rochester quadrajet to the 2101 performer intake issue [Archive] - Chevelle Tech

: rochester quadrajet to the 2101 performer intake issue


1972 El Camino
Dec 21st, 11, 10:16 AM
hey guys,
need help in finding the correct gasket solution for my Rochester Quadrajet to have no vacuum leaks using the edelbrock 2101.

i had a mechanic install the carb and manifold and i have a huge leak at the carb base. (Spraying carb cleaner at the base gasket changes the idle) so im taking matters into my own hands and looking for the correct gasket.

When i got the carb from Shaun murphy he sent me a gasket but the mechanic said there was a huge vacuum leak. the mechanic then got another one but it still has a leak.

anyone have experience or advice the correct gasket/solution?
i found this one - http://www.summitracing.com/parts/MRG-56A/

do i need an adapter or something to make this work using the two together?

i appreciate the help,
Mark

ss3964spd
Dec 21st, 11, 10:44 AM
Mark,

It'll probablyt be faster to just call Edelbrock and ask their tech line which carb base plate gasket to use for the 2101 and QJ combination.

Dan

bracketchev1221
Dec 21st, 11, 10:52 AM
The 2101 is a q-jet intake. Try one for like a 86 Caprice. That one used a 1/4" insulator gasket. I have never had an issue with a q-jet on those manifolds unless he is overtorquing it and destroying the gasket.

496blaze
Dec 21st, 11, 11:17 AM
Just went through this myself.. I would check your initail timing to make sure it has enough to idle properly. In my case, I would spray around the carb base and get a false reaction since it would suck in at the throttle shafts and make the engine happy (thinking I had a vacuum leak) for second since it was idliing with O* timing at idle. Fixed the initial timing and I was able to tune the carb properly.

2 thumbs up for Sean Murphy btw! He builds a killer Q-Jet carb.

1972 El Camino
Dec 21st, 11, 11:21 AM
Just went through this myself.. I would check your initail timing to make sure it has enough to idle properly. I would spray around the carb base and get a false reaction since it would suck in at the throttle shafts and make the engine happy for second since it was idliing with O* timing at idle. Fixed the initial timing and I was able to tune the carb properly.

2 thumbs up for Sean Murphy btw! He builds a killer Q-Jet carb.

you know whats funny? is the car idles with the idle screw all the way out?!? the screw is an 1/8 of an inch from touching where it should to adjust the idle.... and the car idles?!?

when i got the car back from the shop he had the dwell set at 14. i set it to 30, he had the timing mark 3 inches advanced past the timing plate!!!!, i moved it to 6 degrees advanced.
who knows how much he played with the fuel air mixture screws as well... heh

another thing is that the car has since getting the manifold and carb installed making too much of an air sucking sound through or around the carb. i thought it was because now im using an open air element but it doesn't make sense its as loud as it is unless again, im clueless.

496blaze
Dec 21st, 11, 11:26 AM
Do you know what the base idle timing is set at? Are you running a PCV valve?

1972 El Camino
Dec 21st, 11, 11:30 AM
Do you know what the base idle timing is set at? Are you running a PCV valve?

you mean the rpm? its at or around 650rpm.(it doesn't seem like its idling to high or too low.)
yes a pcv valve that has the hoses for the air system hooked up going to the canister and carb port.

ss3964spd
Dec 21st, 11, 11:40 AM
Guys,

Much of this is discussed in Marks other thread.

Mark, from what you described on your other thread you've got a vacume leak at the carb to manifold gasket. You need to focus on that before you start fussing/discussing the timing again.

1972 El Camino
Dec 21st, 11, 11:45 AM
i agree. my main reason for the thread is trying to figure out if i need a special gasket and or adapters etc.
i hesitated in calling edelbrock because its been through two gaskets already, the one Shaun gave me even after i told him i would be using it with a 2101 and the second one the mechanic got.

When i first spoke with the mechanic about it he said the gasket i provided had a leak. He then ordered one and the one that showed up was identical to the one i provided so then, apparently, he went down to the part house to try and find one that would work, that is the one that is in the car now.

ss3964spd
Dec 21st, 11, 11:54 AM
Mark,

Give me a ring and I'll explain it. 703-675-3410.

