how do you know there is no vacuum leak?
22º static timing is ok. Did you verify balancer timing mark?
might be too lean? running hot?
Thats a very small cam?
Hows the power at WFO?

 

Went around everything with propane. I don't think it's too lean... spark plugs aren't indicating that. Runs at about 180 degrees. I know that cam isn't extreme... but not sure if it would be classified as small, would it? Maybe so.

 

Cam timing verified?
Damper Timing verified?
Plugs type?
Timing around 16-18 should be plenty.
The Brawler has problems to begin with, and those coils are very good either.
I'd start with sticking a paper clip in the the IAB's and note what happens.

 

Plugs are NGK 5671A-7, gapped at 0.35". All the timings are verified and good. The Brawler was a suggestion by a buddy of mine. I've never used one. Definitely a PITA to get down (assuming all of this is related). Also, what issues do those coils usually have? That's interesting...

 

you did not say if it makes good power?
Vacuum leak can be under the intake but would likely have oily plug(s)

 

The cam spec's don't suggest that problem to me. What is the lifter preload. 8" of man vac is way low. You say it's sporadic meaning sometimes it seems ok?? Does it do better if you richen it blocking air bleeds. How far are the transition slots at idle from throttle plates. Are the secondary plates closed.??

 

This is essentially the LT4HOT it should idle with about 14-16 inches. Sounds like either a vacuum leak or the cam is off time as installed.

Common leak is the bottom of the intake exposing the valley to the inlet ports. Especially a headache with aftermarket heads and intakes can be really bad with decked blocks.

Another key is the need for a lot of advance this points strongly to the cam not timed to the crank and or the distributor being way off which is easy to do on the Chevy because R&R on the distributor pulls the oil pump drive which pulls the intermediate shaft out of position when the distributor is removed so it goes back at least a tooth off which is about 55 degrees crankshaft error.

I’ve used this cam in my own ride and quite a few customer builds it is a powerful yet very street drivable cam lots of torque and power without any nasty habits.

Bogie

 

This is essentially the LT4HOT it should idle with about 14-16 inches. Sounds like either a vacuum leak or the cam is off time as installed.

Common leak is the bottom of the intake exposing the valley to the inlet ports. Especially a headache with aftermarket heads and intakes can be really bad with decked blocks.

Another key is the need for a lot of advance this points strongly to the cam not timed to the crank and or the distributor being way off which is easy to do on the Chevy because R&R on the distributor pulls the oil pump drive which pulls the intermediate shaft out of position when the distributor is removed so it goes back at least a tooth off which is about 55 degrees crankshaft error.

I’ve used this cam in my own ride and quite a few customer builds it is a powerful yet very street drivable cam lots of torque and power without any nasty habits.

Bogie

Thanks, man. Awaiting my smoke machine to see what I find. If I don't see any obvious leaks... I'm going to look into the cam/crank timing and make sure I didn't overlook anything (again, pretty new to this... but not sure if being off even a tooth could cause these issues).

 

Remove carb and check centering and complete closing of primary and secondary butterflies. I just fixed a brand new out of the box Holley that didn't even come close to closing properly. I loosened the throttle plate screws and throttle stop screws and centered the plates, reinstalled and fine tuned and it runs great. It acted like a huge vacuum leak but it was internal so you couldn't find it.

 

I’m talking about gasket vacuum leaks to the inside of the engine which will not show up with an external inspection. Not that you shouldn't do an external check but finding nothing on the outside doesn’t mean there aren’t any.

Internal vacuum leaks are pretty common especially when mixing aftermarket parts and machine operations with the decks of block and or head.

Another common one with aftermarket heads is not sealing the rocker studs into the heads, though this usually shows up with oil smokey exhaust but not always.

Bogie

 

Verify it is delivering fuel properly at idle first.

The very first thing I would do Is make sure there is fuel going to your carb and leaving your carb. Then I would make sure all the circuits on the carb are clean. And make sure there is fuel leaving the carb and going into the cylinders. Disconnect the fuel line from the carb and make sure it is pouring out. Mechanical or electrical fuel pump. Make sure enough fuel is making it into the float bowl. And make sure the idle circuit is clear. You can use compressed air to blow out the idle circuit depending on which carb you have. Make sure choke is working and not stuck closed or open. My carb edelbrock 1407 has a filter/metal screen built into the carb right by the inlet nipple and one time it got kinda clogged and had sporatic symptoms like this. Sounds like it could be fuel starvation. Somehow I knew it was not getting fuel and I cleaned it out and it ran perfect afterwards. So make sure the fuel filter is good too. Verify the entire primary fuel circuit is getting fuel and not clogged.

If you actuate the linkage you should hear the accelerator pump spraying fuel. But then you know there is fuel in the float bowls at least. Without taking anything apart.

Do you have a vacuum advance hooked up from the distributor? If this is getting weird vacuum readings it could mess with the timing. Maybe the vacuum canister on the distributor is not holding the vacuuum all the time and so it is sporatic and only effecting idle?

Does the engine only have problem idling? Can you rev it up and it runs perfect?

 

As 48 Austin mentioned you need the butterfly valves to close. This makes the gas come out of the idle circuit. Just like how the choke closes off a big section of the carb which makes the fuel get sucked out of the carb too. I would also set the float. Maybe the float is not letting in enough gas into the float bowl because it is closing the fuel inlet valve too early. Maybe see what happens with the float tied closed.

As Bogie mentioned it can be a vacuum leak too from the manifold but on the section you cant test because it is in the valley. If you cant figure it out I would take off the intake and look at the marks from where it was matted up with the head and you should beable to see how it was lined up. It is a good idea to pre assemble the intake with the cylinder head and block to make sure it lines up correctly. You can see the mark it leaves too when you take it back apart. Line up the gasket with the bolt holes on the head and the bolt holes on the intake.

 

Everybody here has me pointing in the right direction, I believe. I'll look into it further Monday and let you all know what I find. Definitely appreciate the leads and advice...

Merry Christmas, folks!

 

Merry Christmas. Best of luck.

 

Any mass produced part is more likely to have something small that is missed in QC.
throttlle plates, throttle bushings, wring IAB, IFR's, gaskets, trash in the passages, etc.
I always take things apart and personally it's what it should be.
Those canned coils just don't put out the energy like a good quality box coil. Period.
it may be enough for most, but yet not enough for others. Even if the specs are about the same.
Id most likely use a -8 but your -7's are probably close enough.
Still need to verify cam and damper timing.

 

You don’t say what it is in or if you have power brakes.

if you have power brakes, make sure your booster is not bad and your vacuum leak is in the booster.

this is a no cost check, unhook and plug vacuum line to the booster, if you have power brakes.