Best EFI for altitude? Does it matter?

[Bronco DLight]

Ok. So first the basics: 1974 Sport, stock 302/C4, stock manifold, heads, cams, etc. BCB headers, stock 2bbl carb, duraspark ignition.

The thing pulls strong, sounds great, and runs like a top at sea level. Just shipped to Colorado to 9000 feet and they can't get it lean enough. Runs OK, but not great. Also, there is no vacuum advance on the distributor apparently. I'm not certain that I'll leave it up there - may use some in TX and some in CO, but need it to run at 11,000 ft and 60 feet above sea level and both on the street and at incline. It is a trail truck, not a crawler.

I guess I could spend the money and try a rejet, but it sounds like an efi conversion would be best final solution considering the range of temps and altitude that I need it to run. I have read a lot of the EFI conversion threads and am wondering if there is a consensus on the best one and also if anyone at high altitudes has had experiences that may help. As I said, it's stock and I don't intend to really modify it to push the hp to the stratosphere.

Any recommendations would help. The mechanic up there usually uses the Holley 2bbl Pro-jection, but I haven't read many glowing reviews on that system. He says that in general anything 2 bbl works better at that altitude than 4s. I understand that reasoning with a carb engine, but does it matter with an efi if it is a 2bbl or 4 bbl set up? If not, will I get better performance with a new manifold and a 4bbl efi setup than the stock and a 2 bbl?

 

[Scoop]

I took my stock carbed trail rig to CO in 2010. Ran like crap. Rejetted to 47's and still ran like crap. It was low on power but ran OK up to about 10K ft. It would not run at all without me almost continuously pumping the throttle when I went over Tin Cup Pass at 12,100 ft.

Took in back to CO last year after an efi install and all the difference in the world. Ran great to top of Trinchera trail which ends at about 12,500 ft. My engine is basically stock and I installed an 88 SD setup off an XR7. So I would recommend a stock Ford set up as the best and cheapest and works great a altitude.

 

[KyleQ]

Foxbody injection - super easy.

 

[jw0747]

Rejetting is super easy and not costly at all. Pull the carb top off and get the float outta the way and change the jets located at the bottom of the bowl. I ran my 2 bbl several summers in the Colorado mtns and went up and over the 12,000-13,000 ft passes without a hitch and never changed the jets from the ones it had here at 975 ft in Texas. Unfortunately I can't remember which size jets it had. Changing over to efi is what I eventually did which costs way far more than rejetting your 2 bbl.

I'd recommend going over to and joining the ColoradoClassicBroncos.com and/or the AlpineClassicBronco.com forums and ask those guys for a jet size recommendation.

 

[ENDLIFE]

X2 on the Foxbody, mass air injection is the best way to go in my opinion. I got tired of re-jetting every time it was time to hit the high hills, so I went to fuel injection and I'm never looking back.
I will almost have a complete setup soon if your interested, as well.

 

[broncnaz]

Id agree the stock ford EFI is the best and probably the cheapest route for EFI.
Id also say that tuning the carb will be the cheapest route. You can also run more timing and I would get a vacuum advance back the the dizzy. On the flip side you'll hav to retune when you go back to sea level. So another option may be to get a spare carb have one tuned for Co and one for TX. cheap and easy. maybe not the easiest but easy.

 

[Broncobowsher]

Bone stock mustang mass air EFI. Measures the air going in regardless of altitude/atmospheric pressure. Then adds the right amount of fuel.

 

[ntsqd]

I'm likely going to pizz off the purists and say that a GM TBI is simpler yet. 4 sensors (1 on the TB unit itself), a TB that bolts on like a carb with ready-made adapters, some wiring and an ECU.

If there's a complication it's the ECU's programming. I'd venture a guess that a 305 donor's fuel map would be close enough to work, but may want some fine tuning.

After I find out how well a 2.8L V6's fuel map fits a 170 slant6 I'll be finding out how well a 350 map fits a 351.

