Holley Carb Identification

Another thread for you experts out there.

My 302 is running rough and I have been told on another thread that it is likely to be the power valve in my Holley carb which is damaged. Only problem is - I dont know which Holley carb I have fitted. I have looked, and looked and looked - there is no manufacturers plate or ID that I can see anywhere, except for "Holley" cast into the housing. Is there anyway that it can be recognised?
Is there an idiots guide to Holley carb identification? I have searched without success, but without identification, I cannot order the requisite bits .
I have enclosed picks from both sides and the rear, if any of you guys can ID it from that.
Looking at the Real Steel catalogue, the 465cfm has a divorced choke and mine has a manual choke, so i reckon that lets that one out. Most likely a 600 or 650cfm (but I am guessing). Or is it just the chokes that change and the body is identical?

Hello Richard !

The number on the Holley is stamped in the front part of the choke housing. Take the air cleaner off, and it will be stamped there on the front vertical surface. It should read something like "List 1850-3" , or something similar. The power valve is located just inside, once the float bowl is removed. It has a one inch hex on it and screws into the back side of the metering block. It is more than likely a 6.5" valve, but the List numer will tell for sure. If you have a radical cam, you will have to change valves accordingly. The power valve protecter kit can be purchased from Jegs, or Summit, or most any of the local parts stores here in the states. The late model carbs have them factory installed now because it is a huge problem with the Holleys. Other than that they are basically a great simple carb. You can get the part number here, for the power valve protection kit. It is the same for all Holleys. Look for #121 in the break down.

A carb break down is here
http://www.holley.com/data/TechService/Technical/4150-4160 Exploded View.pdf

Holley Performance Products Power Valve Check Ball Kit 125-500,

and the instruction sheet here

http://www.holley.com/data/Products/Technical/199R9898-2.pdf

Kindest Regards
Brian

The other thing i noticed whilst shuffling around the carburettor is that the vacuum advance tube (just to the right of the choke mech. in pic1) is not connected to anything - now I dont have vacuum advance on my distributor, but should it just be an open hole - or should it be blocked?

That's a HUGE tube from the advance port. It should be plugged. If you remove that tube you may find that it already is. It's just a pipe thread and i would remove the nipple, if it has one and install a small pipe plug. I would do that before working on the power valve,by the way all Holleys use a common power valve( they are rated for vacuum and flow, but will fit any). The vacuum port is for high speed, not manifold vacuum and you may find that the carb is rich through the whole range when that is plugged. That would mean that it is probably jetted too large. Power valve issues are usually at idle and lower speeds where it loads up...sometimes to the point of making you tear up, it is so rich.

Well, you're fairly lucky in that it doesn't look like an exotic Holley model, I've seen Holleys like this one (vacuum secondary, single-inlet, side hung floats) on factory installations on everything from GM's and Fords to International Harvester pickups.

A bad power valve will certainly affect performance during accelleration at and off-idle, inducing stumbling and bucking and popping and spitting and most often backfiring, too. Looking at the photo from the top, it looks like your primary circuit has been at least over-rich, but I'd venture a guess you have been experiencing those other symptoms, too. It's quite black around those primaries.....

In my experience, there are usually at least two vacuum ports on this sort of Holley.....the larger one is for a power-brake vacuum booster and is usually on the base plate, the smaller is on the primary metering block on the passenger's side and is for distributor vacuum. I see on your first photo that there is a piece of tubing on yours, not a block-off nipple. That's a "rigged" plug, but somehow the bolt or screw that would be inserted into the tubing to block off the airflow has gone missing. If you aren't using it, you should put a plug on it.....otherwise the engine will interpret this as a vacuum leak.

BTW, this might get more attention if you had posted it in the Induction board, you might PM one of the admins and ask them to move it there.

Good luck--I'd say from the looks of the carb from the top, you might be in for a rebuild. Not a difficult process but Holleys have a rep for being tricky....might best be a job for a shop if you're not pretty experienced.

