carb issues
 

Ok, I posted on this last fall, and I am just now getting around to trying to fix this problem.

Long story short, when I put the new cam, heads, and 1.7 roller rockers in the car, I developed what I thought was a vibration at low rpms. It was noticeable right off of idle (leaving a stop sign, it would “stumble”) or at cruising speeds at only a slight throttle off idle (like in overdrive). As soon as I give it throttle, past that very slight point, the vibration would go away. It almost felt like a chug at cruising speeds, but it is definitely not a balancing issue.

Jester suggested a long time ago I change the accelerator pump squirter to one size bigger. I had a few respected local guys tell me to change the accelerator pump cam, one going as far as to say change it 2 sizes up.

My carb had the white cam on it, which is stock according to the Holley website. I changed it out tonight to the red, which is two up from the white, and one over the blue (next over stock).

This change definitely did not make it better, it is definitely worse. Now when cruising I can get the throttle actually caught in a sluggish bog and unless I give it more throttle, it just makes the car shake like something is out of balance.

Should I change the squirter? What else could it be? The floats should be set just fine, and the timing SHOULD be good, but I will check it when I can get a vacuum gage.

I need to just go buy a Holley book and see what I can figure out.

Ryan

Re: carb issues
 

I called Holley and they were confident that I have the wrong powervalve for my set-up. They told me how to check and c which one I need. More to come.
Ryan

Re: carb issues
 

If the power valve is opening to soon, it will load up. Adding a big pump shot will make it worse..

Re: carb issues
 

Just out of curiosity, did you readjust the accelerator pump linkage after swapping accel. pump cams?

Re: carb issues
 

No I did not. I cant say I have ever personally done that. I have been waiting for you to drop in PKRWUD, good to see you.

Dark Night-
Are you saying you think Holley has given me bad advice?

Ryan

Re: carb issues
 

Thanks! It's good to be seen! lol.

Any time you change the pump cam, or the screw hole with which you mount the cam, you must check the linkage, and make sure it's properly adjusted. You want to see fuel come out of the squirter at the slightest tap of the throttle. If someone sneezes hard enough, standing next to your engine, you want to see fuel start to spray out of the squirter. It needs to be adjusted that precisely. On the other hand, though, you don't want to bottom out the pump while there is still more lift coming, otherwise you won't get a full shot. If there is even the slightest delay between tapping the throttle, and fuel coming out of the squirter, you'll have a flat spot on acceleration. As you open the throttle, you are letting in a large amount of air, and without the added fuel the accelerator pump instantly provides, you will experience a lean bog until the fuel can catch up.

Pull the air cleaner, and look into the primaries, and tap the throttle lightly. Does fuel instantly start to come from the squirter?

Re: carb issues
 

Well, I have not pulled the old power valve, but using the Holley way of checking...I used a vacuum gauge with the car warmed up and in gear. I pulled only an eight on the gauge. Holley stated to cut that in half, so I bought the 3.5 power valve. I have not put it in yet, but I am thinking I have the stock 6.5 power valve.

I hope to change it out tom before work and update, I will also check the throttle linkage as you stated.

thanks,
Ryan

Re: carb issues
 

You've only got 8" of vacuum at idle?!?!?

I suspect you'll discover that your engine leans out at the peak of your powerband with a 3.5 PV, but give it a shot and see.

I would install a green pump cam, screw in hole #2, adjusted like I mentioned. Your car will bark the tires every time you just look at the gas pedal. :D

Re: carb issues
 

Now that is what I like to hear! I have the entire pump cam selection, so the Green is no problem. Is the 2nd hole the top or bottom hole? Now that I think about it, I think they might be numbered? Anyway, I will do that and get back with you. Do you want me to do the power valve switch with the pump cam or try them separately?

It did only measure 8", which surprised me. I only have the stage 1 cam.
Thanks,
Ryan

Re: carb issues
 

Check my reply to your last post in Brian's thread.


Also, the green cam (should have '290' stamped on it) will work as promised, but you MUST adjust the linkage correctly, as I described earlier.

Re: carb issues
 

I may be wrong, but that doesnt seem like alot of vac for a stage 1 cam..

And I meant that if the PV is opening early, a bigger pump shot would make it worse off idle..

