Harley carb on a 302 bronco

[DirtDonk]

Good to know!

 

[eou_edu]

With manual transmission. The automatic was still flat tappet

This motor was from a 2001 explorer and I bought it with an automatic 4r70w that I was assumed mated to the motor. The engine has a roller cam. It's possible it was mated to a manual and the auto was acquired separately from the previous owner? But I don't think there were many manual explorers out there.

 

[eou_edu]

I’m not against playing around with odd combinations either, and I happen to like small carburetors.
But one bit of your quoted numbers is possibly off. I don’t know that, but thought I’d throw it out there anyway
If the CFM rating is the same as a 2100 that came on the old engines, remember that the ones that had carburetors, along with the other components were putting out 140 to 160 hp. The Explorer motor had 240 and cams and cylinder heads to go along with that.
Don’t know what, if any difference that might make in how the carburetor responds or how you need to rejet it. But it’s just a thing I was tossing around in my head so I wanted to mention it.

When you choose a distributor, make sure you choose one with a gear that’s compatible with a roller cam material. If not able to find one off the shelf, you’ll have to replace the gear.
The old go to was an 85 Mustang GT distributor. If I remember.

But just because it's rated at that doesn't mean you need to use all the power. The good news is nothing catastrophic can happen. When it runs out of air it runs out of power. Given how I personally drive and the RPM range I would keep it under it's very unlikely I will ever demand more than 100 hp or so. The link to the youtube video I sent the guy eventually dyno his car with the 302 and lawnmower carb and maxed out at 59hp and 3500rpms. He never says what size it was but even a big riding mower can't be more than 20 hp or so.

 

[DirtDonk]

Yeah, saw the video awhile back. Love people getting creative with this stuff.
My best fuel economy carburetor was a Holley 450, and it made the engine a real stump puller off idle.
But it definitely ran out of breath earlier than even the stock carburetor did.
That was probably because I never got a chance to tune it. Just ran it right out of the box.
I changed it out because, even though I’m not a racer either, I do occasionally like to get out of someone’s way.
Driving in traffic with an engine running out of breath are not two things I like to do.

The Explorer V8 never came with a manual transmission that I know of. The distributor we were referring to was when you convert to a distributor, you need to have one with the proper gear
Your engine is known to be a roller cam, so you have to have a distributor from a roller cam engine. There aren’t many choices unless you build it yourself or buy aftermarket. If you choose to just run a stock Distributor, the Mustang application was the one to go to.

But even that’s probably not gonna work in your situation. Pretty sure it’s a TFI and computer controlled distributor now that I think about it.
So you’ll need a different standalone unit anyway, with the proper gear.

 

[eou_edu]

Yeah, saw the video awhile back. Love people getting creative with this stuff.
My best fuel economy carburetor was a Holley 450, and it made the engine a real stump puller off idle.
But it definitely ran out of breath earlier than even the stock carburetor did.
That was probably because I never got a chance to tune it. Just ran it right out of the box.
I changed it out because, even though I’m not a racer either, I do occasionally like to get out of someone’s way.
Driving in traffic with an engine running out of breath are not two things I like to do.

The Explorer V8 never came with a manual transmission that I know of. The distributor we were referring to was when you convert to a distributor, you need to have one with the proper gear
Your engine is known to be a roller cam, so you have to have a distributor from a roller cam engine. There aren’t many choices unless you build it yourself or buy aftermarket. If you choose to just run a stock Distributor, the Mustang application was the one to go to.

But even that’s probably not gonna work in your situation. Pretty sure it’s a TFI and computer controlled distributor now that I think about it.
So you’ll need a different standalone unit anyway, with the proper gear.

I thought he was talking about the engine difference with roller cams......... On your advice I just called pertronix and DUI to see what they have. Pertronix doesn't carry melonized gear distributor. He also said these have a oil pull 1/4" longer than the older 302. Luckily they make a distributor just for people doing this exact conversion that accomodates for both these things. The part number he gave me is 38820. They don't come cheap though, $475 on summit! Thanks for the advice. Could have messed something up if I didn't get pointed in the right direction here. I might make another post out of just this to prevent anybody else in the future doing the same thing.

 

[eou_edu]

The side draft intake is for a small block ford V8. Uses a single Carter side draft carb like the ones used on a '53 Corvette.

Something else to consider it the carburetor airflow ratings don't always correlate the way people think they do. For example a 4-barrel carb is rated at 1.5" of vacuum while 2-barrel carbs are rated at 3" of vacuum. If you go through the big book of Holley specs, the 750 double pumper is a true symmetrical carb front to rear. Same throttle bore, booster, venturi, everything. The exact same specs are on the 500 CFM 2-barrel. If you put that 750 CFM 4-barrel on something big enough to pull 3" of vacuum at full throttle, it would really be pulling 1000 CFM.

I think I'll be updated this thread to scrapping or shelving the idea. Based on your advice and something I overlooked I did a little more math and research on what I was looking for. I found some info online where they tested harely carbs and I figured a harley 51mm was going to flow about 310cfm. A stock autolite 2 barrel these engines had on the bronco's were rated at 287 cfm. Great! Looks like I'll get even more flow from a harley carb than an autolite 2 barrel............ but then there's there's that little fact you brought up about what pressure they are tested to. The testing that gave these carbs a 310 cfm rating was at 12" of water or about 1mmhg. 2 barrels are tested at 3mmhg. The conversion to compare the cfm of the harley carb and autolite 2100 for this is CFM/squre root of what the autolite is tested to. So 310/square root of 3= 179 cfm for the harely carb. I'm not a power hungry junkie and for that would almost be spot on for flow you need out of the 170/200. But you'd be wasting a lot of the power potential of the V8 an that point and you might as well just horse trade with someone who has inline 6 they want more from................ I still might do it just for the fun of it if I end up scrapping that EFI intake anyway just to try something different. More than anything see what happens to MPGs. But for now I'll just stick an edelbrock AVS2 on it and be happy with that!

 

[Broncobowsher]

I'll side track this into another tangent. 25 years ago I bought a new KLR650. While looking the specs over, the bore/stroke was nearly identical to a 327 Chevy, or a 331 stroked small block Ford. I recall it was a few thousandths under a 4" bore and a few thousandths over a 3.25" stroke. I cal also remember see the exotic 4-weber intakes. Thought to myself "if I had 8 motorcycle carburators" That would feed a small block like 8 motorcycle engines. I also recall that the KLR CV carb was also used on some Harley with the addition of an accelerator pump. Even to the point it was easier to find jets and carb kits for the Harley version than the Kawi version. Now the KLR used a 4-valve head and would rev to 7500 RPM. But the nickname for the bikes is also "a tractor" as they are known for running forever and being very much like a tractor in not that much power for as big as they are.

Not a huge Harley guy, but I recall hearing of some monsterous stroker kits a long time ago. I want to say the biggest were in the 160 inch range. About half of a small block.