Holley Carb Identification

[Jack]

anyone using Gross jets?

 

[Jack]

Sorry, it is Grose jets (edit spelling)

 

[RichardH]

I think our two posts must have crossed - but here are the pics yu asked for...

It looks lovely and clean inside - the mottling in the float chamber seems to be just marking in the plating?

 

[Randy V]

hmmm
having just taken the carb to bits (or at least to check the Power valve) - it looks OK - or at least the diaphragm is not obviously ruptured. I might as well check for the check valve while the carb is off the motor - i notice (with respect to your pic, Jac, below) that my carb seems to have some staining around that same area - would that just be dirt - or signs of use?

staining is carbon from fuel reversion and backfiring..

I also notice that the vacuum pipe from the bottom (shown in the same pic) has also not been attached to anything :sad: - is that another for blocking?

Yes - this port is actually a manifold vacuum port and is connected many times for the Vacuum advance unit on the distributor.

I am beginning to think this needs looking at by someone who can recognise these little "irregularities".

If its not the PV tho - back to square one - what is causing the symptoms described in this thread?

With this manifold vacuum port hanging open like it is - this would cause your engine to run excessively lean and not very well at that. Your Power Valve's diaphragm would not be blown out because the excess manifold pressure would most likely have been exhausted through this open port. Still - the PVs are relatively cheap and should be replaced. It takes a 1" wrench. Be careful that you do not damage the sealing surfaces / ridges on the metering block.

Your carb is a 4160 model Holley 600 CFM 4BBL vacuum secondary carburetor that is not meant to meet emissions (that was the LIST-6619 carb).
Your carb typically came from Holley with an 85 (8.5 inches) Power Valve. If you're running an aftermarket cam with a bit of a lump to it - you may want to change out to a 65 PV.

Jetting - they are usually very close from Holley and should only be changed if you dyno test the car and find that the Fuel Air ratio at Wide Open Throttle (WOT) is higher than 12.5:1
There are no jets for the secondaries on the 4160 carbs. Instead you have what's called a Metering plate. You can purchase metering plates with various restrictions in the fuel passages (jets) if need be.

Accelerator Pumps - if the carb was left to sit dry for any period (1 or more years is what I find to be the max) the fuel pump diaphragm gets dry and brittle - soon cracking and leaking - or - not working at all..

 

[Doug S.]

It looks lovely and clean inside - the mottling in the float chamber seems to be just marking in the plating?

Yes, Richard, very nice....your filter is doing it's job quite well. No worries now about inlet valve contamination, but as long as you have the fuel bowl off I'd invert it and measure where the float level is...that might need a bit of adjustment or it might not, but it'll never be as easy to check as right now.

Big-Foot is right about accellerator pump diaphragms...they, too, get old, develop holes or cracks.....if your problem was on accelleration, it's a good idea to replace the accellerator pump, too. Murphy's Law seems to be in full effect with Holley carbs, if you don't replace it while the fuel bowl is off it's SURE to go bad while you're 30 miles from home and it's pouring cold rain! This is yet another very inexpensive replacement that I would make as long as the carb is apart this far.

Doug

 

[RichardH]

I forgot to mention before the PV has 8 5 6(9) stamped on it - so that seems to tie up with your 85, Randy.

Now apart from rebuilding this carb - i suppose I might as well, now I have got this far - or would you recommend "it aint broke - dont fix" - or an exchange one (£200).....

Holley 750 cfm 4 barrel “4160” Carburetor
Features; Remanufactured by Holley-Vacuum secondaries, manual choke, dual inlet fuel bowls, power valve protection. Primary jet 72,secondary plate equivalent to a 75 jet, 6.5 power valve, .031” pump nozzle, plain spring. Centre hung floats & Ford automatic kick down lever. Has a "polished, shiny appearance". Jets relate to 3310-7 list number. Rebuild kit is- QJ123090.QJ123310REB Remanufactured "Shiny version" Vacuum Secondary £195.54

I then have to get back to the original problem - but at least I can block the two open "vacuum pipes".

 

[RichardH]

Problem I have (had) was as follows - after a 4 month lay-up over winter.

symptoms are :------
popping in carburettor.
turning over but not firing
turning over then "siezing" as if it is firing on the compression stroke
taking 20 mins or so to start
sounding like it is running on 4 or 5 (ish)
running fine for a while
stalling at junctions

as in my other thread

 

[Randy V]

Problem I have (had) was as follows - after a 4 month lay-up over winter.

symptoms are :------
popping in carburettor.