Dan

496blaze
Dec 21st, 11, 11:57 AM
you mean the rpm? its at or around 650rpm.(it doesn't seem like its idling to high or too low.)
yes a pcv valve that has the hoses for the air system hooked up going to the canister and carb port.

No, what is the timing set at in degrees at idle? If you have way too much idle timing on a mild engine it will cause it to idle very high as you describe.

All the connections from the PCV are controlled vacuum leaks and will cause the idle to raise. I would try temporarliy plugging them off and see if you can get the idle to come down to where it can be adjusted by the screw after confirming your idle timing is in the 10-14 degree or so range.

ss3964spd
Dec 21st, 11, 12:33 PM
you know whats funny? is the car idles with the idle screw all the way out?!? the screw is an 1/8 of an inch from touching where it should to adjust the idle.... and the car idles?!?
Todd, the above is the key bit of information. If the primary's are all the way closed and the engine still runs the air has got to be getting in somewhere else - like a serious vacume leak. Of course, this assumes the linkage isn't binding and holding the throttle blades open.

Mark, that's another thing to quickly check. Disconnect the throttle linkage to be certain the butterflys are able to close. on their own.

Dan

1972 El Camino
Dec 21st, 11, 12:43 PM
Todd, the above is the key bit of information. If the primary's are all the way closed and the engine still runs the air has got to be getting in somewhere else - like a serious vacume leak. Of course, this assumes the linkage isn't binding and holding the throttle blades open.

Mark, that's another thing to quickly check. Disconnect the throttle linkage to be certain the butterflys are able to close. on their own.

Dan

the throttle cable and even the trans kick down cables are loose. the throttle body is closed all the way.
http://i1192.photobucket.com/albums/aa335/1972_El_Camino/Misc/carb3.jpg

496blaze
Dec 21st, 11, 12:54 PM
Todd, the above is the key bit of information. If the primary's are all the way closed and the engine still runs the air has got to be getting in somewhere else - like a serious vacume leak. Of course, this assumes the linkage isn't binding and holding the throttle blades open.

Mark, that's another thing to quickly check. Disconnect the throttle linkage to be certain the butterflys are able to close. on their own.

Dan

Exactly Dan. That is why I am suggesting he eliminate the PCV and Evap canister (until he can get it to idle with the screw), as they are both controlled vacuum leaks. I believe the evap canister is supposed to be hooked to ported vacuum so it doesn't affect the idle circuit of the carb.

Still need to know what the timing is at idle.

ss3964spd
Dec 21st, 11, 1:06 PM
I hear ya Todd - agreed. Definitely a great idea to remove and cap any vacume ports on the carb to remove them from beign a factor.

In Marks other post on this subject he did mention that he shot propane or other flammable around the base of the carb and saw an increase in RPM. That, along with the other symptoms, still say carb base gasket leak.

I believe that until he can get this thing to idle down around 700 pursuing the timing will be an exercise in frustration for him. Depending on how high it's idling the centrifugal advance might already be starting. No amount of timing advance will keep an engine running if the air is choked off.

Dan

496blaze
Dec 21st, 11, 1:15 PM
I hear ya Todd - agreed. Definitely a great idea to remove and cap any vacume ports on the carb to remove them from beign a factor.

In Marks other post on this subject he did mention that he shot propane or other flammable around the base of the carb and saw an increase in RPM. That, along with the other symptoms, still say carb base gasket leak.

I believe that until he can get this thing to idle down around 700 pursuing the timing will be an exercise in frustration for him. Depending on how high it's idling the centrifugal advance might already be starting. No amount of timing advance will keep an engine running if the air is choked off.

Dan

What is weird Dan is that I just went through this with my car. I was able to have the car idle fine with the idle screw backed off (throttle totally closed) as Mark mentioned and the car idled fine. My car had 18 degrees of initial timing plus the evap canister hooked up to the PCV which was causing it to idle 3-400 rpm higher than it was when hooking it to ported vacuum.

