I thought this was resolved, but apparently not. Just took the 67 for a drive and it runs like crap. Thought it was in the ignition, so I replaced the "replacement" coil with a used Delco Remy one...............no change. It's like when the engine warms up, it starts running poorly. Finally, it just quit on its own while idling, then I noticed gas pouring into the carb, so I guess the PV is shot again. I had replaced the last bad one with a 5.5. BTW, the carb is a Holley 750 DP, new, out of the box, on a new BB engine. Ignition is stock tach drive, point type. Also, I noticed today when setting the timing that the vac port on the side of the carb metering body was not pulling any vac, perhaps because the PV was shot???? So, I connected the vac hose to the ported vac fitting on the base of the carb. Anyway, off to get another PV, probably a 6.5 this time because that's what came in the carb.

I'm open to any and all suggestions. Someone said to replace the condenser, so maybe I'll do that as well. May even replace the carb with the 600 Holley off the 327.

Thanks,
Rex

 

You said gas is "pouring" in, have you set the floats?

 

Yes, floats are set correctly...............

 

put the 600 on it, verify that the car runs great.
then go thru the 750 w/your carb book and set it up, blow air thru needle to clean.
any rust in tank?

 

everything is new................literally everything.

 

great! it should come apart easy. pv should be fine. probably just a speck of dirt. blow out all passages, and
SET IT UP AS PER THE BOOK. New doesn't mean set-up, but, if it is just dirt, and as u say it ran fine for awhile, then it might be acceptable w/cleaning.
Yet u say the pv was replaced before; this sounds USED PLENTY to me

 

Suggest you go back to the full vacum after going thru the carb. Good luck.

Dave

 

I replaced my carb this year with a brand new Holley 650 DP. Out of the box, on the manifold, set the idle mixture and idle speed and I was off down the road whomping all over town. A whole 130 miles later, the thing started running like poo poo and wouldn't idle. I had to take the bowls off and clean out the needle valves as apparently the secondary side was getting stuck and dumping gas down the carb and flooding out the engine at idle. Once I did that the car ran great again, and has, so far (knock wood) ever since. Let's just say the Holley techs were not surprised to hear that I was having that problem with a brand new carb and leave it at that (because I generally think they have been pretty good to me).

 

Crap in the gas, or fuel pump pressure is too high

 

Probably crap in the needle/seat assy as many have said.

 

If you haven't done so already, I would check my fuel pressure with engine running. Can make up a temporary connection with fuel hose, a tee, a few fittings, and a fuel gage. REMOVE after testing.

Larry

 

Is it safe to assume that when you say warmed up that you are not having a fuel percolation issue? A IR temp gun works well for determining that and no part of your fuel system including the bowls should even approach 140 or you will have percolation issues.

If you are having a debris problem in your fuel I would suggest running all your fuel out through your system but just before it goes to your carb attach some extra hose and run it out into a gas can BUT FIRST THROUGH A COFFEE FILTER!!.

If your fuel is real clear you can forgo the paper filter and just use one of the bronze ones that are faster and come with coffee makers to be used in place of a paper filter........ the bronze ones will catch debris but if there is fuel soluble dirt (FLASH RUST APPEARS AS SOLUBLE DIRT AND CAN CAUSE LOTS OF DAMAGE !!) in the fuel the bronze filter will not catch it and for that you need the paper one

It is an easy visual check and will either confirm the presence of debris or soluble dirt in your fuel or give you the piece of mind that you have eliminated one possibility that is causing your poor running condition.

BTW new Holly carbs are designed with PV blowout protection so that should not be your problem. Also be careful in choosing your PV.... if you choose to high of a number you may well get better gas millage but at the risk of a lean condition......... there is a formula for determining the correct PV via your vacuum but I am not sure offhand what it is exactly.

Be nice to see you get over this problem

Doug

 

Were you revving the engine when you checked this vacuum? There is no vacuum on this port, which is located above the throttle blades, at idle, nor is their supposed to be.

Whether to connect the distributor to ported above the throttle blades vs manifold vacuum is a whole 'nother topic with people on both sides of the fence, but either should work.

 

Recently changed vac cannister from B28 to B20. Was told by a very well known TI specialist that the B28 was not correct for my engine, so I installed a new VC1802 from NAPA. Since doing that, the vacuum has not been acting right. Will try a different carb today. Am considering installing a NOS TI distributor.

 

Couple of things to check carefully. Are the transition circuit channels in the throttle base completely clean? Any dirt in there will really foul things up. Is there any dirt in either the idle air bleeds (in the carb main body) or in the main air bleeds (also in the carb main body. Did Holley remember to put a check valve under each of the acccelerator pump nozzle bodies (it happens). Are the little pin holes in the transition circuit tubes (on the metering block) cleaned and open?

It's rare for a new Holley to blow a power valve. Holley puts a backfire check valve in the throttle plate so that backfire pressure can't reach the PV diaphragm. Be sure your throttle plate has that check valve. If not, you can get them in the aftermarket. Here's a whole baseplate, but I know you can get the PV protector separately http://www.jegs.com/i/Proform/778/67...oductId=827390

If you're running a big cam, is the idle setting of the primary throttles so high that the timed vacuum port is exposed? If so, you're sucking extra gas through the transisition circuit. You can cure that by opening the stop point of the secondary throttles to get some extra air (unless you have a four corner idle carb). If you have a four corner idle carb, you can replace the primary (and secondaray) throttle blades with ones that have idle air holes drilled in them. These http://www.jegs.com/i/Holley/510/26-95/10002/-1 will work on a 750. I'm running those on my vacuum secondary 750 and it works perfectly - the idle setting keeps the timed vacuum port covererd. I did have to crack the secondary throttles just a bit.

 

Fuel pressure to high was what caused my problem. Holley only takes a max of 6#'s of pressure. The fuel pump I was running was putting out 9#'s. Not saying that is your problem but it is one thing to look at.

 

I know that QFT says that above 7 pounds is bad however Holley sets at least one their preset electric pumps right at 7 pounds

Doug

 

Fuel pump is a stock AC #40382, std for 427-435 cars.

 

Probably working just fine like they usually do....... do you have sight windows in your fuel bowl. If not they are available pretty cheap and are a good way to observe for bubbles in your fuel as well as the float level

Also just for kicks the next time you are running bad if you can check with an IR temp gun the metal fuel line coming out from behind the battery as well as the fuel pump and the carb bowls we can either eliminate the possibility of any fuel temperature issues or know where the problem might be. 140 is where trouble starts

Another thing is the transition passages in the DP Holley carbs are pretty large and for that reason the aftermarket carbs most often have restrictors in them to cut down on the richness that comes into play everytime you put the clutch in to shift gears........ so if you need them and do not have them your problem will most often show up when you are driving around town and shifting quite often.

Doug

 

Guys with points invite a mis-diagnosis.
I KNOW I KNOW
it is part of the hobby.
guys enjoy tinkering.
20 years ago my plugs were black w/points.
electronic ever since, no more black plugs.
.
This was cleary described as carb flooding, that's why i said PUT ON THE 600 AND SEE IF IT RUNS GREAT
If it doesn't, what else could it be? I've seem old cars w/3 or 4 problems all at the same time. Great fun for the tinkerer.