Cam help from Engine builders

[PbFut]

I just fired a 1st Gen 350 after a top end rebuild. All vacuum ports temporarily capped to eliminate external failures. No vac advance... plugged at this time. Flat tappet hydraulic lifters. I preloaded with ½ turn more at zero lash. Barely could start the motor. Backed off preload ¼ turn. It helped but things are not right. Engine will barely run at 25ish degrees of timing advance. Vacuum is low while in the idle range and comes up a lot when engine is in the 1500-2k range. My suspicion is that I missed, by one tooth, when installing the cam timing chain and the cam is too advanced. Picture of cam card for reference.
I was looking for that old fashioned thump without compromising street manners too much.
Am I on the right track relative to cam degree or is there something simple I am not considering?

[72SB]

did you see if the dots on the 2 timing gears were dead nuts aligned

With the cam gear at 12:00 and the crank gear at 12:00 you are at TDC firing #1 cylinder. With cam gear at 6:00 and crank gear at 12:00 (as recommended for ease of alignment at assembly) you are at TDC exhaust stroke on cylinder #1...and you are actually at TDC firing #6 (1/2 way around the firing order).

what method did you use to lash valves...EOIC or the do these valves at #1 TDC and the other half at #6 TDC method

[PbFut]

Oh ****. I think I have that cam 180 out. I thought it was 12:00 on the crank and 6:00 on the cam to be at TDC on #1 I can't believe the engine started with the cam 180 out.

[Mnguy]

The cam is not 180 degrees off per se. Since it is 2 revolutions of the crank for every 1 of the cam, it will line up the next revolution of the crank. Your distributor will be off 180 if you set it to #1 though. At least it is easier to pull the distributor than the cam!

[PbFut]

Originally Posted by Mnguy

The cam is not 180 degrees off per se. Since it is 2 revolutions of the crank for every 1 of the cam, it will line up the next revolution of the crank. Your distributor will be off 180 if you set it to #1 though. At least it is easier to pull the distributor than the cam!

Even easier to swap the wires. I need to eat lunch as I got the hangries right now. Glad I posted. I would have ripped everything apart not thinking things through. It's been a long time since Iv'e been this deep in the motor and this old brain is not as mechanically spry as it once was. Thanks for the sounding board.

[LS short box]

Depending your engine set up that cam is on the upper side of of mid-size. The 107 lobe separation is going to help low power but it will have a very choppy idle. Not much you can do about the vacuum with that cam.

[72SB]

Have to think about this cam/crank gear being off thing....even if dizzy gets 180 and wires moved on cap....would the balancer and timing tab be right relative to using a timing light??

or would the timing tab need to move to other side of timing cover??

[PbFut]

So having thought about it more, the distributor has to be in correct orientation since I indexed it relative to the rocker positions on #1 and at the time I thought it was odd that I rotated the crank so much. In setting the distributor to the rockers it eliminates theory the distributor being out 180.
I put a call into Comp Cams. The Tech was very knowledgeable. We determined the cam I selected would have done what I was attempting had the compression been in the 11 to 1 range. This engine is no where near that. So I opted to rethink the selection, and smooth things out some. I should have called Comp Cams initially. Relying on written descriptions at summit was not the smart thing to do. Education is expensive.

[RustyPile]

Originally Posted by PbFut

So having thought about it more, the distributor has to be in correct orientation since I indexed it relative to the rocker positions on #1 and at the time I thought it was odd that I rotated the crank so much. In setting the distributor to the rockers it eliminates theory the distributor being out 180.
I put a call into Comp Cams. The Tech was very knowledgeable. We determined the cam I selected would have done what I was attempting had the compression been in the 11 to 1 range. This engine is no where near that. So I opted to rethink the selection, and smooth things out some. I should have called Comp Cams initially. Relying on written descriptions at summit was not the smart thing to do. Education is expensive.

The 107* lobe separation angle is what gives the engine that "big cam" Lopey idle and low vacuum readings. The exhaust valve is not fully closed when the intake valve starts to open. It impresses the middle school kids but doesn't do much for engine performance increases.. You're overthinking this stuff.. No need to redo the timing chain, nor do you need to relocate the timing tab to anywhere.. Leave the valve adjustment alone for now. Either re index the distributor or rotate the wires 180* which will not effect the ignition timing one bit.. Actually, if the distributor were off 180*, the engine would not start under any conditions.. All you'd get would be backfires and spitting through the carburetor, but certainly no bad or funky idle characteristics, because the engine will NOT start or run.

[PbFut]

Thanks Rusty
We came to the same conclusion over the phone with Comp Cams. The Tech was very informative and helpful. And yes, that middle school kid sound was what I was looking for, knowing it was a marketing ploy of the 70s relative to it sounding hot but actually adding little or nothing to power. We came to the conclusion that the engine compression as built is just too low and cam too much. Hopefully the Tech was not trying to sell me another cam. I was on the right path for my original idea, I just goofed a bit on execution. A swap won't be too much effort as the front of the truck is still disassembled. I just had the radiator setting on the frame rails for startup.

[MikeB]

Originally Posted by PbFut

Oh ****. I think I have that cam 180 out. I thought it was 12:00 on the crank and 6:00 on the cam to be at TDC on #1 I can't believe the engine started with the cam 180 out.

No such thing as 180 out. Nothing wrong with dots lining up next to each other, so long as you know that it's TDC compression stroke on #6.

Could be the lifter plungers were compressed a little when you thought you were at zero lash. Zero lash should be more obvious now with oil in the lifters.

[MikeB]

Originally Posted by RustyPile

The 107* lobe separation angle is what gives the engine that "big cam" Lopey idle and low vacuum readings.

Not to mention the 227/241 duration, which would cause a lope even on a 112 LSA.

What is the compression ratio? I didn't see it mentioned. I suspect that cam would like around 10:1 or 11:1.

[PbFut]

Mike
You are absolutely right. This is a cam suited for high compression and where I made the mistake in selection. My bottom end is low compression and as a result have mistakenly over cam'd the engine. I know better yet still made the mistake of putting too much cam in the motor. I had made the decision that I wanted that old school lope to the engine idle commonly heard in the early 70's knowing that I would likely give up a bit of power for it. But I went too far and it was a bad result.

[MikeB]

As I recall, the old skool Comp 268H High Energy cam had a nice little lope, but not enough duration or overlap to hurt driveability. Its specs are 268/268, 218/218, 110LSA, .454"/.454". And it's happy with 9.0:1 compression.

I think that even the 270H Magnum series cam would have better manners. It has much less exhaust duration than your current cam, and a 110 LSA, so its overlap would be significantly less. But it would definitely lope.

You might want to ask for advice over on the HotRodders.com forum, where there's a lot of engine expertise.

The phone support guys at big companies like Comp have so many incoming calls that they can't spend much time with you. And I'm not even convinced they know more than many of their customers.

[kwmech]

I love the way that 268 cam runs in both a 350 and a 400.

[Mid-Pack]

In my young days, I had a 268H cam in my Camaro. It was my daily and drove it 50+ miles 6 days a week for work many years. It had 9.5:1 comp and had a nice little lope to it. No vacuum issues and ran strong. Chose it for driveability and good manners. But like MikeB said, I would probably go with a 270H.

Go to YouTube and check out what cams sound like:
268H
https://youtu.be/ZGgeoQgNBkU
270H
https://youtu.be/1bsPjYt-Zfk