350/357 is a rather sporty roller-lifter piece; in spite of fact seat pressure ~ 80 psi.
350/357 valve lift is speced by GM at 0.473" both I&E. It's same spring PN that's OE in OE iron Vortec production head. Easily good to 6K in that motor with that hydraulic roller cam

Yes, like the OE Vortec springs (which have no dampers), one must delete the Z28 springs' flat dampers in order for spring to fit & hug Vortec guide bosses. Simply pull em out & trash em.

Also, during GM assembly, Many times those OE Vortec VS Seals are Not properly seated down onto guides; that further and unnecessarily restricts-limits valve travel before bottom of retainer smacks seal. There's an illustration and a spec for that fitment in GM Powertrain manual for L30 & L31 Vortec ... I don't have spec handy but it's NOT intended to push seal down until it can't move any farther; that'd be wrong ! ... so, please defer to GM spec.

Ghetto grind retainer material about 0.090" away from bottom of retainer ... No problem so long as locks aka keys are Not proud of bottom of retainer. Dry-fit valve stem, retainer & locks on bench to Confirm locks not protruding below retainer.

I hear ya man , but what was the highest lift in a sbc Chevy when z28 springs were a thing? 327 or 350/375hp .460-.465? Bottom line get the springs recommended for the cam. If you want to half-ass it have at it.

 

[rebelyell]

I hear ya man , but what was the highest lift in a sbc Chevy when z28 springs were a thing? 327 or 350/375hp .460-.465? Bottom line get the springs recommended for the cam. If you want to half-ass it have at it.

Consider some of that roller lifter-heavy spring line of logic stems from motors with heavier valve trains; rather than more modern OE roller lifters and smaller but more efficient valve sizes.

Do ya think GMs engineering & design teams are stupid?

FWIW: retrofit-roller lifters weigh LOTS more than post-'86 factory OE roller lifters. And many of those custom roller motors also have Larger (& thus Much heavier) valves.

In general, Heavier valve trains require Higher spring pressures to Control that Higher mass; and vice versa. A few grams here and there matters; as well as cycle frequency. The faster it goes, the more that mass matters; as well as the slower that mass moves back & forth matters even less.

Both more modern ('though now nearly 40 years old) OE GM roller lifters and smaller valve heads weigh less and require less spring pressures to control.

I'm not against nice parts; but neither am I against using whatever works just as well.

It ain't half-ass chief ... it's the application of some calcs, a pencil and more up to date knowledge. A few hours of frosh physics don't hurt either. Suggest don't be so quick to poo-poo others' proven tech; especially when necessity of working within "stock class" track/division rules have been at play.
Your $ Your choice.