Sounds to be out of time whether that is ignition, camshaft or both. Big cams are really sensitive to this.

Your going to have to wander through this by hand cranking with a wrench the engine, ignition off, to first determine where the rotor aligns with the number one distributor terminal in crank degrees. I hope since this is a high performance engine that it has a damper marked in degrees at least through the first 90 followed by every next 90 degrees position so you can get a decent idea of where the spark is occurring relative to crank position.

The problem here is that if off where it should be can be the cam falling out of time which is usually incorrect installation set up, or wear, or breakage of the timing set, or is within the distributor itself. The latter can be simply miss timing the distributor set up, parts within failing or falling out of synch to wear in the gear mesh with the cam to worn to failing bearings within the distributor.

First thing is to devine where the ignition timing is to crankshaft position might be and most likely it never was timing exactly right Hence never ran right from day one. Stabbing the distributor for either the SBC or the BBC is something of a witch’s art if you don’t know some simple tricks.

Bogie

 

do you have a steel roller cam? Maybe the gear (bronze) failed. Ive had that

 

So I got the car to start and checked the timing. At idle it was WAY high. My brother in law says it’s still at about 40 degrees and that’s after we turned the distributor til the vac adv is almost to the firewall. So it’s starting a little better (not much) but still ‘jumping’ and spitting a little gas up thru and out of the carb. But when it does start it’s rough as hell. Really rough. So I’m thinking of putting the engine on TDC and checking where the rotor is and the timing marks. I think I’m looking at timing chain, distributor gear or cam gear. Any thoughts or suggestions greatly appreciated. Thanks guys.

PS - also where the timing currently is I have the idle screw backed all the way off the accelerator arm on thh my e carb and it’s still at about 1100. I can’t get it any lower.

 

Before you unload the parts cannon and make wild nonsense guesses, just rotate the plug wires one post to the left, or clockwise and re adust timing as needed.

 

ok but something had to change for the timing to be so far off no? If I rotated the plug wires as you say wouldn’t that indicate something is wrong/worn/broken?

 

You not understanding the process of the engine theory or troubleshooting.
Your taking guesses and that always leads to expense and frustration.
You said it's never run well, and now it's worse then before. Of course something changed, guessing takes longer and more money as you open your wallet and toss money at till you get lucky.

FIRST step....Verify everything mechanical, in this case, A leak down test.
Second step is TDC, with a piston stop.
Third step is verifying the dist gear mesh and roll pin condition.

Report back

 

And try a different timing light.

 

Get the crank damper marks to TDC firing number 1. The thinking marks center up in two positions that being number one and again at 6 firing. You can feel for this with the number 1 spark plug out with your finger over the plug hole as it will be pushed out by the compression pressure. This will give you a pretty good idea of where TDC number one firing is. Jiggle the crank at this point to read 0 degrees damper to pointer marks. Now remove the distributor cap to see where the rotor tip is facing to which terminal on the cap. It needs to be mighty close to the terminal connecting the wire to the number 1 spark plug. If it isn’t correct that. Roughly GM installation of the distributor would have the vacuum can pointing between cylinders 4 and 6 with the cap terminal identified as number 1 pointing about a chalk line straight at cylinder number 1. Once so aligned the firing order is wired clockwise around the cap from there.

What is the Chevy 350 Firing Order? - [With Diagram]

Are you looking for the firing orders and cylinder numbers of small-block and big-block Chevys? Read this article to find out all the details, including diagrams.

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Something to consider since this is a built engine is whether the cam used is standard GM firing order or if the cam used has the alternate firing order that switches the number 4 and 7 cylinders, so you need to know this about this build.
Standard Firing order is 18436572
4/7 swap firing order is 18736542

Bogie

 

I checked the firing order the other day when I replaced the components in the distributor. Standard firing order and didn’t see anything in the cam specs to indicate swapping 4 and 7. But tonight I’m going to put it at TDC and check the rotor and timing marks since it’s such a quick thing to do. A friend of mine suggested checking for vacuum leaks but I have no vacuum lines. Maybe around the base of the dominator carb or vac adv on the distributor?

thanks!