Doug

duplicated post

Thanks for your pointers, guys.
I have now been back for another detailed look and - no - there doesnt seem to be any ID at all - I have taken a couple more photos, one from the front of the choke mech. and there isnt any ID there, if that is where I should be looking.
I have also taken a picture looking down the carb - yes they are all pretty black and sooty and each venturi??? has on the top of them the following - 45R-1(11). Does that mean anything(jet size 45)? There is, on top of the metering block? a black ink number 03881, but that might just mean 1st Mar 1988 for all I know. .

That vacuum pipe is definately not blocked - as is the hose . You suggest that it should be - easy job.

Apologies for poor quality pics - its a bit tight in there, so these are a bit out of focus.
I reckon the thing to do is to remove the carb as I will have to do that anyway and look at the Power valve (is it possible to see if it is ruptured -or is it just a replace jobby). I will also fit the protector kit, as that seems to be a good move, too.
Doug - I take your point about Induction, and I will PM a mod. I was hoping not to have to do a full rebuild though - i take it a good dose of carb cleaner is "de rigeur" then?

How about a photo taken from the front, looking over the float bowl, at the front of the air horn for the primaries? I'm not seeing a vent tube on your primary side, but the secondary side is there. Most often the primary vent tube is longer than the secondary......this, too, can cause problems.

Replacing the power valve is one of those things I'd do if I were in there. It only takes one backfire to blow the diaphragm in a power valve, and they are fairly inexpensive, so I always get 2 or 3 when I make a parts run. It's nice that your Holley has a secondary metering block, some have only a metering plate. It's been a long time, and I've slept since then, but IIRC there is no power valve in the secondary metering block, only the primary.

As for carb cleaner, it'll make it look better, for sure.....however, if your problem is plugged passages in the carb body or metering blocks, carb cleaner through the venturis won't do much. If you have the metering block on the primary side off, it might be tempting to just stick the tube up to the orifices on the carb body and squirt a bit through them, but watch out....those orifices lead to places where there are gaskets and o-rings, carb cleaner tends to soften those materials. Small bits fall off into the orifices, plugging them up, and there you are....into a full rebuild.

Doug

Oh, yeah, one more thing learned the hard way....if you go get into that Holley's primary side, make sure you use new gaskets for the bowl's screws. Leaks :thumbsdown:

Doug

Pics attached- Your carb has integral cast in bowl vents.no worrys there, you need to check for further air leaks like the one on the dizzy advance port and rectify, they wont be helping, there may be others around base plate. Power Valve [PV] size should be matched to your engines idle speed manifold pressure reading [vac for all the non believers]. If you get a reading of 8.5 inches then you need a 75 or 65 PV depending on your drive style etc--unfortunately you will have to get the car running cleanly in order to establish this number so start with a 65 on rebuild of the carb, should be OK unless you have the camshaft from hell! If you get a manifold reading around 10.0/10.5 you might need to come up around 85 on PV--------PV pn designates size..25BP-591A-[65] ...Size 'should' be stamped on PV in one of three possible locations on PV as per pic.

The check valve in throttleplate (base plate) may already be there in a late model like yours, but unlikely since its not a performance model. Its simply a small Ball Bearing that lifts & closes the PV channel when a manifold explosion occurs ( backfire). If you have the carb setup spot on & are running 'good' fuel & ign timing curves etc it shouldnt be reqd, but its not a perfect world.

hmmmm - not sure I understand fully. (But i did say I was ignorant on these).

My car has (according to the engine builder) got a "towing cam" which I understand to be a "high torque" cam. I have no idea what the idle speed manifold pressure reading is, and without getting the engine running properly, cant see how I can know what that is. I assume the best bet is to replace like with like on the PV? I also wont know if I have a check valve without removing the carb from the base plate, and once I have removed it, I might as well fit it if it is not there.
Not sure I recognise your first pic, Jac - but the second one is obvious to even me.

The intention was to take it somewhere with a Dyno to have it checked and "tweaked" so that it was running at its best, but without the basics set up, I dont wish to drive it at all - in fact I consider it dangerous at the moment, with its cutting out and difficulties in starting.
As I said previously, the obvious thing now is to remove the carb and have a look-see.

RichardH said:

Not sure I recognise your first pic, Jac - but the second one is obvious to even me.

Click to expand...

