Frankie the Fink

Between moving the timing back and putting two primary jet sizes up in my 4777-7 LIST Holley (mechanical secondaries) I have eliminated the lean surge in the 396ci 'built' motor. Car pulls strongly and no more backfires either.

However, it stalls inexplicably now; usually after a sharp turn....I did try to tweak the front float level but I'm horrible at it. The issue is dangerous as, after a sharp turn, if I lose the motor I have no power steering or power brakes. BTW I have to floor the car and crank the snot out of it to restart after a stall - symptoms of flooding ?
This can happen after a short 10 minute run so I don't think its a perc problem and the carb never did it before my changes.

Something about gas squirting around on a hot manifold just gives me a big pucker factor. The car has 17" of vacuum at idle and I can't find a vacuum leak. So where am I ? If I could just fix this latest annoyance I think I have it knocked. I'm thinking I made the situation worse with my paranoid float adjustment.

INMYBLOOD

Don't know about a sharp turn, but hard stop stalls usually indicate a high float level and it can be either bowl stalling the motor. I've personally had this happen. I have a 650 dp 4150 type. I think you have got it with the float level.

66since71

"Center inlet" ("dual feed", "center hung floats") fuel bowls were designed to fix the hard cornering problem. Don't know which you have on that carb?

Harry

Edit... I googled that list number and see it should already have center inlet bowls. Sorry I couldn't help... I do agree on checking float levels as the next step.

Matt Gruber

2 fixes.
besides lower float u can connect the 2 bowl vents w/5/16 hose, with several 1/8" holes along the top. this prevents gas splashing out, flooding it.
i always just lower the float. was just testing new tires on my 72, very high G's and no complaints from the carb! i'd guess 3/16 to 5/16's lower.

Avispa

Your hot restart problem is actually very common. Called "hot engine soak" and it is not caused by any leakage or percolation.

If you're concerned about setting the float level on a hot manifold, why not do the adjustment with the engine cold, or at least cool? You can safely lower the float levels as others suggested. If you drop your secondary float level, you may want to consider jet extensions to ensure that under hard acceleration the jets stay submerged because the fuel is pushed to the back of the secondary float bowl under hard acceleration.

Matt Gruber

frankie
be sure to lower the REAR float too. that can go lower than the front if necessary.
when the gas sloshes around, the needle lets more gas in. when it gets too high it just pours in thru the booster. front or R, either or both can flood it.
Is the carb too hot to touch the bowl when it is hard to start?

Frankie the Fink

Watched a superb Holley video on setting the floats and did that this morning...the front was way too low and I fixed that...no more lean backfiring and I'll know later if that fixes my cruising surge. http://www.youtube.com/watch?v=ge-mIk6nEYQ

Rear float was spot on !

Car starts right up immediately after being shut off but I still have to floor it and crank it after waiting 10-15 minutes and I'm troubleshooting that. I am VERY familiar with percolation (and hot soak) and I can't believe that's the issue as the car didn't do it before. Also put a fuel pressure regulator in the pump line set at the Holley optimal pressure of 6psi and all this has helped (except for the restart issue). Still testing things out !

leaky4150

66/4150/ 3247 set floats cold by cranking engine over several times and then checking fuel level repeat for rear.

Matt Gruber

how old is the carb? how long since blue gasket change? Ever notice how many holes have to seal on the metering block? When the IFR leaks, gas drips into the manifold BELOW the throttle! sneaky huh? Since it didn't have the hot re-start problem before, SOMETHING has deteriorated

66BlkBB

You can buy the clear plastic sight plugs for simply setting the float level. This way you can do it while the engine is warm and not fear the fuel flow on to the intake. Once you have them set to the correct level you can simply change them out for the brass units. Also, when the car stalls, pull the air cleaner and see if you can see which side of the carb is bleeding over. You should be able to see the fuel dripping from the horn if it is completely flooding out after sitting for a few minutes. JMT

Frankie the Fink

Did that as starting point for float levels per the above video. Really need to do the final adjustment on a running car though (so I did).

Matt.

Got ya there pal. The carb is only about 3 months old and the blue gaskets (metering block AND float bowl) are only 24 hours old...changed them yesterday. They are Holley parts (not aftermarket) and all passages/holes line up properly. Read elsewhere that a hot restart on the 4150s after setting a while requires pumping the throttle twice and then holding it 1/2 way down while cranking. Have to admit - that seems to work

Still get a VERY rare backfire after long periods of idling and then revving it (occurs during deceleration). Only 1200 miles on the car since full resto so I think I'll adjust the hydraulic valves next before dicking with the carb any more.

toms silver 60

Edelbrock.....

tuxnharley

IIRC from a different thread - also on carb issues for this car - he was trying to keep it stock?

Frankie the Fink

I DID try a new Edelbrock 1806 (electric choke) AVS Thunder and it idled great but had a severe bog on hard launch and the hood clearance was crapo on my '67 Chevelle 396ci.

So the 'runs right out of the box' theory is bogus (on some cars at least). Figured if I had to screw around with metering rods, jets, etc.. on a carb then I would do it on the Holley (I already have the jet kit) and not buy more paraphernalia from Edelbrock.

So the Holley is back on the car and running OK from what little driving I could get in during today's rainstorms.

toms silver 60

Bummer on the bogging, surprised to hear about that with an Edelbrock. I have a bunch of tuning parts for a 1405 if you want to play with it any, assume there is some interchange between the 600 and 650 carbs...

Anyway, join the poll on replacement carbs...

6T7L71CPE

Mine broke off overnight before I even started the engine!

Jebbysan

What size power valve?
And have you checked it?

Leaky Power Valve can disguise itself as something else.

@ 17 in of Vacuum....you need an 8.5 valve.

Jebby

Frankie the Fink

Yes - checked out fine.

Holley claims that any car with over 13" of vacuum can use the "out-of-the-box" 6.5 valve in their tuning video and literature.

I now have to change a leaky fuel pump before I go any farther - and the hits just keep on coming !

Jebbysan

Yes the 6.5 will work fine.....but may not open as soon as you like.

Jebby

Frankie the Fink

I may have whipped the Holley into submission...changed the leaky fuel pump this morning (its easier on the 396ci than on a small block) and the car inexplicably idles better. Car pulls out strong and I need to do a highway run to assess if my cruising surge is gone. The VERY rare but annoying exahust backfire on deceleration has returned though....but it only happens on the car when its cold and has idled for a time.

That may just be "life in the fast lane"...we'll see.