1972 El Camino
Dec 21st, 11, 1:19 PM
maybe i'm missing the question of timing, its at 6 after TDC using a timing light. ( but it jumps around as i mentioned before. )

anyway i do need to first resolve the vac leak around the base then i will take information that has been mentioned here when i put it back together. :)

Mark

Philip
Dec 21st, 11, 1:41 PM
Try 8- 10 before TDC for the base timing.

1972 El Camino
Dec 21st, 11, 1:43 PM
Try 8- 10 before TDC for the base timing.

maybe i'm confused on my terminology.... i have mine at 6 degrees,,.. to the left of "0" = before TDC correct? :)

Philip
Dec 21st, 11, 1:49 PM
If by left you mean above the 0, then it is before TDC. Check to see if the high idle cam by the choke is dropping down with the choke open.

1972 El Camino
Dec 21st, 11, 2:03 PM
If by left you mean above the 0, then it is before TDC. Check to see if the high idle cam by the choke is dropping down with the choke open.
exactly what i mean! ill check the high idle cam as well - thanks!

Tom Mobley
Dec 21st, 11, 7:29 PM
some of the performers needed a steel plate with gaskets above and below. On the manifold right in front of the passenger side rear carb bolt there's a big indent in the manifold, many carbs will leak air/vacuum here.

Was this only for Holley carbs? Been too long, can't remember exactly.

BillsCamino
Dec 21st, 11, 7:43 PM
The plate is used to adapt a square carb to the spread bore openings of the intake.

Tom Mobley
Dec 21st, 11, 7:44 PM
this is the one I was thinking of:

BillsCamino
Dec 21st, 11, 7:45 PM
Thats it...

For use with Edelbrock spreadbore intake manifolds when installing a square bore carburetor. Not required on EDL-2101 or EDL-3701 unless using a Holley square bore carburetor.

Tom Mobley
Dec 21st, 11, 7:48 PM
I think Bill is right.

However, many Q's have cavities in the baseplate on the right rear, some have vacuum in those cavities. If they're not covered the will be a leak.

I recommend you pull the carb, turn it upside down over a bucket, let the fuel drain out. then, with the carb upside down, carefully compare the gasket to the bottom of the carb, looking to see that all the cavities in the baseplate are covered by the gasket. You might be a see an imprint of the bottom of the carb on the gasket.

novaderrik
Dec 21st, 11, 8:04 PM
the 2101 is an emissions legal stock replacement part.. you need a baseplate gasket for a stock quadrajet application- the 86 Caprice mentioned before is a good place to start..
i know it sounds kind of stupid, but are you running anything to the 1/4" NPT port in the intake right behind the carb? one of my friends put a Performer RPM on his 302 Ford and couldn't figure out why it didn't run very good at idle.. i took a look at it and asked him why that port didn't have a plug in it.. he stuck a plug in it and it ran perfect.

1972 El Camino
Dec 21st, 11, 8:07 PM
The plate is used to adapt a square carb to the spread bore openings of the intake.
my Quadrajet is spread bore. ;)
Mark

1972 El Camino
Dec 21st, 11, 8:10 PM
the 2101 is an emissions legal stock replacement part.. you need a baseplate gasket for a stock quadrajet application- the 86 Caprice mentioned before is a good place to start..
i know it sounds kind of stupid, but are you running anything to the 1/4" NPT port in the intake right behind the carb? one of my friends put a Performer RPM on his 302 Ford and couldn't figure out why it didn't run very good at idle.. i took a look at it and asked him why that port didn't have a plug in it.. he stuck a plug in it and it ran perfect.
you can see it here, kind of, yes it is plugged off besides the power brake booster and i believe that's a hook up for the transmission? the center one is plugged with a hose and a screw.
Mark

http://i1192.photobucket.com/albums/aa335/1972_El_Camino/Misc/carb1.jpg

1972 El Camino
Dec 21st, 11, 8:11 PM
I think Bill is right.

However, many Q's have cavities in the baseplate on the right rear, some have vacuum in those cavities. If they're not covered the will be a leak.