Jac's first photo is a view of the carb body's front, with the fuel bowl and metering plate removed. He has drawn arrows to where the carb's part number will appear on the front of the air horn as well as the "backfire" passage where the ball bearing should be located should your carb not have one in it yet.

Holleys are notorious for having warped base plates. Once you get it broken down, take a good straight edge and give the mating area between the base and the body a good look...machine work is expensive, if they are off it's probably best to consider a replacement. I have corrected small issues in the past by rubbing the parts over a sheet of wet or dry sandpaper taped onto a piece of glass....window glass (not art glass) has a very level surface. Watch out for rebuilt units, often they just have the replacable parts installed and don't undergo the checks for flatness.

Doug

First pic is front of choke horn with carb part # at end of arrow. It will say something like --List-****, *****.Give me those numbers etc & I can tell you what your carb was meant to have when new, although someone might have been in there already & changed things.

Once again - thanks folks, for holding my hand on this one - will have another look tomorrow.

Richard,
Won't Roy Snook know which carb you have on the car and what mods have been made to it?
Tony

Aaaaaah!

Tiz easy when you know...
a) where to look
b) have the Carb off.

I know realise why I couldnt find the ident before......
I was looking in the wrong place.
it was black writing on black dirt.
i couldnt see the front because of the Distributor and the reflection from inside the car.


I assume that to get to the PV - its a case of removing the front 4 float bowl bolts?

huntsen said:

Richard,
Won't Roy Snook know which carb you have on the car and what mods have been made to it?
Tony

Click to expand...

He might - but is a bit busy usually, so I try and leave him alone. Plus - i wont learn if I keep calling him up every time the car sneezes.

Richard,
I recently replaced the power valve and all gaskets in my carb, I'm pretty sure mine is the same list number.
I got a refurb kit with all the gaskets and power valve and replacement springs. You cannot reuse gaskets in these carbs, so you will need the same kit I guess.
I think I got mine from Real Steel.
When I get home, I'll check for you.

It is not a difficult job.

regards
Dave

Real Steel have quoted me £25.36 for the refurb kit.
Power valve - £7.50
Check valve kit - £8.55

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?



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?

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?

THOSE are the photos we've been talkin' about!! 600 cfm, very common Holley, lots of them out there on all sorts of motors.....and now I see the primary vent tube, all is good!

RichardH said:

Aaaaaah!
I assume that to get to the PV - its a case of removing the front 4 float bowl bolts?

Click to expand...

You are correct. You'll probably need that kit mentioned above.....there are gaskets where the float bowl joins the metering block, where the metering block meets the body of the carb, and for each of the bolts holding the float bowl/metering block to the body of the carb. There will also be O-rings to seal the transfer tube between the front and rear float bowls. Don't forget those O-rings or you'll have fuel all over.

Another thing that is handy about this Holley is that the secondary butterflies are vacuum actuated. Holley sells a kit including a variety of springs....this kit can be used to "tailor" the point in your accelleration curve where the secondaries open. This can have a huge impact on your car's drivability and power. It's nice to have some sort of timer to sort out the effects of the various springs, but not necessary. The effect will easily be felt by the seat of your pants!

Next photo we need is a shot of the inside of the front float bowl.....let's see if you have any gunk in there. If there's contamination in the float bowl, debris can get into the needle-valve and keep it from sealing all the way, allowing too much fuel in there and that can cause stalls.

You're on the right track! The PV is a simple repair, you'll have it off and back on in 15 minutes or so. Don't assume you can tell if a PV is intact by visual inspection, all it takes is a pin hole in the diaphragm or a slight delamination at the edge of the diaphragm where it is hidden by the metal housing. Holley sells a tool to test if they are intact or not, sort of a hand-held vacuum pump with a gauge on it. It's the only way to see if the PV is leaking or not.....a new PV is less expensive than the tool.

RichardH said:

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?

Click to expand...

Yes, that should be blocked IF it is not used. Any auto supply store will sell an inexpensive assortment of vacuum plugs, get one and start putting them on the vacuum ports that are not needed--if you have a dizzy with a vacuum advance, this port is exactly the one you should be using for your distributor's vacuum hose--plug the one on the metering block and use this one.


Doug