Enough Carb?

Sounds to me like you simply need to experiment with accelerator pump squirters and accelerator pump cams/settings. You may need a larger squirter diameter, longer duration squirter cam or both to get the additional fuel volume you need to overcome the flat spot. If you try these suggestions and it doesn't improve, go back to the original setup and we'll look elsewhere.

I'm not leaning toward intake heat being an issue since the big blocks tend to retain decent manifold heat even with the exhaust crossover blocked due to the fact that the underside of the intake is sealed to the lifter valley. I've run Holleys with no exhaust crossover since the '80's and haven't seen it as a contributor to carb issues, though it could be with an air gap manifold like TA's SPX (haven't tried my SPX yet).

Devon

 

Yep,,, the intake for the big blocks runs hotter than the nailheads or the spx type.... when I had the stage 2- 442 inch engine in my skylark I still had the heat in it, because I had tried to run the 950 three barrel without it and it did not work out too good... so I knew that I was putting a bunch of fuel in the engine , so I kept the heat to prevent stumble...with that engine I was running a offy 360 partition manifold.... alluminum, not cast iron....
The nailhead is a different animal,,, fully warmed up, the stock intake is only 127 deg. after an hour of idleing... so you need the heat in it... otherwise the cat pee wont vaporize....
i am like Devon, I think the problem is minor and once you get it worked out , the car will be just fine....and yes, difinitly pick up a full set of accellerator cams from holley, and a set of secondary springs... first move to make is to go to a heavier spring in the diaphragm... and see if it runs better....

 

Well, if the engine has headers on it , most likely you are not getting any heat to the intake manifold because the rt. manifold has a heat riser valve on it that headers dont have... the heat riser valve partially closes the rt exhaust manifold off to force exhaust gasses up thru the heads and into the intake manifold crossover passages to warm up the intake....

 

Thanks for the info guys. Also, I decided to check something that I read someone else had an issue with. I had my wife push the gas pedal all the way down (with the engine turned OFF lol) while I looked at the main throttle butterflies and they did not open 90 deg at full throttle. They were more like 70 degrees or so. Shouldn't they be at 90 at WOT?

 

Yes.

Devon

 

There is a plastic sleeve on the throttle cable that runs from in between where the cable connects to the throttle linkage and the throttle cable support mount. When the throttle cable is moved to WOT this plastic sleeve hits the cable mount and stops it from achieving 90 the degrees open position.

 

This is pretty straightforward if you think about it. You either have to find a further forward point at which to attach the cable end to the Holley's throttle shaft, or find a way to move the throttle cable's mounting bracket further rearward. If all else fails, you can trim the plastic collar slightly for more travel but the other two methods should be tried first.

Devon

 

You can see the sleeve here. I dunno why in the world it would have that... also, check out the kick down on my car... why would you do that instead of the stock pedal switch? He even gave me a pedal mount and switch when I bought the car :spank: Oh and wildcat, do you have any more pics of you car posted besides what's in your garage? That thing is sweet.

 

Thanks for the compliment! I have some more photos but I'd have to check.

The plastic shield on the cable is there to guarantee smooth pedal operation and prevents the cable from getting kinked which leads to fraying and failure. The bell mouth at the end helps alignment between the end of the cable and the cable sleeve, which is why it's undesirable to trim this portion unless you have no other choice. If you trim it so much that you see bare cable at the end of the cable sleeve, you're almost guaranteed to have the cable hang up on you.

That electrical switch is a universal type that you don't need if you have your original pedal-mounted detent switch set up.

Devon

 

Just looked in my service manual... looks like that is the stock cable for the Q-Jet and it is not adjustable, so I guess that would explain why it does not have the proper range of motion for a Holley. It appears that cutting the plastic sleeve will fix the problem, but I am not sure if there any "consequences" to doing that. There doesn't appear to be any...

 

See my post above for why it's not a good idea. It is the very last resort and if you screw it up you throw the whole ball of wax in the trash. Try a setup using these at the big throttle flange hole where your return spring is riding:

http://www.summitracing.com/parts/HLY-26-103/
http://www.summitracing.com/parts/HLY-20-2/

"easy" and "right" are not the same thing. Don't make me sorry I mentioned it!

Devon

 

Yep,,,,, and on a holley , when you do that with the engine off... you can take your hand and open the secondarys too, to see if they are binding or anything....but you have to open the primarys first.....

 

Wildcat looks like bad timing on my part or you can read the future because you answered my question before I even posted it lol.

So looks like that grommet and the ball kit will decrease the total travel of the pedal, but since we are moving the cable forward, that shifts the black plastic sleeve forward so that when the pedal is down, the sleeve does not hit the mount. Brilliant!

Doc, I just tried what you said, and the secondary linkage moves, but it is not very smooth. It feels like the diaphragm is crinkling or popping when it moves.

So, looks like I need to order a new diaphragm, grommet, ball kit, secondary spring kit, and accelerator cam spring kit.

No wonder this thing felt anemic at WOT, because there is no WOT! I need to definitely have a chat with the shop that worked on it. I can't believe the mechanic didn't catch any of this. I should have known though, the guy that was working on it was fired the day I came to go pick it up. He has been working for the shop for a long time, and the owner says he is very knowledgeable, but was getting old, cranky, and lazy. Looks like I fell victim to that.

 

Oooo very nice! I'll have to think about that one. That is definitely more than 15 bucks worth of grommets and ball ends.

 

I did some more tinkering. Looks like I will have to go with the AED part. Moving the throttle cable to the big hole doesn't provide enough travel. Oh well, should be worth the cost.

 

Yeah that is a good price. Thanks for the tip!

 

When I got my car I didn't have the butterfly on the carb.. I called Holley and ordered the butterfly, shaft and other manual choke parts I needed.

After I installed everything I fired it up and it ran like sh%&, I ended up washing the plugs, that's how bad it was running.

I walked away and went back to it the next day and 1st changed the plugs then I looked at the butterfly. It wasn't all the way open, it was only about 75 0/0 open. I played with it trying to adjust it and nothing was working. I finaly had to adjust the rod that attached the butterfly to the choke. Once I did that the butterfly was hitting on the inside of the carb so I new I couldn't adjust it any further open. After that it was a different car. I readjusted the 4 screws and the car runs great now.

So long story short, yes your butterfly should be open as much as it can be.

 

David, we're talking primary throttle blades, not choke...easy to mix up terminology-wise.

Devon