Comp Cams 268H and 1.6 rockers

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98chevy2500SS

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Just bought an 89 C1500 this afternoon with a 350 TBI. Engine needs rebuilt and I will be swapping some Vortec heads on it. I want to run the Comp Cam 268H, but already installed the 1.6 rockers on the heads, will this be safe combo? Or are the 1.6 rockers too much? I have upgraded the springs and the heads+valves have been completely refurbished (essentially they're already put together, just need to thrown on my engine).
 

Schurkey

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Good luck with the Vortec heads.

It's difficult (expensive) to keep the EGR system when using Vortecs. You'll have to deal with either the hyperexpensive GM TBI-to-Vortec intake manifold, or the improper fitment of accessory struts and such with Vortec "carb" intake manifolds + a TBI adapter. You'll have to fabricate something for the bracket that holds the throttle, cruise, and transmission TV cables since the stock bracket is intended to use the angled intake manifold bolts and the Vortec manifold bolts are positioned differently.

In short, the Vortec heads are a pain in the ass with no good solution. Better to get the Summit aluminum "TBI" heads instead of Vortecs. Use the stock intake manifold, and ZERO fitment problems or fabricating.
www.summitracing.com/parts/sum-162108

THIS cam?
www.summitracing.com/parts/sum-162108

.454 lift with 1.5; means .4842 lift with 1.6 rockers. I don't think 1.6 rockers are inherently a problem. You'll need to verify that the valve springs will be stiff enough, and can accept the lift you're going to have--along with retainer-to-seal (or guide) clearance, etc.

These are self-aligning rockers...right? If you don't have self-aligning rockers, you have to get pushrod guideplates and hardened pushrods or the guideplates will scrape the stock, non-hardened pushrods and fill the oil with shavings. The way I remember Vortec heads is that they've got press-in studs, so guideplates are difficult without machinework and new rocker studs.

The bigger question is "why would you install a flat-tappet cam?" Your engine may have a block already set up for an OEM roller cam. OEM roller-cam parts are readily available in the Treasure Yards for little money. You'd end up with a better/more durable system with little chance of break-in problems.

If you INSIST on a flat-tappet cam, make sure you pay extra to have it Nitrided.

No promises on what sort of tuning you'll have to do to make the computer happy with the new cam. That cam has an emissions approval for '87 and older carb'ed engines, but not TBI.
 
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alignman88

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Good luck with the Vortec heads.

It's difficult (expensive) to keep the EGR system when using Vortecs. You'll have to deal with either the hyperexpensive GM TBI-to-Vortec intake manifold, or the improper fitment of accessory struts and such with Vortec "carb" intake manifolds + a TBI adapter. You'll have to fabricate something for the bracket that holds the throttle, cruise, and transmission TV cables since the stock bracket is intended to use the angled intake manifold bolts and the Vortec manifold bolts are positioned differently.

In short, the Vortec heads are a pain in the ass with no good solution. Better to get the Summit aluminum "TBI" heads instead of Vortecs. Use the stock intake manifold, and ZERO fitment problems or fabricating.
www.summitracing.com/parts/sum-162108

THIS cam?
www.summitracing.com/parts/sum-162108

.454 lift with 1.5; means .4842 lift with 1.6 rockers. I don't think 1.6 rockers are inherently a problem. You'll need to verify that the valve springs will be stiff enough, and can accept the lift you're going to have--along with retainer-to-seal (or guide) clearance, etc.

These are self-aligning rockers...right? If you don't have self-aligning rockers, you have to get pushrod guideplates and hardened pushrods or the guideplates will scrape the stock, non-hardened pushrods and fill the oil with shavings. The way I remember Vortec heads is that they've got press-in studs, so guideplates are difficult without machinework and new rocker studs.

The bigger question is "why would you install a flat-tappet cam?" Your engine may have a block already set up for an OEM roller cam. OEM roller-cam parts are readily available in the Treasure Yards for little money. You'd end up with a better/more durable system with little chance of break-in problems.

If you INSIST on a flat-tappet cam, make sure you pay extra to have it Nitrided.

No promises on what sort of tuning you'll have to do to make the computer happy with the new cam. That cam has an emissions approval for '87 and older carb'ed engines, but not TBI.
Since when did the GM Performance Vortec TBI intake become worth $615.00?!?! Holy smokes! I’ve had mine since about 2002-2003 (currently on a all new not reman GM long block with low miles that I pulled out of current build) and I swear I only paid about $300 for it then! Ridiculous prices, I almost fell over!
 

Erik the Awful

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Putting a TBI on Vortec heads isn't terribly difficult.

I don't know of too many spreadbore Vortec manifolds, so unless you want to spend stupid money on the GM TBI-Vortec intake, you're going to need a spreadbore-to-squarebore adapter. In the picture below I have a TBI adapter plate sitting on the squarebore and spreadbore sides of an adapter so you can see how a squarebore manifold is hindered.

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Mounting the throttle linkage and TV cables isn't terribly difficult. Get the Summit kit shown below - on a Holley Sniper, but if you're already adapting to a 4-barrel manifold, it'll bolt on.

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Get a stock roller setup out of a junkyard motor, pull the lifters apart and inspect and clean them thoroughly, and run a roller cam. The failure rate on flat tappet cams is skyrocketing. With a stock-ish spring pressure a set of factory roller lifters will be just fine. I'm running LS2 beehive springs, which are about 10% stiffer than stock L31 springs. Comp Cams 787-16 retainers fit them to stock valves and with umbrella valve seals you can run up to .530" lift with no machining.
 

Hipster

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As said, check retainer to guide clearance. I've had Vortecs in my hands that wouldn't go .460 considering room for the seal plus another .030-.050 "free space". .480 is probably a bit much for stock vortec springs. Get the recommended springs with the cam.
 
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L31MaxExpress

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As said, check retainer to guide clearance. I've had Vortecs in my hands that wouldn't go .460 considering room for the seal plus another .030-.050 "free space". .480 is probably a bit much for stock vortec springs. Get the recommended springs with the cam.
GM ran 0.481 lift on the Ramjets using stock Vortec heads. I have had plenty in my hands that had clearence at 0.492 lift.
 

Hipster

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GM ran 0.481 lift on the Ramjets using stock Vortec heads. I have had plenty in my hands that had clearence at 0.492 lift.
And that's great, if you didn't check you wouldn't know. I kind of doubt they're running those numbers on stock 80# springs. It's a clearance I always check when deviating from stock instead of taking somebody else's word for it.

If you get it wrong, crash, bang, boom, is a bad day.
 

L31MaxExpress

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And that's great, if you didn't check you wouldn't know. I kind of doubt they're running those numbers on stock 80# springs. It's a clearance I always check when deviating from stock instead of taking somebody else's word for it.

If you get it wrong, crash, bang, boom, is a bad day.
GM ran those numbers with stock springs, stock retainers and stock seals.

I agree, best policy is to check.
 
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