The cam is :
COMP Cams Xtreme Energy Camshafts 11-771-8

 

so this is a moderate solid roller? When you fire the engine even running poorly, do all the header tubes get hot? Only takes 5 minutes to lift distributor out and check gear

 

Thanks for the reply. I haven’t actually touched them but I will. Yes my plan for tonight is to set the engine at TDC and check the rotor and crank/tab timing marks. I’d be surprised if those things aren’t way off and then I’ll be pulling the distributor and starting there.

 

I have to agree with Johns, tell us what you do not undestand please?

 

What do you mean?

 

who built the engine?
Was it run on a dyno?
how much race engine tuning do you have?

you do not seem to follow basic trouble shooting in order it should be done

 

basic troubleshooting? I figured I’d check the position of the rotor in relation to the crank before I get into leak down or compression tests since it only takes a few minutes. Is there a reason why I should do the leak down test first?

The engine was built by a local race car driver. A friend of a friend. I took it to a machine shop had it dynod. 675hp. Although it was a dog and couldn’t get out of its own way once I installed it into my car. And that’s with 373 gears. So…. Another local performance guy suggested this cam and a specific converter since the cam that was in it was a 710 lift and I had the 4L80E ready to go. So with the new cam and correct converter It woke the car up tremendously. I haven’t had it dynod with this cam. But it’s a beast for sure. Massive power. It’s always been hard to start. But I drive it not that often at all. I know. I will be changing it to an electric fuel pump. I have no experience tuning a race engine. But I do know that checking that the rotor is facing #1 while the crank is at zero at the timing tab is pretty basic troubleshooting. It maybe a burnt valve or a hole on top of a piston from being outta time and running hot or cam or distributor gear or a timing chain issue or the leak down test showing bad on a particular cylinder. But for the 5 minutes it takes to put the engine at TDC that’s where I’m going to start. I don’t do this everyday. I shoulda left the 383 stroker I had in it in there. So I was looking for some tips or things to look for that a weekend warrior might not think of not looking to get ridiculed. Thanks for your help.

 

Big cams like a lot of initial spark advance, these can be hard to crank when the ignition is firing at the same time, especially as compression ratio increases. I typically intercept the hot lead to the distributor with a switch so I can crank the engine to get it spinning up on the starter before dumping fire on the plugs.


Our suggestions for simple tests is to try and weed out and define possible sources of the problem. There are quite a few possibilities we’re trying to hack away at tge simple and least costly first.

The fact you have the distributor way out of position can be simply that it is installed off a tooth which is a common Chevy reassembly issue when the distributor is R&R’ed. Off a tooth doesn’t sound like much till you count distributor teeth convert that to degrees and multiply by two to get back to crank degrees and suddenly the distributor is fifty some degrees out. The link below is an SBC but this also is good for the BBC

Bogie

 

Thanks I appreciate it. I actually didn’t take the distributor out of the car when I replaced parts. I had a new MSD cap and rotor in the package still. So I bought a new coil, put that in the new cap. Put a new ignition control module and rotor in the dizzy housing while it was still in the car. It wasn’t til after that when I started it and it was still running like **** that I moved the distributor clockwise to get it to stop popping. But it’s still running like crap. But thanks I appreciate it.

 

You do know clockwise retards your timing!

 

Yes. But the timing was super high and it was backfiring like hell. It was the only way I could get it to stop backfiring. Thanks.

 

fire the engine and check all headers pipes for hot FIRST

 

I have a remote kill switch.
My engine is under 11:1 with 22ishº initial
I roll the engine over until the oil pressure gage moves
then hit the fire switch
also good anti theft

 

The only float adjustment I’d make is a swap to a manual choke 850 like this.
A choke will make a world of difference in starting. And it’s still big enough for your motor.

