Hot Rod Forum banner
1 - 20 of 36 Posts

·
Registered
Joined
·
37 Posts
Discussion Starter · #1 ·
Hi all! I've sort of inherited a 1969 Ford XL 429 and It's 99% perfect! I've worked on engines and old cars but it's been 20 years, so I could use some help.
First of all, it's a 429, with the Edelbrock 2045 kit: Performer RPM 506 HP Top End Kit #2045 For 1968-87 BB Ford 460-522 V-8 Engines
And a Holley 4778-8 (700cfm double pumper)
Car starts right up, idles super smooth, when you first get on it though, or rev it, unless you open up the throttle very slowly, it bogs/hesitates, or "stumbles" for a second then takes off smooth. I asked a shop just for kicks, they wanted to rebuild the carb for $500. I said screw that, I'll read and worst case I can get a new one for $500 or even splurge on a Sniper.
I read a few articles including this one: Accelerator Pump Tuning For Holley Carburetors
So I went to start investigating. The accelerator pump linkages was tight, no play. Just for kicks (in case it was too tight) I loosened it until there was play then tightened it back until there wasn't.
Then I check the nozzles. First of all, there was a 28 in the PRIMARY, and a 31 in the secondary. Based on that article, that sounded backwards. Thought, problem solved! Swapped them, no difference I could tell.
Next I went and bought a 35 nozzle and swapped that into the primary, so 35 primary, 28 secondary. I THINK it was better, but hard to tell, problem still there.
Next I had the nozzle, so I put the 31 into the secondary, so 35/31. Now I definately notice it's better. Instead of what seems like a 2-3s stumble, it's a quick pause. Like a rev/pause/go!
I don't want to just keep increasing these are should I? Especially since the 35's were $30! Cam? I haven't looked at that yet, it's untouched.
Any ideas where I should go from here? I'm re-learning all of what I knew and learning new things so any help is much appreciated. I do have an extra 35 I could drill to a 39-40 since they came in a 2 pack (because I have a 1mm drill bit, lol). On hand right now all together I have 1x28, 1x31, and 2x35
Thanks!
 

·
Registered
Joined
·
432 Posts
What is your ignition situation? If I remember right those had a dual point with an advance/retard vacuum unit. The standard timing or +2 should work, but if you get the vacuum lines reversed to the distributor they get weird off idle. That 700 carb should have no hesitation with the cubes you have. Also is there a power valve in the carb or are they plugged?
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #3 · (Edited)
Sorry I forgot to mention that it's been changed as well. It has a Mallory ignition system on it. I see Comp 9 unilite breaker(less?) Ignition (part is rubbed away) Taylor wires and a Promaster coil part no. 29440. I thought about timing but I've long since given my timing light away don't remember how to do it. I can get a timing light and learn! Is that still how it's done?

Just went and looked. No vacuum lines go to ignition equipment. Carb neither, just the breather to PCV. Power valve? Not sure what to look for.
 

·
Registered
Joined
·
15,336 Posts
I’d start by bringing the idle speed up with the spark lead then take some curb idle screw out to bring the idle back to where you have it to see if there is too much transfer slot being exposed since this carb idles on the primaries only.

Bogie
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #6 · (Edited)
Thanks all. Lots to look at tomorrow. I checked that cam now that I know where. Unless it's really faded it's pink on position 1. Isn't that the smallest cam? Seems an odd fit for a big block with all that on it.
Looks like orange in POS 1 on secondary. Could those have been backwards like the nozzles?
 

·
Registered
Joined
·
432 Posts
Get your list number off carb air horn, then look at Holley site to find it on the build sheet. That should tell you what went where when it came out of the box.
The power valve is internal and is in the center of the metering block. It senses vacuum drop and provides enrichment by allowing a bypass to the main jets. They come in numbered steps which indicates what vacuum it would open.
 