Re: carb issues
 

You're not wrong. :)

Re: carb issues
 

The car had 11-11.5 tops Vacuum when in park and idling (warmed up). Are you suspecting a Vacuum leak? I am going to try and tackle this carb tomorrow, I have the whole day to work on it if needed.
Ryan

Re: carb issues
 

Do me a favor and answer the hypothetical question I asked you yesterday. :)

Re: carb issues
 

Do ME a favor, and put the stock cam back on it, and jump up 1 size on the squirter. ;)

I WILL say, as stated earlier. When you change the cam you MUST readjust the linkage! "If someone sneezes next to your car" is almost correct, I use 0.010" clearance between the linkage and the actuator arm, with engine off and "zero" vacuum. :D

Re: carb issues
 

I prefer 0.000 clearance, but I'm funny that way. ;)

Re: carb issues
 

pkrwud-
Slamming on the brakes would not kill the engine, or so I believe. I have gotten on the brakes pretty hard before and it did just fine.
Ryan

Re: carb issues
 

Ok, here is the latest. I bought my own Vacuum gage thinking I might have a Vacuum leak. With the car in park, I had 15.5" and in drive I had 11” Now according to Holley, my 6.5 stock power valve would still be wrong, a 5.5 would be perfect. Is it worth changing?

Put the green cam on, using what I think is suppose to be the 2nd hole (see pic). Adjusted the pump linkage, to where the slightest touch would make it squirt the fuel, and then took it for a drive.

Well....Ryan has some serious traction problems now.....(insert Ryan worshiping PKRWUD) :D . I have no more hesitation off the idle at all.

However, I will say that I still have the shutter in overdrive...and slightly in third, but not always. It is most noticeable when just cruising, with overdrive at 45 mph or so, right at 2,000 rpms? Any suggestions on that one? I am leaning towards Jesters recommendations of slightly bigger squirters now.
Thanks,
Ryan

Re: carb issues
 

Here is the pic.

Re: carb issues
 

Not taking anything away from Jester, cause he's never steered me wrong, but I don't see how changing squirters will solve your shutter problem. :confused:
The squirters only provide a shot of fuel when the throttle is pressed to prevent a lean condition when the throttle blades are initially opened. They do nothing for part throttle conditions.
If you don't have a stumble or bog off idle, then I would say your squirters are fine.
Jester, did I miss something on your line of reasoning here buddy?
I've been reading some of my HOLLEY CARBURETORS book and thought I was starting to figure out how these buggers worked.
I'm also curious who's method of figuring the correct PV is more accurate....PKRWUDS or Holley's.
Holley says to check vacuum at idle, in gear and PKRWUD says check it in Park. :confused:
I ordered an 8.5pv today so I must have decided Chris was right :)

Re: carb issues
 

82gt-
They both have great knowledge and have helped me in the past.

My knowledge of these is still elementary, so I need all the help I can get.
Ryan

Re: carb issues
 

I agree 100% I couldn't agree more. :)

Re: carb issues
 

Holley knows their stuff, believe me. They tend to tune for the average car, though. You seem to be losing power at the end of your run, which is often because the PV closes too soon. I'm not guaranteeing the 8.5 PV will be a miracle cure, but it should be better. If it's too much, you'll run extremely rich at idle.

Ryan-
Sorry about causing you to lose traction. :)

The cams all act differently, and in all the Holley books I've ever read, none of them recommended the green cam, but it's still my favorite. And now you know why. Books are great, but experience is invaluable.

Your vacuum numbers sound better than they did before (8" at idle couldn't be correct if the mixture and timing were on), and by answering my hypothetical question, I can say with confidence that you don't have a vacuum leak (if you did, the engine would stall during a panic breaking condition).

Now that you have the single best tool for working on engines, use it to adjust your idle mixture, and make sure you're on the money. As far as your vibration, I'm thinking you should be looking at your tranny/convertor.

Re: carb issues
 

Oh wow! Time to defend myself I guess! LOL

Last YEAR (Ryan!) when this was brought up, it was presented to me as an "off idle" stumble, so my first thought was squirters. Now it comes up as a partial throttle problem, and I'm gonna go with everyone else, and point the finger at the power valve. I'd just yank it and be done, but that's just me.

PKRWD, nothing at all personal here bro, I value each and every one of your posts. But this one I think we need to have a discussion on. The adjustment on the accelerator pump cam CAN'T be 0.000" for the simple reason that at WOT, you'll rupture the diaphragm on the accelerator pump. Remember, that's all mechanical linkage, and there's no room for errors, or "over run". Like I said, nothing personal, I'm just looking to learn something here! :D

Am I missin' something?

Re: carb issues
 

Nothing personal taken! :) This is a common area of misunderstanding when it comes to Holley carbs. First of all, you won't rupture the diaphragm no matter how badly it's adjusted, thanks to it's design. That's why there is a little spring around the screw and nut you adjust it with. Even when you bottom out the pump housing lever, the spring inside the pump will experience coil bind before the diaphragm would rupture. :) The worst thing that can happen from adjusting the linkage too tight is that you won't get the full 30cc shot of fuel. The perfect adjustment is zero clearance, but most people don't seem to be able to adjust it to zero, so actual clearance is recommended in their literature. But believe me, zero clearance will give you the best possible results.

