1984 Bronco build thread

[StraightSix]

Well, I went out and started it up, it runs smooth, drives well, and now the tach seems to be reading right. Im not sure what happened, looks like I have an intermittent problem to solve.

Gary- thats crazy. I would have hoped for better. The spare box mounted in place is a neat idea though. I might need to go pick up a second box to keep in the back.

I attempted to set my timing with the vacuum guage, but I drew maximum idle vacuum at something like 45 degrees btdc. That seemed like it couldnt be a good idea so I locked it in at 10 btdc. More to come on timing. I was under the impression that you retard the timing until you reach maximum manifold vacuum then back off 2 degrees.

As for what it was doing yesterday, it was running smooth but the tach was reading 2500 at idle. The needle may have had some movement and bounce to it. As for relictor distance, I have no idea. I dont recall any slop in the distributor shaft.

Rob- thanks for the input of my "issue" in second. Im sure it would creep off from a stop in 2nd without any trouble, that would just be poor etiquette in traffic I think. Feathering in the gas definitely prevents any issues. Looks like you have quite the 300 set up btw!

[ArdWrknTrk]

Rob- thanks for the input of my "issue" in second. Im sure it would creep off from a stop in 2nd without any trouble, that would just be poor etiquette in traffic I think. Feathering in the gas definitely prevents any issues. Looks like you have quite the 300 set up btw!

I'm pretty sure that you advance the timing to max vacuum, and retard it a bit if you're worried about knock, or find rattling at cruise.

Crane Cams has very detailed instructions that come with their adjustable vacuum advance kit.

You can get the PDF from Jeg's online documentation.

Just look up the 99607-1 unit.

This will help you set your static timing, but obviously you can't change the limit slot, springs or vacuum profile.

Also note that the I-6 distributor rotates opposite to the V-8 engines. So advance-retard is opposite to them as well.

[StraightSix]

I'm pretty sure that you advance the timing to max vacuum, and retard it a bit if you're worried about knock, or find rattling at cruise.

Crane Cams has very detailed instructions that come with their adjustable vacuum advance kit.

You can get the PDF from Jeg's online documentation.

Just look up the 99607-1 unit.

This will help you set your static timing, but obviously you can't change the limit slot, springs or vacuum profile.

Also note that the I-6 distributor rotates opposite to the V-8 engines. So advance-retard is opposite to them as well.

Thanks Jim! Ill look up that bulletin and see what I can learn.

I just got back from a 40 mile fuel economy test drive. I used the same pump before the drive as I did after. It was mostly rural highway driving, so about 55 with the occasional stop or slowing down for someone turning up ahead. 55mph is about 2200 rpm for me. I came in at 17.3 mpg! Im completely flabbergasted. I know that a test over a longer distance will be more accurate since My drive only consumed about 2.3 gallons of gas, but still, I thought Id be lucky to make 15mpg on pure highway miles. That alone makes all of the work worth ut to me, but the added performance and potential for a much more reliable engine definitely rank pretty highly as well.

[ArdWrknTrk]

Thanks Jim! Ill look up that bulletin and see what I can learn.

I just got back from a 40 mile fuel economy test drive. I used the same pump before the drive as I did after. It was mostly rural highway driving, so about 55 with the occasional stop or slowing down for someone turning up ahead. 55mph is about 2200 rpm for me. I came in at 17.3 mpg! Im completely flabbergasted. I know that a test over a longer distance will be more accurate since My drive only consumed about 2.3 gallons of gas, but still, I thought Id be lucky to make 15mpg on pure highway miles. That alone makes all of the work worth ut to me, but the added performance and potential for a much more reliable engine definitely rank pretty highly as well.

That's awesome!

Congratulations! I'm so happy for you....

It's always rewarding when all the effort pays out.

[Gary Lewis]

Thanks Jim! Ill look up that bulletin and see what I can learn.

I just got back from a 40 mile fuel economy test drive. I used the same pump before the drive as I did after. It was mostly rural highway driving, so about 55 with the occasional stop or slowing down for someone turning up ahead. 55mph is about 2200 rpm for me. I came in at 17.3 mpg! Im completely flabbergasted. I know that a test over a longer distance will be more accurate since My drive only consumed about 2.3 gallons of gas, but still, I thought Id be lucky to make 15mpg on pure highway miles. That alone makes all of the work worth ut to me, but the added performance and potential for a much more reliable engine definitely rank pretty highly as well.

Yes, that is awesome! Glad it is working out so well.

[Sac79]

Thanks Jim! Ill look up that bulletin and see what I can learn.

I just got back from a 40 mile fuel economy test drive. I used the same pump before the drive as I did after. It was mostly rural highway driving, so about 55 with the occasional stop or slowing down for someone turning up ahead. 55mph is about 2200 rpm for me. I came in at 17.3 mpg! Im completely flabbergasted. I know that a test over a longer distance will be more accurate since My drive only consumed about 2.3 gallons of gas, but still, I thought Id be lucky to make 15mpg on pure highway miles. That alone makes all of the work worth ut to me, but the added performance and potential for a much more reliable engine definitely rank pretty highly as well.

Yes, that's a small sample size, but still an excellent return. I haven't managed to get past 15MPG yet. We have very similar setups, only different in ignition, carb size and you have a lower gear in the diff. Maybe that Bronco has better aero efficiency... Bottom line, your tune can't be terrible with that fuel efficiency.

