[1967chevelle454]

I'm planning on using a comp cam 292h magnum cam in my 454. Can I run on 93 octane?

[F-BIRD'88]

Originally Posted by 1967chevelle454

I'm planning on using a comp cam 292h magnum cam in my 454. Can I run on 93 octane?

As long as your savings account holds out.

[Blazin72]

Originally Posted by 1967chevelle454

I'm planning on using a comp cam 292h magnum cam in my 454. Can I run on 93 octane?

More importantly, how much compression do you have? What are the combustion chambers like in the heads?

[1967chevelle454]

I still building the engine right now, looking at pistons. I have a set of open chambered 781 heads, and I'm looking at buying a set of speed pros with about a .340 dome. This should give me around 10.34:1.

[Centerline]

Originally Posted by Blazin72

More importantly, how much compression do you have? What are the combustion chambers like in the heads?

This is the correct question to be asking. It's compression ratio that determines the octane you need to run more than cam timing. I ran that same cam in my pro-street 41 but I also had 9.5 compression. I used regular gas and threw in half a can of octane boost every in every tank, although I probably didn't need it. Never had any pinging that way though.

[Double_v23]

I would say with 10.34:1 you would not be able to run premium. Even if that cam bleeds off a lot of compression because of excessive overlap. You need to shoot for at the most 9.5:1

[F-BIRD'88]

Camshaft overlap do not "bleed off compression".

The engines cranking cylinder pressure is effected by the intake valve closing point (start of compression), not the valve overlap. The cam overlap causes exhaust dilution of the intake charge at low engine rpm. Thats what give the rough racey idle sound.
The overlap induced exhaust dilution at idle and low rpm acts like EGR, diluting the air fuel mix with exhaust gas, This reduces peak cylinder pressure during combustion (at low rpm) as the exhaust will not burn twice. this tends to lower an engines tendency to knock at low rpm with a high compression ratio. Unless the motor is way over cammed, the EGR effect of the cam overlap is gone by the time the motor is near peak torque (high volumetric efficienty).

[1967chevelle454]

So do you guys think I could get away with 10:1 with this cam and pump gas?

[F-BIRD'88]

Originally Posted by 1967chevelle454

So do you guys think I could get away with 10:1 with this cam and pump gas?

If its just 10:1 and not over and you build the motor with proper piston-head quench clearance and use a cooler than stock heat range hi perf spark plug and get the carb jetting and timing just right you should be ok. May have to take a few degrees of spark timing out for street use.

Hi Perf Big Block Chevys work a lot, lot better with a mechanical lifter camshaft.

Here are two better/nicer/sweeter street/strip Magnum solid series cams for your 454.

Comp cams #11-219-4 294S solid Magnum camshaft.

And Comp cams #11-551-5 CB-280S-10 "Magnum Muscle" solid camshaft.
Either, works very well in the type of motor you are building.
( this is the "LS-6 cam on steroids!") A nice S&S cam.

For a +.030" 454 BBC with 10:1 cr use this TRW/Speedpro L2349F-30
combined with a "0 decked block" and open your heads up for a 123CC combustion chamber (deshroud for big valves) 10.09:1 finished cr.

Or you can use this other smaller domed piston #L2399F-30

combined with a "0 decked block" and mill your heads to 110CC chamber volume for 9.93:1 finished cr.

If you don't want to "0 deck the block" then use the factory GM LS-6 .022" head gasket (GM parts dealer item) and just cut .005" off the block decks to clean them up.
Your effective measured cr and net quench clearance will be the same as above.
Can be done either way.

The secret is getting the combustion chamber volume, piston deck clearance ( deck height) and piston dome volume matched up to get you 10:1 even and .040" net piston-head quench clearance.

if you don;t bother to get it right, don't expect it to run on 93 octane gas.

[1967chevelle454]

What's the street-ability and idle quality on the magnum muscle ls-6 cam? Also how do mechanical cams compare to hydraulic in reliability and maintenance?

[F-BIRD'88]

Originally Posted by 1967chevelle454

What's the street-ability and idle quality on the magnum muscle ls-6 cam? Also how do mechanical cams compare to hydraulic in reliability and maintenance?

It's very similar to the hydraulic 292H magnum cam. has the same rough racey idle. But makes more torque and power and will rev higher because it is a mechanical lifter cam. They are more responsive as a rule.
Take a hint from GM , Ford and Chrysler. All the big power top of the heap muscle car motors had a solid lifter cam. 426Hemi, LS-6 454 427-L88
Boss 429 429SCJ 440 Max wedge race, 302/Z28 327-375HP FI Boss 302 all had solid lifter cams.
Reliabilty is the same. They do require periodic valve lash adjustment as part of your tuneup routine. Once or twice over a Summer cruise season is plenty.
usually only a few of the 16 valves will need a touch up lash adjustment.
Once you've done the lash routine a few times, its no big deal.
Takes me about 20 minutes. if you change the oil every 5000 miles, then touch up the valve lash every 5000 miles or so.

A BBC has a big heavy valve train and can really use the high rpm benefits of a solid lifter for superior valve train control at high rpm (no lifter pump up).
Both these cams will outperform the 292H cam.
The CB-280S-10 is a little bit tamer than the Comp 294S cam. (shorter intake duration, little less overlap) My favorite "LS-6 cam on steroids cam" for the BBC. it gets the job done nicely.
It's a matter of degree as the car will drive and idle very similar but the solid lifter cams , expecially the CB280S-10 cam will be snappier and torquer with extended power in the upper range. its just a better setup for the BBC.
The idle sounds a bit more "busy" under the hood with a properly lashed solid lifter cam. Its a cool sound that no wimpy hydralic cam has.
These solid lifter Magnum cams are designed to be a "street cam" and not be a pain to live with.

The 294S has a cool sounding "Take No Prisoners" idle yet drives nicely and makes big power. Both, need a 3200-3500 stall converter just as the 292H does. If you want maximum Street/strip performance, either one of these is what you want. The 292H is for the girliemen. Real men set their own valve lash.

[1967chevelle454]

I'm thinking I'm gonna stick with the 292h I have just because I already have it and I want to stick with hydraulic. I'm not to worried about the lifters floating because I won't be running in the higher RPM much. As you guys can probably tell I'm still a newbie when it comes to engine building, first one! Thanks for all the help. F-bird88, if I want to use your first combo with 10:1 what all do I need to buy and tell my machinist to do?