Can burn or have new maps burnt, and there are vendors who can give you a map based on what you tell them about the engine whose guess will be really, really close.

 

[WheelHorse]

Changing jets takes all of 10 minutes if you have to undo the stock air cleaner housing.

I'm not sure who they are, but they must not be using a wideband to dial it in.

Changing vacuum advance isn't hard either. Hopefully "they" know the difference between port and manifold before claiming the vac advance isn't pulling.

 

[COBlu77]

From many years of snowmobiling and offroading at high altitudes, I thought I was pretty good at tuning carbs to run, but nothing, and I mean nothing will beat EFI. Especially considering the varying altitudes from 0-12k you mentioned. Also, the 10% ethanol crap gas we have here adds to your issues with a carb. Go EFI, do it right once and you'll be happy. My vote goes for stock Ford MPFI. OBD I vintage, preferably MAF. Stock and cheap available parts with a ton of knowledge and support available.

Scoop saw all of us CO guys with EFI having no issues, when all the guys who came in from sea level with carbs were having all kinds of issues at the 2010 RMR in Buena Vista. The altitudes varied from 6k-12k+ on that trip.

 

[Bronco DLight]

From many years of snowmobiling and offroading at high altitudes, I thought I was pretty good at tuning carbs to run, but nothing, and I mean nothing will beat EFI. Especially considering the varying altitudes from 0-12k you mentioned. Also, the 10% ethanol crap gas we have here adds to your issues with a carb. Go EFI, do it right once and you'll be happy. My vote goes for stock Ford MPFI. OBD I vintage, preferably MAF. Stock and cheap available parts with a ton of knowledge and support available.

Scoop saw all of us CO guys with EFI having no issues, when all the guys who came in from sea level with carbs were having all kinds of issues at the 2010 RMR in Buena Vista. The altitudes varied from 6k-12k+ on that trip.

Any specific recommendation for a donor? I really have neither the time nor the knowledge to go part pickin'. I'm sure I'll miss something. Does anyone sell a complete, and I mean complete, setup?

 

[COBlu77]

Any specific recommendation for a donor? I really have neither the time nor the knowledge to go part pickin'. I'm sure I'll miss something. Does anyone sell a complete, and I mean complete, setup?

I'd say 88-92 Mustang, for the most complete and easiest parts donor, but I'm sure many here will have different ideas. The easiest way to get a plug-n-play Ford EFI system is to have a donor car and use all of it's parts. V-8 Explorer or Mountaineer with 5.0 is a favorite. I went the part pickin route and got my info from Ryan McCormack and this site. I converted my original 302 using 91 Mustang parts and then did my current Lightning 351W using the same A9P Mustang EEC with Ryan M designed home brew harness made from the Mustang harness. Not that hard or expensive, but does take some skills and time. Do yourself a favor and do an in tank pump, instead of fooling with accumulators and other crap. I did it all about 8 years ago so I'm not the most current expert here on how-to. Too bad Ford took down Ryan's site!

I haven't heard good things about all the GM TBI clones and got to help on converting a 72 Blazer to TBI. I was not that impressed. The current TBI based systems from Holley, Edelbrock, etc may work, but are very very expensive and you'll be stuck if something goes wrong. I carry an extra TPS and TFI module with me on the trail, but nothing EFI related has given me a problem, since I gave up on the external fuel pump and accumulator.

 

[ntsqd]

I haven't heard great things about the TBI kits sold by various vendors either. Seems very hit and miss, which makes me wonder if it's the kit or the installer.

I've gone the JY route and including the two fuel pumps for the two vehicles I've got about $300 in the parts needed for both. (I'm not including the fuel system re-plumb parts cost for the EB because I'd be doing that regardless.) I figure if the GM ECU's turn out to be painful to deal with that I can always buy MegaSquirt ECU's and tune them myself.

There's no question that for a stock engine that the SEFI is the most likely to be plug-n-play, but it's far from the least complicated.

