Caruretor Help

Mike, does the fuel leak onto the manifold or into the intake? Does it have a tube between the two fuel bowls or do you have dual inlet? Fuel bowl gasket is something to look at. Is it only when engine is running it leaks? Maybe dirt in fuel inlet needles (can be fixed w/o taking carb off/apart). Pictures maybe?

The problems could be related.

I know what I would do. I had a Holley problem once that I couldn't fix. Had the carb off and on 15 times, spent half a tank of gas trying to fix it. Ended up buying a Summit carb. No problems since, better throttle response, most Holley parts fit, no fuel bowl gasket below fuel level (one less risk). If you want to go that way, let me know your engine a bit better, I can give you Summit part#s.

I'm thinking power valve. If not much changes when you adjust the idle mixture screws, the engine must be getting fuel from somewhere else. As for the slight leak - might be related - might not. The rebuild kit should cover that anyway. I've never seen a Holley that didn't weep fuel.

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Originally posted by SoCalCat:
My '73L has pretty much the stock motor but has a Holley 4160 (List 7154) that has developed a slight leak/weep that is NOT the accelerator pump (already had that issue). Bowl gasket?
The second problem is I can't really get much change when I adjust the idle mixture screws. Are thse problems related?
(I have carefully set the float levels and manifold vacuum, at idle, is 18")
I pulled the carb tonight and have the Holley rebuild kit. But, any ideas, places to look for problems would be most appreciated.

Thanks,

Mike

A Holley type carb does tend to leak at the bowl gaskets. They make some resusable rubber bowl gaskets that don't seem to have the leaking problem quite as bad as the cork type. Your other problem could be a blown or leaking power valve.

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Originally posted by No Quarter:
Mike, does the fuel leak onto the manifold or into the intake?

Collects small puddles on the outside of the manifold. It seems to be coming from the front, primary bowl/accelerator pump area, but I can't tell for sure exactly where.

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Does it have a tube between the two fuel bowls or do you have dual inlet?

Single inlet, tube between bowls. No apparent leaks there.

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Fuel bowl gasket is something to look at. Is it only when engine is running it leaks?

Only when running.

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I know what I would do. I had a Holley problem once that I couldn't fix. Had the carb off and on 15 times, spent half a tank of gas trying to fix it. Ended up buying a Summit carb. No problems since, better throttle response, most Holley parts fit, no fuel bowl gasket below fuel level (one less risk). If you want to go that way, let me know your engine a bit better, I can give you Summit part#s.

I hope it doesn't come to that. But, I'd still appreciate your recommendations in case it does. Engine is original '73 unrebuilt (dished pistons, blah) with the stock intake (D3AE, I think). Car has headers but not sure whose, nor what mufflers are installed.

FYI, I received your tuning book for X-mas, so I'll be putting it to use

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Originally posted by UFO-LOW:
I'm thinking power valve. If not much changes when you adjust the idle mixture screws, the engine must be getting fuel from somewhere else. As for the slight leak - might be related - might not. The rebuild kit should cover that anyway. I've never seen a Holley that didn't weep fuel.

Thanks. I'm pretty sure the kit has a replacement, so I should be good to go.

A common leak is from the accellerator pump diaphram. They eventually either wear or dry out.

That's a simple fix. Just change it.

If you are going to rebuild the carb completely, when you disassemble the primary bowl and remove the metering block, notice if the chamber in the main body, the vacuum chamber for the power valve, is wet or has any kind of fuel in it.

If it does, the power valve diaphram is ruptured.

Make sure you install a power valve check valve kit when you rebuild the carb. They do help.

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Originally posted by PanteraDoug:
A common leak is from the accellerator pump diaphram. They eventually either wear or dry out.

That's a simple fix. Just change it.

I'll check it, but I changed it out less than 1000 miles ago, so I doubt it's the accel. pump diaphram.

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If you are going to rebuild the carb completely, when you disassemble the primary bowl and remove the metering block, notice if the chamber in the main body, the vacuum chamber for the power valve, is wet or has any kind of fuel in it.

If it does, the power valve diaphram is ruptured.

Did not know that; thanks.

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Make sure you install a power valve check valve kit when you rebuild the carb. They do help.

I'll check it

Hopefully, I'll get to the rebuild tomorrow; didn't have time today. I'll post how it goes...

You indicated in an earlier post that it was wet with fuel near the accelerator pump.

1000 miles doesn't necessarily mean anything. Especially if you let the car sit long enough for the fuel to evaporated out of the carb.

The diaphragms, once they have had fuel in them need to be kept wet or else they dry out. They dry out very quickly.

If you went to start the car in this condition and were pumping the accelerator to get it started with no fuel in it, you most likely cracked the diaphragm in the accelerator pump.

If the car is in storage, you MUST run it more then once a month to reduce the likeliness this will happen.

You have to keep fuel in a Holley once it has been run. Otherwise all the gaskets will dry, shrink and crack.

