Aftermarket Cam idle woes

I see what you’re saying, in that you never restabbed the distributor after the change. But since the cam spins at 1/2 crank speed I doubt it’s off much. At any rate would not hurt to reset it to be sure.
 
The distributor is driven by the camshaft, so changing the cam position relative the crank will absolutely change the ignition timing. Advancing the cam will also advance the distributor.
 
Timing is measured from the crank... If you're reading 10 BTDC with a timing light, you don't do anything to compensate for the cam being advanced.

If you haven't put a light on it, then there's no way to know exactly what the timing has done since the drive teeth are helical.
 
If 10* = happy cam straight up
12 or 14* may = happy advanced cam??

Valve events are happening sooner, so 10* is now too late.
Theory I have is adv distributor so that it revs good, test drive and listen for deto, which I have a keen ear for.

I'm going to find out
One would think the difference is too minimal but who knows?? Hell I thought A4 meant cam adv 4 * till I learned lol

Yes, timing light says I'm at 10 with the spout out.
Install spout, runs like crap. Feels just like distributor is off a tooth. Runs like it's only firing on 4. Spits out the intake.
Remove spout, adv distributor to like 16, revs like a raped ape but had to shut it off cuz coolant is empty so I could set base timing easier
 
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Popping through the intake is either very lean or timing is very advanced.

Is it safe to presume that you've got the firing order matched to the cam?
 
FMOS Racing said:
Is it safe to presume that you've got the firing order matched to the cam?
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I opened the manual to double check firing order on the distributor but cam is stock. Although I have them labeled, the way it was running was like some were off, but we're all good. Valve lash is good, double checked that,

Either timing is off or cam adv too much for speed density to run.

But one would think if most cam companies adv cams 4* for most street cams, this one adv 4* should be fine? But this is all new to me, I'm in unfamiliar waters since this is the only American engine I've messed with.
 
What does the timing light show at idle with the spout in?


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I'll check when it stops raining, last time I checked it, it bounced around like 14 to 16 13, 15 and so forth as the computer was changing it.
 
jetski247 said:
I opened the manual to double check firing order on the distributor but cam is stock. Although I have them labeled, the way it was running was like some were off, but we're all good. Valve lash is good, double checked that,

Either timing is off or cam adv too much for speed density to run.

But one would think if most cam companies adv cams 4* for most street cams, this one adv 4* should be fine? But this is all new to me, I'm in unfamiliar waters since this is the only American engine I've messed with.
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What the cam is stock in determines the firing order. Any reasonably modern SBF should be 13726548, but if you had an aftermarket cam it could have been 15426378 and would cause problems if you just put the wires back where you had them.

Cam companies advance cams 4 degrees because most stock and stock replacement timing sets are made to retard the cam 4 degrees and they want their cam to go in straight up.
 
All the cams I have are 351 302HO firing order including the custom ground.

I know there's tons of posts but, it's a stock cam installed 4* advanced.

Valve events are happening sooner, so 10* is now too late.
Theory I have is adv distributor so that it revs good, test drive and listen for deto, which I have a keen ear for.

I'm thinking 10* = happy cam straight up
But we ain't straight up no mo. So I think I'm going to try setting crank timing to 12 or 14 to compensate for the earlier cam events.
 
I think you are barking up the wrong tree with ignition timing. The differences in timing, both cam and ignition, that you are talking about are relatively small and aren't going to make huge differences. They are just fine tuning techniques. When this is all over there is a 99.9% chance it isn't going to be related to timing unless it's grossly out of whack.
 
oilwell1415 said:
The distributor is driven by the camshaft, so changing the cam position relative the crank will absolutely change the ignition timing. Advancing the cam will also advance the distributor.
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I was referencing this.

