When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I noticed the throttle plate gasket was covering 2 out of 6 holes, is this normal? Or should I make holes for C & D on the gasket?
*1987 Olds 307 CCC Quadrajet
(Found this when I noticed the lower gasket was wet and have to crank a lot when starting after (say) a week? Followed Cliff Ruggles's YT video and did the epoxy fix as well and then only I noticed this)
Warmly suggest you use the carb number on the driver’s side throttle body to determine what carb you have and get the right gasket for it.
That works, unless someone before you has built a Franken-carb - i.e. mismatched throttle plate and carb body. Then, yeah, your approach of punching holes in the gasket might help. And if you suspect it is a Franken-carb, have a look at the top plate gasket too. If someone was cavalier about main body to throttle plate, there’s no reason they would have cared about the top plate…
Long term solution is get right carb and jetting for your car/year/engine. Short run, if the car doesn’t run right, a gasket is a cheap test to run to make it better.
See qjets.com and other suppliers for parts. The gaskets are a good thing to have multiple copies of on hand so you can replace as needed and modify if needed.
Finally, be aware that on older cars, lots of previous owners torque the h*ll out of the top plate (above the main body). You can get extra thick gaskets to make up for some of the warping that leads to vacuum leaks, but if it’s extreme, you’re more or less looking at a new carb just to _know_ you’ve got good parts.
I wouldn't modify the gasket that goes between the fuel bowl and throttle plate. If your carburetor needs holes for C and D in the picture there should be an appropriate gasket in a carburetor rebuild kit.
BTW, is this the stock Quadrajet from your Oldsmobile? I recall another thread you posted about removing the emissions controls from your Oldsmobile. What came of those endeavors? Here's your newest thread.
Warmly suggest you use the carb number on the driver’s side throttle body to determine what carb you have and get the right gasket for it.
That works, unless someone before you has built a Franken-carb - i.e. mismatched throttle plate and carb body. Then, yeah, your approach of punching holes in the gasket might help. And if you suspect it is a Franken-carb, have a look at the top plate gasket too. If someone was cavalier about main body to throttle plate, there’s no reason they would have cared about the top plate…
Long term solution is get right carb and jetting for your car/year/engine. Short run, if the car doesn’t run right, a gasket is a cheap test to run to make it better.
See qjets.com and other suppliers for parts. The gaskets are a good thing to have multiple copies of on hand so you can replace as needed and modify if needed.
Finally, be aware that on older cars, lots of previous owners torque the h*ll out of the top plate (above the main body). You can get extra thick gaskets to make up for some of the warping that leads to vacuum leaks, but if it’s extreme, you’re more or less looking at a new carb just to _know_ you’ve got good parts.
Hope that helps
Chri
Thanks so much for the reply.
The issue I had was, the car had to be cranked a lot when starting after some time. I checked and accelerator pump wasn't squirting any.
Once the car started, the accelerator pump squirts without a problem. So, I concluded the fuel bowl was leaking.
That's why I went for the epoxy fix and then only found about the covered port.
I have used a Hygrade 1520 gasket kit and it came from R0ckauto catalog for the make and model year. It did have 2 different air horn gaskets and hence why I suddenly had a doubt about this as well. Mine is a E4MC hot air choke CCC Quadrajet from 87 Custom Cruiser. This kit said it fits all 4MC.
I would definitely go ahead with the ID plate from next time onwards.
Do NOT modify the gasket! Those openings, and coverings, are critical! They control how those passages do or don't talk to each other.
Note that fuel bowl leaks through the wells is actually pretty rare these days. That was common on the very very first qjets made, but by the late 60's the install method was improved and rarely leaked.
That said, it doesn't hurt anything so might as well....
I wouldn't modify the gasket that goes between the fuel bowl and throttle plate. If your carburetor needs holes for C and D in the picture there should be an appropriate gasket in a carburetor rebuild kit.
BTW, is this the stock Quadrajet from your Oldsmobile? I recall another thread you posted about removing the emissions controls from your Oldsmobile. What came of those endeavors? Here's your newest thread.