·
More for Less Racer
Joined
·
20,947 Posts
Thanks all. Lots to look at tomorrow. I checked that cam now that I know where. Unless it's really faded it's pink on position 1. Isn't that the smallest cam? Seems an odd fit for a big block with all that on it.
Looks like orange in POS 1 on secondary. Could those have been backwards like the nozzles?
I'll expand a bit on pump cams and nozzles, but first there is one thing you must absolutely verify BEFORE you dive into a bunch of changes...
In your search of internet knowledge, search "Holley Transfer slot exposure" and familiarize yourself with getting that set up right since it also controls the carb transition circuit timing.
If primary throttle plates are open to exposing too much transfer slot in order to get enough air through the carb for it to idle(happens a lot, guys just crank up the idle speed screw willy-nilly when they try to get an engine running).
It can eat up all the beginning travel enrichment the transfer slot is meant to supply. Presents like it is a pump shot problem, but it really isn't.

Now, once you've got that squared away...

Pink is one of the bigger cams, but it is slow in rate, throttle has to be cranked open a large amount to get the full squirt from that cam.
Since you have the orange, try swapping them and see what the result is. Orange is faster initially but ends sooner.
Pump cam rate of lift and pump nozzle size is a balancing act.....
Large pump cam and small nozzle result is smaller shot stream stretched over a longer period of time....might be too small initially and engine stumbles.
Small pump cam and large nozzle result is larger shot stream that is over quickly, maybe too quick and the engine stumbles either initially or goes/stumbles/goes at tip in.

You've got an assortment of nozzle sizes that should more than cover anything that carb CFM should need on gasoline....now you need the pump cam assortment so you can balance shot timing with shot amount.
you can find a chart that lists the amount of lift per degree of opening for the pump cams, and what screw hole position gives xxx curve.

With that said about the cams and nozzles...
a large portion of initial stumbles like this are ignition timing rather than a carb problem....typically too little initial timing.
Set-up like yours I would expect to see initial timing at 12-16° with a full advance total of 36-40° full advanced by 3500 rpm.

If timing is good and no vacuum leaks are present the 700 DP should be almost razor responsive on 429 cubes.

I could not find the as-delivered spec for pump cam colors on the 4778-8, but the #28 primary/#31 secondary nozzle size is stock going all the way back to the first revision of the original design 4778....the 4778-1 thru -8 use same nozzle sizes.

It should not need 35 or bigger unless on E85 or Alcohol.
 

·
Registered
Joined
·
4,734 Posts
When tuning a double pumper to get rid of a bog you always want to make sure your timing is very correct and accurate before messing with the carb itself and like mentioned above you want to make sure your primary transfer slot is not over exposed. The best range is no less then about .020 give or take a hair and then no more then .040. You want to keep it square so the carb is taking most of the fuel from the idle discharge ports versus the transfer slot.

If the transfer slot is exposed to much and pulling too much fuel it will cause a very rich idle and the idle mixture screws might not adjust well or at all. After your set there you want to readjust your idle mixture screws out and start at about a 1 and a half turns from the seated position. You want to start to slowly turn them in about a 1/4 of a turn each time and go back and forth from side to side. If you hook up a vacuum gauge look for the highest vacuum reading you can get but don't leave it there unless its a bone stock motor with a very tiny camshft, if its a bigger size cam then the highest setting on the vacuum reading in most instances will leave it to lean but once you get the highest reading go back out on each idle mixture screw about an 1/4 of a turn and it should be about the best spot.

If its an automatic transmission while setting the idle mixture screws once you have it set correctly drop it into gear and make sure it will still hold a smooth constant idle without the engine shaking and almost quitting. If it does then adjust the idle mixture screws just a hair more out and it should be good if the carb idle circuit is properly calibrated to the said engine build but I won't post all that stuff right now.

When it comes to pump cams you have to look at the chart and the tuning process goes like this. The shooter size numbers you usually have to go up or down .003 difference in size in order to get enough of a change. The difference on the number sizes goes like this. The bigger the number the quicker the shot comes and the quicker its over during throttle opening. The smaller the number the longer of a shot it will have during throttle opening and will take a little bit longer to be done.