 

[broncnaz]

Its a little of both on TBI kits. TBI is ok but it really doesnt adjust lot and it seems they can be hard to dial in if the engine is not stock the programmers really have to get it right or it sucks.
Ford Also had a TBI or CFI as they called it during the early-mid 80's on 302's a few people have used it with ok results but the gm version is much easier to get. I believe the CFI will bolt to any 2 barrel manifold without the need for a adapter unlike TBI.
TBI/CFI is still not the best thing it has faults similar to carbs. I like to refer to TBI as a computerized fuel leak.

 

[Broncobowsher]

Now that I am thinking of the altitude part of the question a little more...
I might buck the trend a little and recommend the '94/5 mustang 5.0 mass air. The reason is the spark tables are active under load where the older systems go into fixed tables.

The fixed tables are preferred by drag racers who want consistent runs throughout the night. They don't like it when the air gets better (or worse) and the timing changes throwing off there dial in. That is why you see comments about going back to the older systems. Since you are dealing with getting the best running engine at altitude (not a consistent drag racer) the last gen EEC-IV mustang 5.0 would probably be better.

 

[Rox Crusher]

While re-jetting or re-carbing it when you are in TX or CO isn't that much work I would really recommend going with a Ford EFI system. Either TFI Distributor mass air or the new Explorer OBDII set up that is quickly becoming the preferred set up.

The big benefit of EFI is obviously that it adjusts itself for altitude but the other thing to remember is that the fuel system is pressurized which fends off vapor lock common during Colorado summer adventures.

PS.........we have a really active Bronco community here in CO and you may even be able to get some hands on help in the conversion or maybe even someone may take care of it for you. I know a couple guys that work on them during winter downtime.

PM me if you want some details.

 

[ntsqd]

Re-reading the OP, I wouldn't mess with the Holley TBI. The GM ECU is smarter (and that's not saying a lot). So if you're willing to test and tune and want more of JY sourced simple solution then I think the GM TBI or the GM TBI system driven by a Mega-Squirt ECU is the way to go.

Bowsher brings up a good point though, and one that I think is important. I'm not sure that the M-S systems have active timing under load either. If if you'd rather BE out on the trails than testing and tuning an EFI system so that you eventually can be out on the trails then SEFI.

 

[bronconut73]

I'm likely going to pizz off the purists and say that a GM TBI is simpler yet. 4 sensors (1 on the TB unit itself), a TB that bolts on like a carb with ready-made adapters, some wiring and an ECU.

If there's a complication it's the ECU's programming. I'd venture a guess that a 305 donor's fuel map would be close enough to work, but may want some fine tuning.

After I find out how well a 2.8L V6's fuel map fits a 170 slant6 I'll be finding out how well a 350 map fits a 351.

Can burn or have new maps burnt, and there are vendors who can give you a map based on what you tell them about the engine whose guess will be really, really close.

Howell TBI already makes the modded computer and harness to put GM TBI on a SBF.

 

[Broncobowsher]

Howell TBI already makes the modded computer and harness to put GM TBI on a SBF.

I have seen several Howell system that started and ran good. But when the tune was actually checked (wide band O2 tuning) the tunes were always far off the chart out of tune. A good rebuilt used carb is usually closer to being in tune then the Howells are.

 

[garberz]

a Ford EFI system. Either TFI Distributor mass air or the new Explorer OBDII set up that is quickly becoming the preferred set up.

I did the OBDII Explorer route. The donor vehicle would be 96'-01' 5.0 Explorer. I bought the whole vehicle, took what I needed, and sold the remains. You can send the engine harness and ECU to EFI guy, He will taylor the harness for your needs and configure the computer. The OBDII uses a few less sensors, No distributor and no TFI sensor. Parts are more plentiful than the Mustang stuff and the are quite a bit cheaper for now.

Here's the thread for EFI guy's services.

http://classicbroncos.com/forums/showthread.php?t=224697

Mark