Causes - Lean condition / Timing too far advanced

turning over but not firing

Causes - Not enough fuel (carb problem), Ignition problem

turning over then "siezing" as if it is firing on the compression stroke

Causes - Timing too far advanced

taking 20 mins or so to start

Heat soak caused Fuel percolation / ignition problem

sounding like it is running on 4 or 5 (ish)

Lean condition (open vacuum port) or ignition problem

running fine for a while

Runs better when cold because of choke? Igition Problem.

stalling at junctions
as in my other thread

Lean condition (running rough) / Ignition problem/

In short - Fix the carburetor, check out condition of distributor cap and rotor, Set the timing to proper spec - come back and tell us how it runs!


Hope that helps!

 

[RichardH]

Thanks Randy
What I didnt mention was that ALL of these symptoms occur at the same time - or rather it has been all of those symptoms on the 1 occasion I have taken it out. It was running fine before the lay-up, so why should the timing suddenly advance whilst the car is sitting in the garage and although the carburation is obviously not correct - it has been like this for the last 3 years, at least, including 2 trips to Le Mans and has (apparently) run sweet all the time. It has been a bid of a sod to start when cold, from time to time, but then the choke never has been connected - I just use 2 or 3 pumps of the throttle to "prime" the carb, after about 3 minutes running (with an unsurprising tendency to stall) it has then run fine.
These problems all occurred on the first trip out this year and all within the 7 mile or so run.
It would appear that something has altered/stuck whilst sitting in the garage over winter - but for the life of me, I cannot think what it is. Hence the back to basics stuff. But Yes - I will sort out the carb, do a compression test (better safe than sorry) and attempt the timing.

 

[Doug S.]

Now apart from rebuilding this carb - i suppose I might as well, now I have got this far - or would you recommend "it aint broke - dont fix" - or an exchange one (£200).....

Holley 750 cfm 4 barrel “4160” Carburetor

Richard, what is the displacement on the motor you're using? If it is a standard 302, I'd be very careful before I replaced that 600 cfm carb with one a full 25% larger. Bigger is not necessarily better on the street, same goes for mechanical secondaries. If it's a 351 or a stroked 302, well, you might just have enough displacement for the larger carb....it's a gamble and an expensive one at 200 pounds per carb. I found that my mildly modified 351 Cleveland ran better with a 600 CFM Holley than with a 780 CFM Holley, size DOES matter in this case.

What is important here is how your carb "senses" demand, it's based on the "vacuum signal" at the venturi, which is EVERYTHING when it comes to getting the fuel to flow through those metering blocks and the passages in the carb. Larger venturi=lower "demand signal", which really messes with the fuel delivery and can create much larger problems than a smaller carb, which will more accurately sense the demand. Simple explanation for a much more detailed problem, hope it helps.

If you do find that the carb must be replaced, however, what might help you more than a larger carb is a carb of the same size but with center-hung floats. If you do much spirited driving on twisty roads or track your GTD, you might have noticed some fuel starvation coming out of tight corners...that's a function of having the hinge for the float in the fuel bowl hung on the side of the bowl housing. If you can find a Holley with center-hung floats in the correct CFM range, you'll find it much more responsive in that regard, won't make much difference in straight-line accelleration, though. An added bonus is that the center-hung floats can be adjusted while the engine is running.....no need to take the bowl off and check the float's adjustment :thumbsup: .

I'd agree with Randy, get those vacuum leaks plugged, put in a new PV, put it back on and get the timing set right and see what happens......that carb might very well just be sooty on the outside from the backfiring and other malfunctions.

One other thing, in the future when you plan on letting your car set up for such a long period, I'd suggest you find a way to run it dry on fuel. When petrol evaporates, it leaves a very nasty residue (often called shellac) that tends to plug things like little orifices up.....I usually run the car as low as possible on gas and then find a place where it can idle safely until the carb runs dry. Even then, I tend to back off on the bowl screws a bit, "drain" the fuel out of the bowls, and then tighten the screws back up. The car will stall when the fuel gets below the level of the jets, which in a Holley is pretty low, but better no fuel than even a little during a storage period.

