C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

Change cam in sb 406

Old 06-12-2019, 12:06 AM
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Default Change cam in sb 406

I have a Dart SHP smallblock 406 that I went too conservative with for the Howard's cam when I had it built, I would now like to replace the cam with a more agressive Howard's cam that the engine builder, TriStar in Wisconsin, would have normally put in. However I've never changed one and I'm unclear if the cam has be degreed like I've seen in some videos, or is it pretty much a simple replace and check for push rod length changes? The videos I've seen for degreeing your cam all show the heads being off which I do NOT want to do.

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Old 06-12-2019, 07:17 AM
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Degreeing came is not really necessary. The guy who made the cam is usually not stupid. It is interesting and reassuring to see you got what you paid for. But heads do not need to come off.

Last edited by derekderek; 06-12-2019 at 07:19 AM.
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Old 06-12-2019, 07:27 AM
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I’d be more concerned with piston to valve clearance than making sure it is precisely decreed in. I have degreed many cams in SB motors and they are all within 1 degree. If your engine builder speced this cam out the piston to valve clearance should be OK. Go by what he said since he built the motor.
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Old 06-12-2019, 08:19 AM
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What are the specs of the original and what are you going to
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Old 06-12-2019, 10:32 AM
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Default roller cam: cast or steel

FWIW, all those zillions of iron head Vortec V8 truck motors GM made from about 1997 thru about 2002 ... all, ALL had billet STEEL roller cams, Not iron.
Although their roller cams were relatively mild & small & their OE Vortec roller lifter valve springs had a seat pressure well under 90 psi; cam was STEEL.

Today, so many of the aftermarket roller cams are made on a cast iron core or a cast austenitic iron core.
If I had to guess, probably most aftermarket roller cams sold today are ground on some sort of a cast iron core; Not Steel.

Comp, Howard etc offer roller cams on either cast iron or Steel cores. Also, Crane & Chev-GM performance offer several Hi-Po Steel hyd roller cams.

As cam becomes more aggressive, stronger valve springs are called for.
As spring pressures increase, so do wear & tear on cam lobe.

Suggest OP choose a cam ground on a real Steel billet core.

Melonized distributor gear may be called for (as was OE GM Vortec's dist gear).
If fuel pump is Hi-Performance mechanical; bronze-tipped fp PushRod may be called for.
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Old 06-12-2019, 12:19 PM
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I’d call TriStar and tell them what you’re doing, and ask if you’ll need to change out pushrods. They do a lot of builds with Howard’s and will probably know off the top of their head. If you need any different parts they will sell you those as well. If it isn’t a drastic change in lift, probably no change pushrods or springs, but they will know - or look at the parts match-ups on the Howard’s catalog online. A little confusing but info is there.

Do you know what cam p/n you started with, and what you are moving to? I can take a look.

No special disti gear required on the Howard’s cams, at least in the case of my Retro Roller.

Last edited by JoeMinnesota; 06-12-2019 at 12:22 PM.
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Old 06-12-2019, 12:28 PM
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Oh - and as for replacement, you’ll need to obviously open up the front of the motor, drop front of pan (unless you have the luxury of a 2-pc timing cover), pull rockers, pushrods and intake (to pull lifters). Heads can stay on no problem. Degreeing the cam is recommended by many but not crucial, and if you need to swap springs there are ways to do that with the heads on the engine - compressed air to hold valves closed, fitting for spark plug ports and a spring compressor. It’s not a small job but very doable.
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Old 06-13-2019, 11:28 AM
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Default Can change

What length rods was the engine built with, if they were stock rods there is no problem. When you change to the 5.7 rod or any after market rods the cam lobes will hit the rods big end by the head of the rod bolts on a few of them. They must be clearanced . Some rod manufacturers are better than others. Or you can run a small base circle cam. They need to be checked, call your engine builder.
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