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rochester quadrajet to the 2101 performer intake issue

29K views 70 replies 14 participants last post by  1972 El Camino 
#1 ·
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
 
#3 ·
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.
 
#4 ·
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.
 
#5 ·
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.
 
#7 ·
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.
 
#8 ·
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.
 
#9 ·
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.
 
#15 ·
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
 
#16 ·
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.
 
#17 ·
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
 
#19 ·
maybe i'm confused on my terminology.... i have mine at 6 degrees,,.. to the left of "0" = before TDC correct? :)
 
#20 ·
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.
 
#22 ·
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.
 
#26 ·
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.
 
#30 ·
i plan on taking it off in the next couple days and doing just what you explained. :)
thanks!
Mark
 
#27 ·
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.
 
#29 ·
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

 
#31 ·
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.
 
#33 ·
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.
 
#34 ·
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?

 

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#35 ·
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.
 
#37 ·
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.
 
#39 ·
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
 
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