Carb/spacer question/confrimation

[yewhi]

Hi all,

I am replacing my current carburetor (autolite 2100 w/ manual choke) with an identical rebuilt carburetor (engine= stock 302). I was having intermittent problems with hot starts (among other things) and decided to go with a 1/4" phenolic spacer (felpro) in place of the current 1" spacer that is currently in place (vacuum port currently plugged) when I do the swap.

My question is whether or not there will be an issue with the reduction in height of the spacers? I apologize if this has been discussed before. I attempted to search the topic and was able to find some information but not a direct answer to my question.

Thanks in advance!

Tim

 

[SHX669]

I've done it without issue on aftermarket intakes . Not sure if you'll have clearance problems with throttle linkage, PCV hose and choke with the reduced height.
SHX

 

[badmuttstang]

Clearances should not be a problem you will lose some power as the 1" spacer acts almost like having a high rise intake (adds more volume to intake) it also aids in air flow as far as mixing the fuel and air together. the lose of power is something you will not notice for a stock intake and motor. Im sure others will have their own opinion.

 

[yewhi]

Thanks Gentlemen!

 

[baddad457]

You're not going to see any reduction in power vs the stock PCV spacer. I would go with a taller phenolic spacer though. Or just add that 1/4" to the PCV spacer, I would also hook the PCV back up to it. The PCV provides more benefit than loss.

 

[yewhi]

You're not going to see any reduction in power vs the stock PCV spacer. I would go with a taller phenolic spacer though. Or just add that 1/4" to the PCV spacer, I would also hook the PCV back up to it. The PCV provides more benefit than loss.

Thanks! I had trouble finding a taller spacer but a trip to NAPA might be more helpful than just surfing the web.

With regard to the PCV. It is connected to a port on the back of the intake manifold. This is how the PO had it configured. The vacuum line snakes around the front of the carb (1st image) and then connects to a port with a bit of an octopus on the top/rear of the intake manifold (2nd image) with the vacuum port at the rear of the spacer plugged. It's ugly as sin but seems to work. I'm a bit naïve with regard to this. is there a reason to reconfigure this (other than aesthetics)?

Thanks again for the advice!

 

[TwoDalesDad]

Broncos run better when the engine is clean on top.....less stench inside the cab...

 

[jckkys]

Your photo indicates an approximately '68 engine. The 1" aluminum spacer has a PVC port about 3/8" diameter in the back. This introduces crankcase gases into the intake equally to both throttle bores just below the idle ports to evenly distribute it to all cylinders for a smooth idle.There is no better place to attach your PVC, and no better spacer, even after market. If heat soak is a problem you can add 1/4" insulating gasket over the aluminum spacer. Try Felpro 60716. Your 2100 is in great shape. Rebuilt it. A so called rebuilt carb is unlikely to be correct, as the "rebuilders" don't try to keep the parts for a particular carb together. They rarely even see one as nice as yours to rebuild. You may not get the manual choke, a hard to find feature, or the correct metering orifices. The 2100 is very easy to rebuild and the knowledge and experience will serve you well. If you want to buy one, keep yours. It's worth more than the core charge and if the one you buy doen't work correctly you have a back up.

 

[badmuttstang]

You could also double the gaskets top and bottom of the spacer to act as an insulator

 

[bmc69]

That is a bad place for the PCV connection; it is never supposed to be connected to a vacuum source that is tapped in to just one manifold runner; that tap is for operating vacuum devices that use only the "pressure" but with almost no flow....like a power brake booster. The PCV vacuum source is the one that is tapped in to the base of the carburetor...in some cases the carb itself has the PCV connection while in others, like yours, its in the spacer under the carb.

Connecting the PCV to the tap on a single runner does two bad things:

1. It introduces a continuous stream of air in only the one cylinder, causing that cylinder to run artificially lean.

2. All the crankcase oil vapors that are intended to be passed and burnt equally in all 8 cylinders are all being pass through just the one.

 

[baddad457]

If anything his PCV is going into one half of the cylinders, not one runner. A look at the underside of the carb will confirm this, or show that that port runs into both throttle bores. And one more thing, be careful torquing the carb nuts down with that 1/4" spacer, it's going to be somewhat "soft" and you can easily break off the corners of the base plate by applying too much force. Come think of it, if it's the spacer I think it is, the bolt holes are in hard plastic bushings, so this may not be a problem, check and see though. If you add the 1/4 spacer to the 1" spacer, you're going to need longer intake studs.

 

[yewhi]

That is a bad place for the PCV connection; it is never supposed to be connected to a vacuum source that is tapped in to just one manifold runner; that tap is for operating vacuum devices that use only the "pressure" but with almost no flow....like a power brake booster. The PCV vacuum source is the one that is tapped in to the base of the carburetor...in some cases the carb itself has the PCV connection while in others, like yours, its in the spacer under the carb.

Connecting the PCV to the tap on a single runner does two bad things:

1. It introduces a continuous stream of air in only the one cylinder, causing that cylinder to run artificially lean.

2. All the crankcase oil vapors that are intended to be passed and burnt equally in all 8 cylinders are all being pass through just the one.

Thanks BMC! I need to double check what else is connected to that octopus but it should be easy to reroute the PVC line to the correct port. Besides, I'd love to get rid of the octopus. I've always hated looking at that. It survived because it was hidden out of sight behind the carb.

Thanks again!