On pump cams the more cc's over throttle travel it does such as the pink pump cam the less of an initial shot while opening the throttle and has more throttle shaft travel duration before its done and gives a lesser initial shot with longer travel across the throttle position. When you go to say an orange pump cam the orange pump cam is kind of like in the middle and compared to the pink it will give a way bigger initial pump shot but has less travel till its done across the throttle shaft opening duration time. It basically will give a quicker bigger instant shot but will be over with sooner. ON the pump cam position the number one spot will activate the shot sooner and the number two spot will activate it a tad later. The number two spot on the primary side is normally used when an engine has a 1000 rpm or higher since when setting the primary idle the pump cam position in the number one spot can sometimes have lost just enough on its ramp to give a slightly lesser shot from its profile carved into the cam profile.

That is just a reference point but not etched in stone but just a starting guideline point and can still be used in different situation regardless of the idle setting rpm and depending on the engine specs and what it likes.

Below is a chart to help you out with and recommend getting a pump cam kit which will be highly good especially for a double pumper. When tuning the pump shot on them it can be a little bit aggravating at first as you have to get the front tuned down to have no bog and then you have to work on the secondary side and it can sometimes need to be slightly tweaked on the front in order to transition from the front and back when you punch it from partial throttle to wide open throttle and not have any bog or hesitation at all. As long as the vehicle has the right gearing and a good transmission and proper stall if its an automatic it can be done.

You always have to do a trial and error on tuning the pump shot circuit and it sometimes can be frustrating but with experience you can get the hang of it.
Rectangle Font Slope Parallel Pattern
 

·
Race it, Don't rice it!
Joined
·
8,828 Posts
You already have your answer.
You have an idle to booster transiet lean spot and you can't cover it up with more nozzle. Well, actaully you can but it's not the right way and it'll bite you later.
That lean spot is going to lay somewhere in the idle circuit.
Transfer slots, idle mix screws, idle feed restrictions, idle air bleeds, float levels. etc

I'd take the carb down, put EVERYTHING back to factory and work at it from there. Holley is typically very close but over the years people who don't know go to messing with stuff and get things way out in the weeds and then shelf the thing to try on some other project. Usually when they get lucky and find a carb that just happens to work well on a particular combo, it's called a good carb. If unlucky, it's a bad one or needs rebuilt or whatever.
If you don't have the capacity to work it over your self or need a quick turnaround a custom builder is probably a good direction.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #12 ·
Thanks again everyone. SOunds like I'm in the wrong order, should be timing/idle, then carb.
So, I reset the carb to stock and got a timing gun. Here is a pic of the timing marks, the white mark I think is stock (5.5 BTC it seems)
But, the timing is NOT that. When you say 12-16, I assume that's BTC?
The timing is reading what would be 20 or 30 ATC! How is it even running? I put a red mark about where the timing actually lines up with the engine marker, even though it's out of pic. I put the timing light clamp on wire 1 (marked 1 on distributor and goes to front passenger side cylinder)
Hood Automotive tire Grille Motor vehicle Bumper
 

·
Registered
Joined
·
432 Posts
It would appear to me that the white mark was at 0. But your pointer is on the wrong side. This could mean a couple of different things.
1. The pointer was installed on the wrong spot on the timing cover. Many are just on 2 bolt holes.
Your 12 degree btdc mark appears in the normal position or where the pointer should be.
2. The degree marks on the damper have moved from the weight shifting on the damper rubber cushion.
The shifting of the weight is not unheard of.

From what I have seen 360, 390, 428, 429, 460, engines should all time at approx. the 10 o'clock position on the crank.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #14 ·
That was looking from under the engine. I kept clicking it to get that to top and gave up.
Told you it's been a while though, lol, I just plugged the timing light in forgetting they have a dial for advance. That was set to like 30! So, I set it to 0, and the timing is currently running about 7-8 BTC. Now I get why it's running. So, I need to increase that to 12-16? BTC?
 

·
Registered
Joined
·
15,336 Posts
The basic rule is to give the engine what it likes. These really low initial advances are from the factory. They are working emissions issues of stock production engines not trying to improve performsnce. You engine has neither stock heads nor cam so going back to Ford’s recommended timing will prove to be insufficient.

Aluminum head’s like more timing as they move heat pretty heat pretty quickly especially compared to iron, so adding some base timing at idle helps them do better.

Your also running a little cam with the Edelbrock top end kit. Bigger cams like more base timing.

I’m not a real big fan of dial back timing lights far too many of them have problems so unless you have the equipment to essentially test them for accuracy they really can’t be trusted unless you are able to test them yourself or have sent yours out to be certified for accuracy.

