Cam advanced too far?

[alexwelsh]

Years ago, I assembled a 350 SBC for a project that went dormant. Late '80s 350, factory roller, 1-piece rear seal motor. It's still fresh, never been fired. I used a new GM roller cam from a ZZ383 crate engine that the owner had replaced before he fired the engine. I couldn't pass, got the cam for free and it was brand new. After some research, I discovered that Crane ground the cams for most of the GM crate engines, and it's listed in their catalog as Part# 109831. GM called it the "846" cam. At the time, Crane was out of business and I didn't have the cam card, but I knew the specs from an old Crane catalog, and so I installed it 4 degrees advanced. Fast forward 8 years, and I wake up in a sweat and something told me to call Crane (now back in business) and ask if they put any advance into the cam when they ground it. Turns out, they put 5 degrees in it. So, I now have a cam that's advanced a total of 9 degrees. I'm curious if I'm OK, or if I have to take the 4 degrees back out to get it to run right. I'm curious if this took the guts out of this little cam and made an even bigger turd out of it. I'm back to working on the truck again, but I won't fire the engine until this gets sorted out.

Cam Specs: 222/230 @ .050, .509/.528 lift on a 112.

The Engine: 9.63-1 compression, Modified 062 Vortecs (cut down guides, correct valve springs, stock ports, some bowl work, 1.5 Crane roller rockers), RPM Air Gap, 750 Holley vacuum secondary (3310), headers, MSD HEI ignition. 700r4 trans, 2200 stall converter, 3.73 rear gear with a 31" tall rear tire. Truck weighs approx. 4300 lbs.

The compression was gained using the factory -22cc dished pistons, a Felpro .015 shim headgasket, and a 64cc chamber. I don't think that at .509 lift, I'm pushing the intake valve that deep into the chamber, but I'm just not sure. The engine will turn over by hand with no restrictions, but can't be sure what it'll do at 6000 rpm.

Thoughts?

[NormS]

I assume you used a 4 degree cam bushing when you assembled the engine , without actually checking the cam advance with a degree wheel. Depending on the tolerances of the crank key way placement , crank gear keyway placement, and cam gear hole for the advance bushing, your actual timing could be way more or way less than 9 degrees advanced.
The only way to know for sure is to go back and check your lobe centers with a degree wheel.

[GARY C]

Years ago, I assembled a 350 SBC for a project that went dormant. Late '80s 350, factory roller, 1-piece rear seal motor. It's still fresh, never been fired. I used a new GM roller cam from a ZZ383 crate engine that the owner had replaced before he fired the engine. I couldn't pass, got the cam for free and it was brand new. After some research, I discovered that Crane ground the cams for most of the GM crate engines, and it's listed in their catalog as Part# 109831. GM called it the "846" cam. At the time, Crane was out of business and I didn't have the cam card, but I knew the specs from an old Crane catalog, and so I installed it 4 degrees advanced. Fast forward 8 years, and I wake up in a sweat and something told me to call Crane (now back in business) and ask if they put any advance into the cam when they ground it. Turns out, they put 5 degrees in it. So, I now have a cam that's advanced a total of 9 degrees. I'm curious if I'm OK, or if I have to take the 4 degrees back out to get it to run right. I'm curious if this took the guts out of this little cam and made an even bigger turd out of it. I'm back to working on the truck again, but I won't fire the engine until this gets sorted out.

Cam Specs: 222/230 @ .050, .509/.528 lift on a 112.

The Engine: 9.63-1 compression, Modified 062 Vortecs (cut down guides, correct valve springs, stock ports, some bowl work, 1.5 Crane roller rockers), RPM Air Gap, 750 Holley vacuum secondary (3310), headers, MSD HEI ignition. 700r4 trans, 2200 stall converter, 3.73 rear gear with a 31" tall rear tire. Truck weighs approx. 4300 lbs.

The compression was gained using the factory -22cc dished pistons, a Felpro .015 shim headgasket, and a 64cc chamber. I don't think that at .509 lift, I'm pushing the intake valve that deep into the chamber, but I'm just not sure. The engine will turn over by hand with no restrictions, but can't be sure what it'll do at 6000 rpm.