 

[yewhi]

Your photo indicates an approximately '68 engine. The 1" aluminum spacer has a PVC port about 3/8" diameter in the back. This introduces crankcase gases into the intake equally to both throttle bores just below the idle ports to evenly distribute it to all cylinders for a smooth idle.There is no better place to attach your PVC, and no better spacer, even after market. If heat soak is a problem you can add 1/4" insulating gasket over the aluminum spacer. Try Felpro 60716. Your 2100 is in great shape. Rebuilt it. A so called rebuilt carb is unlikely to be correct, as the "rebuilders" don't try to keep the parts for a particular carb together. They rarely even see one as nice as yours to rebuild. You may not get the manual choke, a hard to find feature, or the correct metering orifices. The 2100 is very easy to rebuild and the knowledge and experience will serve you well. If you want to buy one, keep yours. It's worth more than the core charge and if the one you buy doen't work correctly you have a back up.

Thanks! I have the Felpro 60716 and the studs from the intake manifold are not long enough to accommodate both the spacer and the insulating gasket. Based on the advice I've gotten here I think I'm going to forego the insulator and just install the original 1" spacer and connect the PVC to the appropriate port.

Regarding rebuilding the carburetor. Yeah, been there done that. 3 times actually in the past two years. The pictures were taken 3-4 years ago after the bronco had been sitting for 8 years (it's much cleaner now). I'm always good about completely disassembling it, soaking the parts in a bucket of carb cleaner, blowing out the ports with compressed air and then reassembling with the right parts (usually from Mike's). They usually work fine for a while but then begin with different issues (not all at once) that have included hard cold starts, bad gas smell, and trouble with hot starts (after the most recent rebuild). I've even had gas squirting from the accelerator pump onto the manifold even though the cover was tight (warped maybe?). You could probably chalk some of that up to EtOH in gas, or maybe I just suck at rebuilding these but I thought I'd give another carb a try.

I bought the carb that is identical. I matched the venturi and jet sizes and I plan on keeping the old one (just in case). We'll see. It was worth a shot.

Thanks again!!!

Tim

 

[jckkys]

The insulated base gasket I sugested was to address your hot start issue. Heat soak after shutting off a hot engine can cause flooding that won't allow easy starts. The boiling fuel in the float bowl sends vapor out of vent hole too and that's often what you smell. These issues are unusual unless overheating is also a problem so the original spacer is still best for your truck. The fuel squirting from the accellerator pump is likely because the cover is bent from over tightening. I just bend them striaght so the gasket surface is flat. Every 2100 or 4100 I've built had that problem.

 

[72_EB]

bmc69 is on the money with the PVC connection on your 2100. Bronco Graveyard has the correct hose to run from the spacer to the PCV on the rear of the passenger valve cover. The driver's side filler cap should be vented and in good condition.
As far as the fuel leak, yes, the covers on the accelerator pump and power valve are commonly warped and may require flattening of filing prior to your rebuild gaskets.
Boiling fuel has been more prevalent for me lately with the newer fuel mixes but I've actually been working with Kurt on the board to produce a phenolic spacer that replaces the factory cast spacer like the one on the 2100. I've tested two already on my last resto and daily driver with great success. We'll be offering them as soon as we can punch out a few more for production and sale. Hope I didn't steal the thread with a sales pitch, but been meaning to mention something on the spacer. It should be a helpful piece for those of us still running the stock carb and fighting the vapor lock battle. We will add something to the vendor section when get a complete kit available. *I did find a picture of the prototype this morning (not great but you get the idea). I'll add some more when I can dig them up and take a few.

 

[bmc69]

but I've actually been working with Kurt on the board to produce a phenolic spacer that replaces the factory cast spacer like the one on the 2100.

Awesome! The non-egr 1" factory spacers are often corroded out and hard to find anyway.

Oh..and after looking at that sanitary engine compartment pic you posted....I now officially hate you.

 

[72_EB]

Ha. Thanks man. I'll send some of my '72 POS DD later, BMC. That will make you feel better. I couldn't get this one out my garage fast enough once done before a bike fell on it or the dog jumped all over the door wanting a ride. Fun to do but a nerve-wracking son of a gun.

Awesome! The non-egr 1" factory spacers are often corroded out and hard to find anyway.

Oh..and after looking at that sanitary engine compartment pic you posted....I now officially hate you.

 

[yewhi]

bmc69 is on the money with the PVC connection on your 2100. Bronco Graveyard has the correct hose to run from the spacer to the PCV on the rear of the passenger valve cover. The driver's side filler cap should be vented and in good condition.
As far as the fuel leak, yes, the covers on the accelerator pump and power valve are commonly warped and may require flattening of filing prior to your rebuild gaskets.
Boiling fuel has been more prevalent for me lately with the newer fuel mixes but I've actually been working with Kurt on the board to produce a phenolic spacer that replaces the factory cast spacer like the one on the 2100. I've tested two already on my last resto and daily driver with great success. We'll be offering them as soon as we can punch out a few more for production and sale. Hope I didn't steal the thread with a sales pitch, but been meaning to mention something on the spacer. It should be a helpful piece for those of us still running the stock carb and fighting the vapor lock battle. We will add something to the vendor section when get a complete kit available. *I did find a picture of the prototype this morning (not great but you get the idea). I'll add some more when I can dig them up and take a few.

Actually, this is great info! When you get around to producing the spacers definitely put me down for one. In the mean time let me know if you need another beta tester.

And that engine bay truly is spectacular!

 

[baddad457]

If anyone wants a 2 bbl PCV spacer, I've got three extras to sell. Cheap. Bought em for my 3x2 but they don't work on that intake's carb pads.