377sbc 10.5:1 AFR 195s etc, MSD Pro billet Coil in cap.
Cam Comp CS-XS282S-10
Adv dur int 282 Exh 290
@0.50 Int 244 Exh 252 lobe sep 110
Lift int 520 exh 540.

Engine was setup on a dyno and ran 488hp and 465tq and ran to 6200rpm on 98 oct

put engine in started fine.

Due to covid not driven, Waiting interior parts.

On start ups engine wont run on cold start and struggles until its warmed up and has started to backfire and flame up through carb.

Put a Premium Vacume gauge on it and a Snap on Timing light.

Timing on idle is over 30deg
and vaccume reads well below where it should be.

I dont know if the Vac Advance that is never hooked up has been locked up, hence the 30+ deg at idle.

Car struggled to crank and cranked slow. but started, sounded like the battery was flat, Its definately timing issue but the crazy off the scale readings i am seing is out of my field of knowledge..
Scared to play around or damage the alloy heads with detonation issues. BUT the CAR NEEDS TO BE STARTED AND MOVED. ..

 

What was the timing at idle the first time you started it?
Have you removed the cap to see if anything is out of place or stuck?
Have you tried removing the cap and putting a hose on the vacuum advance and sucking on the hose to see if it moves?

 

I didnt check the timing after it came off the dyno as i normally dont have issues adjusting and checking it.this time its out of my league.

i never saw reading +30 deg.at idle on anything i have owned.

distributor is not sticking and all in place,

i just rang the engine guy and he thinks the advance was locked up when the cam was setup.

i will take the car to the engine guys on a trailer to get his take on where i should be.

 

"Out of (your) league"? What's so hard about adjusting the timing? Set it to 36 degrees @ 3,000 RPM with vacuum advance disconnected, and then check it at idle and make a note of the reading at idle for future reference...

 

its at 36 at idle bro, thats in my league i aint stupid and didnt install the cam or advance it or turn it over. on install,

 

So what happens when you give it less timing?

 

It doesn't matter who installed the cam. We're talking about ignition timing. 36 at idle is too much unless it's locked out for an engine that is exclusively set up for racing. Maybe I'm not fully understanding your question...

 

If the Distributor is Locked (not ideal for a Street Vehicle)...
an MSD Start-Retard Ignition Controller would be very helpful.

 

Assuming you have a distributor with mechanical advance weights and also vacuum advance. It's possible that either the vacuum advance or the mechanical advance are locked, or the base timing is just set too far advanced (maybe the distributor was accidentally rotated). Should be pretty easy to verify all of this with a timing light.

Fire it up with the vacuum line to the distributor disconnected and verify the timing at idle. Then bring the RPM up to 3000 or so and see if the timing advances and how much.
To check the vacuum advance, measure the timing at idle with and without the vacuum line connected (assuming the vacuum line is connected to a manifold vacuum source, not ported) and see how much the timing changes.

This will tell you if your distributor is working correctly and you need to know that before doing anything else.

 

im not a carb guy but in the efi world, cold start doesnt run right it’s probably because its not rich enough. Engine always needs more fuel and typically touch more timing cold, then hot idle settles down with less timing and fuel

big cam may want 28-30 deg at idle to give best vacuum, depending on rpm. 36 is high but its not gonna hurt anything at idle.

 

Yes, 30 degrees advance at idle with the vacuum advance connected is usually OK. But, if the distributor is locked at 30 degrees at idle with no vacuum advance connected, that's not good. It needs to fall back to base timing with mechanical advance based on RPM while starting and under load. Trying to start the motor with 30 degrees of timing would be pretty hard on the starter motor.

 

What happens if you give it less timing? What happens if you give it more? Better/worse? Find out until it's the best it can be.

Ask THE ENGINE what it wants. It will tell you. "If it RUNS good, it IS good", if I may be allowed to paraphrase one of the GOATs in a completely unrelated field. Don't outsmart yourself over the "number" your eyes hallucinate that they see. THE ENGINE knows what makes it run the best, better than YOU ever will.

 

Mine is locked at 37* but it's also not a street driven engine and I use a start retard to get the engine started. Less changes means more consistency at the track. I also have a timing control in the car that allows me to manually adjust the timing simply by turning a ****. If I want to bump my total timing a degree or 2 in either direction to see if the engine likes it or not, it's a very simple process.

Without know what they did on the dyno, it's hard to say what's wrong. On a dyno, the first thing that is set is the timing. Changing jetting, plug gap etc won't change where the engine wants the best timing so once the best total timing is determined, that's where it's kept before the vacuum advance is reconnected. Vacuum advance will change the timing due to engine load so it could be all over the place.

First of all, ignore the vacuum advance. Disconnect and plug the hose and make sure the canister is in the fully extended position or completely disconnected from the distributor. Your cam profile indicates that your base/initial timing should be in the 14-16* range. If the dyno says that the engine makes the most power at 32* total timing and the base timing is set at 14* then the distributor would have to be set up to have 18* of mechanical advance built into it. If you bumped the base timing up to 16* then the total timing would get bumped to 34* because the mechanical advance is still set at 16*. To maintain a correct total timing, the distributor would have to have the mechanical advance reduced 2* to bring the total back down to 32*. The weights and cam inside the distributor control how much mechanical advance is built into it. The weights and cam can be mixed and matched to achieve the proper mechanical advance. The springs control the rate at which the advance is applied. 2 light springs and it gets to full advance very low in the rpm range. 2 heavy springs and it gets to full advance at a much higher rpm range. Springs can be mixed and matched to change where the distributor reaches full advance.

As for the vacuum advance, it's only for part throttle operation. At an idle, there should be no vacuum on the port and when connected to the distributor, should make no change in the timing but as engine rpms increase, the vacuum signal increases and adds more advance to the timing. If your total timing is set to 32* and the vacuum advance can provide an additional 15* then the engine could see up to 47* of timing but it could only see that at a higher rpm where the mechanical advance is maxxed out and with a high vacuum signal.