And it dawned on me last night before bed. My heads have the smog holes in the exh ports, although they're capped at the rear of the head, this Edelbrock intake has the ports still there but EGR now dumps behind TB right into the manifold, could these exposed ports still in the intake and heads cause some strange vacuum and or running issues if air or exhaust is sleeping in still like unmetered air? I believe the plenum gasket covers the hole coming from the heads up the intake. I didn't block them with intake gaskets, just plenum gasket. I'll do more research on this.......
 
oilwell1415 said:
I think you are barking up the wrong tree with ignition timing. The differences in timing, both cam and ignition, that you are talking about are relatively small and aren't going to make huge differences. They are just fine tuning techniques. When this is all over there is a 99.9% chance it isn't going to be related to timing unless it's grossly out of whack.
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I actually wrote a long missive last week along these same lines, but didn't post it because I figured it just muddied the waters even further. I 100% agree. This isn't a 4 degrees of timing (cam or ignition) issue.
 
FMOS Racing said:
I actually wrote a long missive last week along these same lines, but didn't post it because I figured it just muddied the waters even further. I 100% agree. This isn't a 4 degrees of timing (cam or ignition) issue.
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I have done the same a few times. In the end I feel like I've caused more questions than I've answered. Diagnosing driveability issues on the internet is damn near impossible unless it's a pattern failure situation, which this doesn't seem to be.
 
Sorry about that, daddy duties got in the way.

When I read t Moss's article about advancing the camshaft four degrees and he gained power throughout the entire rpm, I now can attest to that is the TRUTH!!! I gained power from idle all the way through the entire range with torque to back it up, on speed density........in fact, pulls harder and better than the custom ground, minus the punch. This cam compliments the lazy stock shift patterns programmed into the stock ECU much better this way but I'm sure gas mileage or longevity may suffer. Idles smooth like stock, doesn't die at a light, vacuum in gear is 18.5.
When I say punch 👊, upper rpm throttle response seems slower, the custom ground and MAF seemed to be/have the best throttle response so far but may just be how speed density is....?

only problem that I'm having now as I think I'm running out of fuel at about 4,200 RPM the engine just kind of stalls right at 4200 and sits there and kind of fluctuates up and down a couple hundred RPM so either my fuel pump isn't putting out enough fuel (which is 2 months old) like the sock is clogged or the fuel filter, but more than likely my pressure's dropping at wide open throttle or my parts just flow too much air, but I noticed it after I installed the one inch phenolic spacer on the Edelbrock upper lower even with the custom ground. I noticed it with the aftermarket Cam that it did the exact same thing all of the sudden at 4200 RPM the engine would just kind of stall. Not sure if a 1" TB spacer, 1" phenolic plenum spacer, on top of an already larger port Edelbrock upper/lower causes any kind of wot vacuum issues???🤔
Usually when something is clogged the truck will just fall on it's face at wot and run fine till about 2500rpm.

my baumannator was set to shift at around 4k and didn't notice it till I switched back to speed density, stock shift points are at 4500, which I can't get to, so now I have to rig a hose to be able watch pressure under load while I drive. Cuz at park/neutral checks fine, even revving.

also noticed my temp Guage is all over the place, if I roll the window up and down the needle goes up?? If I roll the window all the way up and keep the button down, the needle will climb all the way to max..........so, not sure whats going on with that. And a CEL popped up after 10 miles or so, which I lost my code reader so gotta jump the test connector.

So far so good, I'm happy with the performance so far, this is with stock 1.6 rockers, cobra 1.72's are on the bench.

Timing is set to 10 deg with spout out. Spout in shows 10 at idle as well. And I've got a awful loud belt squeal now...........new belt to, well less than a year old. Not sure if something got misaligned???? Idler pulley and tensioner are new.
 
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It has a single high flow magnaflow it's only a couple years old. It's the high flow y pipe cat combo for f150,s I hope it's not clogged

I've been reading tmoss,s too much plenum volume, not sure if it applies to a 351

And when I replaced the fuel pump I replaced the fuel filter and sock and the tank was cleaned.
 
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