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I know what I would do. I had a Holley problem once that I couldn't fix. Had the carb off and on 15 times, spent half a tank of gas trying to fix it. Ended up buying a Summit carb. No problems since, better throttle response, most Holley parts fit, no fuel bowl gasket below fuel level (one less risk). If you want to go that way, let me know your engine a bit better, I can give you Summit part#s.

Bringing a 72 back to life after 22 years of storage. Exactly which Summit carb did you purchase?

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Exactly which Summit carb did you purchase?

For most engines it's the 600 vacuum you need. Have it on my Longchamp and had it on my previous Pantera.
http://www.summitracing.com/parts/sum-m08600vs
and remember to buy a
Summit Racing SUM-220104 - Summit Racing® Dual Feed Fuel Lines

If you have Holley parts on the shelf, most will work. I've bought
Summit Racing SUM-M08060 - Summit Racing® M2008 Carburetor Rebuild Kits

You can also buy 8040 and 8041 to tune the special tunable parts, but you won't need to...

It's the carb that Holley should have made, but never bothered to because they had too much invested in the old format IMHO

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Originally posted by No Quarter:

It's the carb that Holley should have made, but never bothered to because they had too much invested in the old format IMHO

Holley did manufacture it ... but it never sold well for them. Summit bought the rights to the carb from Holley. Holley manufactures it now for Summit.

-G

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Originally posted by No Quarter:

quote:

Exactly which Summit carb did you purchase?

For most engines it's the 600 vacuum you need. Have it on my Longchamp and had it on my previous Pantera.
http://www.summitracing.com/parts/sum-m08600vs
and remember to buy a
Summit Racing SUM-220104 - Summit Racing® Dual Feed Fuel Lines

If you have Holley parts on the shelf, most will work. I've bought
Summit Racing SUM-M08060 - Summit Racing® M2008 Carburetor Rebuild Kits

You can also buy 8040 and 8041 to tune the special tunable parts, but you won't need to...

It's the carb that Holley should have made, but never bothered to because they had too much invested in the old format IMHO

I have no parts on any shelves!! Since the car is bone stock, and Kansas City is at 900' mean sea level, I would hope no tuning would be needed.

Some questions -
1)given the differences in the layouts of the two carbs, how much rearranging of things will be needed?
2)any other parts needed for the conversion?
3)is the carb lower profile than the Motorcraft 4300? That would make fitting a phenolic spacer easier.
4)what driveability issues does the stock carb have?

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1)given the differences in the layouts of the two carbs, how much rearranging of things will be needed?
2)any other parts needed for the conversion?
3)is the carb lower profile than the Motorcraft 4300? That would make fitting a phenolic spacer easier.
4)what driveability issues does the stock carb have?

1) Not much I think. The accelerator cable pulls from the front on Pantera, so you need some pivot thing attached to the lower part of the bracket, as it is today
2) Make sure to get the fuel lines. But if you have rubber today, there might be a fitting or two you need
3) Sorry don't know, anybody know? (IMHO the engine cover should be taken off and put in the attic until the "original" wave hits the Pantera community. I want to see my engine in the rear view mirror, why hide it?)
4) Well a perfectly tuned carb: None. But the design is not optimal so slight misadjustment gives bog. Actually that applies to most carbs, if you look at a co2 air/fuel ratio instrument, the engine is always lean just when you push the accelerator. All I know is that the Summit carbs I've owned and the one we put on Timster's Pantera, worked perfectly after 1 minute of adjusting as described in my book. I can't stand a car that bogs down, I want instant power, or I hate driving the car. That's why I don't like modern cars with electrical accelerators instead of cables, there's a slight hesitation, I hate it. Had a Audi A4 V6 and a Jeep Hemi, both company cars, with plenty of power for their size, both were dreadful to drive because of electrical accelerator

Picture of my Longchamp carb after 2 years of use (yes, laugh at my points distributor, after having tried two Mallory electronic dist/modules and got stranded, I'm back to points just now)

OP here with a little feedback.
Finally got the carb back together, and boy did I find a few things wrong!
Bowl gaskets were shot; probably where the leak was coming from.
Power valve blown (also, it was labelled 7.0 and I thought they only came in 0.5 increments)
I replaced it with an 8.5 as that is what the Holley spec for my list number (7154) indicates. I also have a 6.5, if needed.
The vacuum secondary diaphram was torn/out of position and it doesn't look they they've been opening for a long time. The spring was wrong compared to the one specified (purple). I ended up buying the quick change kit and the whole box o' springs. We'll see...
Air bleeds on the secondary side were plugged.
The only thing okay was the accelerator pump that I'd previously replaced

Well, out to the garage to bolt it back on the car. Looking forward to a bit of improved performance!

Mikael, I have been autocrossing a "warmed up" Saturn Sky for five years. I absolutely HATE "fly by wire" throttles. Will now be racing an E36 BMW. The only "wire" in the throttle is the CABLE !!!!!