Holley 850 CFM Double Pumper Carburetor - Manual Choke - Mechanical Secondaries - 4150

Quantity: Sold Individually Manufacturer: Holley Manufacturer Part#: 0-4781S CFM: 850 cfm Number of Barrels: 4 Fuel: Gas Flange: Square Bore Choke Type: Manual Fuel Inlet: Dual Finish: Silver Throttle Linkage Type: Universal Kickdown: Includes Ford Provision. Or GM/Chrysler with additional...

blueprintengines.com

 

I need 4500. 4150 won’t work.

 

Off time like that is pretty common after an R&R of the distributor. Removal causes the rotor shaft to rotate as the spiral gear teeth disengage this causes the oil pump drive to rotate a little. At replacement the blade of the distributor when aligning the rotor to the marks made before removal will not engage the oil pump shaft’s slot. The point where it will advances the rotor by about one terminal hence its pointing at #8 instead of #1. The link to MyVintageIron in reply #17 is the slickest way to reinstall the Chevy distributor for Gen 1&2 SBC’s and the BBC the other is to use an oil pump priming tool and rotate the shaft once it engages the oil pump drive in the counter clock wise direction by the distance of one distributor csp terminal, this however is dependent on whether installing to tool caused unintentional movement of the pump drive shaft.

The Dominator is a racing thing (or is that beast?) without a choke it is something of a pain on the street. If you’re willing to live with that then you have what you get when cold starting and into till the engine warms the intake enough to where the fuel vaporizes. Engines run on finally atomized to vaporized fuel, liquid fuel running into the cylinder doesn’t burn well to where even if the amount of fuel delivered by tge metering system has the potential to result in a correct AFR the engine will act as if it’s running lean hence back fire out the carb while at the same time the stink at the tail pipe is rich. Racing is done at high RPM at these engine speeds there is enough violence of motion inside the intake that cold liquid fuel globs are ripped apart into a fine atomized mix with the air. At idle and highway speeds for racing carbs this violence isn’t happening so a lot of fuel is streaming rather than mixing. That portion that does atomize or vaporize burns while the streaming fuel doesn’t. So you get this staggering idle with pop backs through the carb which unburnt fuel fumes at the exhaust. The whole purpose from the factory of exhaust or coolant heated intakes and even to the point of pulling intake air over an exhaust manifold is put enough heat into street engines to force tge fuel to vaporize which as with fine atomization burns nicely in the cylinders. A rave engine meant to deliver max power at max RPM eschews these features. On the street this is mighty hard on cylinder walls, piston rings and skirts as the liquid fuel washes the lubrication away from these parts greatly shortening their useful life.

So this is the Root Cause of the troubles of running a race bred engine on the street.

I used the terms “atomized” and “vaporized” as depending upon the heat inside the intake there will be a phase change or not of the gasoline. Gasoline in a liquid state to the surprise of many people does not burn. It burns either in a finally divided spray I’m calling atomized which is still in a liquid state but as a fine mist easily vaporizes or as a change of state to a vapor early on in the intake when the intake is heated. The road to power is to walk that fine edge at the atomized condition as technically the fuel is still a liquid. When fuel vaporizes within the intake the phase change results in a large expansion in volume which reduces the mixture density being inhaled past the intake valve so while tge engine runs nice and smooth power is way down. The trick is to get the fuel into an atomized condition where it is in physical state still a liquid in as it travels the intake tract till into the cylinder then get the phase change to a true gas or a vapor inside the cylinder so it burns well plus inside the cylinder the phase chance absorbs heat which helps control detonation of the end burn by keeping that mixture fraction from disassociating into self-igniting compounds before the flame front gets there.

Bogie

 

Thanks. I just posted something regarding the carb just before you posted this.

 

I disagree with getting an 850.
l use a 950 on my mouse with a bigger cam than you have. dominator works well. whats the part number ?
you might need more initial timing

 

I’ll have to check tonight when I get home. Probably 630 est.

 

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Bogie

 

thats a 2 circuit carb. should respond to standard style tuning.
are all the pipes hot? a dead hole can cause issues. have you adjusted the valves?
,more info makes for more help

 

Yes the pipes were all hot. I have not adjusted the valves. It’s been a while since I’ve done that back on old school cam/lifter setups. Probably 20+ years ago. I’ll have to check YouTube.