I recommend you pull the carb, turn it upside down over a bucket, let the fuel drain out. then, with the carb upside down, carefully compare the gasket to the bottom of the carb, looking to see that all the cavities in the baseplate are covered by the gasket. You might be a see an imprint of the bottom of the carb on the gasket.
i plan on taking it off in the next couple days and doing just what you explained. :)
thanks!
Mark

novaderrik
Dec 21st, 11, 8:28 PM
is the fast idle cam releasing when the choke opens all the way up?
that might be why it's idling with the idle speed screw away from the arm.. push down on the funky counterweight looking thing behind the choke coil to release the fast idle cam.

looks to me like you need to baseline everything- idle mixture screws 1.5 turns out, idle speed screw just barely touching the throttle arm with the ast idle cam disengaged, initial timing set at 12 degrees or so with the vacuum line unhooked..
make sure the choke opens up all the way when there is power tothe coil- it should only take a few minutes to open all the way.
hook the vacuum advance line from the distributor to the port on the carb that gives you full manifold vacuum and start the car.

tider66
Dec 21st, 11, 8:44 PM
I'm running a Quadrajet on that same Edelbrock intake with a 1/4" insulator gasket specifically for a Quadrajet and I have no problems with leaks at all.

Philip
Dec 21st, 11, 9:23 PM
I am also running the same manifold and the 86 Monte style gasket with no problems. The tee on the PCV to the canister may be part of the problem. like said before that should not purge at idle.

Tom Mobley
Dec 21st, 11, 10:18 PM
that's a nice looking carb. Looks like somebody did a nice job on it.

anyway, the red arrow points to the area where I've seen many Q's with vacuum leaks. you might be able to see up there with a mirror if you have one of the little round telescoping ones. See how the black gasket disappears under the carb?

http://www.chevelles.com/forums/attachment.php?attachmentid=47888&d=1324523921

Tom Mobley
Dec 21st, 11, 10:24 PM
also, unless you know that carb has had the idle feed restrictions opened up I'd start with the mixture screws about 3.5 turns out from seat.

Highway Star
Dec 21st, 11, 10:29 PM
Tom, he said (maybe in another thread?) that he got the carb from SMI. Once the vacuum leak is fixed everything will be fine...set the timing and go.

Tom Mobley
Dec 21st, 11, 10:37 PM
aw jeez, I must be getting old. The choke mount, the thing bolted to the manifold with 2 allen head bolts, kinda right under the choke, is upside down. This can cause a vacuum leak by not letting the carb sit down flush against the manifold. I have seen several carbs with the rear mount ear of the baseplate broken off because of this. guys kept tightening up the carb bolts till the ear broke off. verify by sitting the carb on the manifold with no gasket. I think you'll find that it rocks back and forth on the choke mount, won't sit down flush on the manifold.

Make sure the choke mount is sealed well against the manifold. either a good gasket or no gasket with hi-temp RTV.

novaderrik
Dec 21st, 11, 11:10 PM
aw jeez, I must be getting old. The choke mount, the thing bolted to the manifold with 2 allen head bolts, kinda right under the choke, is upside down. This can cause a vacuum leak by not letting the carb sit down flush against the manifold. I have seen several carbs with the rear mount ear of the baseplate broken off because of this. guys kept tightening up the carb bolts till the ear broke off. verify by sitting the carb on the manifold with no gasket. I think you'll find that it rocks back and forth on the choke mount, won't sit down flush on the manifold.

Make sure the choke mount is sealed well against the manifold. either a good gasket or no gasket with hi-temp RTV.

good catch on the choke mount/blockoff plate.. i knew it looked kind of weird, but yeah, it's upside down..

1972 El Camino
Dec 21st, 11, 11:51 PM
Thanks guys! Yet another thing to point to the guy that did the manifold/carb install was the wrong choice. Ill check and rotate that plate when I remove the carb.
Tom, is it possible the gasket is on wrong and that's where you pointed to? He possibly has it flipped over? I'll look at it tomorrow.
Mark

Philip
Dec 22nd, 11, 12:16 AM
Mark IIRC the gasket is symmetrical. I am running the same carb, mine was built by Tom.

http://i80.photobucket.com/albums/j199/64elcamino/77%20Nova%20project/engine/P1010062.jpg