Re: carb issues
 

Ok, so it is at all possible that the power valve, needing to be slightly smaller then it is now, would cause the shutter I still have?

I have a Holley book coming (thanks Brian) so I should be a little more educated on this by some time next week.

PKRWUD-
I know you think tranny/converter...which I will look at, I am just not sure at this point what in those two pieces may be the cause of this. The converter is suppose to be pretty stout, not saying it still couldn't fail though.

Thanks all, we are half way there!
Ryan

Re: carb issues
 

It just sounds more like a possible issue with the convertor lock up than a carb issue, but it's really hard to tell online.

On a side note, I think a 3.5 PV will only hurt your performance, but I'm interested to know if it solves your problem.

Re: carb issues
 

<---- Thinking, taking this all in.

I'll be back later. :D

Re: carb issues
 

I had that low rpm cruising stumble once. Since the carb is running almost entirely off of the idle/transition circuit at those low cruising rpms, the idle being set too lean will cause a stumble sometimes under those conditions. How many turns out are your idle mixture screws out from the closed position? I had to richen mine a little more to get rid of the stumble but then it was a little rich at idle. I eventually had to open up the low speed or idle bleeds to get everything just right.

Rev

Re: carb issues
 

I really don’t know what it is set at, I will check it tom and see what I find. It could be the converter, but I am hoping not right now.

PKRWUD-
I didn’t mean to say I wondered about installing the 3.5 power valve. According to Holley’s way of thinking, the 5.5 would be what my vacuum in gear called for.

Ryan

Re: carb issues
 

Looks like I had another hidden issue. I noticed a small tapping noise coming from the driver's side bank of cylinders today when I was going to a buddy’s house to adjust the idle mixture screws.

The tapping noise sounded like plastic on metal, not the sound I have heard from detonation in the past. The noise got louder, and the car finally started to lose power. I was able to get it home, where I realized my distributor hold down was lose :o , so I am not sure if the distributor was moving or not. The wires look good, and appear to be seated on the plugs.

The one odd thing I noticed was when it started to run crappy and rough, I went behind the car and could hear a serious change in my exhaust sound. The car actually sounded smoother and reminded me of what a Honda would sound like.

I believe I may have a bad plug, although they are only 1.5 years old. I have autolite 25's in it and hope to put some 24's in it tonight after work.

I will say this, I have pretty much eliminated the Trans and t.c. from the shutter problem now. I also had a slight backfire out the exhaust while I limped the car home, going down a pretty good sized hill.

Ryan

Re: carb issues
 

Do you think it could be the U-joints causing the shutter...or maybe your carb. just needs rebuilt.
Out of curiousity, why are going to Autolite 24's instead of staying with the 25's? Are the 25's too hot a plug?

Re: carb issues
 

The carb was rebuilt either last summer or the summer before. I decided on the 24's because I cant leave anything alone, and thought I would try the hotter plug-which I was informed was the 24's.

Re: carb issues
 

Uhh...I hate to tell you this but the 24's are a colder plug.
I know for a fact, at least for autolites, that a higher number means hotter plug. Hold the 24 and 25 next to each other and you will notice the 25 has a slightly longer reach into the combustion chamber. That's how you tell how a plug is hotter or colder than another.

Re: carb issues
 

Well, I guess thats what I get for goin to the auto parts store and leaving it up to them to give me the right ones.....lol....
Ryan

Re: carb issues
 

That all sounds like a timing issue, and if your distributor hold down was loose, I'd bet the farm that the distributor moved. Reset your timing, and all should be well again.

Re: carb issues
 

I reset the timing, still have the new issues. I thought the same thing. Now I am trying to decide what is causing the problem. The ignition is pretty simple on this thing....Mallory brain coil and a Mallory Unilite. The Unilite’s module has gone bad on me in the past.
Ryan

Re: carb issues
 

Well, looks like I lose the farm. lol. It's been my experience for more than 20 years that Mallory makes junk. I will never buy another product of theirs, all though in all fairness, the coil in our sprint car is a Mallory, and it still works.

What is your timing set to? Had it changed?

Re: carb issues
 

Mallory was in the car when I bought it, otherwise I will never buy their stuff. I plan to put MSD in when this one goes bad.

I wish I could tell you where my timing was, but here is the thing. When I swapped in the new 91 5.0, but kept some of the early style front dress, meaning timing chain cover, alternator bracket, water pump, I haven’t been able to find a pointer that would work. Reason being the pointer that works with this set up is designed for the passenger side if I remember right and I needed one for the driver's side where the lower radiator hose was not in the way. I couldn’t find one that would work though so I made one for it, but I must of been off a little. Last time I tried checking it, I was WAY off (like way past 16 degrees). So to answer your question, it was timed by advancing it as much as I could, then I would shut the car off for a minute. I then backed it down a little at a time until it would "hot" start...then I locked it down there.

