Hesitating Holley

[YENKO DEUCE REGISTRY]

It's taken me a while to get things changed around on my carb! But, it's off the car and I'm changing the jets etc... Pete, or others, do you use a blocked power valve in the secondary side? What is the advantage, if any, of doing so?

[John Brown]

Marlin, if you block the rear power valve you must increase the rear jet size 6 to 8 jet sizes to compensate. The power valves job is to keep mixture lean while crusing and richen when accelerating. However since the rear barrels are either fully closed or fully open on the dragstrip, there is no need for a variable air/fuel mixture. The advantages to blocking the power valve are that the power valve now can't stick closed and cause a lean condition, and won't blow out and leak if you should have an intake manifold backfire.
You gonna go to Norwalk? [img]/ubbthreads/images/graemlins/[/img]

[Chevy454]

John's right on all counts. But, I'm running both my power valves...is that best? Probably not, but it's worked ok so far. As for blowing it out, I did the backfire protection piece that Holley sells, so that isn't a threat. I'd like to block the power valve and try it before Norwalk, but I'm running out of time. So, should I keep a lookout for a Gobi Deuce when I'm there?

[JoeG]

The only reason I am mentioning this is because you said everything was O.K. before you stored the car for the winter. I would also lay my car up for long periods of time and when started would not respond crisply. I found that I would have to take the metering blocks off the carb and gunk all passageways to get rid of any varnish build-up.Put a gas stabilizer in your tank or a good fuel additive. You should also read your plugs after each carb adjustment. JUST A THOUGHT. [img]/ubbthreads/images/graemlins/wink.gif[/img]

[YENKO DEUCE REGISTRY]

Many thanks for the info! I plan to install a blocked power valve and use all of Pete's COPO Nova setup suggestions from earlier in this thread. I'll let you know how I make out.

I would like to make it to the drag strip this month - but it won't be Norwalk [img]/ubbthreads/images/graemlins/frown.gif[/img] I have not installed the driveshaft safety loop yet, not sure I like that extra spacer between the trans and the mount. I'm going to try to make the bend modification to mine like Casey did on his. I don't expect to break into the 13's my first time out, but would still like to have the loop installed for safety reasons. I've been re-reading all the stock racing topics in this category in preparation for my jaunt to the drag strip one of these Grudge Nights [img]/ubbthreads/images/graemlins/smile.gif[/img]

[YENKO DEUCE REGISTRY]

This may sound stupid, but I have a funny feeling that the metering block gaskets might be reversed on my carb after getting it rebuilt last winter. How can you tell which gasket goes where? If they are switched, what would that do to driveability?

[MotownMadman]

Marlin, I read this whole thread, one thing comes to mind as for an initial stumble, you said it worked fine until you removed, rebuilt and reinstalled. One thing I would check is for a vaccum leak on the base gasket, even the smallest leak coming off idle can cause enough of a unmetered air draw to make the car stumble. Several ways to check for a leak, I am sure you know the protocol on that. Just a thought.
Motown [img]/ubbthreads/images/graemlins/beers.gif[/img]

[YENKO DEUCE REGISTRY]

Matt;
Good call! When I reinstall it this time I will put my hand over the carb to see if the idle speed picks up, and also spray a little carb cleaner around the gasket areas. A small vac leak would indeed create a hesitation.

One thing I noticed yesterday was that if I moved the clear acc. pump cam to the number 1 hole instead of the number 2 hole, I could see a 'more' immediate shot of fuel from the squirter. I did not drain the fuel from the bowls right away, this way I could recreate the scenario on the bench. So, I'm anxious to reinstall the carb to see if that helped as well.

So little time to work on these things, especially with 21 month old Benjamin trying to climb under the car every time I turn around [img]/ubbthreads/images/graemlins/smile.gif[/img] Kids are a joy, he can't really talk yet but makes the engine rev / burnout sounds! I have no idea where he learned that from [img]/ubbthreads/images/graemlins/naughty.gif[/img]

[JoeG]

The metering block has pins so you can't reverse gasket, make sure everthing is tight. [img]/ubbthreads/images/graemlins/wink.gif[/img]

[YENKO DEUCE REGISTRY]

JoeG;
Ok, thanks - I was starting to go crazy yesterday thinking how that scenario may have happened. I saw on the secondary side that the gasket covers several of the holes in the main body, and was running away with the possibilities that the gaskets were swapped!