1972 El Camino
Dec 22nd, 11, 8:21 AM
you can see the gasket would go on one way for sure. http://www.summitracing.com/parts/MRG-56A/
i can see in your picture that my choke mount/pull of plate IS up side down!
btw where can i find the breather you have on the driver side valve cover? right now i just have a piece of hose that i prop under the air cleaner.
my PCV, and breather are on opposite sides. :)

http://i1192.photobucket.com/albums/aa335/1972_El_Camino/Misc/elcammanifoldcarbswap4.jpg

novaderrik
Dec 22nd, 11, 8:29 AM
you can see the gasket would go on one way for sure. http://www.summitracing.com/parts/MRG-56A/
i can see in your picture that my choke mount/pull of plate IS up side down!
btw where can i find the breather you have on the driver side valve cover?
my PCV, and breather are on opposite sides. :)

if you want, just swap the covers side for side to flip them around.. but yours is the one that's "correct" according to how the factory did it.. you can pick up a breather that will fit into the stock breather hole at pretty much any parts store- get one with a 3/4" nipple on it.. at the very least, pick up a piece of hose with a 90 degree bend in it to hook up to the air cleaner- that pinched off piece of heater hose you have isn't letting very much air thru to clear the nasty fumes out of the crankcase..

regarding the upside down plate- if you have a 1/2" socket and a 3/16" allen wrench, it would literally take you 5 minutes to unbolt the carb and move it far enough out of the way to flip that plate over and bolt the carb back down. you don't even need to unhook any lines or cables or anything to do this- just remove the 4 carb mounting bolts and flip the carb out of the way enough to get to the allen bolts on the plate.. your hands won't even get very dirty and you shouldn't need any new gaskets unless the one under the plate has been there for a while and it falls apart..

this is the carb gasket you should have- it's 1/4" thick and has plastic bushings around each mounting bolt to prevent you from crushing it. it's a stock replacement part for pretty much every GM vehicle that got a quadrajet from the mid 70's to the late 80's... get it locally for around $8..
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?A=FPG60482_0158547739&An=599001+101986+50012+2012014+29051+4012044+59999 99&Ar=AND%28P_RecType%3aA%29

this is a NAPA link, but any parts store will have it- but if it's the little plate that's holding up your carb you won't need it..

Tom Mobley
Dec 22nd, 11, 3:52 PM
that gasket you linked to at Summit is not right for your setup. You need the one Derrick linked to. Looks to me like you already have it.

1972 El Camino
Dec 22nd, 11, 4:23 PM
okay so i got a couple gaskets.
you can see the one Derrek recommended has the inserts.

the grey one is for a 71-73 chevy v8 4bbl. Different material and has more of an open center to it. as well it has no inserts.

they both are the same thickness and seem to be thicker than the one i have in the car currently.

each gasket has one side that is slightly rounded compared to the other side. is it safe to assume that flat side goes down on the manifold?

http://i1192.photobucket.com/albums/aa335/1972_El_Camino/Misc/quadrajetgaskets.jpg


also i checked that bracket and it does not get in the way of the carb base. but i will reverse it as well.

http://i1192.photobucket.com/albums/aa335/1972_El_Camino/Misc/DSC01129.jpg

Tom Mobley
Dec 22nd, 11, 4:37 PM
use the black one with the plastic bushings around the bolt holes. but check it against the bottom of the carb as discussed earlier.

Maybe it's Holley's that hit the choke mount?

ss3964spd
Dec 22nd, 11, 6:46 PM
Factory QJ manifolds used studs and nuts to secure the back of the carb and I noticed that you are using bolts. When you pull the carb make certain the bolts are not too long. If they bottom out in the holes before they actually tighten down the carb. Wouldn't hurt to check the two in the front for the same issue.

novaderrik
Dec 23rd, 11, 2:14 AM
i've never really noticed anything different as far as quadrajet baseplate gaskets are concerned- i just use the one that has the plastic limiter bushings and throw it on whichever way i happen to be holding it.. once they are used, you want to make sure to not flip it over if you take the carb off, but it's easy to see how it was installed before.

when you take the carb off, take a screwdriver or torx driver (depending on what style of screws it has) and check all the screws that go up into the main body of the carb thru the baseplate.. if they are loose, you might get a weird vacuum leak..

