BBC 396 wil not idle with any carb

[Adriank]

I think understanding and getting to know the engines cam should be paramount.
Then start over, with the attitude that you are putting an engine together.
Too many unknowns, like was it built for racing, towing, expected RPM range, it looks like it has roller rockers, obvious stuff is the bored .030 over and RPM heads, what year block is it, correct spark plugs, valve lash set, degree the cam, reseat the manifold. If had acquired an engine in this manner I would try to understand as much of it as possible before installing - not after. Worse case, take it apart to know what it was built with.

I under completely. Just trying to see if anyone had any ideas before i yank it back out and dis assemble it completely. And yes roller rockers.

 

[Adriank]

Just an update on vacuum today. Had few mins so fired it up. Ran about a 10 on my vacuum gauge. Motor ran about 900 rpms for about 10sec before acting like it was starving. I checked at manifold vaccum on the carb itself. Did learn that with choke closed it would let me give it throttle. But not for long. And thats on the newer carb.

 

[Ricko1966]

Have you checked fuel delivery,if it will take throttle with choke closed,you either have not enough fuel,or too much air. See how much fuel you get putting the fuel line in a pop bottle and cranking the engine,see how much you get in 30 seconds. Could still be a big vacuum leak.

 

[Rustisbest]

Your vacuum advance is still on ported if that's a picture from today. Bigger cam is gonna need extra idle timing. Air gap intakes idle like **** til they get some heat in them too.

 

[Adriank]

Have you checked fuel delivery,if it will take throttle with choke closed,you either have not enough fuel,or too much air. See how much fuel you get putting the fuel line in a pop bottle and cranking the engine,see how much you get in 30 seconds. Could still be a big vacuum leak.

Ok i will try that. As you can see on the pic i do have a fuel filter and it stays full. And was about 6.5 to 7 psi on the gauge but im will to try it.

 

[Adriank]

Your vacuum advance is still on ported if that's a picture from today. Bigger cam is gonna need extra idle timing. Air gap intakes idle like **** til they get some heat in them too.

I swapped it back to that ported cause on have one manifold vacuum on the carb. In my manual for the new car shows to be spark port?

 

[Rustisbest]

Good luck. I tried.

 

[Ricko1966]

Ok i will try that. As you can see on the pic i do have a fuel filter and it stays full. And was about 6.5 to 7 psi on the gauge but im will to try it.

Did not know you had checked fuel pressure and had a full filter. My bad.

 

[Ricko1966]

I swapped it back to that ported cause on have one manifold vacuum on the carb. In my manual for the new car shows to be spark port?

New O.E means nothing at this point,different engine,different carbureator,different intake,camshaft,etc. put it on manifold vacuum,you are going to need the extra advance at idle. The ported vacuum is mostly an emissions thing,light the fire late at idle,let it finish burning in the exhaust manifold and clean up the idle emissions. Those are not your concern.

 

[Adriank]

Good luck. I tried.

Thanks.

 

[Adriank]

New O.E means nothing at this point,different engine,different carbureator,different intake,camshaft,etc. put it on manifold vacuum,you are going to need the extra advance at idle. The ported vacuum is mostly an emissions thing,light the fire late at idle,let it finish burning in the exhaust manifold and clean up the idle emissions. Those are not your concern.

Yeah ive had it on both port and manifold vaccum. Most time on manifold. For the most recent pic i put on port just cause i had my vacuum gauge on the manifold port to see what was going on and didnt have little plug handy so throw hose on there. But i just read that the manual looking for clues and seen it had said spark port. Whats a rough estimate on timing i should be running at idle? I understand not know thing cam size which seem to really bite me in the ass. But i just trying to work with what i got till i decide to tear this own thing down.

 

[Ricko1966]

Yeah ive had it on both port and manifold vaccum. Most time on manifold. For the most recent pic i put on port just cause i had my vacuum gauge on the manifold port to see what was going on and didnt have little plug handy so throw hose on there. But i just read that the manual looking for clues and seen it had said spark port. Whats a rough estimate on timing i should be running at idle? I understand not know thing cam size which seem to really bite me in the ass. But i just trying to work with what i got till i decide to tear this own thing down.

If you can't get it to idle you can't set timing anyway, so put it where ever it runs best for now. If the rpms are too high the weights will already be partially out so the numbers really will mean nothing.