Doug

 

[RichardH]

i get what you say - no point in spending £200 for a bigger (but possibly worse) setup. I have never used my motor "properly" on a track - just "parade laps" like Le Mans. The rest of the time it is a road machine and is usually fine for that. I will check compression, sort out this carb, refit it and then look at the timing. When it is running happily then I would like to get it Dyno'd for final setting up.

It is a "Standard" 302 with a "towing" cam. Has been balanced tho.

I will be back - and once again, thanks to you all.

 

[Jac Mac]

One further point- use a piece of 2mm wire rod to permanently 'lock' your choke in the off position if you dont intend to use it- they have been known to flip to the closed position after a backfire ( which in turn will cause most of your hard start symptoms as well ). Simply bend a 'hairpin' on one end of the wire & fit in the clamp bracket area on the secondary diaphragm with the other plain end in the choke lever arm.

Power Valve--just looking wont find the hole if it has one, your really need the tester. If you like the taste of gasoline you can do it with a short piece of rubber hose, a mirror, and a bit of your own lung produced negative pressure----not necessarily good for your health though.

 

[Al Jones]

This may sound obvious, but... I was reading some articles about this problem and one piece on the Barry Grant techline mentioned blocked air bleeds as a source of ragged operration/missing/and especially backfiring.Apparently these block up rather easily when left to sit with stale gas. Just a thought as this would be easier to check before spending a bunch of money. A.J.

 

[RichardH]

I dont suppose anyone has a Holley carb rebuild/service manual in pdf format, that I could scrounge?

 

[flatchat(Chris)]

Do a compression test --to make sure you haven't a burnt / stuck or broke /collapsed valve spring (common on Windsors)
Be sure you have fresh fuel from a reputable and reasonably high turn over "servo"
The transition between winter and summer fuels can be troublesome due to additives etc .
If you run catalytic converters -- they can become clogged with soot due to the very rich condition of high (toluene) additives. --runs like a pig.
Otherwise, Hollies are pretty simple do deal with -- but, a bit sensitive if theres foreign matter stuck in the float needle and seat or main jets.
A good micro filter is a must here --the paper element one usually causes the above grief when they start to fall to bits (crumble)
Good luck !

 

[RichardH]

My intention is to do a compression test prior to firing up again. Is it worth taking the Rocker covers off - would I see anything significant?

 

[RichardH]

I dont suppose anyone has a Holley carb rebuild/service manual in pdf format, that I could scrounge?

Now obtained - thanks.

 

[RichardH]

Halfway thro the carb strip and rebuild...
Arent the Holley kits awful. The instructions are mainly pictures with instructions which are not clear and the kit just has a couple of bags of bits - trying to identify part numbers is next to impossible - its a guess which bit looks similar to your original.

Mind you - think I am getting there - so far everything looks OK except I had no Power Valve check valve - so the base has now been machined and the check valve has been fitted.

 

[Doug S.]

Halfway thro the carb strip and rebuild...
Arent the Holley kits awful....so the base has now been machined and the check valve has been fitted.

Yeah, Holley's kits and instructions are pretty confusing....you'll have way too many parts in that Holley kit so don't be put off by that. Glad to hear you've machined the base and put in the check-valve....that might well avoid the blown PV issue in the future.

I'm sure hoping it's the Holley and not the dizzy's drive gear. A ground up drive gear means dropping the pan and cleaning out a bunch of debris, maybe even a new oil pump and possibly even a pressure-flush of the oiling system.....much better if the Holley rebuild solves the problem.

Dugly

 

[RichardH]

Yeah, Holley's kits and instructions are pretty confusing....you'll have way too many parts in that Holley kit so don't be put off by that. Glad to hear you've machined the base and put in the check-valve....that might well avoid the blown PV issue in the future.

I'm sure hoping it's the Holley and not the dizzy's drive gear. A ground up drive gear means dropping the pan and cleaning out a bunch of debris, maybe even a new oil pump and possibly even a pressure-flush of the oiling system.....much better if the Holley rebuild solves the problem.

Dugly

"I'm sure hoping it's the Holley and not the dizzy's drive gear" - so far nothing obvious wrong with the Holley .

"A ground up drive gear means dropping the pan and cleaning out a bunch of debris, maybe even a new oil pump and possibly even a pressure-flush of the oiling system." - Oh dear - it gets better and betterer :cry:.

We will see what I find after the Carb rebuild.