1972 El Camino
Dec 23rd, 11, 9:53 AM
Update.

I flipped over the choke mounting plate with no issue. interesting that the two allen screws were loose enough that i removed them with my fingers. flipped and tightened it down.

I did check the length of the rear two carb mounting bolts and they are not too long.

After i got the gasket Derrek recommended (the black one with the inserts) it appeared to me it was the same one i have on the car so i just loosened all for 4 bolts and then tightened them in an x pattern. not too tight but snug. the idle does not change with carb cleaner and i dont hear as much of a sucking sound as i thought i did before.

The issue with idle screw appears that the choke was open because now it is sitting where it should against the plate making the car idle. (this may have been my greenness and the choke was simply keeping the car at fast idle)
i did put a meter on the choke wire and it is getting 9 volts.

I plugged the carb fittings that go to the vac advance, the canister and the the PCV valve and the timing still jumps around. (its odd because its not like i can hear the idle changing as to go along with the timing mark jumping around. although when i am out driving the car, especially after 40-50 miles or so, at a stop light the car is running slightly rough as if its missing or surging)

anyway the vacuum is still as it was, alot of vac from the fittings that go to the canister and pcv valve but barely anything, really nothing, that goes to the vac adv. again with everything hooked up the idle does not drop or change at all when i remove the hose to the vac adv.

I appreciate all the help on this. (everyone that has contributed to this thread lead me to try and do what i have done thus far)

I'm thinking i may just go and get another distributor and see if that resolves the jumping idle... unless anyone has anymore food for thought?

thank you!

Mark

novaderrik
Dec 23rd, 11, 10:53 AM
you want 12 volts to that choke coil.. where is it getting power from?

Philip
Dec 23rd, 11, 1:42 PM
A bad plug wire can also may the timing mark appear to be jumping. Try looking at the timing mark with your light attached to #6 wire. If it is steady it is the wire.
Worn advance weight pivots, a weak advance weight spring, bad contacts in the cap or on the rotor all could contribute to the mark not being steady too.

Tino
Dec 23rd, 11, 6:22 PM
Before trying another distributor, check your distributor weights and springs if they are sticking. Also check if the holes in the weights are elongated from wear.

1972 El Camino
Dec 24th, 11, 10:53 AM
you want 12 volts to that choke coil.. where is it getting power from?

ill have to figure out where he took it from.

1972 El Camino
Dec 24th, 11, 10:53 AM
A bad plug wire can also may the timing mark appear to be jumping. Try looking at the timing mark with your light attached to #6 wire. If it is steady it is the wire.
Worn advance weight pivots, a weak advance weight spring, bad contacts in the cap or on the rotor all could contribute to the mark not being steady too.
just put new wires on it. ill try #6.

1972 El Camino
Dec 24th, 11, 10:54 AM
Before trying another distributor, check your distributor weights and springs if they are sticking. Also check if the holes in the weights are elongated from wear.
the dist is not even a year old purchased from Autozone. ill check it out.

1972 El Camino
Dec 25th, 11, 9:54 AM
While I'm thinking about it, where can I get the tool to adjust my fuel air mixer nuts? These are not screws. Thanks

Philip
Dec 25th, 11, 10:33 AM
Lots of places sell them. I think Harbor Freight has one on a flexible shaft.

Snap On (http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=11181&group_ID=1441&store=snapon-store&dir=catalog)

novaderrik
Dec 25th, 11, 11:01 AM
While I'm thinking about it, where can I get the tool to adjust my fuel air mixer nuts? These are not screws. Thanks

go to Sears- they have a Craftsman carb idle speed screw tool that has a flexible shaft comes with a few different sockets that store in the handle.. the bigger mall stores generally have it in stock, but the little tiny outlet stores generally don't have things like that and are staffed by people that only know plasma tv's and washing machines..

77 cruiser
Dec 25th, 11, 11:05 AM
The port that you have the vac. advance hooked to is ported vac. The one with the cap on above the fuel inlet is manifold vac.

