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CC Advertisers
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 33Likes
06-04-2024, 09:52 AM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,025
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Not Ranked
And there are two easy ways to check for vacuum leaks. First, just get a mirror and angle it so you can see under the base of the carb and look to see if the port tubes have lost their little black rubber cap. The second way is to have your engine idling and use a butane torch that is not lit to spray gas around the base of the carb while it's idling to see if it revs up by sucking the gas in. But for now, let's just stick with the first way.
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06-04-2024, 10:01 AM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,025
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Not Ranked
Here's a before and after pic of my distributor after I cleaned it up a bit. Note those two springs and how they are attached. They are attached to weights that spread out from centrifugal force. The strength of the springs control how quickly or not they spread out. Spreading out actually changes the timing, so you want them to spread just right, not too fast and not too slow.
[IMG]  [/IMG]
Last edited by patrickt; 06-04-2024 at 10:10 AM..
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06-04-2024, 11:19 AM
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CC Member
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Join Date: Jan 2022
Cobra Make, Engine:
Posts: 161
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Not Ranked
Quote:
Originally Posted by patrickt
And there are two easy ways to check for vacuum leaks. First, just get a mirror and angle it so you can see under the base of the carb and look to see if the port tubes have lost their little black rubber cap. The second way is to have your engine idling and use a butane torch that is not lit to spray gas around the base of the carb while it's idling to see if it revs up by sucking the gas in. But for now, let's just stick with the first way.
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Ugg. Checking the vacuum tube ports under the base of the carb would have been a LOT easier before I installed the turkey pan. I just tried to squeeze my phone in there to snap a few pix, but no joy.
In an attempt to eliminate the carb as the likely culprit here, I sent the carb out earlier this Spring to be rebuilt by Dave Bergeron. Just re-installed it this past weekend. Which of course does not guarantee that the ports are plugged as they should be.
But then again, do I want to try the butane approach when I had a backfire in the carb? 
If I need to pull the carb to confirm the ports are plugged as they should be, then so be it.
Last edited by CompFi; 06-04-2024 at 11:24 AM..
Reason: added response to latest post, corrected typos
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06-04-2024, 11:57 AM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,025
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Not Ranked
Google some pics of your carb so you know exactly what you're looking for. There's a pretty big vacuum tube towards the rear that is for the brake booster. Maybe you have that hooked up to your PCV. If that was just unplugged and completely open it would be a monster vacuum leak. Then you're going to have a smaller vacuum tube, mine is on the front base of the carb slightly towards the passenger side. When I put a vacuum gauge on it I have to use a tool, I can't do it with my fat fingers. Then there will be another tube, maybe on the primary metering block. Once you get the hang of looking for them they'll jump right out at you.
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06-04-2024, 12:45 PM
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CC Member
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Join Date: Nov 2007
Location: Clayton,
IN
Cobra Make, Engine: ERA 838
Posts: 1,146
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Not Ranked
Some of the High Performance 850-950 Holley style carbs have NO vacuum fittings.
I suspect the shop that worked on it may have changed some carb settings or jets/bleeds.
If the timing is right - roughly 16 degrees at idle and 34-36 degrees at 3000 RPMs, I would bet for lean condition.
I would go thru the Holley dial in procedure step by step.
John
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06-04-2024, 01:43 PM
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CC Member
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Join Date: Jan 2022
Cobra Make, Engine:
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Quote:
Originally Posted by Grubby
Some of the High Performance 850-950 Holley style carbs have NO vacuum fittings.
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John - thanks for the tip here. As I would like to avoid pulling the carb if at all possible.
Here is a pic of the underside of my carb that I pulled from the Holley website.
Problem is that I have no idea whether this pic depicts any vacuum fittings  |
06-04-2024, 01:54 PM
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CC Member
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Join Date: Nov 2007
Location: Clayton,
IN
Cobra Make, Engine: ERA 838
Posts: 1,146
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No vacuum connections in the carb shown in the photo.
John
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06-04-2024, 02:00 PM
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Senior Club Cobra Member
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Join Date: Jul 2000
Location: Chilliwack,BC,
BC
Cobra Make, Engine: F5 Roadster
Posts: 1,422
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Msd
hi,
Do you have an msd ignition box? if so that's the signs of it failing.
Perry 
__________________
F5 cobra Mark 4 roadster, **SOLD** Ruby Wine Red with pearl,
dual 2" roll bars, warmed up 302, Edelbrock AVS carb and heads, E Street aluminum Heads, Comp cam and roller rockers, AOD, 4.10 Eaton Posi, Power Baer/disc brakes, block hugger headers, 2 1/2" under car exhaust, F500 18" black spoke wheels.
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06-04-2024, 02:09 PM
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CC Member
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Join Date: Jan 2022
Cobra Make, Engine:
Posts: 161
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Quote:
Originally Posted by Grubby
No vacuum connections in the carb shown in the photo.
John
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i was hoping you would say that! |
06-04-2024, 01:54 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,025
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Not Ranked
What's the exact model number for your carb?
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06-04-2024, 02:12 PM
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CC Member
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Join Date: Jan 2022
Cobra Make, Engine:
Posts: 161
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Quote:
Originally Posted by patrickt
What's the exact model number for your carb?
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80805-1
Date code: 1177
My deciphering from the Holley website, the above info for my carb translates to “950CFM ULTRA XP CARBURETOR”
https://www.holley.com/products/fuel...rts/0-80805HBX
Date code translates to 117th day of 2017, or 27 April 2017 |
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