Holley HP1000

I was wondering if I could get a little carburetor help. My car is a 72 Skylark convertible. I have a 1970 455 that has been rebuilt with small valve heads, stock compression ratio, a TA 288-94h cam (234/240), headers, TA SP1, GM HEI ignition with MSD 6AL box. My trans is a SP 400 with a Burek converter and I have a 12 bolt posi with 3.73 gears. Before I switched from the stock intake to the SP1, I was running a tired Qjet that was giving me fits. So, since I figured on eventually getting decent heads, I saw a board member with a Holley HP1000 carb for sale at a decent price. We made a deal and I installed the carb on my new SP1. I made it up to Yardley’s spring picnic, but was having some tuning issues...the carb would bog at just about anything over ¼ throttle. It was fine if you eased into it, but nail it and it would fall over, sometimes backfiring through the carb. My timing is set at 12 initial and 22 mechanical (in by 2000rpm)
So I bought the book “Super Tuning and Modifying Holley Carbs” by Dave Emanuel and figured I could solve this. I started digging into the carb and obviously went the wrong way with the tuning. As it is now, I can even get the car to idle. In fact, it is so freaking rich that you can’t even stand to be out in the garage when I do start it. And when it is started, when you shut it off, it won’t start again, like it is flooded.

My hope is that I can explain the current set up and perhaps get some ideas as to which way to go with the tune. Currently the carb is set up with 78 jets on the primary side with a 4.5hg power valve and a 31 squirter. On the secondary side, I have 84 jets, a blocked power valve and a 36 squirter. I have a billet baseplate and metering blocks too. The metering blocks are set up with 37’s for the idle feed restrictions and my emulsion bleeds are set up the same on both side with 28, 28, 28 and 40 (see picture)


One thing I noticed when trying to tune the carb was that the idle mixture screws had no effect...I could turn them in to seat them and the car would still run, no stumbling or anything. I checked the transfer slots and have them both set to .020. But when setting them, I noticed what appear to be two holes drilled into the baseplate on the secondary side. Are they supposed to be there (Pictures below). They are the holes directly below the text in the pictures.




All I can think of is that with these seemingly additional holes, I am getting too much air past the throttle blades. Can I compensate for that somehow?

And the final issue, the return spring on the secondary throttle shaft, should this be tight enough to return the throttle blades completely closed? See the video below, the spring doesn’t seem to be tight enough to me. Thoughts?

http://www.youtube.com/watch?v=XtuTPC0UX38

I was really hoping to have the car able to go to Columbus, but that looks about impossible now. But my nephew is getting married in September and would like to use my car from the church to the reception, so I would like to solve this in time for that.

I know that the carb is large, but I have heard a million times on this board that Buicks like big carbs. Help me make mine right PLEASE????!!!

Frustrated in Maryland...

 

Thanks Larry, it is getting frustrating. And yes, they are easy to work on (easy to take apart and parts are available/plentiful) and they are very tunable, but that may be my downfall...there are TOO MANY varibles to get the right combination (at least for me). I mean Main jets, squirters, powervalves, accelerator pumps and cams, emulsion bleeds, high speed and idle air bleeds...I am just not lucky/knowledgeable enough to land on the right combination yet.
Naturally Columbus is not in my future because the car is not running...AGAIN.

Thanks as always for your reply and offer of assistance. I am hoping that maybe after the BPG, some of the holley gurus can chime in and offer some suggestions.

 

Hi, I have a 950HP and can say from experience that they are very easy to work on and tune to your taste. Taking the bowls off to change jets is just four screws and if you use the blue gaskets, they can be re-used. You can change the float levels, idle, air mixture, everything very easily.

 

The carb will run rich untill you get some tunabilty from the idle circut. It controls the idle mixture and part throttle mixture. You must get the idle mixture screws to work. I believe your throttle blades are to far open for the idle circut to work.
The HP carbs have a 4 corner idle circut. All 4 idle mixture screws should be turned the same outward. Try .010" clearance for the pri. & sec. throtlle blades. There is an adjustment for the secondary side too. You gotta get it from underneith. If the cam is wimpy you may have to go to .008". You may have to turn idle mixture screws only 1/2 to 1 turn out but the carbs idle circut will be working.
Adj. the floats until gas just is at the level of the sight hole on the sides of the bowls.
My 950's throtlle blades all have the holes you speak of.
The above should work. If you want more tunability you can get larger air bleeds (the 2 outer on top the carb). This will pull out less fuel and make the idle circuit work.
I have a Holly book around here somewhere if you want to know what jets and squirters were stock.
Once the car is running decent get a power valve for the primaries 2 sizes below the vacuum the engine has at hot idle in gear. You will want one more than 4.5.
Ray

 

I tried your AED specs Larry and frankly it ran so rich it burned my eyes and still could not get it to idle. So I dialed the jets back a bit.

Phil, yeah they are easy to take apart and put back together...and I do have the blue gaskets (thank goodness!), but the trick is getting the combo of parts right which is where my problem lies.