More than 4 years lapsed between driving my truck in it's 'stock' form and now with the upgrades. So I can't say for certain that it's a night and day difference, but I definitely don't remember ever being impressed with my truck's performance before... And it's no slouch now. Not that I drive it or want it for performance. But as you say, it's just nice to know that all the work and money isn't just for show...

[StraightSix]

Yes, that's a small sample size, but still an excellent return. I haven't managed to get past 15MPG yet. We have very similar setups, only different in ignition, carb size and you have a lower gear in the diff. Maybe that Bronco has better aero efficiency... Bottom line, your tune can't be terrible with that fuel efficiency.

More than 4 years lapsed between driving my truck in it's 'stock' form and now with the upgrades. So I can't say for certain that it's a night and day difference, but I definitely don't remember ever being impressed with my truck's performance before... And it's no slouch now. Not that I drive it or want it for performance. But as you say, it's just nice to know that all the work and money isn't just for show...

Well, Im off work this week and will be driving the bronco criss cross around the state, so hopefully I can get a more accurate idea of the milage. And hopefully you guys wont be getting any frantic road side messages from me!

I bet that 500 cfm carb really opens up the top end. Ive noticed that mine is now much more useful above 2500rpm. Before, it would spin faster than 2500 but nothing great really happened up there. No reason to do it unless you were in top gear and wanted to go faster. Now, it makes good power (by the calibrated foot test) up to atleast 3250 which is the highest Ive pushed it. Before I always shifted at about 2500 regardless of what gear I was in, now I find myself shifting 2nd to 3rd aroud 2500 and then 3rd to 4rth at about 3000-3200 which lands me in 4rth at 35mph and 1500 rpm. It seems sorta spun out in 4rth below about 1500. Overall driveability is significantly better

[ArdWrknTrk]

Well, Im off work this week and will be driving the bronco criss cross around the state, so hopefully I can get a more accurate idea of the milage. And hopefully you guys wont be getting any frantic road side messages from me!

I bet that 500 cfm carb really opens up the top end. Ive noticed that mine is now much more useful above 2500rpm. Before, it would spin faster than 2500 but nothing great really happened up there. No reason to do it unless you were in top gear and wanted to go faster. Now, it makes good power (by the calibrated foot test) up to atleast 3250 which is the highest Ive pushed it. Before I always shifted at about 2500 regardless of what gear I was in, now I find myself shifting 2nd to 3rd aroud 2500 and then 3rd to 4rth at about 3000-3200 which lands me in 4rth at 35mph and 1500 rpm. It seems sorta spun out in 4rth below about 1500. Overall driveability is significantly better

The 300 was never a high revving engine (Frenchtown Flyer may disagree) but I'd think EFI manifolds are doing more for you than a 500 cfm carb.

I gave Josiah Thorngate a 435 cfm 4160 for his truck a few years back, and it seemed more that enough with his cam, EFI manifolds, Walker Y-pipe (opened up) and Offy intake.

Sometimes smaller primaries give better signal even with annular boosters.

Anyway, we're all looking forward to your report after next week.

[Gary Lewis]

Well, Im off work this week and will be driving the bronco criss cross around the state, so hopefully I can get a more accurate idea of the milage. And hopefully you guys wont be getting any frantic road side messages from me!

I bet that 500 cfm carb really opens up the top end. Ive noticed that mine is now much more useful above 2500rpm. Before, it would spin faster than 2500 but nothing great really happened up there. No reason to do it unless you were in top gear and wanted to go faster. Now, it makes good power (by the calibrated foot test) up to atleast 3250 which is the highest Ive pushed it. Before I always shifted at about 2500 regardless of what gear I was in, now I find myself shifting 2nd to 3rd aroud 2500 and then 3rd to 4rth at about 3000-3200 which lands me in 4rth at 35mph and 1500 rpm. It seems sorta spun out in 4rth below about 1500. Overall driveability is significantly better

Yes, looking forward to the report. And, hopefully, no calls for help!

[Sac79]

Well, Im off work this week and will be driving the bronco criss cross around the state, so hopefully I can get a more accurate idea of the milage. And hopefully you guys wont be getting any frantic road side messages from me!

I bet that 500 cfm carb really opens up the top end. Ive noticed that mine is now much more useful above 2500rpm. Before, it would spin faster than 2500 but nothing great really happened up there. No reason to do it unless you were in top gear and wanted to go faster. Now, it makes good power (by the calibrated foot test) up to atleast 3250 which is the highest Ive pushed it. Before I always shifted at about 2500 regardless of what gear I was in, now I find myself shifting 2nd to 3rd aroud 2500 and then 3rd to 4rth at about 3000-3200 which lands me in 4rth at 35mph and 1500 rpm. It seems sorta spun out in 4rth below about 1500. Overall driveability is significantly better

Yeah, I don't know if the bigger carb does anything other than drink more gas(which probably just goes out my tailpipe)... But the intake and EFI manifold combo does the trick I believe. If you watch the Powernation build, the stock engine achieves peak power at around 2500 and torque falls off steeply from 1500(the start of their graph). With all the improvements peak power comes around 3500 and torque at 2500... And I can believe that from driving my truck.

Before the rebuild I never got above 2000Rpm in anything other than 4th. Now it will happily pull up to 3500 in 3rd at which point I chicken out, not the truck. I don't really push it in 2nd and in 4th the limiting factor is the wall of air I'm trying to push through at 80MPH!

Enjoy driving the Bronco this week!