Just don’t forget that once you get past about 10 degrees base advance you need to start taking an equal amount out of the centrifugal inside the distributor. Games you can play is to use the vacuum advance if you have enough manifold vacuum to bring up some of the idle advance which will go away as the throttle is opened, but here you may well need softer springs in the centrifugal to bring it in sooner. There’s always this game you have to play with modified engines to find the advance combinations it wants. This is to a great extent not easy to do without a dyno simply because the experiment, try and cut, then re-experiment nature of doing this with the engine installed in the vehicle is a pretty big PIA.

Remember the old adage that most carburetor problems are electrical.

Bogie
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #16 · (Edited)
Hi again! So, I got timing to 16, no pinging or anything. Idle went up so I dropped it a bit. I don't have a tach, got one on order, so I'm going by ear (about 600, that right? I saw something about 600 vs 1000 depending on motor but don't recall where/what)
I would say the improvement is about the same as when I increased nozzle size (those are back to stock though). So better, but still not gone.
So, with tons of information and things to look at above, I'm taking baby steps, what should be the next step? More timing advance? Back to something on carb?
The distributor does not have vacuum advance BTW (Comp 9000 Unilite). I think there are some parts you can change out inside it, but I have no knowledge on that. I just turned it until I got 16 and locked it in. I have 12psi vacuum, I did check that. The Edelbrock kit says to expect 10-12 so that seems great (checked with my vacuum gauge directly off the manifold).
To summarize since so much is going on now, at least in my head, I have the carb at stock settings/nozzles, timing 16BTC, idle ~600, slight hesitation/bog now. Still not as much pull after the hesitation as I would expect from this much power either (but, the rear ratio is either 2.8 or 3.25, so I suspect that has something to do with the in the seat feel too). Sure sounds like 450hp but doesn't feel like it!

EDIT: Couldn't find time before because I was looking at the kit. Looked at the cam in the kit and it says 10-14 so I'll back it to 14 first and try.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #17 ·
OMG, still an idiot. Sorry folks. TMI going in and out last couple days. MGK was correct, I missed the 1 at the bottom near ATC. The white Mark marks 0! So, I only got it to 11 today then, I just set it to 14 (for real, triple checked). Seems even better but have to try tomorrow. Dark and raining now.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #18 ·
Ok, this is where I'm at and it's the best it's been! It's still there, but it's a blip, rev/pause/go.
Timing is up to 16 BTC, no pinging or issues I can hear (running premium fuel)
Carb has stock nozzles (28 primary, 31 secondary), the cams that were on it (pink primary, orange secondary, both on position 1 which is how it got to me).
What would be my next step? Doubt I want o push timing any further since that's the top of the ranges I've heard.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #19 ·
I don't have a blue right now but OMG it's now so close!! I swapped the cams like someone mentioned above. So now 16BTC, 28 primary, 31 secondary, orange on PRIMARY spot 1, pink now on secondary in spot 1. It's so slight now that if someone else drove it they probably wouldn't notice. And it has pull/power!!
Anything I can do from here to get that last tiny bit of pause out since this is working so well?
Thanks so much everyone, this thing is night and day from a week ago.
 

·
More for Less Racer
Joined
·
20,947 Posts
Anything I can do from here to get that last tiny bit of pause out since this is working so well?
Thanks so much everyone, this thing is night and day from a week ago.
Yes....get the pump cam assortment so you can experiment with a cam that has a sharper initial pump action than the Orange cam has.

Here's a rate graph for colors, and #1 or #2 hole position.

Green and Blue on either hole are both sharper initial action than Orange
note the brown vertical line that denotes when the secondary starts to open and where the primary shots run out

Colorfulness Rectangle Slope Plot Line


Try the Orange cam on hole #2 in the cam and the linkage, it is a little faster rate and a little more lift than it is in Hole #1
After than, if the Blue or Green cam on primary side doesn't fully cure it, you can try swapping the pump nozzles to the bigger #31 on the primary side.

You could actually try that #31 nozzle primary side now with the Orange cam and it may be all you need. (y)
 
1 - 20 of 36 Posts
Top