1984 Bronco build thread

[StraightSix]

Yes, good that you are getting it dialed in. 14.3 is spot-on, and 14 - 15 will work well. But that leaning out at WOT might be your accelerator pump rather than the power valve. The accelerator pump is to cover up the hole in the fuel delivery that occurs when you rapidly open the throttle as fuel is heavier than air and therefore can't move as quickly. It is a one-shot thing, one and done. But the power valve works until you lift the throttle.

So if the leanness is transient then I'd bet it is the accelerator pump that's the problem.

Gary,

I couldnt agree more. I just replaced the pump shot diaphragm and the the rubber check valve. The linkage is set for the largest possible stroke. I dont know how (other than drilling out the nozzles) to increase the size of my pump shot any more. pulling off from a stop in 2nd feels great, if anything its aggressive. In 4rth at highways speeds, Im hoping that the power valve opening earlier would cause it to recover from bogging earlier, but it shouldn't bog at all..

There is a lot of tuning/carburetor discussion going on at Fordsix on my thread there if anyone is curious to get down into the weeds with us. Of course, Id appreciate any help from folks here too!

https://fordsix.com/threads/300-build-for-a-1984-bronco.82577/page-22

[ArdWrknTrk]

Gary,

I couldnt agree more. I just replaced the pump shot diaphragm and the the rubber check valve. The linkage is set for the largest possible stroke. I dont know how (other than drilling out the nozzles) to increase the size of my pump shot any more. pulling off from a stop in 2nd feels great, if anything its aggressive. In 4rth at highways speeds, Im hoping that the power valve opening earlier would cause it to recover from bogging earlier, but it shouldn't bog at all..

There is a lot of tuning/carburetor discussion going on at Fordsix on my thread there if anyone is curious to get down into the weeds with us. Of course, Id appreciate any help from folks here too!

https://fordsix.com/threads/300-build-for-a-1984-bronco.82577/page-22

A bigger jet would give you a faster shot but it won't change any volume.

As you say, that is down to the stroke of the linkage.

With a Holley you can get 30 or 50 pump bodies.

IIRC this is a 3 or 5 ml shot.

[StraightSix]

A bigger jet would give you a faster shot but it won't change any volume.

As you say, that is down to the stroke of the linkage.

With a Holley you can get 30 or 50 pump bodies.

IIRC this is a 3 or 5 ml shot.

Thanks Jim.

Gary, I tried your trick of using zip ties to put a vacuum gage on the windshield wipers. Im at 21 inHg, 650 rpm and 12.5 AFR for idle currently. I was pretty happy with the vacuum numbers.

driving on the road, I found that my cruising AFR on flat ground at 50-55 is about 16-17 inHg.

I had hear recommendations to size power valves to half of cruising vacuum (8.5) as well as half of idle vacuum (10.5). I took another drive and watched that AFR and vacuum gage in 4rth gear and concluded that 10.5 inHg and crossing 15 AFR on the way to lean normally happened at about the same time so I opted for a 10.5 power valve which I was able to find at Mikes carburetor parts. Im hoping that having the power valve come in sooner and stay in longer on bog downs in 4rth will alleviate the problem a bit. I do still think I need to figure something out on my pump shot.

All in all I think things are going fairly well. I threw in the rest of the jets to round out the full set from 60-50, and a set of 62s as a hail Mary for 0 F days at the beach.. or something like that. I suspect that will round out all of my jet related needs.

Here are some photos of the current state of the engine bay.

 

[Gary Lewis]

Thanks Jim.

Gary, I tried your trick of using zip ties to put a vacuum gage on the windshield wipers. Im at 21 inHg, 650 rpm and 12.5 AFR for idle currently. I was pretty happy with the vacuum numbers.

driving on the road, I found that my cruising AFR on flat ground at 50-55 is about 16-17 inHg.

I had hear recommendations to size power valves to half of cruising vacuum (8.5) as well as half of idle vacuum (10.5). I took another drive and watched that AFR and vacuum gage in 4rth gear and concluded that 10.5 inHg and crossing 15 AFR on the way to lean normally happened at about the same time so I opted for a 10.5 power valve which I was able to find at Mikes carburetor parts. Im hoping that having the power valve come in sooner and stay in longer on bog downs in 4rth will alleviate the problem a bit. I do still think I need to figure something out on my pump shot.

All in all I think things are going fairly well. I threw in the rest of the jets to round out the full set from 60-50, and a set of 62s as a hail Mary for 0 F days at the beach.. or something like that. I suspect that will round out all of my jet related needs.

Here are some photos of the current state of the engine bay.

Things are looking good. I hope the power valve will come in at just the right time and pick the AFR up just a bit.

Does your 2150 have metering rods? Some do, some don't, but if it does they can be tweaked to come up earlier and enrichen the mix a bit.

Also, I see you have an open air cleaner. You might want to read the Description tab on our page at Documentation/Fuel & Air Systems/Air Cleaners. As explained there, an open element air cleaner is not conducive to keeping the AFR constant across a wide range of temps.