1972 El Camino
Dec 26th, 11, 7:47 AM
Jim are you sure? so both Philip and i have the vac adv hooked up to ported vac? i thought manifold vac would be closer to the bottom of the carb?

and here i was thinking that maybe the black gasket i'm using IS wrong and covering up a air passage it shouldn't be where the grey one would not block that hole.

http://i1192.photobucket.com/albums/aa335/1972_El_Camino/Misc/quadrajetgaskets.jpg

novaderrik
Dec 26th, 11, 9:29 AM
the only air passages are in the throttle bores.. if you can open the throttle without it hanging on the gasket, then you are good.. i don't know what purpose or application the more open gasket is for, but i always use one that looks like the black one.

Jim Mac
Dec 26th, 11, 9:47 AM
Just a thought. If the mechanic installed the choke boss upside down is it posible he used a thin gasket. Opted it down and warped the base of the Carb? Have you run a straight edge on the bottom of the Carb?

1972 El Camino
Dec 26th, 11, 9:51 AM
Just a thought. If the mechanic installed the choke boss upside down is it posible he used a thin gasket. Opted it down and warped the base of the Carb? Have you run a straight edge on the bottom of the Carb?

the choke boos did not get in the way of the carb base and the gasket he used is not thin. the vac leak seems to be gone once i loosened and torqued the bolts again.

1972 El Camino
Dec 26th, 11, 9:53 AM
the only air passages are in the throttle bores.. if you can open the throttle without it hanging on the gasket, then you are good.. i don't know what purpose or application the more open gasket is for, but i always use one that looks like the black one.

it was just a thought again trying to figure out why there was no vacuum from that port on the carb but maybe its hooked to the wrong port on the carb and needs to be plugged in else where.

1972 El Camino
Dec 26th, 11, 9:54 AM
The port that you have the vac. advance hooked to is ported vac. The one with the cap on above the fuel inlet is manifold vac.

Jim, so this one and mine are hooked up to ported vac?

taken from here - http://chevellestuff.net/tech/articles/vacuum/port_or_manifold.htm

"Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle."

(maybe i'm assuming there physical location on the carb has to do with whether they are above or below the throttle plates.)


Philip, when you unplug the vac adv does the idle change? do you feel vacuum with your thumb on the hose at idle?

i see no change at idle removing this hose from the vac adv and feel no vacuum when i put my thumb over that hose leading to the carb.

Philip's

http://i80.photobucket.com/albums/j199/64elcamino/77%20Nova%20project/engine/P1010062.jpg

mine

http://i1192.photobucket.com/albums/aa335/1972_El_Camino/Misc/carb1.jpg

rkd
Dec 26th, 11, 10:22 AM
Have that intake and an Eddy 1406 carb. I got a gasket at an O Reillys that worked.

Philip
Dec 26th, 11, 12:43 PM
Mark I'll double check but am sure the fitting my vacuum advance is connected is not ported. When the hose is plugged in the timing advances. I have not tried the others to see if they are ported, full or some where in between.
The engine is not running right now (waiting on new rocker arms) but when it is I'll check all three. The ported one needs to be found to use as a canister purge line.

1972 El Camino
Dec 26th, 11, 1:09 PM
Thanks Philip! yours sounds like it functions as it should!

77 cruiser
Dec 26th, 11, 9:53 PM
Try the other one & see if it's manifold vac.

1972 El Camino
Dec 27th, 11, 8:18 AM
Have that intake and an Eddy 1406 carb. I got a gasket at an O Reillys that worked.
do you remember what your gasket looked like?
http://i1192.photobucket.com/albums/aa335/1972_El_Camino/Misc/quadrajetgaskets.jpg[/QUOTE]

1972 El Camino
Dec 27th, 11, 9:39 AM
Try the other one & see if it's manifold vac.
call me obsessive but it just wouldn't sit right finding another that works knowing that that port should be working. its more about why doesn't it work right now. :D thanks though!

1972 El Camino
Dec 31st, 11, 12:49 PM
installed a new distributor and the mark no longer bounces.
i did notice that on old dist that on the plate where the weights move back and forth had some dirty gunk on it and probably cleaning that would have resolved the bounce but i decided to just go with new dist, cap rotor points condenser and be done with it.
thanks for all the help!
i'm going to start a new thread with questions about vacuum readings i'm getting on the rochester carb.
Mark