I will show some pictures just to clarify. Also on a side note, no matter where I put the timing, I can’t get it to run right now. This is more then a "timing" issue. Something definitely has failed.

Ryan

Re: carb issues
 

Well, the plugs still look new and all the wires were on good, so I am not sure where to go from here. I went ahead and put in the new plugs, and only found one slight burn/crack in one of the plug wires boots. The crack didn’t appear to be overly deep. I checked it with the car running and no lights on in the garage, no arcing that I could see or here.

I am in a wedding this weekend, so the rest of today and tomorrow is shot with that. I will put a timing light on it for you PRWUD, but I am sure it will say something crazy like 20* advanced. Anyhow, I am not sure what it is, the car gets so few of miles, I am really not sure what is causing my good sounding stang to sound like a dang Honda.
Ryan

Re: carb issues
 

Are you saying that your balancer is marked for a passenger side pointer?

How do you know it hadn't moved if you can't time it?

Here's the best way to time it, in your circumstance:

Hook up your new vacuum gauge, and start it. Turn the distributor, however you need to, so the you get the highest reading on your vacuum gauge, then retard it until the reading on the gauge goes down 1/2" (half a number). Tighten down the distributor, put away the vacuum gauge, and test drive it.


Let's continue this via email.

pkrwuds@pacbell.net

Re: carb issues
 

Lol, I was just about to ask you that, cause with a little help, I think I can get you the timing numbers you are looking for. Email to follow

Ryan

Re: carb issues
 

Amen Bro!

Prolly not for long! LOL

Ryan, you said "metal hitting plastic", and loose distributor bolt. Did you yank the cap and make sure the rotor didn't eat the inside of your cap, or vice versa? ;)

Re: carb issues
 

No, I got this darn wedding today, so I haven’t been able to do much else tinkering on it. Come Monday, I am going to get a good timing mark set up, and check all of the other stuff...like the cap and electrical pick up thingy.

Right now though, I am somewhat suspicious of my module in the Mallory distributor. It is acting a lot like it did last time it went, although it did a lot more back firing that time. Maybe Rev will chime in here and tell me what his did when it went bad. I also had one go bad and it just wouldn’t start.
Ryan

Re: carb issues
 

82GT had a few go bad too. Maybe he'll help out here. Maybe time to upgrade to an MSD?

On a side note, My Duraspark has seen 9,000 RPM (crank speed, which is 4,500 ditzy) and NO problems! :eek:

Re: carb issues
 

Yep, I've had two go bad so far and each time came with NO warning....it just quit! The first time it happened, it just wouldn't start. Second time it happened, I was driving to my friends house and it just quit and left me set along the road until my friend came and towed me home.
Mallory has made a new module called the E module, which is supposed to be better than the original and half the price. That's what I have in now and so far...so good.

Just a reminder though, you CAN NOT jump start a car with the module hooked up with those Mallory modules.
You can also buy an inline filter that protects against current spikes, which is what actually kills the modules. You MUST also run a ballast resistor inline with the module....or it eventually kills the module.
But like I said, the "new" modules are supposed to be not as sensitive to current fluctuations but still need to be taken care of.
I don't like Mallory stuff either but I would still rather have one of their fuel pumps instead of this JUNK Holley blue pump.

Ryan, did you get that book in the mail today? If not, you'll prolly get it Monday. Let me know when it arrives though.

Re: carb issues
 

When my Unilite modules fail, the engine just stops as if you had turned off the ignition switch. Then it would start right up again for some unknown period of time. I did call Mallory the first time that happened and they told me that was what the module did when it was beginning to fail. I did have one that would cause a backfire because it would turn off the spark momentarily and the turn it back on again. None of this sounds like what your engine is doing though. Wish I could be more help.

Rev

Re: carb issues
 

You're KILLIN me dude!!! You are one of the FEW peeps I've let tip-toe naked through my brain! LMAO ;)

Something wrong with the mounting on your Blue pump. NOT supposed to be that loud.

The only "official" Mallory product I've owned is a fuel pressure regulator (came with the car) and it now lives in the weeds along side a local race track. Pretty sure it's still there, haven't looked lately. LOL :D

Re: carb issues
 

I don't know what's wrong with it but it's LOUD! I guess the good thing about that, is if I'm driving down the road and I don't hear the pump anymore then I'll IMMEDIATLY know the pump quit. There will be no guess work there as to what happened...LOL

Re: carb issues
 

BTW, if anybody out there has a mallory fuel pump and wants to trade up for a Holley, then let me know. I'll mail this POS out the same day!
I won't be able to take take it off fast enough!