[ArdWrknTrk]

Things are looking good. I hope the power valve will come in at just the right time and pick the AFR up just a bit.

Does your 2150 have metering rods? Some do, some don't, but if it does they can be tweaked to come up earlier and enrichen the mix a bit.

Also, I see you have an open air cleaner. You might want to read the Description tab on our page at Documentation/Fuel & Air Systems/Air Cleaners. As explained there, an open element air cleaner is not conducive to keeping the AFR constant across a wide range of temps.

Your engine bay is looking very nice!

I know it took a lot of time and effort.

An open element air cleaner is not really conductive to keeping the inlet air temp constant across the seasons or operating modes....

I can't get away with one up here, unless I wanted to be fussing with my carburetor every few days.

Try the 10.5! A lot depends on your style of driving and how your vehicle is set up (gear ratio & weight v engine output)

10.5 would be way too soon for me in my truck, with my gear ratio, tare weight and 4V vacuum secondary carb.

Just be mindful that Holley's recommendations are geared towards performance enthusiasts.

Someone should probably tag Bill...

 

[StraightSix]

Your engine bay is looking very nice!

I know it took a lot of time and effort.

An open element air cleaner is not really conductive to keeping the inlet air temp constant across the seasons or operating modes....

I can't get away with one up here, unless I wanted to be fussing with my carburetor every few days.

Try the 10.5! A lot depends on your style of driving and how your vehicle is set up (gear ratio & weight v engine output)

10.5 would be way too soon for me in my truck, with my gear ratio, tare weight and 4V vacuum secondary carb.

Just be mindful that Holley's recommendations are geared towards performance enthusiasts.

Someone should probably tag Bill...

Thanks guys.

I may have a lead on an 85 f150 with a 302, it would be a parts truck or even a trailer candidate. Ive been eyeballing its factory air cleaner. In theory, getting it to sit on my carb shouldn't be too hard unless it interferes with the heater core box. I dont have a hot air stove anymore and I dont guess the efi 300 manifolds were ever configured with one. I might be able to MacGyver one though. Im sure it would make keeping a steady tune easier.

I figured Id start with a 10.5. It makes sense looking at my vacuum gage and afr while driving and at this point Im ready to have a "too rich" problem, so far Ive been fighting "too lean". Id like to never end up much above 15 for afr even if it means small fuel economy sacrifices. Its just not worth the heart ache of tearing up the new engine. Especially when under load.

Im still running 89 for a bit of knock protection and probably will continue to until Ive got the tuning work dialed in.

[ArdWrknTrk]

Thanks guys.

I may have a lead on an 85 f150 with a 302, it would be a parts truck or even a trailer candidate. Ive been eyeballing its factory air cleaner. In theory, getting it to sit on my carb shouldn't be too hard unless it interferes with the heater core box. I dont have a hot air stove anymore and I dont guess the efi 300 manifolds were ever configured with one. I might be able to MacGyver one though. Im sure it would make keeping a steady tune easier.

I figured Id start with a 10.5. It makes sense looking at my vacuum gage and afr while driving and at this point Im ready to have a "too rich" problem, so far Ive been fighting "too lean". Id like to never end up much above 15 for afr even if it means small fuel economy sacrifices. Its just not worth the heart ache of tearing up the new engine. Especially when under load.

Im still running 89 for a bit of knock protection and probably will continue to until Ive got the tuning work dialed in.

Yes, the efi 300's had no provision for heat from the exhaust manifolds.

I suppose it wouldn't be difficult for you to rig up some kind of shroud, but in Georgia I'd be much more concerned with summer under hood temps at a stop than any kind of carburetor icing in winter.

Fresh air from in front of the radiator shroud would help.

Ford needed to keep inlet temperature nearly constant in order to meet federal emissions. I believe they chose 105f.

 

[85lebaront2]

Thanks guys.

I may have a lead on an 85 f150 with a 302, it would be a parts truck or even a trailer candidate. Ive been eyeballing its factory air cleaner. In theory, getting it to sit on my carb shouldn't be too hard unless it interferes with the heater core box. I dont have a hot air stove anymore and I dont guess the efi 300 manifolds were ever configured with one. I might be able to MacGyver one though. Im sure it would make keeping a steady tune easier.

I figured Id start with a 10.5. It makes sense looking at my vacuum gage and afr while driving and at this point Im ready to have a "too rich" problem, so far Ive been fighting "too lean". Id like to never end up much above 15 for afr even if it means small fuel economy sacrifices. Its just not worth the heart ache of tearing up the new engine. Especially when under load.

Im still running 89 for a bit of knock protection and probably will continue to until Ive got the tuning work dialed in.

Ok, since I was tagged on this one, and just pretty well read most of the 13 pages. Awesome amount of detail (still doesn't approach Gary's 76 page micro analysis). Are you still running the 1.08 venturii carb? if so that should be a good match as that was a pre-catalyst 302 size.

Holley and Ford power valves are rated by manifold vacuum in inches of mercury, 10.5 is a fairly early tip in, 8.5 is the normal size, basically the lower the number, the later it opens. With an AFR meter and an accurate vacuum gauge you can decide if it needs to be changed.