Thoughts?

If you have enough piston to valve clearance it will be perfect for nitrous with a very early evo but may hurt tq straight motor.

If the cam was ground on a 107lsa with 4* built in you would be on the same intake center line as you are now.

[PRH]

I never arbitrarily advance or retard a cam.

IMO, the only way to do it is degree it in, and put it where you want it.

[F-BIRD'88]

I'd put it back. Might look at the real engine compression ratio if that matters.
I bet it is lower than you think. Would run great with a supercharger. That cam is a good one for that
on a low cr 350.

For N/A you'd want to be at about 10:1cr.

How did you arrive at -22c piston dish volume. I was under the impression that factory dished 350 pistons are about -15cc. Replacements should be very close.
IMHO that would be a strong runner 350 vortec motor with -6cc flat top pistons.
with the Crane cam installed as per cam card.

[Tuner]

You owe it to yourself to check. It's a lot easier to fix it now than after it's installed in a vehicle. Use two dial indicators, one on each lobe I and E, and see where the equal lift point is. If it is more than 4* BTDC you should fix it. Usually best equal lift point for SBC is 2* BTDC.

[alexwelsh]

I spent some time last night going though my paperwork and found the notes from when I degreed the cam. Come to find out, I did not add any advance to the cam. I basically degreed the cam as I've always done, but what threw me is that the cam came in at 4 degrees advanced and that number stuck in my head. The call to Crane's tech line and them telling me for that they ground 5 degrees into it totally confused me and I mistakenly added the two numbers together (9 advanced). That's the problem with assembling something in 2010 and coming back to it 7 years later. Every assumption is automatically looked at from a worst case scenario. I'm good to go. Thanks for the replies, guys!

[gottago]

re-

You owe it to yourself to check. It's a lot easier to fix it now than after it's installed in a vehicle. Use two dial indicators, one on each lobe I and E, and see where the equal lift point is. If it is more than 4* BTDC you should fix it. Usually best equal lift point for SBC is 2* BTDC.

Is that 2* applicable to all sbc "no matter which cam"..

[mag2555]

You would have a hard time going wrong with putting it in at 109 to 110!
One thing to note with a Cam this size is that checking cranking compression gains with advancing the Cam many times cuts off a bunch of top end !
As with any motor it should be viewed as a air pump first and foremost unless your way under in what the Cam calls for compression wise.

[Geoff2]

The only way to know what THAT engine likes is to try different ICLs. You have tried one already....

[treyrags]

re-

You owe it to yourself to check. It's a lot easier to fix it now than after it's installed in a vehicle. Use two dial indicators, one on each lobe I and E, and see where the equal lift point is. If it is more than 4* BTDC you should fix it. Usually best equal lift point for SBC is 2* BTDC.

Is that 2* applicable to all sbc "no matter which cam"..

He said "usually"

[Newold1]

"When in Doubt, Check it Out" !

[swampbuggy]

NEVER assume anything, assuming oftentimes brings sad regrets Spend a little more time and be SURE. JMHO Mark.

[gottago]

re-

You owe it to yourself to check. It's a lot easier to fix it now than after it's installed in a vehicle. Use two dial indicators, one on each lobe I and E, and see where the equal lift point is. If it is more than 4* BTDC you should fix it. Usually best equal lift point for SBC is 2* BTDC.

Is that 2* applicable to all sbc "no matter which cam"..

He said "usually"

I am used to setting up cam mainly by icl, I've never set by equalizing lift points. I guess my question is, how applicable and universal is this other method? Is the 4degrees (

If it is more than 4* BTDC you should fix it.

something one should check for? When does this stop being applicable? "Usually" applies to what range of cam? What doesn't it "usually" apply to?

[MadBill]

In the absence of experience or direction from the grinder, 4°actual advance and checking P/V clearances is about the closest you can come to a 'universal' index.
Best I can tell, something over 10% of all cams will be substantially 'off' if bolted in dot-to-dot. My last handful have all been Jones and about as close as I can measure, but a number of years ago I put a Lunati in a 455" Buick 'on the marks' and found it retarded 17°.