Yes, I would use the carb ID and get the best fitting gasket kit next time. I thought someone would know what these three ports do.
Yes, this is the stock Qjet from my Olds. Yes, I've removed so many emissions items.
Had to do a lot of jobs prior to this, hence why I didn't update a lot here.
Broken cam gear tooth new timing set all lifters were clogged up with gunk like this had to disassemble each lifter to clean new intake manifold gasket
Now the car runs a lot better, didn't video the latest status yet. I've removed the entire AIR system (as cat was missing already), keeping EGR, currently the anti-diesel solenoid is disconnected. (it's still connected in the photo). EFE system was removed, charcoal cannister purge system is removed, thermac system is removed. Yet to set the MC solenoid duty cycle and TPS. Once the fine tuning is done, I would upload all the information on that thread.
Do NOT modify the gasket! Those openings, and coverings, are critical! They control how those passages do or don't talk to each other.
Note that fuel bowl leaks through the wells is actually pretty rare these days. That was common on the very very first qjets made, but by the late 60's the install method was improved and rarely leaked.
That said, it doesn't hurt anything so might as well....
Thank you!
Just curious what these ports at the primaries would do. There's idle discharge (below throttle) and fast idle discharge?? (just above the throttle)?
I posted this question on several groups on FB, didn't get any clear answers so I just left it like that, like you said.
Just curious what these ports at the primaries would do. There's idle discharge (below throttle) and fast idle discharge?? (just above the throttle)?
I posted this question on several groups on FB, didn't get any clear answers so I just left it like that, like you said.
There are two good quadrajet books - one by Ruggles and one by Roe - that are good reads to learn about the carbs. The Ruggles book is newer and has a bit more information about the CCC carbs. Generally the CCC carbs aren't modified or used on hot rods as often as the earlier carbs, so there's less information readily available.
The hole under the throttle blade is the idle discharge. There should be a vertical slot that is the transition slot - it provides the same idle emulsion as the blades open to help transition from the idle discharge to the main venturi. The idle emulsion (mixture of air and fuel) is created in a series of vertical passages around the front of the main venturis. The fuel is pulled up through one passage from the fuel bowl and pulled across to mix with air coming from the idle air bleed at the top of the venturi and back down to the discharge areas.
Usually there's some extra passages for things like manifold vacuum and ported vacuum. Ported vacuum is a hole above the throttle blade. No fuel or anything - it's usually used by the distributor for spark advance. At idle where the blade is below the hole there's no vacuum signal. As the throttle opens the blade exposes the hole to the vacuum in the manifold and you get the vacuum signal.
It can be a bit of a maze to follow the passages and what they do. All three gaskets are important - they control which passages can talk to each other or the manifold for the engine. So even passages on the bottom may not actually go anywhere - many are just there for manufacturing or transfer of air/fuel/mix.
I have used a Hygrade 1520 gasket kit and it came from R0ckauto catalog for the make and model year. It did have 2 different air horn gaskets and hence why I suddenly had a doubt about this as well. Mine is a E4MC hot air choke CCC Quadrajet from 87 Custom Cruiser. This kit said it fits all 4MC.
Whoa. Wait. You said yours is an E4MC? 4MC gaskets typically will not interchange with CCC carb gaskets. Some may, though, depending. There may be gaskets in the kit that do fit, but I've never seen "universal" kits that fit CCC and non-CCC carbs all in one. I could be wrong on that, and I hope it works for you. I've only used ACDelco kits specifically called out for the carb based on the number stamped on the side of it so I'm not real familiar with the aftermarket offerings.
The 1987 Y engine used carb #17086008. It was also used for 1986 and 1988 G-body, and B-body for 86 and 87. 1988-89 B-body only used carb #17088115. But they all used the same rebuild kit part number.
Carb kit was ACDelco 76141, or GM p/n 17176141, but they're now real hard to find.