Float level, the 2150 carb is pretty forgiving on fuel level, but too low will cause a sudden opening stumble. 7/16" from the toe of the float to the bowl rim is a good setting if in doubt.

One thing a lot of people don't understand is the relationship between fuel and spark, they both need to be optimized for best power and efficiency.

On the electric choke, since you have a pull-off diaphragm, you can safely seal the inlet fitting, with the piston style break, it needs to have some flow to work.

[StraightSix]

Ok, since I was tagged on this one, and just pretty well read most of the 13 pages. Awesome amount of detail (still doesn't approach Gary's 76 page micro analysis). Are you still running the 1.08 venturii carb? if so that should be a good match as that was a pre-catalyst 302 size.

Holley and Ford power valves are rated by manifold vacuum in inches of mercury, 10.5 is a fairly early tip in, 8.5 is the normal size, basically the lower the number, the later it opens. With an AFR meter and an accurate vacuum gauge you can decide if it needs to be changed.

Float level, the 2150 carb is pretty forgiving on fuel level, but too low will cause a sudden opening stumble. 7/16" from the toe of the float to the bowl rim is a good setting if in doubt.

One thing a lot of people don't understand is the relationship between fuel and spark, they both need to be optimized for best power and efficiency.

On the electric choke, since you have a pull-off diaphragm, you can safely seal the inlet fitting, with the piston style break, it needs to have some flow to work.

85Lebaront2,

Thanks! I hope it was a good read.

I am still running the 1.08V 2150. I picked it for just the reason you said, A factory 302 is the same size as my 300 +/- 1% and Id be lucky to get even a heavily worked over 300 to breath as well on the top end a sa 302, so it seemed like a good choice ins simple, adequately sized carbs.

Ive been playing with a live AFR and vacuum gauge while driving. The current power valve is not marked for opening point, but I can feel that the mix stops getting leaner and starts turning around in the neighborhood of 6-7 inHg. I know the 10.5 will open fairly early by any standard, but Im also making more vacuum at cruise than most v8s make at idle. we will see, if it seems like too much I can always pick up an 8.5 or 9.5 to try. its also worth noting that the pump shot is still likely to be the real root cause here. I did notice that 10.5 in Hg in 4rth seemed well enough correlated to the point at which I get a little leaner than Im comfortable with on the AFR.

Ill check float level next time I pull the lid off. why does low level cause a stumble?

Im running a recurved DS2 distributor from Bill Ambler. I assume its good, and it does seem to drive well, then again I dont know what I dont know.

I have to sheepishly admit Im currently running a manual choke. my choke housing has aged badly and has lots of cracks, it wasnt sealing. I may get around to swapping that back to an auto choke at some point.

Thanks for the tuning advice!

[FuzzFace2]

85Lebaront2,

Thanks! I hope it was a good read.

I am still running the 1.08V 2150. I picked it for just the reason you said, A factory 302 is the same size as my 300 +/- 1% and Id be lucky to get even a heavily worked over 300 to breath as well on the top end a sa 302, so it seemed like a good choice ins simple, adequately sized carbs.

Ive been playing with a live AFR and vacuum gauge while driving. The current power valve is not marked for opening point, but I can feel that the mix stops getting leaner and starts turning around in the neighborhood of 6-7 inHg. I know the 10.5 will open fairly early by any standard, but Im also making more vacuum at cruise than most v8s make at idle. we will see, if it seems like too much I can always pick up an 8.5 or 9.5 to try. its also worth noting that the pump shot is still likely to be the real root cause here. I did notice that 10.5 in Hg in 4rth seemed well enough correlated to the point at which I get a little leaner than Im comfortable with on the AFR.

Ill check float level next time I pull the lid off. why does low level cause a stumble?

Im running a recurved DS2 distributor from Bill Ambler. I assume its good, and it does seem to drive well, then again I dont know what I dont know.

I have to sheepishly admit Im currently running a manual choke. my choke housing has aged badly and has lots of cracks, it wasnt sealing. I may get around to swapping that back to an auto choke at some point.

Thanks for the tuning advice!

I just went over the posts in the link you posted and got to say WOW!

On the lean at WOT I would not worry to much if it dose not bog and comes back to the 14 - 15 AFR.

I would also not worry about it going rich into the 13's at times if you are mostly in the 14 - 15 AFR.

I would be thrilled if my carter v1 ran in the ARF as yours dose.

My take on your AFR at idle going all over the place do you heat the intake manifold floor?

You have a large intake ports and that leads to low air flow. With low air flow you can have fuel falling out of the air and forming fuel drops on the intake floor.

The drops then dribble into the chambers and it shows up rich on the AFR gauge.

You will see this on v8 motors that use intakes with high RPM ranges, large carbs and stock cams and they cant get them to not idle rich / load up no matter what they do.

That is my take on your AFR at idle.

Oh wait till you get the air temp changes from cold to hot and back what the AFR gauge dose LOL

Dave ----

ps if you want to see what happens to vacuum to the dist. the same time as manifold vacuum you cant Tee in but need to run a 2nd vacuum gauge.