Ray, I tried the idle mixtures screws to lightly seat, then backed them all out 3/4 of a turn...I start the car and try to adjust them and they still have no effect. I just double checked my transfer slot exposure and it is set to .020 on both primary and secondary side. My secondary throttle blades are adjustable the same way the fronts are. I was just curious if those holes were supposed to be there or not, I have heard of people drilling holes in the throttle blades, but not in the baseplate itself before. It just seems odd that they are placed differently...which is what led me to believe that they were just drilled in there. Regarding the powervalve, I have also tried a 6.5 both front and rear and it didn't seem to have any effect either.

 

Paul,
How much vacuum do you commonly pull with the motor?
This page has a pretty simple discussion regarding the power valve relative to vacuum along with other Holley tips: http://www.mortec.com/carbtip1.htm

 

Be sure the accelerator pump arms are set at 0 -.005" clearance. They can give a rich mixture at idle if they are missadjusted always giving fuel. You must adjust the idle screw then the readjust the accelerator pump arm for .000 too .005 clearance on the primarmy side. The secondary side pump arm should be the same clearance.
Ray

 

I had seen that Steve and other web articles that give different advice...like taking your vacuum measurement and dividing in 2 for a powervalve size. I have 12 ~14 hg of vacuum at idle which is why I have tried some 6.5's.

Could I have an unidentified vacuum leak? Would that cause similar symptoms?
When I am trying to get the car to idle, I can see fuel dripping out of the squirters and when I shut it down, I get smoke out of the carb.

 

did you check your float level ?(try lowering the float a little) what is your fuel pressure ?(7 to 7 1/2psi) is fuel dripping out your accelrator pump squirters or your boosters ? if you take it apart check that the metering block sits flat against the main body with no gasket. i once tried billet metering blocks and the power valve was touching the the main body preventing a good seal of the gaskets. the rear was really bad with a power valve plug in it. looking at the pic of your metering block i have a ?. if you put a gasket on the metering block does the hole on top of the gasket for the idle air bleed line up with the idle feed channel in your metering block ? also check the kill bleed(the tiny hole at the top of the emulsion channel) poke a wire through and make sure its clear of any obstructions. some people are have problems with the anodizing restricting the hole.

yes the spring on the secondaries should be strong enough to close by itself.

hope some of this helps.

 

I am just learning about Holly's also but it is pretty obvious that fuel is getting in through some place it is not supposed to. The most interesting thing is that changing the jets changes the idle mixture. This should not be happening. Changing main jets should not effect the idle. Someone can correct me on this but I think that until the idle works correctly nothing else is going to work properly. Do not worry that much about the main jets. Most of us are running 78 to 82 on the primaries and 82's with a power valve on the secondaries or 88 to 90 without a power valve. If it was me I would set it up 80 squared and try and find the leak. That jetting will be close enough to start to look for the other problems.

Eliminate the accelerator pumps for a while. Back those off so they are kind of sloppy. Just make sure they are not effecting the idle.

A Holly should work good with the vacuum you are pulling. It does not take many turns out for my 950HP with all four corners working, I start at one out and work in tiny amounts on each screw.

Did you use real Holly power vavles? I have heard that some others can be real junk brand new. If the power valve is working again it should have no effect on your idle.

I really like the clear float level screws. Let you know right away if you have a problem there.

Just throwing some more ideas out, hope one of them does you some good.

 

Hey Dave, thanks for the response, I checked the metering blocks and they do seem to sit flat against the main body. I also did as you suggested and ran some wire in the metering block holes, all seemed ok. I just dry set the floats and will reassemble the carb tomorrow and try mounting it again to see what I get. I will adjust the flaots with the bowls full as well...I have the clear sight windows. Regarding your question about the gasket, all holes/chennels seem to line up fine. I am using the reuseable blue gaskets and all other components that I am useing all holley brand (power valves, jets, etc...).

On that secondary spring, could I adjust it by just winding it one more time? That should provide more than enough spring tension to snap them shut I would assume.

Doug, I will try backing off the adjustment for the accelerator pump arms too. I had them set with no play and with the throttle wide open I made sure that I had .015 before the pump arm would bind. But I will back them off as sugested to eliminate that as a concern.

I really appreciate all the input here...I just have to get this thing running right. It's driving me batty. And Larry, thanks again for the call...best of luck in Ohio!:TU:

 

I have that same cam and Jim W. told me to run 15 initial with it which is up from your 12 ....you may want to try that.... My car isnt running yet with that cam BUT I had a pretty stout cammed Chevy 350 in my 32 Ford that had a brand new Holley 750 d.p. on it...like yours when I nailed it or tipped it in quick it felt overcarbed , overloaded , boggy etc....after talking to a knowledgeable racer friend he suggested simply putting another 3-5 degrees intial in and it woke it right up / was like night and day and cured all my carb problems with that combo......J .

 

You did make sure that power valve's not ruptured (blown), right?

Devon

 

I thought the HP Series Carbs all had power valve blow out protection, at least that is what it says on Holleys website. And when I did order new powervalves (different sizes) they were Holley branded if that matters.

 

if fuel is leaking from the accelerator pump nozzle, remove the nozzle and check to make sure the steel check valve is under it. are the metering block gaskets new ?

 

There should be a check ball in the squirter nozzle?

The metering block gaskets/fuel bowl gaskets are not new, they came when I purchased the carb from a board member. But I am ordering new gaskets and needle/seat assemblies tonight. Any advantage to running titanium .150" needle/seat assemblies or should I stick with the standard .110" units?

At this point, just about everything is new on this carb.