Personally, I'd have chosen either: Walker 15897B
or
Standard 1569A
Usually there's some extra passages for things like manifold vacuum and ported vacuum. Ported vacuum is a hole above the throttle blade. No fuel or anything - it's usually used by the distributor for spark advance. At idle where the blade is below the hole there's no vacuum signal. As the throttle opens the blade exposes the hole to the vacuum in the manifold and you get the vacuum signal.
.
This is exactly what I was looking for!!!
The holes closed by the gasket should be the ported vacuum holes like you said, which are above the throttle blade and the distributor in CCC doesn't use vacuum advance for spark.
The idle mixture screw holes are the ones sit below the throttle blades.
Whoa. Wait. You said yours is an E4MC? 4MC gaskets typically will not interchange with CCC carb gaskets. Some may, though, depending. There may be gaskets in the kit that do fit, but I've never seen "universal" kits that fit CCC and non-CCC carbs all in one. I could be wrong on that, and I hope it works for you. I've only used ACDelco kits specifically called out for the carb based on the number stamped on the side of it so I'm not real familiar with the aftermarket offerings.
The 1987 Y engine used carb #17086008. It was also used for 1986 and 1988 G-body, and B-body for 86 and 87. 1988-89 B-body only used carb #17088115. But they all used the same rebuild kit part number.
Carb kit was ACDelco 76141, or GM p/n 17176141, but they're now real hard to find.
Personally, I'd have chosen either: Walker 15897B
or
Standard 1569A
But that's just me.
Superb, yes, I should get one of these sets real soon. Thanks so much!
The generic rebuild kits are just fine, at least for most of the parts. I would buy two of the cheap rebuild kits for all the small parts, then go to a specialist like quadrajetparts.com to get thick air horn gaskets, good fuel needle kits and accelerator pump seals.Those parts in the generic kit are also good for a regular daily driver, especially if the carb isn't warped, but the accelerator pump seal may not be as resistant to ethanol.
Nope, used it as it is with some grease on both sides temporarily, until a new set arrives from the US. I literally live across the world
OK friends, it took me a few days to reply for a reason. See above? Well, after fitting the carb, the carburetor was flooding like a b*****.
Immediate reaction was, "oh, I have messed up re-using the old gasket (because that's what changed really), so I better look for an alternative".
Found a leftover cork sheet so I drew up a template on that using the old gasket, used a blade to shape and a hand drill set to finetune it into shape like below.
Yes, that's pure cork
Then I applied shellac on both sides and inside the cuts one application at a time, let it dry for each day. Too bad I couldn't take a photo afterwards. (yes, I know, this is a temporary fix, or maybe an experiment if you will?)
Then I read on internet that flooding happens when the float gets messed up.
I thought "OK, I might have messed up the needle when I turned it over", so I removed the air horn, drilled out the TPS adjustment screw cover while it is out, reset the float needle and fitted it back.
Still, it was the same, fouling plugs and starting to miss badly.
While plugs were removed to clean today, I took the endoscope down the carb, kept the ignition off and ran the starter while keeping choke lever disconnected and secondary covers open.
Fuel pump is active but there was no sign of fuel leaking down from primaries or secondaries.
Then I connected the plugs and started, it suddenly ran so well. Then what caused the issue?
I've forgot to connect the vacuum hose to the RVB, and it kept the choke closed all the time and that was the cause for severe flooding
Lesson learnt the hard way!
(This is the first time I am messing with a carburetor, I'm more used to EFI)
Connected everything and adjusted the idle to max vacuum (no ILC or idle speed screw touching primary throttle lever) and it idles like a train.
By the way, my primary mixture screws have two nice brass plugs with O rings (resting on the radiator in photo) that could be rotated by fingers to adjust. I've read that you even have to cut the base plate to uncover these on E4M Qjets.
Nice! Congrats!
Yeah, the models after the mid-70's have a lot of attachments that are critical for the carb to work correctly. The engineers were kind of trying to do all the same things the EFI computers do, but via a mechanical air valve (the carb). A chassis manual is critical and don't skip any of the details!