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. The only "wire" in the throttle is the CABLE !!!!!

Amen to that!

Got 'er running. Not without a bit of trouble, however. It turns out it's real easy to mis-align the power valve gasket
Pulls real atrong now, but a little bog off the line; probably need to refine the accel pump cam and/or shooter.
I still can't kill the motor with the idle mixture screws; runs best with them all the way in I carefully set the float levels and I know the power valve is good (I checked it when I installed it, and no backfires upon starting)
Any other places to look?

SoCalCat, its a little worrisome that your carb had a blown power valve. This was so prevalent on old Holleys that in about '92, Holley changed the throttle assembly to include a check-ball to prevent backfires from blowing the PV diaphragm. If your carb is older than that (and 4160s have been around since the '60s), it may not have that upgrade; its pretty easy to check, and to add a ball-check if it's missing. In fact, the instructions for doing this used to be in every speed shop in the nation, pre-Internet.

Basically, you find the base passage that feeds vacuum to the power valve and drill it slightly oversized ALMOST all the way thru the bottom (from the carb body side towards the intake manifold surface) so there's a ledge left. Then you stick a Phillips screwdriver in the drilling and LIGHTLY tap it to emboss an 'X' in the ledge at the bottom. Drop a small ball bearing in the hole; the ball floats between the bottom of the hole and the gasket between the base and body. Under vacuum, the ball pulls down but the embossed 'X' allows a connection from intake vacuum to the power valve so it works as-stock. If there's a sneeze or backfire, the ball slams up against the gasket & body, sealing off the passage before the surge can rupture the power valve diaphragm. Newer Holleys already have all this done.

The other problem we used to run into with old carbs is, the throttle shafts run directly on the zinc casting, and after a million miles, the holes go egg-shaped. The carb then no longer holds vacuum and the idle will be all over the place from extra air leaking in around the shafts. It's possible to bush the throttle shafts, or to chamfer the zinc casting and add teflon o-rings with a washer & a little spring (4 places) to hold the soft o-ring in the chamfer & seal.

But unless you're poor or emotionally attached to an old carb, its far easier/faster/better to buy a more recent-built carb that doesn't have these problems.

quote:

Originally posted by Bosswrench:
SoCalCat, its a little worrisome that your carb had a blown power valve. This was so prevalent on old Holleys that in about '92, Holley changed the throttle assembly to include a check-ball to prevent backfires from blowing the PV diaphragm. If your carb is older than that (and 4160s have been around since the '60s), it may not have that upgrade; its pretty easy to check, and to add a ball-check if it's missing. In fact, the instructions for doing this used to be in every speed shop in the nation, pre-Internet.

I think mine is older than '92 as I don't believe I have the check ball. Guess I need to pull the carb and make sure the new PV isn't blown; unlikely, since no backfires, but I need to rule it out.

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The other problem we used to run into with old carbs is, the throttle shafts run directly on the zinc casting, and after a million miles, the holes go egg-shaped. The carb then no longer holds vacuum and the idle will be all over the place from extra air leaking in around the shafts. It's possible to bush the throttle shafts, or to chamfer the zinc casting and add teflon o-rings with a washer & a little spring (4 places) to hold the soft o-ring in the chamfer & seal.

Ah, interesting. Is there a way to test if the PV is seeing vacuum and staying closed at idle? BTW, it idles very smooth with a very steady 17" manifold vacuum; no 'all over the place', just a steady 800 rpm.

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But unless you're poor or emotionally attached to an old carb, its far easier/faster/better to buy a more recent-built carb that doesn't have these problems.

LOL! Yeah, that'd be the smart thing to do. But, between the rebuild kit, the quick change kit, the set of secondary springs, and the shipping charges...I've 'invested' $100. So, my stubborness demands I figure it out

Thanks for your comments and help!

Spent $100 already on a pre 92 multiple problem carb? Hhmmm, I've done the same thing often, but now I've gotten older and maybe wiser, I say buy a new one. You can do a lot to an old carb, but dirt does accumulate as does wear on throttle plate axles. Just my $0.02. Good luck

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Guess I need to pull the carb and make sure the new PV isn't blown

Is it a NEW PV? In later years, maybe due to cost cutting, the PVs have become lower quality, so if a PV not being used for a year or two the membrane can go hard and give very erratic performance. Test by having two PVs of same rating, press gently towards each other, should move the same and with no erratic movement.
(PVs are the worst part of a Holley, so crude, so failure prone. Open a Rochester carb and look how beautiful it can be made, and with infinite adjustment possibilities)

The best deal going is to buy a Holley rebuilt carb. They look and run like new.

The PV check valve just reduces the likeliness of a blown PV. It doesn't eliminate it.

Holley like so many other companies, has gone "offshore" with sub-contractors that build parts for them, like the PV's.

Quality has gone completely out the window although the PV has always been susceptible to a blow out.